Proceedings of the Sixteenth Annual Congress OF THE South African Sugar Technologists' Association

HELD IN DURBAN AND AT MOUNT EDGECOMBE 21st-23rd April, 1942 [The Copyright of these papers is the property of the Association]

The Association does not hold itself responsible for any of the opinions expressed in papers published herein.

To assist in conserving the supply of paper, the Association has co-operated with the Printers by publishing this year's Proceedings in a reduced size of type, and hopes that the present emergency will exist for a temporary period only.

PUBLISHED BY THE South African Sugar Technologists' Association STABILITY BUILDINGS DURBAN PRINCIPAL CONTENTS

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OFFICERS OF THE SOUTH AFRICAN SUGAR TECHNOLOGISTS' ASSOCIATION iii.

LIST OF MEMBERS AND GUESTS iv.

OPENING CEREMONY by DR. J. FISHER 1

VICE-PRESIDENT'S ADDRESS 2

ANNUAL SUMMARY OF CHEMICAL LABORATORY REPORTS, by H. H. DODDS and, J. L. DU

TOIT 5

ON EFFICIENCY INDICES IN SUGAR MILLING, by PROF. P. STEIN 30

VARIETAL MILLING TESTS IN EAST AFRICA, by F. D. WHEELER 34

VARIETAL MILLING RESULTS IN NATAL, 1941, by G. C. DYMOND 37

A REVIEW OF FUEL ALCOHOL PRODUCTION AND DUNDER DISPOSAL, by G. C. DYMOND 43

MANUFACTURE OF GLYCERIN FROM SUGAR BY FERMENTATION, by J. O. DUCHENNE ... 45

Two WAR-TIME MEASURES, by C. MARTINDALE 48

COMPARISON OF JACKSON AND GILLIS AND DIRECT POLARIZATION, by G. S. MOBERLY ... 50

OBSERVATIONS OF FERTILIZER VALUE AND WAX CONTENT OF FILTER CAKE, by THE

CHEMICAL DEPARTMENT, S.A.S.A. EXPERIMENT STATION 52

SOME EXPERIMENTS ON SUGARCANE MEALYBUG, by J. DICK 55

THE PRESENT FERTILIZER POSITION, by H. H. DODDS, 57

PIG MANAGEMENT FOR BEGINNERS, by P. FOWLIE 64

EIGHTH PROGRESS REPORT ON EXPERIMENTS AT UMFOLOZI, by P. FOWLIE and F. L. ALMOND 69 AGRICULTURAL CONDITIONS AND ACHIEVEMENTS OF RURAL POLICY IN GREECE, by PROF. A. J. BOYAZOGLU 76 A SYMPOSIUM ON COMPOST : PAPERS READ AT A SPECIAL MEETING HELD AT THE S.A.S.A. EXPERIMENT STATION, JANUARY 30TH, 1942.

EXPERIMENTS ON THE COMPOSTING OF SUGARCANE TRASH, by A. MCMARTIN ... 78

ORGANIC MANURES IN MAURITIUS, by G. C. DYMOND 83

COMPOSTING GARDEN REFUSE, by P. ROBERTSHAW 85

»«= =*«= =»•«= =»«= =*e= =S"8= =frS= :*«= =8-8= =»«= =»«= =»•«= =&«= =&t* OFFICERS 1942-1943

President. Vice-President. A. McMARTIN. G. BOOTH.

Hon. Secretary. Hon. Technical Secretary. (MRS.) I. M. ASHTON. J. L. DU TOIT.

Former Presidents.

1926-27 M. MCMASTER. 1931-32 G. C. DYMOND. 1936-37 G. C. WILSON. 1927-28 M. MCMASTER. 1932-33 G. C. DYMOND. 1937-38 J. RAULT. 1938-39 P. MURRAY. 1933-34 B. E. D. PEARCE. 1928-29 H. H. DODDS. 1939-40 P. MURRAY. 1929-30 H. H. DODDS. 1934-35 E.CAMDEN SMITH. 1940-41 E. P. HEDLEY. 1930-31 G. S. MOBERLY. 1935-36 G. C. WILSON. 1941-42 F. W. HAYES.

Former Vice-Presidents.

1926-27 L. E. ROUILLARD. 1932-33 A. C. WATSON. 1937-38 P. MURRAY. 1927-28 H. H. DODDS. (G. C. DYMOND. 1938-39 E. P. HEDLEY. 1933-34 1928-29 G. S. MOBERLY. 'IE. CAMDEN SMITH. 1939-40 E. P. HEDLEY. 1929-30 G. S. MOBERLY. 1934-35 B. E. D. PEARCE. 1940-41 F. W. HAYES. 1930-31 G. C. DYMOND. 1935-36 E. CAMDEN SMITH. 1931-32 A. C. WATSON. 1936-37 J. RAULT. 1941-42 A. MCMARTIN.

Council of the Association. G. BOOTH. J. L. DU TOIT. P. FOWLIE. F. B. MACBETH. A. MCMARTIN. W. BUCHANAN. G. C. DYMOND. W. G. GALBRAITH. J. MUNGLE. J. RAULT. H. H. DODDS. O. A. FELTHAM. E. P. HEDLEY. D. B. B. MUNRO.

m. South African Sugar Technologists' Association.

Sixteenth Annual Conference

The Sixteenth Annual Conference of the South African Sugar Technologists' Association was held at the Kenilworth Cinema Lounge, Beach, Durban, on Tuesday and Wednesday, April 21st and 22nd, and at the South African Sugar Association Experiment Station, Mount Edgecombe, on Thursday, April, 23rd, 1942.

The following members and visitors were present.:—

A. McMARTIN, President.

G. BOOTH, Vice-President

ALMOND, F. L. DODDS, H. H. HINCHY, Dr. V. M. ' PLATT, C. DUCHENNE, J. O. HUNTLEY, J. K. POUGNET, J. BEATER, B. E. Du MOLLARD, J. POUGNET, J. F. BECHARD, R. M. DUNN, G. A. JANSEN VAN RENSBURG, POWELL, L. H. BIGARA, L. C. Du TOIT, J. L. H. Bijoux, J. C. R. DYMOND, G. C. JOHNSTONE, P. RAULT, J. BLACKLOCK, L. RICHARDSON, F. A. ROBBINS, W. T. BOOTH, G. ELYSEE, A. D. KING, G. S. C. BOYAZOGLU, Prof. A. J. KIRKWOOD, J. V. ROSSOUW, Dr. G. S. H. BRAITHWAITE, F. G. KUHL, L. H. FELTHAM, 0. A. SALMON, P. BROMLEY, C. K. FERGUSON, D. BROWN, R. ELLIS. LALOUETTE, H. SIMPSON, J. R. FOWLIE, P. SlVITSEN, S. BUCHANAN, W. FISHER, Dr. J. MACBETH, F. B. SPARKS, A. E. BUCHANAN, W. F. FOURMOND, T. MARCHAND, R. H. STEIN, Prof. P. CHRISTIANSON, W. O. MARQUES, J. V. STEYN, C. L. COBLANS, Dr. H. GALBRAITH, W. G. MEREDITH, 0. SWALES, A. W. COIGNET, P. I. J. GARLAND, H. L. MILES, E. CROOKES, F. N. N. GARDNER, J. MILLAR, J. D. VIGER, M. CUNNINGHAM, J. D. MOBERLY, G. S. HALLIDAY, I. G. MORRIS, J. W. H. WEST, L. S. DEDEKIND, E. T. J. HAYES, F. W. MCINTYRE, A. WHEELER, F. D. DICK, Mrs. B. HEDLEY, Dr. E. P. MCKENNA, H. G. WILLIAMSON, J. DICK, Dr. J. HENDRY, D. W. W. MCMARTIN, Dr. A. WYLES, J. W.

IV. 1

SIXTEENTH ANNUAL CONGRESS

Proceedings of the Sixteenth Annual Congress, held at the Kenilworth Cinema Lounge, Durban, and the South African Sugar Association, Experiment Station, Mount Edgecombe, 21st to 23rd April, 1942.

Dr. A. McMARTIN (Vice-President) was in the Chair.

OPENING CEREMONY. tion during the war period. The surplus areas, marginal lands, The VICE-PRESIDENT : We have been fortunate in securing etc., have faded into the background. They are, however, only the services of Dr. Fisher to open the Congress lor us. To intro­ blacked out. lor the time being, unless with the terrific upset in duce Dr. Fisher to an audience here is really not necessary, as the supply of petrol, a new avenue opens which will consume ho has on several occasions in the past read us papers which the surplus in the form of alcohol for power purposes. This, no have been widely appreciated. I cannot say anything about Dr. doubt, is one of the urgent problems which will be constantly Fisher which you do not know, so 1 will simply call upon him investigated by your committees, so that if and when conditions to open this Congress for us. demand this, action will be already planned. There is perhaps another aspect of the utilization of the OPENING ADDRESS BY DR. JOHN FISHER. surplus molasses. This coming winter, I gather, will see a I appreciate very fully the honour you have done me in shorter crop of sugar than for several years past. There will be asking me to open this Sixteenth Technologists' Conference. less by-products, but the by-product molasses is of great value for stock feeding with the short maize crop of the Union this It has come to be the time in the year when there is a special coming season and with the high price of 15s. per bag, maize course, or the time to deal with subjects of special interest to for stock feed will be greatly reduced. A 7 per cent, carbo­ the sugar industry, to brush up one's knowledge in view of a hydrate food will thus be practically non-existent for stock feed, further year's experience. Such procedure seems to be very and molasses with over 60 per cent, carbohydrate would be sound, and especially so at the present time when food supplies very acceptable, particularly for beef cattle, and in certain are urgently needed. Any method of processing the cane crop admixtures for dairy stock. With the shortages of groundnut which gives greater results, better extractions, less wastages, cake and other protein-rich concentrates, the almost complete etc., is greatly desired. During the course of the Conference absence of bran, pollard and other normally available foods, the many of these points will no doubt be discussed. avenue is widely open for placing molasses or compounds con­ It is many years since you held your Congress at the Railway taining molasses on the up-country markets for stock owners. Institute. 1 recall addressing your meeting there when I made Another question at the moment is the shortage of straight a plea for the establishment of an Experiment Station. Now nitrogenous fertilizers. Nitrogen per unit to-day is very high in you have had a Sugar Experiment and Research Station for a price, and yet we have an atmosphere, miles high, full of it. number of years and I know that this station has done very- Can we utilize molasses in a way that they will gather nitrogen good work for the sugar industry as a whole. Whilst it often in combination or co-operation with the free nitrogen fixing seems that progress is slow, when a retrospect is made over a bacteria of the soil ? What is the worth of molasses for applica­ few years it is obvious that progress has not been so slow. tion to the soil to enable Azotobacter, Clostridium, etc., to fix I remember at that time that the whole sugar industry de­ free atmospheric nitrogen ? If the question has not been fully pended upon the good behaviour of the foundling "Uba," streaked studied I would suggest that the present is a most opportune it might be, full of fibre it might be, requiring much more power time to begin to examine and study this idea with a view to for crushing, etc. Yet it was the one variety on which the in­ proving its practicability or otherwise. dustry was built up. There was to all intents and purposes no All ideas or all scientific facts are not applicable to produc­ other cane grown. Now, instead of a C.P.S. we have a S.P.S., tion ; and the practicability of the idea must never be lost sight a sugar protective service, with a commandant and assistants of. There is, too, the question of the utilization of cane tops. in the way of scientists. They are there to watch the health of Many tons of cane tops are returned to the soil each year. They the cane and to ensure that no measly, lousy, diseased, illegal are not altogether wasted, but no method has yet been devised entrant, in the form of a prohibited immigrant, enters the sugar whereby tractors can be turned out to fill up with cane tops in belt. When you enter the sugar belt now it almost seems neces­ place of petrol or paraffin. The oxen can do this, but there are sary to take oft' your shoes from your feet. not sufficient oxen to eat all the tops. There arc many oxen Under these changed conditions it is now found that Uba does up-country that would eat the cane tops. The problem is one not measure up to the standard which is set. I, however, pay of contact—oxen to the coast, or tops to the oxen. The latter tribute to the old variety, which was the sole support of the aspect seems to fail when viewed from the point of practicability. industry for many years and which laid the foundation of the Labour, truckage, railage, and the handling at the destination present industry. of what will be incipient silage arc the snags visualized. We cannot live in the past, however. Our lives arc important I should like to refer for a moment to sunn hemp. This im­ not for what has passed but for what we can still accomplish. portant crop is grown largely on the coast as a green manure This Conference meets at a time of great stress and anxiety and crop. The seed is very expensive. Very little is grown for seed in unison with other industries the sugar industry is faced with on the coast, and supplies of seed have been short. Inquiries very grave difficulties. The difficulty of surplus cane no longer made reveal the fact that some strains are very shy seed- exists, and the green light has been given for an all-out produc­ bearers. Whilst in other disrticts, drought conditions affect the 2

yield of seed. This condition will seldom obtain in the coastal effect. But, although we do our utmost to make as much sugar belt. A further point, however, has been made by the Senior as we possibly can, there must be a ceiling. That ceiling is the Plant Pathologist of Southern Rhodesia, who states that a capacity of the mills, and it is unnecessary to remind you that plant-sucking bug affects the young maturing seeds with a it will probably be difficult, in the near future, to provide mill fungus in the manner of the well-known cotton stainer bug. replacements. Seed production may be reduced from four to five bags per acre down to quarter or half bag per acre. Does this same condition The growers feel they have contributed largely to the progress occur on the coast and is this low seed production due to this to which Dr. Fisher referred because of the excellent quality of fungal infection of the seed through the agency of the bug ? the material that we have given you to work with. But we must acknowledge that the technologists have done their share, It is a generally accepted position that where vegetative especially in regard to milling efficiency. We appreciate that in growth is very vigorous there is no necessity for seed produc­ the transition from Uba to the new varieties difficulties were tion and plants do not attempt seed production. They do this met with to overcome which, experiments had to be made to overcome adverse conditions. Are the conditions on the coast before adjustments were effected. That those experiments were so good for vegetative growth that there is little need for seed successful is illustrated in the fact that in 1930 the recovery production ? If this is so then the poorer types of soil might be figure for the industry was as low as 78.4 ; to-day it is as high the ones on which to try and grow sunn hemp for seed. The as 81.7. I do not often get an opportunity of addressing tech­ thought is put forward for consideration. nologists, and I take this opportunity of stating that I think they were rather hard on planters in 1926 when they declared There is one further point which I should like to comment that cane with a purity of 78 or less had no milling value. That upon. It is this, in the sugar belt there is a heavier annual declaration cost the growers a quarter of a million tons of cane rainfall than there is up-country, yet in the sugar belt there is in rejections. I do not suggest that that declaration was made nowhere nearly the erosion that there is in the midlands or on because the milling qualities of Uba were so unsatisfactory, and the high veld. Why should this bo ? I believe there are two I give credit for the fact that (since to-day that declaration is main reasons for this. The first one is that it has always been non-existent) sugar technology had advanced considerably. the general endeavour of the sugarcane grower, whether planter Growers are vitally interested in your progress. You have pro­ or miller, to maintain the fertility of the soil. Any diminution gressed to such an extent that we have to-day an efficiency of the plant-food in the soil and which lessens the rooting system figure of 81.7, and when the opportunity occurs, and I hope it and the hold of the plant on the soil, must tend towards erosion. will occur in the near future, for the revision of the price scale, The other point is that in the sugar belt contour ploughings we shall ask that that revision shall be more in conformity with and plantings have been the rule for years. But I think the improved milling efficiency results obtained. further aspect which has prevented erosion is that the land is nearly always covered by crops, so that the heavy rains shatter There is one paper to be read here which I would like to their force on the vegetation and not on the soil. The spray commend to the special attention of Congress. It is a paper by from the rain falls softly on the soil, or the bulk runs down the Mr. F. D, Wheeler on varietal milling tests. I have not had an vegetation and into the soil along the roots. This vegetal cover opportunity of reading it, but I did glance at the part where a is the surest safeguard against erosion. In the manner of work­ summary of the experiments dealt with was given, and I could ing the sugar lands the soil is only occasionally left as an un­ not help but feel there was confirmation there of the argument conformity on the subsoil on account of the time that the lands we have put up during the last few years. are under crop without reploughing. There is formed direct continuity again from the surface down into the subsoil. I will conclude these few remarks by again thanking Dr. Fisher for coming here to-day and opening this Congress. It is the absence of this direct continuity in constantly ploughed lands, coupled with lowered fertility, which results in erosion. Mr. BOOTH : I shall now call upon our Vice-President, Dr. Bare lands invite erosion ; low fertility lands favour it. Well McMartin, to give us his address. protected soils due to good crop cover obtainable in fertile soils are the surest proof and greatest security against soil erosion. VICE-PRESIDENT'S ADDRESS. The soils, or some of them, in the sugar belt of the South The lot which has fallen to me of presenting this address Coast, do not seem particularly suited for sugar, and the effect marks an innovation for this Congress—it is the first time that on these soil on cane growth for the past fifty years is now a biologist has been called upon to perform such a duty. To fairly evident. Some other system of utilizing these lands, apart the sugar chemist and engineer the sugarcane is the material to from cane farming, may have to be found. If cane farming be processed, while the sphere of activity of the biologist is tends to go out in some of these areas, what kind of farming that of the cane field itself. It will be understandable, therefore, shall replace it ? if the remarks I make to-day are concerned more with develop­ ments and problems of the cane growing section of the industry, Lastly, though I personally think it a remote contingency, is than with those of the manufacturing side. the sugar belt sufficiently protected against incendiary bombs which might be scattered indiscriminately through it by raiding The last few years have witnessed revolutionary changes in aircraft ? the varietal position in Natal, changes which have been amply recorded from year to year in our own Proceedings. What, in I have now much pleasure in declaring your annual Con­ effect, has taken place has bees the movement from the culture ference open. of a single variety, and that of a more or less primitive botanical The VICE-PRESIDENT : I call upon Mr. Robbins to reply type, towards the culture of several varieties of complex heredit­ to Dr. Fisher. ary constitution, thus coming into line with other progressive sugarcane growing countries. The inherent danger in relying for Mr. W. T. ROBBINS : It is my pleasant duty to-day to crop production on a single variety has been repeatedly demons­ propose a vote of thanks to Dr. Fisher. I enjoy listening to trated elsewhere, and Natal has also had its warning of late him, since he always has the happy knack of being interesting. years. There are, nevertheless, those who sigh for the old days, In his address Dr. Fisher referred to the Experiment Station. and who would like to see a return, if not to Uba, to the culture The establishment of the Experiment Station has proved one of of some single variety which will meet all the requirements of the most profitable, if not the most profitable, investments the the Natal coast. industry has ever made. The prosperity we have lately enjoyed has undoubtedly been due to the new cane varieties which have It is not generally realized, however, that when a new variety been released by that station, and it is gratifying to know that is introduced, a train of natural events is set in motion, which there are new varieties under observation there which may- once begun, may be difficult to stop. Different varieties have prove to be even more profitable than the popular varieties of different habits and growth forms, different attractiveness to to-day. wards the insect populations of the cane fields, and different susceptibilities towards parasitism by the various forms of micro Dr. Fisher referred to the green light of unlimited production. organisms which abound everywhere. I think it has been proved the world over that unlimited pro­ duction, without a measure of control, is dangerous. Fortunately The substitution of a variety by another of different growth in this industry we have an agreement which has a limiting habit leads to an alteration of the micro-climate of the cane 3

field ; this, being accompanied by an alteration in the other In Natal this disease was identified only a few months ago in biotic factors intimately associated with the growth and develop­ the Eshowe district, where the position is serious on Co.290. ment of the crop plant, is followed by an alteration in the Its presence in this country has not been recorded before with composition of the other types of life which are met with under any degree of certainty, but the circumstances of the outbreak, these conditions. together with its identification in small patches of cane in isolated localities, suggest that it has been present in an incon­ It may come about, therefore, that although tested and found spicuous degree previously. immune or highly resistant towards diseases or pests which are at the moment of introduction a limiting factor in production, The warning about the possibility of new insect pests arising a new variety may be an unknown factor as regards its ability has also not been untimely, as the outbreak at Umfolozi of a to provide conditions suitable for the multiplication of some new stalk border has proved. organism which constitutes part of the local flora or fauna, and These examples cited, then, suffice to show that we have the which could become a menace to the continued growth of the diseases and pests here; we must guard if possible against particular variety. providing them with suitable hosts on which to flourish. It must therefore be constantly kept in mind that the minor One safeguard, obviously, is the multiplicity of 'varieties, and disease of to-day may rank as the major disease of to-morrow, the continued introduction and testing of new varieties to a situation which can have disastrous results, as can readily be replace any that fall by the way, as with agricultural crops the imagined, under the system of cultivation which employs only cheapest method in the long run is the growing of a resistant one variety. variety, and the presence of several varieties grown commer­ cially offers a certain amount of safeguard that there will always The attention of this Congress to the possibility of such a be cane to cut if an epidemic should break out on one particular situation arising is not being drawn to-day for the first time. variety. Looking back through some of the older Proceedings published about the time when the introduction of new varieties was It is not intended by any manner of means to present an biing considered, this warning was issued by others, who pointed alarming view of the situation, but it may be that by the ex­ out that the mere replacement of Uba would not necessarily tensively increasing culture of the variety Co.281 we will arrive mean the end of all troubles, but that the possibility had to be at a stage in which too much reliance is being placed on the taken into account of other parasites becoming prevalent and performance of this variety. So far it has stood up very well dangerous. to cultivation here, but it might be mentioned in passing that in Louisiana it is doubted if its cultivation is any longer economic, It is instructive to examine now the position to-day. and to being infected with mosaic to the extent of almost 100 per cent. see whether these words of warning gave a true forecast of our This need not alarm us, as the strain of mosaic existing there present status. is apparently different to that present here ; it reminds us, how­ A good example was provided for us at the Experiment ever, that this variety might not indefinitely maintain the Station a few years ago demonstrating how one of these minor reputation it has so far gained here for freedom from disease. diseases could develop into a serious trouble, by the outbreak of It is felt, therefore, that our efforts should be directed towards eye spot in an acute form on the unreleased variety Co.419. the maintenance of several varieties and to have in reserve a This disease, which must be familiar to most of you, causes selection of sugarcanes ready to fill any gap created by the small brownish-red spots on the cane leaves, and does no more. collapse of a commercial variety. On the above-mentioned variety, however, these spots enlarged, The introduction of new varieties for trial under our Natal formed runners which extended the length of the leaf to the top conditions is fortunately made possible for us by the willing and, finally coalescing, destroyed the greater part of the leaf co-operation and good spirit shown by our colleagues in the tissue; the central bud was killed and the disease spread clown various sugarcane breeding stations wherever this crop is grown; on to the top internodes of the stalk, producing large discoloured sugarcane variety exchange knows no national boundaries and areas. The stalks eventually dried out with a loss in sucrose. no reward is asked. Fortunately, this variety was being grown in a replicated plot Such a spirit, I feel, could be well emulated by others : had trial, and as not all of the plots were attacked, we were able to international affairs been activated by the same disinterested­ assess the amount of damage done. ness with which sugarcane breeders exchange their materials, our fellow scientists in some countries would not be undergoing From one healthy plot a crop of 43.4 tons cane per acre was the ordeal of oppression by the hand of armed might. cut, with a sucrose of 16.74 per cent, or 7.27 tons sucrose per acre ; from a nearby diseased plot 31.6 tons cane per acre were By such free exchange, therefore, we can draw upon the cut, with 8.86 per cent, sucrose, or 2.80 tons sucrose per acre. resources of India and Hawaii, Egypt and the United States of This disease is one of the major diseases in Hawaii, and one America, Queensland, Mauritius and others too numerous to could imagine what serious economic loss could be entailed mention here. We can obtain the old varieties which were the should such a susceptible variety be grown on a commercial mainstays of the sugar industry in other countries in their early scale here. days; and we can obtain (with very few exceptions) the latest products of their cane breeding programmes, or we can obtain More recently, however, a situation has arisen which brings specimens of the primitive sugarcane species which have been home more forcibly still the soundness of the point of view that used in such cane breeding. If we wish to raise our own varieties diseases are present waiting for the opportunity to develop. I from the start by sowing the seed, portions of their seed harvests refer to the outbreak of red rot in Co.290. This disease has a have been placed at our disposal. sinister reputation in other, particularly sub-tropical, countries, where it appears to be characterized by sudden outbreaks of We, in turn, have been distributors of varieties, and from the epidemic intensity. In Louisiana, after P.O.J.213 had been collection of sugarcanes at Mount Edgecombe, sugarcanes have established as a leading commercial variety, red rot appeared, been sent to Egypt and elsewhere in Africa, the United States and in 1930 thousands of acres of cane failed or were so reduced of America, Queensland, to Kew Gardens for scientific studies, as to make their cultivation unprofitable. It was estimated and to other countries interested. We are thus playing our that in 1930 and 1931 the loss to the sugar industry was up to part in keeping these varieties in circulation, and it is our hope 1,100,000 dollars. This did not take into account poor stands that the time is approaching when varieties with Natal numbers that were carried into succeeding crops. attached to them will be among those being requested from abroad. In India a few years ago red rot, whose presence had been I have referred to the unwise situation of a large industry known previously, became serious, till now it is recorded that relying on one variety of a crop for its raw material; it now thousands of cane fields of the predominant commercial variety occurs to me that this automatically raises the wider question: Co.213 are almost completely devastated. In affected areas the is it wise for an agricultural community to be concerned solely "crush" of the factories was reduced in 1938-39 to about one- with the production of one crop ? third of the normal amount, and in 1939-40 to one-half. In 1940-41 the epidemic was still raging and had spread into new I realize that the system under which sugarcane is grown here areas. does not lend itself to rotational cropping as understood in 4

some other farming systems, and that: the acreage under cane is war conditions, and for some time thereafter, the economic governed by such factors as quotas and crop restriction, or lack problem is not so much a question of cost and profit margins of restriction, which in turn are dominated by the international as one of need and production to fulfil that need. 1 consider it situation. our bounden duty to find and produce raw materials needed for our country's war effort, even at some sacrifice. Indeed, the The fact nevertheless remains that increased yields due to war must be won on the home front of production as well as scientific progress lead to diminution in acreage under cane when the battle front of destruction. restriction is enforced ; and apart from this, are there not fields which might be more profitably employed in some other form On behalf of all present I thank you, Dr. McMartin, for your of food production ? instructive address, and I have no doubt that the deliberations of this Conference would be helpful towards enhancing the status The attention of this Congress has been drawn from time to of the sugar industry in our national economy. time to the possibility of other farm commodities being pro­ duced on the sugarcane farm. Beef production was the subject The VICE-PRESIDFNT : Ladies and gentlemen, we have of a paper a few years ago by Mr. Decnik, of African Explosives with us here this morning His Worship the Mayor of Durban. and Industries, and this year we are having a paper by Mr. His Worship is well aware that he does not attend any meetings Fowlie on pig management. without saying a few words. I call upon Mr. Ellis Brown, the The possibility of the production of pineapples for canning, Mayor, to speak. soya beans, and groundnuts, the growing of more food crops for rations for labour, to mention a few, are questions that The MAYOR (Councillor Rupert Ellis Brown) : It hardly arise when considering the agricultural economy of the sugar seems a year ago since I addressed you last, but time flies and belt in its widest aspect. I know that there are those who main­ much has happened since. For one thing, you sugar people and tain that sugarcane growing is in itself a whole-time occupation. Technologists are beginning to come into your own. You have Many others, however, appear to feel that while they are first lab -Hired a long while under difficulties. You were not allowed and foremost cane farmers, they could find time and ground to produce as much sugar as you could, and overseas market, to devote to some other form of husbandry and on their own were not encouraging. To-day, however, the demand is greater initiative are experimenting with something new. than the supply and your problem is no longer to find markets but rather how to share your products amongst the various It is, I feel, a pity that no active effort is being made, as far markets successfully. as I am aware, to keep in contact with these pioneers ; their experiences, their successes and failures, could constitute valuable In our own country there is serious talk of sugar rationing. records towards the economics of sugarcane lands, and scien­ I know, of course, that your industry can easily cope with needs tifically conducted experiments would help them with the of this country. England, however, needs all the sugar she can problems they have set themselves. I therefore hope that the get, and your biggest problem will be to satisfy that need. I time will come when the study of sugarcane varieties, their know that you will do everything in your power to accomplish diseases, pests and plant-food problems, will be looked upon as this, and I wish you all success in your endeavour. only one side of the scientific investigations conducted by the Dr. Fisher spoke of the possibility of incendiary bombs being sugar industry, and that the whole problem of cane growing dropped in your cane fields. I do not expect a direct invasion, will be viewed as part of a scheme of rural economy in which but a destructive raid with planes forms a distinct possibility. diversified crops and animal husbandry will form part of the I feel sure that the hint that Dr. Fisher has dropped will receive pattern. your attention. Mr. BOOTH : I have pleasure in calling upon Dr. Rossouw I should like to make use of this opportunity to thank the to reply to Dr. McMartin's address. sugar industry for the very generous response it has made to the various war funds. Your industry has been an object lesson Dr. ROSSOUW : I have much pleasure in replying to Dr. to some of the industries further inland. It has been most McMartin's presidential address, which I feel sure all of us have helpful on all occasions, and I would be failing in my duty if I enjoyed very much. I was particularly struck by his analysis did not take advantage of this opportunity to say how much of the economics of varietal culture from the standpoint of a I appreciate, and how much the Mayoress has appreciated your practising biologist. Indeed, the danger of concentrating our splendid donations. production on one variety or following the short-sighted policy of cultivating a variety with high-yielding properties but low The VICE-PRESIDENT: I now call upon Mr. Booth to resistance to disease should ever be guarded against. The in­ reply to the Mayor. dustry should be thankful that we have at the Experiment Station, in the person of Dr. McMartin, an able and highly Mr. BOOTH : Mr. Chairman, I am gratified to have the qualified officer to safeguard its welfare in these matters which opportunity of thanking His Worship the Mayor, who has are so readily taken for granted without much thought or always been very helpful and kind to our Association, for his concern. address to us this morning. Last year, he reminded us of that I was also impressed by his suggestions that more research old axiom that a spoonful of treacle is better than a barrel ol and investigaiton be undertaken by the industry into auxiliary vinegar when one wishes to attain one's ends, and in the light crops for the sugar belt. In this connection there should, no of the experience of the last twelve months, one feels sure that doubt, be a two-fold objective, firstly, to find different auxiliary- the Mayor has adopted that axiom as a signpost through hi: crops which a cane grower might undertake to round off his arduous duties. In again thanking the Mayor, I think the least farm economy in the matter of supplying some of his own re­ we can do, as an Association, is to wish him and his very able quirements or augmenting his income by the sale of such products and charming lady all good wishes for the very arduous diffi­ on nearby markets ; and, secondly, to find an industrial crop culties with which they are confronted to-day. May they soor more or less comparable with cane, that is, a crop that could come to an end. serve as a raw material for processing and manufacturing in­ dustries. Mr. MOBERLY proposed the following resolution, which wa: passed unanimously: I consider this second objective highly important in these days when the exigencies of the war have necessitated industrial "This Congress expresses its sympathy with the people o development in South Africa along lines formerly not contem­ Australia in general, and the Queensland Sugar Technologist plated. Investigation might show that sugarcane production in particular, in the grave trial presented to them. The Con should be greatly expanded, not so much for the purpose of gress hopes that the danger will be averted without loss o. sugar manufacture but rather as a basic raw material for other distress to them and their homes and families." industries, e.g., alcohol, cellulose and other chemical industries. Investigation might also show that other auxiliary crops might The HON. TECHNICAL SECRETARY road telegrams fron be grown on vacant lands during the off-season period, or for Messrs. W. Nelson, Brian Pcarce, Vernon Crookes and Dr. J. F that matter throughout the year, which could equally serve as van Zyl expressing regret that they could not attend, and wishin; raw material for similar chemical or other industries. Under the Technologists' Association a very successful Conference. 5 ANNUAL SUMMARY OF CHEMICAL LABORATORY REPORTS FROM SOUTH AFRICAN SUGAR FACTORIES. SEASON: I 941-1 942. By H. H. DODDS, M.Sc, F.I.C., and J. L. DU TOIT, M.Sc.

In our Annual Summary for 1940-41 presented last year we The proportion of Uba has diminished greatly in Zululand, pointed out that the weather conditions of 1941 up to the not so much in central and southern districts. Co.281 is in middle of March were very unpromising for the coming crop, creasing in popularity everywhere, no factory crushing less than and that a small crop was to be expected for 1941-42. 20 per cent, of this variety. The P.O.J, canes are now largely confined to the Zululand alluvial flats. WEATHER CONDITIONS. This forecast was amply fulfilled. Although the rainfall did Co.290 is diminishing except in certain districts where it is improve considerably during the latter part of March and in best suited, while Co.301 is increasing very rapidly, especially in April, it was too late to be of much avail, and the result was the central North Coast, several of the factories in that area the smallest sugar crop since the 198U-37 season. already recording more than 10 per cent, of the crop in this variety. Not only were the crucial growing months of January and February very deficient in rainfall, but a drought of unex­ The average cane analyses for the 13 factories where the ampled length and severity lasted from April 19th to September Central Board testing service is in operation shows the same 11th, over which period a total of no more than 1.75 inches of relative positions as last year in the different varieties in sucrose rain fell at the experiment Station. This no doubt partly content and purity, but the difference in sucrose content between accounts for the highest sucrose content of cane for the season Uba and the other varieties is not quite so marked as in recent in our records, but was also responsible for the great falling-off years. This may possibly be accounted for by Uba benefiting in quality of cane towards the end of the season. more than the other varieties from the. factors that have con­ tributed !o a high sucrose content of cane generally, or it may The rainfall for December was also very deficient, only !.7() be partly due to the fact that more mixed consignments of Uba inches, and the total for the year at the. Experimenl Station and other varieties have been sent to the factory and recorded 24.35 inches, the lowest on record at. Mount Edgecombe;, records as Uba for payment purposes. going back 55 years. The average for 444 recording stations in the sugarcane belt was 20.18 inches, the normal over the past Per cent. Per cent. Sucrose Purity of Java 13 years being 40.90 inches. Variety. total total per cent. crusher A feature was the incidence of drought over the whole area, cane. sucrose. cane. juice. Ratio. the district rainfalls ranging from 10.45 inches or only 47 per Uba 15.04 14.51 13.63 86.43 76.99 cent, of normal at Riverview (Umfolozi) to 39.08 inches or 78.5 Co.281 44.85 45.41 14.30 89.00 76.93 per cent, of normal at Mtunzini. Besides in the extreme north Co.290 28.64 28.37 13.99 87.94 78.93 from Mtubatuba to Mposa, the drought was also very marked Co.301 6.05 6.05 14.12 88.20 76.83 in the extreme south from Port Shepstone to Esperanza, which P.O.J.2725 and had only about half the normal rainfall. 2878 5.42 5.66 14.76 88.81 80.68

PRODUCTION FIGURES. Total 100.00 100.00 14.12 88.13 77.68 Cane production for the season amounted to 3,921,436 tons of 2,000 lbs. (3,557,409 metric tons), which yielded 452,119 tons These figures refer to 60 per cent, only of the sugar output, of 2,000 lbs. (410,149 metric tons) of sugar, a ratio of 8.67 of but may be considered fairly representative of the whole, except cane to sugar, or a yield of 11.53 per cent, of sugar on weight in their proportion of P.O.J, canes, which is 3 per cent, below of cane. the actual, because one of the factories omitted from the returns In view of the short crop and increased demand for sugar, all is Umfolozi, crushing 60 per cent, of P.O.J, canes. except 3,000 tons of cane was supplied as main quota. GENERAL QUALITY OF CANE. The source of cane classified according to type of grower shows relatively little percentage change from last season. The sucrose content of cane for the season, 14.00 per cent., is the highest in our records, compiled since 1925. This is Tons of cane Per cent. partly due to drought conditions, other high seasonal figures Type of grower. harvested. of total. being 13.88 per cent, in 1933 and 13.84 in 1931, both years of European planters ... 2,241,567 57.1 severe drought. Sugar manufacturers ... 1,359,790 34.7 Native and Indian planters ... 320,689 8.2 The peak month was, as usual, September, when the sucrose content of cane was 14.80 per cent., after which there was a 3,922,046 100.0 sudden fall to 14.08 in October. The fibre content of the cane was also abnormally high, The falling-off in cane production is most marked in the case being 15.66 per cent, for the season, which is the highest since of the Indian and Native grower, who has produced nearly the drought-stricken years of 1931 and 1933. 1 per cent, less of the total than last year. Like last season, and unlike any other previous seasons, the CANE VARIETY DATA. fibre content steadily increased from 15.33 per cent, in June to Recent tendencies in the change of varieties harvested were a maximum of 15.94 in November. This is a characteristic of continued. Coimbatore canes which we may expect to become normal Per cent, of total crop. experience in this country, now that the crop consists largely of 1941/42. 1940/41. 1939/40. 1938/39. Co. varieties. Uba 16.6 23.2 30.2 32.2 The purity of mixed juice for the season was 85.67, which is Co.281 42.4 37.5 28.3 21.0 about the average of recent years. The peak of purity was not Co.290 26.5 28.2 30.0 35.0 as usual in October, but in September, when it was 86.23. Co.301 5.9 3.3 2.4 0.3 It fell off rapidly thereafter and was only 85.26 for November, P.O.J.2725 and 2878 8.C 7.8 9.1 11.3 the lowest for that month for many years. 100.0 100.0 100-0 100.0 The reducing sugar ratio in mixed juice for the season was also about normal at 3.35. 6

One welcome feature of the season was that the largest pro­ content of cane. The previous best reduced extraction in this portion of car.e since 1935 was harvested in what we have termed country was 93.72 in 1940. the "optimum period" from July to November inclusive. Al­ though a relatively large quantity of cane, 821,155 tons, was The boiling house recovery, sucrose in sugar per cent, of milled in May and June, the crop was practically finished by sucrose in juice, was 88.40, a figure that was surpassed in the the end of November, only about 82,531 tons being left to cut 1938 and 1939 seasons, when, however, the purity of mixed later than that. Consequently much less sucrose has been sacri­ juice was much better. The reduced boiling house recovery, ficed through unseasonable harvesting than in recent years. calculated to an assumed purity of 85 in mixed juice, is 87.76, the highest ever recorded in this country.

Similarly the overall recovery, sucrose in sugar per cent, of Comparison of results from cane harvested during the July— sucrose in cane, 81.66 for the season, was somewhat higher in November period, compared with those of earlier and later 1939, when there was a lower fibre content and higher purity months of the harvesting season. of mixed juice. Purity Percent. Ratio Sucrose Fibre Mixed The reduced overall recovery, calculated to an assumed fibre total Cane. Cane/Sugar, per cent, percent. Juice. content of 12.5 per cent, and a mixed juice purity of 85, is 82.61, which has never been excelled in this country, the previous best being 82.07 in 1940.

The sucrose content of the bagasse, 3.03 per cent, is only very slightly higher than in 1940, when the original sucrose content of the cane was much less. The primary juice loss, 41.12, is the lowest on record for this country. The ratio of cane to sugar, 8.62 actual, and 8.39 on an assumed polarization of 96°, is the best on record in South Africa, the previous lowest being 8.80 and 8.58 respectively in the 1937 1031 Optimum period 77.86 9.29 14.13 15.57 85.33 season, another year that combined a high sucrose content of Balance of crop . 22.14 10.20 12.75 16.23 84.32 cane with improved efficiency figures. The moisture content of bagasse is still very high, 51.50 per 1932 Optimum period . 81.10 9.32 13.70 15.44 85.01 cent, for the season, and appears to be at present the principal Balance of crop . 18.30 10.82 12.28 16.25 84.76 obstacle in getting really excellent extraction results. Imbibi­ tion is high, 34.76 per cent, of cane, and the sucrose content of 1933 Optimum period . 73.97 8.93 14.17 15.68 85.51 bagasse compares favourably with that of most countries. Balance of crop . 26.03 10.27 13.03 15.74 83.47 With the increased use of modern continuous filters, the loss of sucrose in filter cake in South Africa has diminished very 1934 Optimum period . 81.35 10.54 11 .95 15.12 84.09 considerably in recent years and will now compare favourably Balance of crop . 18.65 11.16 11.52 15.57 83.83 with that of almost any country.

1935 Optimum period . 78.80 0.03 13. S3 15.81 86.62 Total boiling house losses continue to be somewhat high, Balance of crop . 21.20 9.78 13.06 15.94 85.74 however, due to high losses of sucrose in molasses, associated with a high purity of final molasses at most factories. 1936 Optimum period . 75.71 9.02 13.62 14.85 85.73 Balance of crop . 24.29 10.27 12.27 15.46 84.12 SEASONAL FLUCTUATIONS. The peak month of extraction was, as usual, September, 1937 Optimum period . 71.73 8.46 14.32 15.02 86.22 when it was 92.58, but the best boiling house recovery, 88.91. Balance of crop . 28.27 9.81 12.67 15.51 83.66 was as early as August. Consequently the best overall recovery, 82.31, was also gained in August. 1938 Optimum period . 73.80 8.57 14.04 14.37 86.84 Balance of crop . 26.10 9.95 12.50 14.77 84.43 The best ratio of cane to sugar, 8.12, was recorded in Sep­ tember, however, because of the higher sucrose content of cane 1939 Optimum period . 66.56 8.55 13.89 14.65 87.10 in that month. Balance of crop 33.44 9.85 12.46 15.11 85.06 INDIVIDUAL FACTORY RECORDS. 1940 Optimum period . 66.83 8.86 13.63 15.54 86.02 The identity of the numbers representing the factories remains Balance of crop 33.17 10.07 12.27 15.63 83.85 the same. The only factories not included in our returns are three small factories that have not complete chemical control ; Mean, , 1928/1940— their combined output of sugar is only 6,700 tons, or 1.5 per cent. Optimum period 74.43 9.13 13.75 15.30 85 86 of the industry total. Balance of crop . 25.57 10.27 12.55 15.71 84.39 As in the 1940/41 season, but not quite to the same extent, Optimum period there were wide differences between the closing dates at various 1941 76.55 8.42 14.28 15.69 85.91 factories, a fact that needs to be borne in mind when con­ Balance of crop . 23.45 9.35 13.09 15.56 84.89 sidering factory performances and relative efficiencies. Obviously, those factories which were in a position to confine their manu­ facturing activities more closely within the best months of the season scored in improved quality of cane and consequent GENERAL FACTORY PERFORMANCE. recoveries. This has shown a further considerable improvement, made possible by the smaller crop and less overloading of the factories. The highest sucrose content of cane was recorded at factory The extraction, sucrose in juice per cent, of sucrose in cane, No. 21, 15.17 per cent, for the season ; the only other one with has increased to 92.37 for the season, the previous best being over 15 per cent, was No. 3. 92.24 in 1939. This is in spite of the high fibre of cane ; the re­ duced extraction calculated to an assumed fibre content of 12.5 Although these two factories are located widely apart, both per cent, is 94.13, which compares favourably with the reduced draw the bulk of their sup] es of cane from land at a con­ extraction of most other countries having a much lower fibre siderable altitude and some d tance from the coast. 7

Factories Nos. 3 and 4, both closing down before the end of WORLD PRODUCTION OF SUGAR. October, had the lowest fibre contents of cane, 14.23 and 14.54 Willett and Gray's estimates have again been freely drawn on per cent, respectively. No. 2, which did not close down until to supplement our private sources of information, but we can January 5th, also had the relatively low fibre content of 14.72 this year estimate the world's cane sugar production only ; owing per cent. to the war no information is available concerning the beet sugar output of many European countries. Factory No. 3 recorded also the highest purity of mixed juice, 88.82, followed by No. 21 with 88.27. The following is the estimated sugar production of the British Empire for 1941/42:— Factory No. 15 again showed the lowest reducing sugar ratio in mixed juice, 2.30. India The highest extraction is gained by factory No. 3 with 95.22 ; the only other factory with an extraction of over 94 is No. 1 with 94.(52. Since No. 1 had a much higher fibre content to Australia contend with, it has the lower milling loss, 4.77 ; but No. 3 Great Britain gains the lowest extraction ratio, 0.34, and the lowest primary British West Indies juice loss, 28.81. South Africa Two factories have a boiling house recovery of over 90— Mauritius No. 16 with 91.17 and No. 20 with 90.01. British Guiana The highest overall recovery, 85.1.6, is gained by factory Fiji No. 3 ; two others, Nos. 16 and 20, reached 84.72. The only Canada other factory with an overall recovery of over 84 was No. 1 with Ireland 84.46 ; it should be pointed out that this factory made most of its sugar into a refined grade of average polarization 99.9°, and Total that its average polarization of all sugars was 99.43°. The other three factories gaining a higher recovery made mainly sugars of polarization under 99°. As before, there is a range of over 10 units between the highest and the lowest factories in this most important figure. Thus South Africa has fallen from third to fifth place in Factories Nos. 2, 15 and 18, and expecially No. 3, show the Empire production of sugar, and its proportion from 8.8 to 7.0 biggest improvement over last season's work in this respect. per cent. The lowest ratio of cane to sugar, 7.67, was gained by No. 3, The total world cane sugar production for 1941/42 is esti­ No. 21 also showing a ratio of less than 8. mated to be 18,987,610 tons, of which South Africa contributed 2.1 per cent. No. 3 factory also achieved the very low moisture content fo bagasse of 43.32 per cent, only three other factories showing less SUGAR PRODUCTION IN SOUTH AFRICA IN than 50 per cent. RECENT YEARS. To economise in space, we have this year recorded sugar The lowest purity of final molasses was gained by No. 16 production only from 1929/30. For earlier years we must refer with 36.36 ; only three others had less than 40, while some were our readers to our annual summary for 1940/41. over 46. Production figures are in tons of 2,000 lbs. Two factories crushed over 400,000 tons of cane, No. 5 making 54,390 tons of sugar and No. 1, 51,419 tons ; the latter The rainfall figures now quoted are the average of 44 record­ had the highest crushing rate, 127.04 tons of cane per hour in ing stations in the sugar-growing districts, and not, as hereto­ a single train of mills. No. 5 factory, with 125.84 tons, and fore, the annual rainfall at the Experiment Station only. No. 12, with 102.49 tons, are both double tandem mills. Ratio Cane Inches of Sugar Cane/ RESULTS FROM OTHER SUGAR INDUSTRIES. Season. crushed. rainfall. produced. Sugar. Although we have not received reports from certain other 1929/30 ...... 3,005,663 48.30 298,635 10.06 countries overseas, such as Hawaii and Formosa, we record, as 1930/31 ...... 3,803,883 37.20 393,205 9.67 in recent years, results from Mauritius, Queensland and Puerto ... 3,130,783 29.39 325,899 9.61 Rico, and have added this year British Guiana, India, Trinidad 1931/32 ... and Louisiana, all of which are of much interest and information 1932/33 ...... 3,489,980 48.20 358,905 9.72 to us. 1933/34 ...... 3,673,375 31.12 391,173 9.39 358,738 10.80 ACKNOWLEDGMENTS. 1934/35 ...... 3,874,215 44.60 46.12 417,289 9.27 We are indebted for these data to the Sugar Technology 1935/36 ...... 3,867,536 Division of the Department of Agriculture of Mauritius, the 1936/37 ...... 4,180,973 50.10 446,409 9.37 Queensland Bureau of Sugar Experiment Stations, the Sugar 1937/38 ...... 4,489,022 39.48 507,219 8.85 Producers' Association of Puerto Rico, the Central Laboratory 1938/39 ...... 4,658,962 40.38 522,732 8.91 of Booker Bros., McConnell & Co., Ltd., Demerara, the Sugar 47.63 595,556 8.98 Technologists' Association of India, the Sugar Manufacturers' 1939/40 ...... 5,346,006 Association of Trinidad, and Gilmore's "Louisiana Sugar 1940/41 ...... 5,309,227 43.37 572,880 9.72 Manual." 1941/42 ...... 3,921,436 26.18 452,119 8.67 8 APPENDIX

SUGARCANE STATISTICS, 1940/41 CROP, BASED ON THE UNION GOVERNMENT DEPARTMENT OF CENSUS REPORTS FOR SUGARCANE OWNED BY EUROPEANS.

The Special Census of Sugarcane Plantations for this season Area Reaped, Yield of Cane, and Average Yield per Acre. 1940/41 was received from the Office of Census on 25th March, Period 1st May, 1940, to 30th April, 1941. and the following data are quoted or calculated from the statis­ tics given therein. Area reaped. Yield Tons per % non- % non- acre. It will be recollected that although the rainfall for 1940 was Acres. Uba. Tons. Uba. Uba. Uba. very unfavourably distributed, the total for the year was not Non- much below normal, except on the South Coast and the Umhlali- Plant cane 38,681 98.6 1,343,220 98.9 26.7 34.8 Chakas Kraal area ; it was, in fact, considerably above normal at practically all Zululand stations. Consequently the total crop First ratoon ... 48,966 93.1 1,448,654 94.6 23.2 30.1 was only slightly below that of 1939. Second ratoon 43,099 76.8 1,087,121 79.0 22.8 26.0 The area of cane harvested was the largest for some years in Third ratoon.. 23,139 42.6 521,438 44.9 21.6 23.8 nearly every district, 174,131 acres in all being harvested. This Fourth ratoon 11,540 21.7 226,919 27.0 18.3 24.5 increase was more marked in the districts south of the Tugela, which supplied 66.8 per cent, of the total area harvested, one Other ratoons 8,706 9.1 169,876 11.0 19.1 23.6 of the largest proportions on record ; while the proportion from each of the Zululand divisions showed a slight fail, except in Total 174,131 74.6 4,797,228 80.7 21.0 29.8 the Eshowe district, over recent years. The quantity of cane harvested showed an appreciable falling- off in all South Coast districts and over the greater part of Zulu- Herewith are yields of cane and sugar per acre for recent land, but increased in the central North Coast districts of Inanda seasons:— and Lower Tuyela. The latter again produced the largest quan­ Tons Sugar Tons Cane tity of cane of any single division, amounting to 1,299,769 Tons Cane per acre per ton tons, 27.1 per cent, of the total, from 47,529 acres. Inanda per acre. harvested. of Sugar. came second and Lower Umfolozi third in cane production with 1926/27 .. 20.44 2.06 9.92 17.0 and 16.0 per cent, of the total respectively. 1927/28 .. 19.28 1.99 9.69 YIELD OF CANE PER ACRE, 1940/41 SEASON. 1928/29 .. 20.38 2.15 9.49 Every district showed a considerable falling-off in yield per 1929/30 .. 20.75 2.06 10.06 acre, this being most marked in the South Coast districts that 1930/31 .. 22.39 2.33 9.59 had suffered very deficient rainfall in 1940, besides the general unfavourable distribution of rain. 1931/32 .. 18.90 1.98 9.53 1932/33 .. 19.29 2.02 9.61 The highest yield of cane per acre was again recorded for Inanda with 33.24 tons, being 26.34 tons for Uba, and 36.43 for 1933/34 .. 20.24 2.18 9.28 all other varieties combined. 1934/35 .. 20.84 1.95 10.67 Lower Umfolozi, as before, came second in this respect with 1935/36 .. 20.10 2.19 9.19 31.00 tons per acre, 19.71 for Uba and 32.09 for all other 1936/37 .. 21.27 2.29 9.29 varieties. Zululand as a whole again maintained a larger yield 1937/38 .. 23.75 of all cane per acre than the rest of Natal, which it has now- 2.70 8.80 done for four successive seasons, although the yield of Uba cane 1938/39 .. 27.37 3.08 8.89 is less in Zululand than south of the Tugela. 1939/40 .. 30.22 3.38 8.95 For the country as a whole the yield of cane per acre was 1940/41 .. 27.55 2.98 9.26 27.53 tons for the 1940/41 season, second only to the 1939/40 season, when it was 30.22 tons. The average yield for Uba This table shows the improvement in yield of sugar per acre in was 20.95 tons per acre, a figure which has remained remarkably recent years due to increased yields of cane per acre and lower constant since 1926, except for the boom year of 1939 when it ratios of cane to sugar. was 23.34, notwithstanding the fact that the Uba cane now being harvested is nearly all second, third and fourth ratoons. This is only part of the story, however ; there has undoubtedly The average yield for all other varieties in 1940/41 was 29.79 been a tendency to cut cane after a shorter period of growth tons per acre. than formerly. Unfortunately, there seems to be no way of arriving at the average age of the cane crop at time of harvest­ The gradual elimination of Uba cane is well shown in the ing, but most probably the yield of sugar per acre per annum following tables. It must be kept in mind, however, that these has increased more than the above table indicates. statistics refer only to European planters ; and it is evident that Indian and Native planters are still growing considerable proportions of Uba. GENERAL ACKNOWLEDGMENTS. The writers wish to thank all those whose co-operation has made this compilation possible ; this includes, besides those in other countries who have been mentioned, the South African manufacturing companies who have contributed their individual reports and data, the Union Government Director of Census, the Sugar Industry Central Board, and the clerical staffs of the Durban office of the Sugar Association and the Experiment Station.

Experiment Station, South African Sugar Association, Mount Edgecombe, April, 1942. Average Manufacturing Results by periods for Natal Sugar Factories Reporting to the Experiment Station, Season 1941/42.

MAY 31, JUNE 28, AUG. 2, AUG. 30, SEPT. 27, NOV. 1, NOV. 29, SEASON Period ending . • .. .. 1941. 1941. 1941. 1941. 1941. 1941. 1941. 1941-42.

Tons of 2,000 lbs. Cane crushed This period 176,551 600,461 785,465 622,856 611,442 661,197 253,687 To date 821,155 1,606,618 2,206,377 2,856,127 3,517,324 3,771,011 3,853,542

Tons of 2,000 lbs. Sugar bagged and estimated This period 17,807 65,468 91,114 75,774 75,321 77,315 28,923 To date 87,926 179,070 252,265 331,985 409,301 438,268 447,009

Tons Cane per ton Sugar This period 9.91 9.17 8.62 8.22 8.12 8.55 8.77 To date 9.34 8.97 8.75 8.60 8.59 8.60 8.62

Tons Cane per ton cf Sugar, calculated as sugar his period 9.65 8.93 8.39 8.00 7.90 8.32 8.56 96° Pol . date 9.09 8.73 8.52 8.37 8.36 8.37 8.39

Sucrose per cent. Cane This period 12.43 13.30 13.99 14.58 14.80 14.08 13.77 To date 13.09 13.53 13.83 14.03 14.04 14.02 14.00

Fibre per cent. Cane This period 15.75 15.53 15.60 15.62 15.66 15.78 15.94 To date 15.58 15.59 15.59 15.61 15.64 15.66 15.66

Java Ratio This period 78.28 78.58 78.22 77.88 77.81 76.74 76.43 To date 78.49 78.35 78.23 78.11 77.85 77.76 77.74

Sucrose per cent. Bagasse This period 2.83 3.04 3.10 3.11 3.11 2.94 2.92 To date 2.97 3.03 3.05 3.07 3.05 3.00 3.03

Moisture per cent. Bagasse This period 52.23 51.67 51.56 51.16 51.23 51.50 51.80 To date 51.93 51.75 51.62 51.50 51.50 51.52 51.50

Imbibition per cent. Cane .. This period 35.03 34.86 35.03 35.22 34.87 3-1.72 33.78 To date 34.86 34.94 35.03 34.96 34.92 34.84 34.76 <°

Extraction This period 91.85 91.98 92.21 92.58 92.65 92.62 92.39 To date 91.99 92.10 92.27 92.33 92.38 92.38 92.37

Recovery on Mixed Juice This period 87.16 87.86 88.64 88.91 88.67 88.46 88.19 To date 87.67 88.17 S8.39 88.46 88.47 88.46 88.40

Overall Recovery .. .. This period 80.06 80.81 81.73 82.31 82.15 81.93 81.48 To date 80.65 81.20 81.56 81.67 81.73 81.72 81.66

Purity of Mixed Juice This period 84.11 85.18 85.84 S5.S7 86.23 85.93 85.26 To date 84.97 85.41 85.55 85.70 85.75 85.71 85.67

Reducing Sugar Ratio This period 4.61 3.90 3.35 3.28 3.04 3.02 3.19 To date 3.98 3.67 3.55 3.43 3.33 3.31 3.35

Purity of Syrup This period 85.68 87.07 87.76 87.90 88.26 88.30 87.51 To date 86.73 87.24 87.42 87.61 87.75 87.73 87.69

Sucrose in Filter Cake (A) This period 0.82 1.92 2.00 1.90 2.11 1.72 2.11 To date 1.92 1.96 1.86 2.05 2.07 2.08 2.09

Purity of Final Molasses This period 38.32 41.87 41 .93 43.45 44.15 44.57 45.70 To date 41.97 41.54 42.52 42.84 43.20 43.38 43.45

Average Polarization of Sugar This period 98.63 98.59 98.58 98.64 98.68 98.61 98.40 To date 98.59 98.59 98.61 98.61 9S.61 98.60 98.58

This period 69.80 58.69 54.65 49.32 49.35 45.47 52.61 To date 61.31 58.54 51.94 51.25 50.12 50.33 50.86

(A) Arithmetic averages. COMPARATIVE RESULTS FOR RECENT YEARS.

COUNTRY NATAL

YEAR 1931. 1932. 1933. 1934. 1935. 1936. 1937. 1938. 1939. 1940. 1941. CANE— Per cent. Sucrose 13.84 13.48 13.88 11.88 13.65 13.30 13.92 13.64 13.41 13.19 14.00 Per cent. Fibre 15.75 15.65 15.78 15.24 15.92 15.01 15.14 14.51 14.80 15.56 15.66

JUICES— Purity of First Crusher 87.92 87.89 87.46 86.03 89.35 88.18 88.15 88.37 88.45 87.44 87.94 Purity of Mixed Juice 85.27 85.30 84.92 84.02 86.49 85.43 85.6U 86.36 86.46 85.34 85.67 Purity of last Roller Juice 79.99 79.20 78.26 76.71 78.05 76.87 76.81 76.86 77.07 76.15 77.46 Purity of Syrup 86.82 86.84 86.57 85.53 88.28 87.53 87.70 88.22 88.12 87.11 87.69 Drop in purity Crusher to Mixed Juice. . 2.65 2.59 2.54 2.01 2.86 2.75 2.55 2.01 1.99 2.10 2.27 Drop in purity Crusher to last Roller 7.93 8.69 9.20 9.32 11.30 11.31 11.34 11.51 11.38 11.29 10.48 Drop in purity Crusher to Syrup 1.10 1.05 0.89 0.50 1.07 0.65 0.45 0.15 0.33 0.33 0.25 Increase in purity Mixed Juice to Syrup 1.55 1.54 1.65 1.51 1.79 2.10 2.10 1.86 1.66 1.77 2.02 Reducing Sugar Ratio of Mixed Juice 3.35 3.09 4.01 4.21 2.65 3.04 3.23 3.08 3.27 3.81 3.35

JAVA RATIO 76.92 76.99 77.27 78.66 76.24 77.44 77.43 78.87 78.70 77.94 77.74

BAGASSE— Per cent. Sucrose 4.22 3.83 3.71 3.05 3.48 3.40 3.40 3.30 3.11 3.02 3.03 Per cent. Moisture 50.09 51.89 51.62 52.11 51.93 52.76 52.01 52.17 51.79 51.60 51.50

EXTRACTION— Imbibition % Cane 27.86 29.66 30.45 30.25 33.04 32.40 31.84 31.70 31.28 32.59 34.76 Sucrose in Mixed Juice % Sucrose in Cane 89.40 89.86 90.28 91.07 90.64 91.08 91.53 91.90 92.24 91.91 92.37 Reduced Extraction (based on 12.5% Fibre) 91.90 92.19 92.59 92.90 92.94 92.78 93.22 93.18 93.62 93.72 94.13 Primary Juice loss 56.70 54.65 51.88 49.67 49.43 50.71 47.47 47.73 44.67 43.93 41.12

FILTER CAKE— Per cent. Sucrose 4.79 4.50 4.04 3.65 3.69 3.20 3.37 2.63 2.19 2.03 1.71 Weight % Cane 5.01 5.41 5.18 5.07 5.01 4.71 4.75 4.74 4.78 5.12 5.63

FINAL MOLASSES— Purity 46.04 45.06 44.92 42.58 46.00 43.89 43.69 43.12 42.67 42.91 43.45

RECOVERY— Sucrose % Cane lost in manufacture .. . . • 3.63 3.36 3.27 2.52 2.94 2.71 2.73 2.55 2.42 2.52 2.57 Sucrose in Sugar % Sucrose in Cane 74.39 75.73 76.63 77.59 78.40 79.64 80.41 81.31 81.98 80.86 81.66 Reduced Overall Recovery (12.5% Fibre, 85° pur. Mixed Juice) 76.18 77.34 78.67 80.14 78.76 8O.73 81.33 81.16 81.89 82.07 82.61 Sucrose in Sugar % Sucrose in Mixed J uice 83.27 84.27 84.88 85.20 86.52 87.44 87.85 88.48 88.88 87.98 88.40 Reduced Boiling House Recovery (based on 85° pur. Mxd. Juice) 82.90 83.89 84.97 86.27 84.74 87.01 87.25 87.10 87.47 87.57 87.76

YIELD— Tons Cane per ton Sugar 9.53 9.61 9.28 10.67 9.19 9.29 8.80 8.89 8.95 9.26 8.62 Tons Cane per ton Sugar of 96" Pol. 9.33 9.40 9.03 10.40 8.96 9.06 8.58 8.66 8.73 9.03 8.39

LOSSES— Sucrose in Bagasse % Sucrose in Cane (A) 10.86 10.14 9.72 8.93 9.36 8.92 8.47 8.10 7.76 8.09 7.G3 Sucrose in Filter Cake % Sucrose in Cane (B) .. — — 1.37 1.14 1.15 0.91 0.78 0.60 0.52 Sucrose in Molasses % Sucrose in Cane (c) — — — — — — — — — Undetermined Sucrose % Sucrose in Cane (D) .. 10.87 10.30 9.97 9.68 9.48 10.43 10.18 Sucrose lost in Boiling House % Sucrose in Cane (B) + (c) + (D) 14.56 14.13 13.65 13.48 12.24 11.44 11.12 10.59 10.26 11.03 10.70 Sucrose in Total Losses % Sucrose in Cane (A) + (B) -f (c) + (D) 25.42 24.27 23.37 22.41 21.60 20.36 19.59 18.69 18.02 19.12 18.34

SUGAR— Average Polarization of all Sugars 98.08 98.14 98.68 98.45 98.42 98.43 98.50 98.60 98.36 98.44 98.58 COMPARATIVE RESULTS FOR RECENT YEARS.

COUNTRY MAURITIUS. QUEENSLAND, i BRITISH PUERTO RICO. GUIANA. INDIA. TRINIDAD. LOUISIANA 1 YEAR 1939. 1940. 1939. 1940. ; 1940. 1941. 1939. 1940. 1940/41. 1940. 1940. CANE— Per cent. Sucrose 12.71 13.29 15.88 16.04 12.79 13.27 12.38 12.19 12.18 13.40 9.82 Per cent. Fibre 13.00 12.60 11.56 11.58 i 13.36 13.19 13.03 13.18 16.18 14.34 13.06 JUICES— Purity of First Crusher 87.40 88.10 89.85 89.65 85.25 85.35 84.06 82.15 82.70* 85.75 79 .'44 Purity of Mixed Juice 84.60 85.30 — — 82.61 82.70 — — 80.45 83.55 .— Purity of last Roller Juice 73.50 74.50 78.76 78.26 ! — — — — 71.08 75.76 — Purity of Syrup 84.00 85.80 89.77 89.46 83.80 84.28 82.99 80.85 — — — Drop in purity Crusher to Mixed Juice 2.80 2.80 — — 2.64 2.65 — — 2.25 2.20 — Drop in purity Crusher to last Roller 13.90 13.60 11.09 11.39 — — — — 11.62 9.09 — Drop in purity Crusher to Syrup 2.50 2.30 0.08 0.19 1.45 1.07 — — — — — Increase in purity Mixed Juice to Syrup 0.30 0.50 —. — 1.19 1.58 — — — — — Reducing Sugar Ratio of Mixed Juice '. 4.20 4.00 — — — — — — 8.02 JAVA RATIO 79.04 79.51 83.45 83.41 79.29 79.37 80.87 81.49 77.53 78.00 78.19 BAGASSE— Per cent. Sucrose 2.60 2.62 2.98 2.92 2.56 2.65 3.59 3.71 3.19 3.28 3.07 Per cent. Moisture 44.70 44.60 49.63 49.8S 48.03 48.28 46.22 46.27 — 47.73 48.94 EXTRACTION— Imbibition % Cane 20.49 20.78 — — 24.6S 25.76 24.43 23.72 19.79 24.85 15.00 Sucrose in Mixed Juice % Sucrose in Cane 94.90 95.20 95.34 95.46 94.26 94.30 92.29 91.78 91.22 92.68 91.30 Reduced Extraction (based on 12.5% Fibre) 95.10 95.20 94.91 95.05 94.68 94.64 92.65 92.26 93.43 93.75 91.73 Primary Juice loss 34.13 33.30 35.65 34.67 37.22 37.51 51.46 54.15 45.48 43.73 57.92 FILTER CAKE— Per cent. Sucrose 7.30 7.30 2.98 2.93 2.60 2.48 5.09 5.56 3.56 4.20 3.93 Weight % Cane 1.61 1.56 3.10 3.42 2.31 2.42 1.66 1.84 3.47 2.22 2.09 FINAL MOLASSES— Purity 39.70 39.70 36.51 36.39 31.69 30.67 31.27 33.41 32.95 31.71 — RECOVERY— Sucrose % Cane lost in manufacture 2.06 2.01 2.11 2.03 1.67 1.72 2.24 2.60 2.49 2.12 2.05 Sucrose in Sugar % Sucrose in Cane 83.80 84.80 86.70 87.34 86.94 87.04 81.89 78.69 79.58 84.18 79.15 Reduced Overall Recovery (12.5% Fibre, 85° pur. Mixed Juice) 84.45 84.68 — — 88.52 88.50 — 85.04 86.02 •— Sucrose in Sugar % Sucrose in Mixed Juice 88.40 89.14 90.94 91.49 92.23 92.31 88.73 85.74 87.22 90.83 86.69 Reduced Boiling House Recovery (based on 85* pur. Mxd. Juice) 88.80 88.95 — — 93.49 93.51 — — 90.92 91.75 — YIELD— Tons Cane per ton Sugar 9.26 8.61 7.15 7.03 8.72 8.40 9.50 10.04 10.29 8.58 — Tons Cane per ton Sugar of 96° Pol 9.01 8.39 6.97 6.85 8.63 8.31 9.47 10.01 9.90 8.51 12.35

LOSSES— Sucrose in Bagasse % Sucrose in Cane (A) 5.10 4.80 4.66 4.54 5.55 5.50 7.71 8.27 8.78 7.32 8.70 Sucrose in Filter Cake % Sucrose in Cane (n). . 0.92 0.86 0.58 0.63 0.47 0.45 0.68 0.84 0.79 0.59 0.S4 Sucrose in Molasses % Sucrose in Cane (c) — — 5.12 5.30 6.72 6.63 6.94 8.91 9.68 7.11 9.87 Undetermined Sucrose % Sucrose in Cane (D) .. 10.18 9.48 2.94 2.19 0.32 0.38 2.78 3.29 1.17 0.80 1.44 Sucrose lost in Boiling House % Sucrose in Cane (B) + (c) + (D) 11.10 10.34 8.64 8.12 7.51 7.46 10.40 13.04 11.64 8.50 12.15 Sucrose in Total Losses % Sucrose in Cane (A) + (B) + (c) + (D 16.20 15.14 13.30 12.66 13.06 12.06 18.11 21.31 20.42 15.82 20.85 l SUGAR— - Average Polarization of all Sugars • 98.70 98.50 98.52 98.46 96.99 97.03 96.31 96.26 99.75 96.76 •—

* Primary juice. YIELDS OF CANE HARVESTED BY DISTRICTS (EUROPEAN PLANTERS ONLY).

COMPILED FROM UNION DEPARTMENT OF CENSUS RETURNS.

YIELD OF CANE IN TONS.

1930. 1931. 1932. 1933. 1934. 1935. 1936. 1937. 1938. 1939. 1940.

PORT SHEPSTONE 68,770 60,231 81,823 64,018 67,974 59,259 56,685 75,028 74,856 89,585 81,811

UMZINTO 449,410 486,803 638,701 508,308 611,231 553,401 564,427 692,159 663,609 744,981 733,332

DURBAN AND PINETOWN 164,849 136,979 159,020 138,096 185,118 137,805 146,676 124,109 188,183 213,958 193,938

Total South of Umgeni River 683,029 684,013 879,544 800,422 864,323 750,465 767,788 891,296 926,648 1,048,524 1,009,081

Ratio to 1926 (= 100).. .. 153.2 153.4 197.3 179.54 193.9 168.3 172.2 199.9 207.9 235.2 226.3

INANDA 414,466 375 763 455,816 504,540 618,853 672,954 629,945 615,227 683,261 807,094 816,215

LOWER TUGELA 873,467 648,693 754,022 829,067 1,012,784 1,033,633 1,184,839 1,138,342 1,122,528 1,285,888 1,299,769

Total for North Coast between Um­ 1,287,933 1,024,456 1,209,838 1,333,607 1,631,637 1,706,587 1,814,784 1,753,569 1,805,789 2,092,982 2,115,984 geni and Tugela Rivers

Ratio to 1926 (= 100) 155.5 123.7 146.1 161.00 197.0 206.1 219.1 211.7 218.0 252.7 255.5 Total for Natal South of the Tugela (ex- eluding Zululand) 1,970,902 1,708,469 2,089.382 2,134,029 2,495,960 2,457,052 2,582,572 2,644,865 2,732,437 3,141.506 3,125,065

Ratio to 1926 (= 100) 154.7 134.1 1C4.0 167.51 195.9 192.9 202.7 207.6 214.5 246.6 245.3

MTUNZINI 434,124 331,561 360,130 353,287 414,821 403,121 413,802 435,154 462,271 525,787 507,644

ESHOWE 146,256 109,525 105,836 120,099 130,104 128,191 120,935 151,020 193,847 243,829 240,962

LOWER UMFOLOZI 580,925 426,516 525,498 582,636 489,547 496,591 616,326 713,675 703,527 777,371 765,381

HLABISA 110,840 59,657 74,379 80,552 63,866 50,529 74,276 136,249 140,794 155,775 158,176

Total North of the Tugela (Zululand) . 1,272,145 927,259 1.065,813 1,136,574 1,098,338 1,078,432 1,225,339 1,436,098 1,500,439 1,702,762 1,672,163

Ratio to 1926 (= 100) 140.0 102.0 117.3 125.08 120.9 118.7 134.8 158.0 165.1 187.4 184.0

GRAND TOTAL FOR NATAL (including ; Zululand) 3,243,107 2,635,728 3,155,195 3,270,603 3,594,298 3,535,484 3,807,911 4,080,963 4,232,876 4,844,268 4,797,228

Ratio to 1926 (= 100) 148.6 120.8 144.6 149.85 164.7 162.0 174.5 187.0 193.9 221.9 219.8 YIELDS OF CANE HARVESTED BY DISTRICTS (EUROPEAN PLANTERS ONLY).

COMPILED FROM UNION DEPARTMENT OF CENSUS RETURNS.

DISTRICT. PER CENT. OF TOTAL TONNAGE.

1928. 1929. 1930. 1931. 1932. 1933. 1934. 1935. 1936. 1937. 1938. 1939. 1940.

PORT SHEPSTONE 1.8 1.9 2.1 2.3 2.6 2.0 1.9 1.7 1.5 1.8 1.8 1.8 1.7

UMZINTO 17.8 17.8 13.9 18.5 20.2 18.3 17.0 15.6 14.8 17.0 15.7 15.4 15.3

DURBAN AND PINETOWN '. 4.7 4.8 5.1 5.2 5.0 4.2 5.1 3.9 3.9 3.0 4.4 4.4 4.0

Total South of Umgeni River 24.3 24.6 21.1 26.0 27.9 24.5 24.0 21.2 20.2 21.8 21.9 21.6 21.0

INANDA 13.3 14.8 12.8 14.3 14.4 15.4 17.2 19.0 16.5 15.1 16.2 16.7 17.0

LOWER TUGELA .' 24.8 24.5 26.9 24.6 23.9 25.3 28.2 29.2 31.1 27.9 26.5 26.5 27.1

Total for North Coast between Umgeoi and Tugela Rivers 38,1 39.3 39.7 38.9 38.3 40.8 45.4 48.3 47.6 43.0 42.7 43.2 44.1

Total for Natal South of the Tugela (excluding Zululand) 62.4 63.9 60.8 64.8 66.2 65.2 69.4 69.5 67.8 64.8 64.6 64.8 65.1

MTUNZINI 13.4 12.5 13.4 12.6 11.4 10.8 11. 6 11.4 10.9 10.7 10.9 10.9 10.6

ESHOWR 3.5 2.7 4.5 4.2 3.4 3.7 3.0 3.6 3.2 3.7 4.6 5.0 5.0

LOWER UMFOLOZI .. 18.3 18.6 17.9 16.2 16.7 17.8 13.6 14.1 16.2 17.5 16.6 16.0 16.0

HLABISA 2.5 2.4 3.4 2.3 2.4 2.5 l.S 1.4 1.9 3.3 3.3 3.2 3.3

Total1 North of the tugela (Zululand) 37.6 36.1 39.2 35.2 33.S 34. S 30.6 30.5 32:2 35.2 35.4 36.1 34.9

GRAND TOTAL FOR NATAL (including Zululand) 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 YIELDS OF CANE HARVESTED BY DISTRICTS (EUROPEAN PLANTERS ONLY).

COMPILED FROM UNION DEPARTMENT OF CENSUS RETURNS.

DISTRICT. TONS CANE PER ACRE.

1928. 1929. 1930. 1931. 1932. 1933. 1934. 1935. 1936. 1937. 1938. 1939. 1940. 20.47 16.34 14.78 13.51 21.53 29.33 26.52 18.15 PORT SHEPSTONE 19.98 17.40 18.60 18.80 19.57 21.68 20.69 18.20 18.22 22.41 23.50 25.94 23.02 UMZINTO 19.33 20.10 22.30 20.80 22.24 23.00 23.34 20.27 19.77 20.42 27.65 31.76 24.74 DURBAN AND PINETOWN 22.64 24.80 26.77 22.90 21.75 18.21 18.02 22.04 24.65 27.00 22.83 Total South of Umgeni River 19.77 20.60 22.76 21.00 21.87 21.79 20.76 98.75 97.72 119.52 133.68 146.42 123.81 Ratio to 1926 ( = 100).. .. 107.20 111.70 123.40 114.10 118.60 118.17 112.58

25.95 26.19 31.27 36.57 33.24 INANDA . . . . 18.45 20.50 22.01 19.20 20.14 22.80 25.90 26.76 22.61 22.90 25.19 29.51 27.35 LOWER TUGELA 20.08 20.80 22.12 18.20 18.36 19.45 21.62 20.83

Total for North Coast between Um­ 22.83 23.67 L3.96 27.19 31.89 29.35 geni and Tugela Rivers 19.48 20.68 22.08 18.60 18.99 20.59 23.07 122.68 127.19 128.75 146.10 171.36 157.71 Ratio to 1926 (= 100) 104.70 111.10 118.10 100.00 102.00 110.64 123.97 Total for Natal South of the Tugela (ex­ 21.65 23 27 26.27 30.07 26.87 cluding Zululand) 19.59 20.65 22.31 19.40 20.11 21.03 22.21 21.19 116.71 125.44 141.62 162.10 144.85 Ratio to 1926 (= 100) 105.60 111.30 120.30 104.60 108.40 113.37 119.73 114.23 18.85 20.97 24.67 27.86 27.06 MTUNZINI 20.84 20.70 22.53 18.10 17.55 18.40 19.56 18.75 16.69 17.26 20.69 28.03 29.89 26.62 ESHOWE 22.76 20.60 20.22 18.90 17.47 17.95 17.64 18.63 23.04 28.81 34.40 33.25 31.00 LOWER UMFOLOZI 22.99 21.60 23.83 18.00 19.84 17.93 18.28 16.17 18.60 25.36 30.91 28.81 29.60 HLABISA 18.58 17.80 19.55 14.60 17.31 14.79 12.72 17.86 20.52 24.68 29.62 30.51 28.91 Total North of the Tugela (Zululand) . 21.83 20.92 22.50 17.90 18.91 18.28 18.00 74.95 86.11 103.57 124.30 128.03 121.32 Ratio to 1926 (= 100) 91.60 87.80 94.40 75.20 79.35 76.71 75.54

GRAND TOTAL FOR NATAL (including 20.24 20.84 20.10 21.27 23.75 27.37 30.22 27.55 Zululand) 20.38 20.75 22.39 18.90 19.29 104.06 116.19 133.90 147.85 134.78 Ratio to 1926 (= 100).. .. 99.70 101.50 109.50 92.60 94.40 99.02 101.96 98.34 50.10 39.48 40.38 47.63 43.37 Rainfall of all Districts (inches) 48.30 37.20 29.39 48.20 31.12 44.60 46.12 (Average from 44 centres) AREA OF CANE HARVESTED AND YIELDS BY DISTRICTS (EUROPEAN PLANTERS ONLY). COMPILED FROM UNION DEPARTMENT OF CENSUS RETURNS.

TONS CANE PER j PERCENTAGE (AREA) OF N ON-UBA CANES ACREAGE UNDER CULTIVATION. APRIL 30TH. DISTRICT. ACRE, 1940/41 UNDER CULTIVATION. APRIL 30TH. PLANT CANE.

Total Plant Cane, Uba. Non-Uba. 1935. 1936. 1937. 1938. 1939. 1940. 1941. 1940. 1941. 1941, % Total Plant Cane, 1940. PORT SHEPSTONE 13.03 22.24 4.4 19.5 36.3 48.8 56.4 70.6 86.6 1,381 1,963 142.1

UMZINTO 19.28 25.20 10.3 23.4 40.8 50.3 56.4 59.9 70.3 6,143 9,447 153.8

DURBAN AND PINETOWN 19.39 26.70 12.1 30.2 48.9 67.4 76.5 81.7 85.4 3,228 3,501 108.5

Total South of Umgeni River.. 18.51 25.24 10.0 24.0 41.4 53.0 60.0 64.7 74.7 10,752 14,911 138.7

Ratio to 1926 (= 100) .. 100.38 136.88 — — — — — — — — — —

INANDA 26.34 36.43 14.3 24.6 36.4 49.4 59.8 69.7 77.7 12,218 11,175 91.5

LOWER TUGELA 20.91 30.14 16.5 32.3 45.5 55.3 64.1 71.0 77.5 17,949 20,696 115.3

Total for North Coast between Umgeni and Tugela Rivers.. 22.82 32.25 15.8 29.9 42.5 53.4 62.7 70.6 77.6 30,167 31,871 105.6 Ratio to 1926 (= 100).. 122.62 173.29 — — — — — — — — — — Total for Natal South of the Tugela (excluding Zululand) 21.02 29.71 13.6 27.8 42.1 53.2 61.7 68.4 76.5 40,919 46,782 114.3 Ratio to 1926 (= 100) .. 113.32 160.16 — — — — — — — — —

MTUNZINI 21.87 27.86 16.4 31.0 50.0 66.6 77.1 83.8 90.9 10,963 10,926 99.7

ESHOWE 19.78 27.49 8.7 22.1 49.6 67.5 79.3 89.0 93. S 6,118 5,967 97.5

LOWER UMFOLOZI .. 19.71 32.09 20.0 40.6 61.1 73.1 83.0 89.3 94.0 12,246 12,490 102.0

HLABISA 18.43 30.72 17.2 34.5 52.2 70.2 80.0 90.6 92.5 2,940 2,399 81.6

Total North of the Tugela (Zululand) 20.50 29.92 17.2 34.5 55.1 69.9 80.2 87.5 92.8 32,267 31,782 98.5 Ratio to 1926 (= 100).. S6.03 125.56 — — — — — — — — — —

GRAND TOTAL FOR NATAL (in­ cluding Zululand) 20.95 29.79 14.9 30.1 46.5 58.8 67.9 74.8 82.1 73,186 78,564 107.3

Ratio to 1926 (= 100).. 102.50 145.74 — — — — — — • — — — — . Average Rainfall of all Districts 43.37 43.37 — — — — — — — — — — 18

EXTRACTION AND RECOVERY FIGURES, 1930/1841

1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 Extraction Sucrose of Cane Fibre % Cane Extraction

Purity of Mixed Juice Recovery on Mixed Juice 20 GENERAL REPORT ON WEATHER CONDITIONS FOR THE YEAR 1941.

RAINFALL. The annual rainfall recorded at this Experiment Station to The year 1941 has the most unfortunate distinction of having date is as follows :— the lowest rainfall on record, here or at Natal Estates, Moun Edgecombe, the records of the latter going back to 1887. The total rainfall for the year at this station was 24.35 inches, which is only 05.9 per cent. of normal. Not only is this tota very deficient, but the distribution was unfavourable. The two most important growing months of January and February had a total rainfaIl of only 3.70 inches, or less than 43 per cent. of normal, thus giving the sugarcane crop a very severe setback at the beginning of the year. March, with 3.43 inches rainfall, was not quite so bad, and April, with 4.93 inches, had a rainfall above normal. This, however, is late in the growing season, and the temperature had of course fallen considerably. From April 19th to September 11th a time of unexampled drought set in, the total rainfall over that period of nearly live months being only 1.75 inches. September and October were better, and eventually good planting conditions supervened which continued throughout November, though good soaking rains which might have replenished soil reserves of moisture and benefited the older canes wore still conspicuously absent. The year ended characteristically in unseasonable dry conditions once more with abnormally hot and dry atmospheric conditions The total number of rain days, 107, while considerably below the average for this station, is not so extremely low as to account This abnormally dry season of 1941 follows a cycle of seven for the very low rainfall. The average rainfall per rain day, successive years with only one rainfall below normal and an however, was only 0.227 inch, which is much below the fifteen- annual average of 41.34 inches. It may be that this is an iso- year average of 0.314 inch and was only lower once, in 1926, lated dry year like 1937, but more so, or we may be at the be- when it was 0.219 inch. ginning of another period of mainly dry years, such as began in 1926 and continued till 1933, and had an average annual fall The heaviest fall for any single day was 1.68 inches on April of only 33.23 inches. 19th, and the only other days with a rainfall of over an inch were March 21st with 1.60 inches, and April 18th with 1.15 inches. The annual normal rainfall is now 36.95 inches, which is very This is very remarkable, since there are normally many days in close to what it was calculated to be at the beginning of our the year with over one inch of rain, and usually a few with records. It declined to as low as 36.56 inches at the end of the 2 inches or more. dry cvcle in 1933, and had increased to 37.18 inches at the end of 1940. Following is the rainfall for 1941 by months compared with the 54-year average :— DISTRICT RAINFALL RETURNS. 1941. Mean l887/1940inclusive. The drought was experienced in every part of the sugar- growing area, and the general deficiency was even greater over the 44 recording stations as a whole than at the Experiment Station. Thus the average rate for the 44 stations was 26.18 inches, the lowest on record, and only 63.9 per cent. of the 13-year annual average, whereas the rainfall at the Experiment Station was 65.4 per cent. of normal. The lowest rainfall recorded for any station reporting to us was Riverview, at the extreme northern end of the sugar belt, where it was only 16.45 inches or 47.1 per cent. of normal. Another station with a rainfall of less than 20 inches was Es- peranza on the South Coast with 19.49 inches, or 49.1 per cent. of normal. There are as many as eight other stations with a recorded rainfall of less than 23 inches—Effingham, Blackburn and Ottawa in Natal Estates group, Tongaat and Chakas Kraal in the central North Coast, and Mposa, Kwambonambi and Eteza in the northern Zululand section. Mtunzini with 39.08 inches, or 78.5 per cent. of normal, recorded the highest rainfall, and Eshowe was second with 36.57 inches or 70.4 per cent. of normal. Felixton had 30.08 From the year 1926 inclusive the rainfall has been recorded inches (60.4 per cent. of normal), so that the wettest: area was at the Experiment Station. For the 39 years preceding this again the Eshowe-Mtunzini-Felixton triangle, which has a period the records of Natal Estates, Ltd., factory at Mount normal rainfall of 50.54 inches, which is considerably larger Edgecombe have been used, applying a factor, 0.9259, that is than anywhere else on the Natal coast. indicated by the 15 years 1926 to 1940 inclusive as the ratio of the rainfall at the Experiment Station to that at Natal This year, as in 1939, Gingindhlovu was also included in this Estates' factory. According to this ratio the average rainfall at area of relatively high rainfall. the Experiment Station site for these 39 years was 37.24 inches, Five other stations topped the 30 inches mark—Durban the factory average being 40.22 inches over that period. (Berea), 30.06 inches (73.2 per cent. of normal) ; Durban (Point), 21

ANNUAL RAINFALL, 1929-1941. 22

34.95 inches (73.5 per cent. of normal) ; Cornubia (Natal Es- 1941. 1928-1940 inclusive. tates), 30.66 inches (73.5 per cent. of normal) ; Kearsney, 31.91 inches (71.2 per cent. of normal), and Gingindhlovu, 30.35 inches (68.4 per cent. of normal). The deficiency of rainfall was most marked at the extreme north and south, the four most northerly stations of Riverview, Eteza, Kwambonambi and Mposa having an average rainfall of 19.97 inches or 50.5 per cent. of normal, and the three most southerly stations of Port Shepstone, Umzumbi and Esperanza an average of 22.13 inches or 54.3 per cent. of normal.

In the area from Durban to about Mount Edgecombe the deficiency of rainfall was loss marked, a group of seven neigh- bouring stations having a rainfall of from 72 to 75 per cent. of normal, the only station exceeding this percentage of normal being Mtunzini with 78.5 per cent. as already stated.

This year our district rainfall record going back to 1929 has been considerably extended to include nine stations not pre- viously listed. These are Effingham, Westbrook, Milkwood Kraal, Saccharine, Cornubia, Burnside, Blackburn, Beach, and Ottawa, all within Natal Estates and are distributed over an area of approximately eight miles long and seven miles wide, It will be seen that every month had a temperature above giving now a total of 11 stations within this limited area. normal ; and in fact the months of April, May and October had This perhaps tends to overweight this area somewhat in the highest mean temperatures ever recorded for those months. arriving at the general mean of all stations, especially since As usual, February was the warmest month and July the the average rainfall of the 11 stations in this district is 37.81 coolest. inches, compared with a general average of 40.96 inches for all stations. The mean temperature for the three months ending February, 1941, is the highest on record for that period, and was only According to "Rainfall Normals" published by the Union equalled once before for any three-months period, the first Meteorological Office in 1927. part of the Durban North and quarter of 1940, when it was also 75.6°. Mount Edgecombe area is one of the very few places where the 30 inches to 40 inches annual rainfall zone characteristic The mean daily range of temperature, 17.4°, was higher than for about 200 miles inland of the upland regions immediately normal, probably due to the lack of the moderating effect of behind the sugar growing belt, penetrates that belt and the rain on temperature. only place where it actually reaches the coast anywhere between Port Shepstone (excepting possibly near Umzumbi) and Portu- No doubt for the same reason there were some abnormally guese Africa. The rest of the sugar-growing belt is within the high temperatures. Thus there were the unusual number of 40 inches to 50 inches zone, except for a section between the 12 days with a maximum shade temperature of between 90° mouths of the Amatikulu and Umfolozi Rivers, extending back and 100°, and two days of over 100°—October 10th with 101.5° from the coast at one point as far as Eshowe, within the 50 inches and December 30th with 113.5°. The latter is the absolute to 60 inches zone. maximum for this station, the previous highest shade tempera- ture being 104° on January loth, 1932. However, the inclusion of the new recording stations men- tioned only brings down the 14-year general average from 41.26 The mean maximum shade temperature for the year, 78.6°, inches to 40.96 inches, and since they each represent important is the highest on record at this station, the previous highest sugar-growing centres where accurate rainfall records have been being 78.2° for 1940, and the mean of the 13 years ending kept for many years, they have been included. 1940, 76.7°. The absolute minimum screen temperature for the year was 45° on August 6th. For the seventh successive year there were TEMPERATURES. no ground frosts, although the grass thermometer recorded a The mean average daily temperature in the shade was 69.9°, temperature as low as 35.5° on August 6th. The average grass the highest on record for any year at this station excepting 1940, thermometer minimum for the year was 56.6°, the annual which was the same. normal being 55.2°. Mean shade Annual means The mean solar radiation maximum temperature (vacuum temperature at date bulb thermometer) for the year was 126.7°, and the absolute in degrees F. in degrees F. maximum 167° on December 30th; the previous absolute 1928 maximum 160° on January loth, 1939. 1929 1930 The mean earth temperatures were the highest on record at 1931 each of the 1ft., 2ft. and 4ft. levels; they were 72.7°, 73.7° 1932 and 73.7° respectively. They ranged from 80.4° in February at 1933 1 ft. and 2 ft. levels to 63.2° at the 1 ft. level in July. They 1934 indicated that irrigation of sugarcane would have resulted in 1935 increased growth during every month except those of June to 1936 September inclusive, and would have been particularly beneficial 1937 in the months of January, February, March and December. 1938 1939 ATMOSPHERIC CONDITIONS. 1940 The mean true atmospheric pressure for the year at 300 feet 1941 elevation was 29.74 inches, which is the lowest on record for any year at this station. July, as usual, was the highest with a mean pressure of 29.92 inches, and December was the lowest with a mean of only 29.62 inches. Following are the screen temperatures in degrees Fahrenheit The range for the year was from 29.19 inches on December by months:— 22nd to 30.26 inches on August 22nd. 23

The mean humidity for the year is the lowest ever recorded The total hours of sunshine during the year were 2,345.2 or for any year at this station, being 69.9 per cent. of saturation 53.5 per cent. of total hours of daylight, which, as in 1940, is at 8.30 a.m. and 61.1 per cent. at 1 p.m. The most humid considerably above normal for this station. months were March and April, that had moderate rainfalls, and the driest were June with a relative humidity of only 54.8 per The sunniest month was again May with 72.4 sunshine per cent, of saturation at 1 p.m., and December with a mean rela- cent. of hours of daylight, and the cloudiest February and tive humidity of 56.3 per cent. of saturation at 1 p.m. and 61.8 October with 41.4 per cent. and 41.8 respectively. per cent. at 8.30 a.m. CONCLUSION. On the abnormally hot day of December 30th the relative 1941 may be considered a disastrous year for sugarcane humidity was only 8 per cent. of saturation at 1.20 p.m. growing owing to a record deficient rainfall, especially in the The mean daily rate of evaporation from a free water surface most important growing months of January, February and was 0.13 inch for the year, ranging from 0.07 inch in July to December, when the loss of moisture by transpiration was par- 0.20 inch in January. ticularly heavy. The drought was also very severe in July and August, adversely affecting the condition of the harvested sugar- The total evaporation for the year was consequently 48.46 cane crop and the renewed growth of ratoons. The results are inches, or almost double the rainfall, a further indication of the seen in the lowest crop of sugar for several years, and an even aridity of 1941. lower present estimate for the 1942 crop.

Experiment Station, South African Sugar Association, Mount Edgecombe. March, 1942. 24

TEMPERATURE AND RAINFALL BY MONTHS 25

ANNUAL RAINFALL *W

^'•yG*

*>* 26

THE FOLLOWING ARE ABSTRACTS FROM RE- remainder flows to the filters. The work of the filters is eased and their capacities increased. PORTS SUBMITTED BY VARIOUS FACTORIES ON The following savings were effected on 4,515 tons of sugar THE SEASON'S WORK. made:— DARNALL SUGAR FACTORY. Report by M. Viger. Weather.—The rainfall was very poor from the month of January and has been unusually low throughout the season. Only 25.27 inches were recorded in 75 days.

Quality of Cane.—The season started with a fairly high sucrose No ill-effects were observed in the factory through the reduc- of 12.70 per cent. for May and reached its peak unusually early tion of the chemicals. The recovery was normal and the sugar on the week ending 20th September, when it was 14.99 per cent. of excellent quality, pol. 99.05 and nitration rate 114. After that the sucrose started to decline up to the end of the season. The average for the crop was 13.72 per cent., the The study of two other processes of clarification (patented) highest obtained since 1933, when it was 14.03 per cent. has been started in the laboratory. So far the results observed have been very encouraging. Purities of crusher and mixed juices were rather low (87.2 and 84.27) considering the high sucrose. The severe drought Filters (Oliver Campbell).—Darnall possesses a 2 (8 feet by 12 had a deleterious effect on juice purity. The average ash per feet) Oliver Campbell filter, the total filtering area being 600 cent. brix of the mixed juice, 3.59 per cent., is the highest square feet for 105 tons of cane per hour. This gives a ratio of figure on record. The juices were of a refractory nature, the sq. ft. filter area of 5.7 non-sugars high, and the amount of final molasses produced Tons cane per hour excessive, 3.63 per cent. cane or 5.03 gallons per ton of cane (at 85 brix), is the highest on record. This is rather inadequate to deal ratio of 8 will suit all conditions. The fibre was high, 15.78 per cent., considering 75.85 per cent non-Uba was crushed. During the season twenty-one half-hourly tests were made. The items were as follows :— Hot Water Imbibition.—During the season hot water imbibi- tion was tried out on the mills. The temperature of the water varied from 150°F. to 158°F. The condensate obtained from the second, third and fourth calandrias of the evaporator, which usually runs to waste, was used to this effect with a fair amount of success. The advantages of using hot condensate for imbibition, in comparison to cold water, are as follows:— 1. The water is clean, and being practically distilled water it is free from salts. 2. The condensed water being hot is economical, as a certain The settlings are filtered at a temperature varying from 195° amount of heat is transferred to the juice. to 205°F. The temperature of the wash waters varied from 200° to 210°F. 3. The intermediate carriers and milling plant are kept in a better hygienic condition, being more free from fermentation The filtered liquor, which includes the muddy and semi-clear growth. juices, had the following composition : brix 12.58, purity 82.1, 4. For Darnall it means a saving of 203,500 gallons of water and drop of purity from clarified juice 3.2. No extensive from the river a day. deterioration took place in the juices from the Oliver Campbell filters. The average reducing sugars in the clarified juice was 5. Extraction was increased from 0.35 to 0.40 per cent. 3.92 per cent, and in the Oliver Campbell juice 3.99 per cent. The pH of these juices was 7.4 and 7.3 respectively. 6. It was also observed that steam was better when using hot imbibition. This was probably due to the fact that hot A number of screening tests made on the bagacillo added to bagasse loses its moisture more readily before reaching the the settlings show that on the average 83 per cent. passes through furnaces. an 8-mesh screen. When hot imbibition was used, no difficulty whatever was observed in the boiling house. The filters have been dismantled and thoroughly examined There is evidence of slight corrosion on the rocker arms and Clarification.—This department consists of three Bach con- trough, which seem to have been constructed from a very poor tinuous subsiders, which have given entire satisfaction and saved metal. The galvanised iron ducts, the fan casing and impeller both labour and steam. Towards the end of the season experi- were badly worn. The stainless steel filter screens were clogged ments were conducted with a view to reducing the amount of with sand, which could not be removed in the ordinary way chemicals used. The results were fairly successful. The process and the holes had to be cleaned by means of a small needle. consists in abstracting a portion of the settlings (about 40 to This is tedious and will shorten the life of the screens. 50 per cent.) obtained from the subsiders and returning the same to the preliming tanks, where it is thoroughly mixed with pH Determinations.—It was found that considerable errors the incoming preheated raw juice (temperature 140°—150°F.) were made in colorimetric pH determinations. When a clarified which has been previously conditioned to a certain pH (8.0 to juice is examined with bromo-thymol blue and the pH is 8.7) by the addition of a portion of the lime. The mixture is found to be 7,3, then the reading of the glass electrode poten- then further limed in another preliming tank, then pumped to tiometer will indicate 7.0. There is, of course, a considerable a sulphitation tower, when the juice is sulphited and is allowed drop in pH from clear juice to massecuite and molasses, and to flow out at a pH of 5.8 to 6.0 into the correcting tanks to the danger of sucrose inversion is always present, especially if be conditioned to the required pH with lime and phosphoric the pH of the clear juice is on the low side. According to observa- acid. The whole system is continuous. A certain portion of the tions bromo-thymol blue reads +0.3 too high and phenol red settlings is being continuously introduced into the juice and the + 0.5 too high. 27

DOORNKOP SUGAR ESTATES. scope heating element. In practice, as the temperature increases, Report by G. Booth. the current is switched off so as to hold any particular tem- perature for a period of about two minutes while the effect can Clarification.—The past season presented no particular diffi- be observed. The temperature is advanced 1 degree F. at a time. culties in juice clarification, despite the fact that the throughput We have found on repeated tests that a variation of two to was the speediest yet accomplished. One particular fact asso- three degrees F. in the saturation point is quite common on ciated with certain fields again manifested itself, viz., the juice different samples of the same massecuite. This, however, is of from cane cut from these fields could not be clarified. In how no serious consequence, since in factory practice the temperature far this peculiarity can be associated with the uptake of certain of the circulating water used for heating should be adjusted to plant-foods or lack of other elements is not known. It is sug- 5 degrees F. below the apparent saturation temperature. gested that a possible connection between availability of the sucrose in the cane and the type and treatment of the soil from In all systems where reheating of the massecuite is practised, whence the cane was obtained is well worthy of study. it is important that no further dilution of the massecuite should be used after the saturation temperature has been determined Massccuites and Molasses.—The outstanding problem last and the temperature of the circulating water set, otherwise year was the behaviour of low products. The third massccuites serious remelting of sugar will occur. Should it become necessary could not be concentrated to the usual density. Molasses pro- for any reason whatsoever to dilute the massecuite, either with duction increased, and from August onwards the purity of water or molasses, then a new saturation point should be de- exhaust molasses rose considerably for no apparent reason. termined. Unfortunately, due to staff shortage, observations on the The determination of the saturation point is in our opinion glucose/ash ratio could not be undertaken. an absolutely necessary control figure. We have found that Rapid methods of analysis to assist in factory control are two massecuites of the same purity and of the same density at required, so that information as above indicated may be made the time of striking can have saturation temperatures differing available in as short a time as possible. In this connection the by 12 to 15 degrees F. This apparently is caused by the amount salometer, for example, is described by some as a useful adjunct of injection water used in steaming out the pan and also by the to the laboratory. Some technologists do not agree. As the amount of dilution used on the massecuite after striking. factory chemist is not always in a position to test out the use- While realising that it has nothing whatever to do with the fulness of an instrument, a definite opinion on local observations saturascope, we feel that whether reheating of the massecuite would be welcomed. Similarly, the saturascope seems to have is practised or not, the saturascope has shown that the habit good possibilities now that the reheating of massecuites is of steaming out pans after striking is one that cannot be too common practice. As each massecuite has its own characteristics strongly condemned. The remelting of sugar which occurs when as revealed by cuitometer control, a line of study on this instu- boiling hot injection water is added is very great, and it does ment is indicated. not appear to show that it ever crystallizes to the same extent.

NEW GUELBERLAND SUGAR FACTORY. ESPERANZA SUGAR FACTORY. Report by C. Jelly. Report by W. G. Galbraith. Observations on the Use of the Saturascope.—This instrument Weather Conditions and Cane Quality.—The season has been which was in use at the factory the whole of the 1941-42 season, one of the driest on record. During the whole crushing season was used in conjunction with the Stevens heat-treatment plant, only 7.87 inches of rain fell, as against 19..94 last year. For- which we have installed in the mixer of our foreworking centri- tunately the cane was not affected to any great extent as far fugals. as its milling and factory qualities were concerned. The sucrose The saturation temperature, or the temperature to which a was exceptionally good, being 15.17 per cent., the highest in massecuite may be heated without dissolving sugar, is a very the industry and also a record for the factory. The purity of important control item whenever reheating of the massecuite, the juice was very good, and the fibre only slightly higher than either in crystallizers or in centrifugals, is practised. last year. Towards the end of the season, however, the condi- It is not necessary to describe the saturascope, as this is tion of the cane fell off somewhat, due to young cane, trash and done in detail in the I.S.J. 1936, page 189, but we have found green tops. by experience that the equipment as described must be modified Factory Performance.—The overall recovery was a record for if the saturation temperatures of all "B" and "C" massecuites the factory—extraction being 0.74 per cent. better than last are to be determined as a part of regular laboratory routine year and boiling house recovery showing an improvement of 0.24 work. per cent. This record was attained notwithstanding the fact Since a single determination will usually take about fifteen that a high percentage of white sugars (43.0 per cent.) and a minutes, it becomes evident that the microscope used should be high percentage of Government grade sugar (25.2 per cent.) were a good one, as continued use of an inferior instrument may made and a high rate of output was maintained. result in permanent injury to the eyes of the operator. The To indicate the progress made in factory recovery, extraction instrument we have in use at the factory is a Leitz Inclined and overall recovery, the following tabulated figures are given :— Binocular. The light is supplied by a microscope lamp using special filament six-volt globes. The source of supply of current is 220 volts A.C. and a small transformer with tappings at 4, 6 and 8 volts is interposed. A new heating element of German silver wire was inserted in the saturascope. The gauge of the wire being such that the saturascope was heated from room- temperature to 140 degrees F. in a period of five minutes. The 4-volt tapping on the transformer was invariably used, and no red filter on the microscope lamp is necessary. In respect of the optical equipment to be used on the microscope we must con- demn the suggestion in the I.S.J. that a 30x eye-piece and a l0x objective should be used. Theoretically the idea is very sound, since the greater the magnification of the objective the less depth of focus is obtainable, and by using an objective as suggested the depth of focus is comparatively great. The use of a 30x eye-piece, however, imposes very severe eye-strain on the operator, and we have found that results can be equally well observed when using a 12x eye-piece, thus giving a total Moisture per cent. Bagasse.—This showed a decrease of about magnification of 120. one per cent., and would have been even better had trouble not developed in No. 5 mill, causing the moisture to rise considerably The operation of the saturascope is otherwise substantially over a period of four weeks. as described in the article in the I.S.J., except that the rheostat can be dispensed with and a switch installed before the satura- Clarification.—Clarification was normal throughout the season. 28

Filtration.—The Oliver Campbell filter performed its duties At times the capacity of the evaporator was so reduced as to very satisfactorily and is undoubtedly a great asset from the necessitate a "slowing down" of the crushing plant. manufacturing point of view. The only trouble experienced was due to a shortage of bagacillo at times, particularly when No. 5 Vacuum Pans.—These operated satisfactorily and at no period mill was not functioning properly, and the moisture in bagasse was there any difficulty in boiling the massecuites. rose to 54 per cent. and higher. This caused the screw at the Centrifugals.—Excessive viscosity caused the output of the boilers to clog and bagacillo could not be obtained in sufficient centrifugals to be reduced to 40 per cent. at times. As each quantities. Provided sufficient bagacillo is available, the filter charge remained longer in the basket there was a loss in recovery works and handles all the scums comfortably, allowing plenty as a result of erosion of sugar. The viscous massecuites imposed of time to shut down the filter and wash out frequently, which an excessive strain on the conveyor drive and some trouble is essential. occurred through breakages. Reheating of massecuites would have improved conditions considerably, but this facility is as Chemicals Used in Manufacture.—A big saving in lime and yet not available. sulphur has been noticed since the installation of the Oliver Campbell filters. No lime is now necessary in the scums prior THE GLEDHOW-CHAKAS KRAAL SUGAR CO., LTD. to filtering, and in consequence less sulphur is required to neutralise the excess lime previously necessary to induce good (GLEDHOW ESTATES). filtration. More phosphoric acid is now used, but this is due to Report by F. L. Chiazzari. more white sugar being made. Quality of Cane.—The season was characterized by a large Boiling House.—The work in this department has been greatly proportion of drought-stricken cane, consequently quite a few facilitated by the installation of a new 800 cub. ft. calandria consignments contained dead cane, and when burned were often pan; also by the installation of a spray cooling system, for the wholly charred. In this respect it was noticed that Co.290 was cooling of injection water, in place of the cooling tower pre- mostly affected. Furthermore, higher topping was practised and viously used. The latter would only cool the water 9°F. as young bull shoots were included in an endeavour to increase against 25°F. obtained with the spray system. The chief ad- field yields. Towards the latter part of the season, when some vantages gained were (1) better vacuum, (2) economy of water. young immature cane was being milled, the clarification was Quadruple.—A good deal of entrainment took place, particu- difficult and phosphoric acid had to be increased. larly in the third and fourth vessels. It is proposed to install the The season started with the highest sucrose ever recorded for cone type save-all to combat this trouble. that time of the year, and this position was maintained up to the peak week ending 6th September, when 15.05 per cent. was Boiling House Losses.—A summary of the throe main losses registered. Thereafter an alarming decrease occurred and in is tabulated below to show the progress achieved over the last eight weeks the sucrose dropped to 12.53 per cent. Two weeks eight years:— in particular revealed falls of 0.57 and 0.54 per cent. respectively. Losses in Losses Losses Over the same period the mixed juice purity dropped from molasses undeter- in filter 86.8 to 84.9. Season. (A) mined (B) A+B cake. Factory Performance.—The pans boiled remarkably well and 1934 ... — — 14.58 1.40 all massecuites purged freely except for an occasional third. 1935 ... — — 12.92 1.10 The massecuites were, however, more viscous than last year. 1936 ... — — 12.87 1.12 In spite of removing a large percentage of molasses forming 1937 ... 8.72 2.80 11.52 0.53 bagacillo the molasses per cent. cane showed an increase over last year. The crop was concluded with the record boiling house 1938 ... 7.66 2.04 9.70 0.44 recovery of 89.27 per cent. 1939 ... 7.49 2.28 9.77 0.48 1940 ... 7.41 2.09 9.50 0.06 The extraction was disappointing, and this was due to the cane being affected by the low rainfall. The crusher and first 1941 ... 7.18 2.15 9.33 0.08 mill were not expressing as usual, and these two units are the It will be noticed that the losses in molasses, and the losses first to feel the strain of difficult milling cane. in molasses and undetermined losses, have been gradually de- The only new machinery installed was a Peck strainer. It creased. The low losses in filter cake in 1939 and 1940 are helped appreciably, for apart from diminishing an "undeter- due to the installation of the Oliver Campbell filters. mined" loss in the form of weighed bagacillo, the Dorr clarifiers appeared to give a better clear juice. Gumming-up of the UMZIMKULU SUGAR CO., LTD. screen was common trouble and steaming-down carbonized and hardened rather than removed the matter. Running for a few Report by C. L. Steyn. hours in a 10 per cent, solution of caustic soda, followed by a There has been no change in the process of manufacture, nor hosing down with hot water, gave good results, however; but it has any new machinery been installed that would have influenced was often found that this had to be repeated every three days the manufacturing efficiency. or so. Weather and Cane Quality.—The protracted drought (25.29 CENTRAL FACTORY, LTD. inches of rainfall for the year) has been the worst on record Report by J. D. Millar. and adversely affected the manufacturing quality of the cane. All varieties were affected ; but Co.290 appears to have suffered The past season was, from a pan boiler's point of view, about most. the worst for many years. It was extremely difficult to get a uniform grain of fair size. The difficulties were probably due to Milling.—The conditions of working and mill settings were drought-stricken and over-ripe cane being milled. identical to the previous season. The decrease in extraction and increase in moisture per cent. bagasse were due to the poor quality of the cane. The crushing of these drought-stricken canes was a tough proposition. Although 87.18 per cent. of The VICE-PRESIDENT, in opening the paper for discussion, "soft canes" was crushed, these canes had developed crushing- said he thought in future a whole morning session should be set resistant properties under the prevailing drought conditions and aside for dealing with the Annual Summary and mill reports. they were very hard. This can partly be attributed to the large proportion of nodes. These hard canes also gave rise to an Mr. RAULT agreed with the Vice-President. He welcomed the increase in the moisture per cent. bagasse and increasing the fact that more information was now available as a result of hydraulic pressure on the top rollers had little effect. individual mill reports. New ideas were brought forward and they would be tested out. He suggested that the various items Boiling House.—The clarification of the juice proceeded nor- might be subdivided and discussed as such. mally and the mud volume in the settlers was not excessive. At the triple effect some difficulty was experienced. Gummy Mr. Rault pointed out that the severe drought resulted in substances from the partly dead cane were probably the cause. lower yields of cane per acre, but the purity of the juice was 29 not very low. It was difficult to correlate cane quality and were, however, disappointing. Deterioration was checked, but rainfall. The fibre per cent. cane was higher than in the previous definitely not prevented. season, yet the extraction was better. Theory once more was Mr. Moberly thought that there must necessarily be a corre- not borne out by experience. lation between climate and working quality of the juice. The Tests with an experimental Herisson crystallizer indicated correlation between weather conditions and purity, and the corre- that a massecuite could be treated systematically with a very lation between purity and working quality, however, was not at large amount of water without dissolving sugar or increasing all obvious. the purity of the molasses. Better exhaustion and better yields were obtained. Mr. DYMOND said that the Central Board would have ob- tained better results if smaller samples had been used and the Boiling house recovery had gone down somewhat this season, brix done by refractometer. This was done in the original but that was due to the very large percentage white sugar that experiments at Darnall. was made at his factory. Mr. DUCHENNE mentioned that he had preserved samples Mr. BOOTH agreed with Mr. Rault that these unofficial of juice overnight by using mercuric iodide and that no change factory reports were of the greatest value and, after being sum- of purity had been observed. This preservative had given marized, should be put on permanent record. As Mr. Buchanan satisfaction since 1930. said in the Chemical Control Committee, personal contact was very necessary, and he thought that when transport difficulties Mr. BIJOUX said that their experience at Darnall had been came to an end, future meetings for discussion of factory reports that it was necessary to freeze the juice. Under these circum- should be held. It was the only real method of getting the stances they kept juice for more than a week and there was no points of view on many phases of factory work. deterioration. It was necessary, however, to melt and mix the juice before analysing it, as the top and bottom parts differed These reports had taken considerable time and trouble to in composition. write and should not be pigeon-holed, as they were as valuable and instructive as any information that came in front of the Mr. DODDS pointed out that purity of juice was not much Congress. affected during the earlier parts of the season, but we had refreshing rains in March and April. After August, however, Mr. MOBERLY gave the experience of the Central Board in the purity of the juice fell off very rapidly indeed, and that connection with laboratory refrigeration of mixed juice samples. was just the time that the drought made itself fell seriously. The idea was to eliminate the night-shift by keeping the juice samples in a refrigerator. The juice was not frozen but brought The speaker thought that the differences between colori- to a temperature as low as 3°C The addition of a preservative metric and potentiometric pH determinations referred to by was also tried. The preservative used was mercuric iodide in Mr. Viger in his report was a matter which concerned the formalin, as recommended by the S A.S.T.A. and the best results standardization of the indicator, and it should be taken up were obtained by using 1 ml. The results of the experiment with the suppliers. 30 ON EFFICIENCY INDICES IN SUGAR MILLING

By PROF. P. STEIN.

INTRODUCTION. PART 1. The indices commonly used to estimate the efficiency of the In his paper Mr. Bechard1 investigates the effect of fibre crushing process in the sugar industry are (1) the fraction of the content on the value of the Noel Deerr coefficient v. He finds juices in the cane which is extracted by crushing, and (2) the that in general v increases as the fibre content diminishes, and quantity of juices per unit quantity of fibre left in the fibre. calculates the average regression of v for 13 mills over a period Calling these e and v, l00e is the percentage extraction, while of thirteen years. This average regression value works out at v is one of the. Noel Deerr coefficients. — 0.04397.1 for every one per cent. of increase in fibre. He also If f is the fibre in unit quantity of cane, e, v and f are con- obtains a formula for the variation of v. On referring to his nected by the formula2:-- manuscript, Mr. Bechard gave me a result which, with a slight change in notation, can be stated as follows:—

If f is the fibre content of a cane and f is near 0.1545, and f1 the fibre content of another cane, then if x = .100 (f1 -f), v and v1 Generally speaking, efficiency is high if e is high and v is low. the corresponding Noel Deerr coefficients, then However, in order to correctly appreciate in what way a high value of e or a low value of v measure efficiency, it is necessary to know how e and v vary as f varies. An interesting and original paper by R. M. Bechard1 gives valuable information on this Suppose we make the hypothesis that e is constant and topic. Analyzing statistical data in the South African sugar attempt to check this hypothesis with the help of Mr. Bechard's industry, Mr. Bechard concludes that v increases as f decreases figures. We have— and obtains a formula connecting v and f. One of the objects of this paper is to reconsider Mr. Bechard's statistical data and the formula he derives. It appeared to the writer that simpler results connecting e, v and f might be obtained by attempting to get the statistical relation between e and f rather than between v and f. The hypothesis was made that e was a constant, i.e., independent of f. This hypothesis was tested using Mr. Bechard's calcula- tions. It was found that although his final formula is not in complete agreement with the hypothesis, his preliminary results are. Reasons are given why greater weight is to be placed on the preliminary results than on the final formula, and it is con- cluded that the hypothesis that e is independent of f is well supported by Mr. Bechard's statistics. Taking e as a constant, the variation of v with f can then be calculated by the Noel Deerr formula. The calculations and arguments are given in Part 1 of this paper. Part 2 consists of some suggestions as to how the indices e and v may legitimately be used to measure efficiency. These suggestions are based on the theory that e is independent of fibre content. The average of v for the 13 mills over the period of 13 years is given by Mr. Bechard as 0.52727. Taking this as approxi- Part 3 is rather theoretical. In it the writer attempts to mately equal to v corresponding to the average fibre 0.1545, initiate a mathematical theory of costing in sugar recovery. we get:— If £a. is the cost of extracting juices per ton juices extracted, then a is a useful efficiency index. However, in comparing one mill with another the use of this index may lead to misleading If we compare this with Mr. Bechard's formula (1), neglecting information, for the reason that the cost per ton depends not the x3 term, we find the coefficients of x-0.04035 and -0.04279 only on efficiency of staff and plant, but also on the percentage agree sufficiently. However, the coefficients of x2, although extraction. There is the law of diminishing returns, and a mill almost equal in value, are different in sign. This discrepancy is with a higher percentage extraction may be expected to have a too serious for Mr. Bechard's formula to be considered, as well higher cost per ton of juices extracted. supporting the theory that e is constant.

Making some plausible hypotheses, an index of costing is The hypothesis that the same process applied to a cane will obtained which purports to be a basic index, i.e., one in which extract the same percentage of the juices in the cane is, however, the factor of extraction percentage is eliminated. This index, very attractive on theoretical grounds. It is thus worth while or some such index which may subsequently be obtained by to scrutinize Mr. Bechard's calculations more closely. further study of the process of juice extraction, is a more satis- factory index of the efficiency of staff and plant than the figure Mr. Bechard based his formula on the statistics obtained from giving the cost per ton of juices extracted. 13 mills over a period of 13 years. His main problem was to Owing to the law of diminishing returns, a stage may be eliminate the time trend. His method was as follows. He cal- reached in the development of a mill when further expenditure culated the average regression coefficients over the 13 years, to increase percentage extraction is economically unjustifiable. over the 5 years with the lowest fibre content, over the 5 years A figure is obtained which purports to give the maximum per- with the highest fibre content, and used a method of inter- centage extraction economically attainable in any given mill, polation. working a definite average quality cane. A figure is next ob- tained of the percentage of juices lost which may be economically He had the table :— recovered. My thanks are due to Mr. R. M. Bechard for the kindly manner in which he assisted me in many ways in the preparation of this paper. 31

His method of eliminating the time trend in obtaining the regression values seems to be entirely satisfactory and one can accept the regression values obtained.

and attempt to find b, c, d (as Mr. Bechard did) by interpola­ tion from the above table, as we cannot be sure that b, c, d are not affected by the time trend, we must be sure that our regres­ sion coefficients are independent of the time trend. Unfortunately the five years of lowest fibre all occur in the last seven of the 13 years used ; also the five years of highest fibre all occur in the first eight of these years. Hence, one may conclude that although the regression values are themselves satisfactory, they cannot be used to find b, c, d without the risk of error. We thus accept Mr. Bechard's table of regression values, but consider his formula not sufficiently accurate. Returning to the theory of constant extraction, bearing in mind the smallness of the coefficient of x3, we may take the average regression as given by this formula at the fibre level 0.1545 and v = 0.52727 as the coefficient of x in equation (2), i.e., 0.04035. The average value of v for the five years of lowest fibre content is 0.4957 and the fibre level is 0.1493. Carrying out the calculations by which equation (2) was obtained, the co­ efficient of x (and so the average regression coefficient) works out as — 0.03902. For the five years of highest fibre level f— 0.15H9, v —0.8544, and the regression coefficient works out as -0.04143. We have the following table :—

Column (.1) gives Mr. Bechard's weighted averages. Column (2) represents the regressions as calculated by the constant extrac­ tion hypothesis. Column (3) is an unweighted average from Mr. Bechard's figures. It will be seen that the differences between the weighted averages and the computed figures are in no single case as high as 10 per cent, of the values of the averages. Working with unweighted averages the differences are even less. Mr. Bechard gives as the standard error of the value —0.04397 as ±0.008456. The standard errors in other cases, obtained from fewer data, should not be less. Hence the computed values are well within the standard errors. We contend that Mr. Bechard's statistical data is good evidence supporting the theory that e is constant. PART 2. Of the two indices e and v, we may assume that e is inde­ pendent of fibre content, while v varies as the fibre content varies, e is a simple efficiency index. Disregarding the efficiency of plant and staff, e measures in particular the development of a mill. v is not a mill constant, v varies as f varies according to the formula where e is a mill constant. v diminishes as f increases. The average value of v may, however, be used to give useful information. In the process of extracting juices from the cane, as the quantity of juices accom­ panying unit fibre gets less and less, more and more effort (and so cost) is required to extract a given quantity of juices from the fibre. Suppose we have two mills, which have the same value of e (and so may be taken to be equally highly developed), and the one mill deals with a cane of a lower average fibre content, it then follows that this mill has a higher value of v. In conse­ quence it would cost less to extract additional juices in this mill than in the other. Hence, it would be more profitable to develop this mill further to extract additional juices. 32

If two mills equally developed (having the same e, say 0.92) were taken, then if mill (1) were crushing cane of 15 per cent, fibre and mill (2) cane of ]2.5 per cent, fibre, than v for mill (1) would be 0.4533 and v for mill (2) would be 0.5(500. If mill (2) were, however, further developed to give an extraction of 93.524 per cent., then its efficiency would become 0.4533 and the two mills would then be equally efficient. Now 93.524 was, of course, the extraction of mill (1) reduced to 12.5 per cent, fibre. Mills having the same efficiency v must have the same reduced ex­ traction and vice versa. These two measures were inseparably bound up by formula and definition. It did not follow, however, that the cost of attaining the same efficiency was the same. Part three of Prof. Stein's paper dealt with something com­ pletely new, c„, the maximum extraction economically possible. This index could be of the greatest value to the factories, but then it was absolutely necessary that, it should be taken up and used. The actual test of its validity would only be found in practical application. Should its value be established in this way it would bring other developments. An exact system of costing would be necessary and it might prove the desirability of an economist as part of the factory personnel. The following example was worked out by Mr. du Toit, who pointed out the figures of costs were purely arbitrary :- - Mill extraction 92.0 per cent. Cost of extracting I ton of juice = 3.7/-.

If e0 be the maximum extraction economically attainable we calculate e0 by the Noel Deerr equation and obtain

As a useful milling index it is suggested that we calculate the value of 100 (e0 - e). This gives the percentage of extraction that may be regarded as lost and which is economically recoverable. This index takes into account fibre content, costs and value of sugar, and is thus an overall index of economic development.

As a subsidiary overall index the value of — might be taken. The formula giving this is

References. Therefore 100 (e„-e) = 100 (0.9387-0.92) =1.87. 1 Bechard, R. M. (1941): "Natal Sugar Mill Results." Froc. S.A. Sugar Tech. This mill, therefore, offered economic possibilities for in­ Assoc., 15, 52. creasing its extraction. If e0 were equal to e, then extraction 2 Deerr, Noel (1933): "The Reduction of Sugar Factory Results to a Common was at its maximum, while the process was uneconomical if e Basis of Comparison." I.S.J., 35, 214. were greater than e0.

The value e0 did not only depend on the cost of extraction, but also on the cost of further recovery of the sugar, and this Mr. DU TOIT said that in the first part of his paper Prof. might be affected by increasing the extraction. Stein obtained the remarkable result that extraction was inde­ pendent of fibre. This result was derived indirectly and the It was perhaps unfortunate the Prof. Stein had used e0 for speaker would have preferred a direct proof. Secondly, this maximum economic extraction, as this was also the notation relationship was proved for a very limited range of fibre (14.93 used by Noel Deerr for reduced overall recovery. per cent, to 15.89 per cent.). Prof. Stein, however, saw no reason why extraction should not remain constant for a wider Mr. BECHARD said that what Prof. Stein called plausible range of fibre. hypotheses were not hypotheses at all but facts. It was due to these facts that mill manufacturers could guarantee that a par­ In the second part of his paper Prof. Stein accepted v, ticular unit would extract a certain percentage of the residual primary juice loss per unit fibre, as an efficiency index which juice in the material received. varied with fibre. Although not mentioned in his paper, Prof. Stein was of the opinion that reduced extraction was a figure The cost of running a mill plant depended primarily on both unnecessary and wrong. That, too, was the conclusion operation and maintenance costs, plus interest, depreciation, that Mr. Bechard came to in his paper "Natal Sugar Mill supervision and administrative costs. These costs were not Results"' presented to the Conference last year. The value of affected to any extent by juice concentration. primary juice loss as a basis of comparison had been realised for a long time and it was always included in our Annual Summary. Prof. Stein's paper gave the answer to such questions as Mr. du Toit maintained, however, that if primary juice loss whether further development was justified, which of the known were a useful index, then reduced extraction must be one as forms of development would be the best, and how this would well, as these two figures were derived in a similar way. affect the balance sheet. 33

A milling plant of six milling units obtained an extraction of tracted would increase from 78.5 to 82.0 per cent, and the cost 92.82 from a cane of 15.43 per cent, fibre. The coefficient of per ton of juice to unit loss v was therefore 0.3935. The cost of milling one ton of juice was £0.091 and the value of one ton of juice £1.06.

The value of juice would also decrease to £1.058 and the following balance sheet could be prepared :—

The limit of profitable extraction at equal efficiency would therefore be 96.97. The last four units of this particular plant averaged an ex­ traction of 25 per cent, of the residual juice. It was therefore possible to prepare the following table :-— These formula: could also be used to see how much cost would have to increase due to industrial legislation or increase cost of material before it would be necessary to curtail develop­ ment. This could be done by taking the following values :—

It would therefore be necessary to add another three units From this it followed that the maximum permissible cost was to attain the limit of development of the plant. The juice ex- £0.195. VARIETAL MILLING TESTS IN EAST AFRICA. A COMPARISON OF Co.281, Co.290, P.OJ.2878 AND UBA. By F. D. WHEELER.

With the advent of seedling canes to replace Uba, the suit­ The latter cane has proved the most troublesome in milling. ability of certain new canes for particular circumstances becomes This may partly be duo to the poor steaming qualities of the a leading question. The planter is particularly interested in his bagasse, causing a shortage of high-pressure steam, in addition returns of both sugar and cane per acre, taking into account to the unsuitable mill settings for this low fibre content cane. the ratooning value of each type of cane. The miller, with a Although the bagasse, from P.O.J.2878 has burned well in the factory balanced for the crushing of Uba cane, will have to furnaces, there has always been a shortage of fuel when crushing consider whether any alteration in the capacities of the various this seedling. In both these cases, P.O.J.2878 and Co.290, back departments will have to be made when crushing seedlings as pressure steam was very low, and steam necessary for the against Uba. boiling house had to be augmented with steam from the boilers during these trials. This applied to tests of both plant and This paper has been compiled from results of factory tests ratoons canes of these varieties. There was no difficulty in made throughout the 1940 season, and although in the results crushing Uba, and during the tests sufficient fuel was always obtained and summarised there are some cane value figures, such available, whilst back pressure steam was always sufficient for as the comparative values of the seedlings under examination manufacturing purposes. When crushing Co.281 surplus fuel as against Uba in plant and ratoon canes, and also the tons of was available with both plants and ratoons, and sufficient back cane per ton of sugar figures, this paper deals essentially with pressure for all the manufacturing departments in the factory, the factory results obtained when crushing different varieties whilst the milling of this cane, as already mentioned, was carried of cane. out with ease. The seedlings compard with Uba were P.OJ.2878, Co.281. and Co.290, and the tests, made fortnightly, have been carried From the results observed during these tests Co.281 was out on plant and first ratoon canes of all the varieties men­ superior to all the other canes for crushing and steam-producing tioned, whilst only a few tests at similar "periods of the season qualities, and in cane tonnage per hour has proved to be equal were possible on second ratoons. These latter tests were carried to P.O.J.2878 in both plants and first ratoons. out on consecutive days, and are therefore comparative for that It will be seen from the tables that mill extractions obtained period. The figures obtained have been included in the com­ on the plant canes varied respectively with the fibre contents parative valuation summary tables in this paper. of each cane with the exception of Co.281, which, although of a higher fibre content than P.O.J.2878, nevertheless had a From the purity of mixed juice obtained in the milling test, higher mill extraction. available sucrose (converted into 98.5° pol. sugar), has been calculated, taking as a basis for molasses purity 40°, an ap­ In the first ratoon trials Co.281 had the lowest mill extrac­ proximately average figure obtained throughout the season. tion, 0.70 per cent, lower than P.O.J.2878 and 0.44 per cent, This available sucrose figure was calculated by Prinsen Geerlig's lower than Co.290, although it must be noted that the fibre formula, and has been taken as an approximately comparative content was over 2 per cent, higher than either of these canes. figure for boiling house recovery. All canes having been dealt In all cases P.O.J.2878 had the highest sucrose per cent, cane with in the same manner, comparative results have been obtained, figure, followed by Co.281, Co.290 and Uba in this order. With although such results cannot include the variations in final the exception of the plant canes, Co.290 had the lowest purity molasses purities obtainable with the different varieties, nor the of mixed juice throughout, Uba being next. Co.290 first ratoon variations in purity increase due to clarification, and also a purity improved slightly on its plant cane purity, but fell below similar undetermined loss has been neglected, assuming this that of Uba in the second ratoons, whilst Co.281 maintained a figure to be the same for all canes. higher purity than P.O.J.2878 in both first and second ratoons. The purity of the Co.281 plant cane juice being only 0.1 degree Owing to alterations in the clarification equipment of the below the P.O.J.2878, the average of the three years' canes gives factory testing these canes, the increases in purities due to the lead to Co.281 in purity. clarification has not been obtainable, although a comparison in the ease or difficulty of clarification can be given by the ex­ Higher purities theoretically give a higher available sucrose perienced gained during the tests. figure, which, in turn, helps the boiling house recovery, less impurities having to be worked. Admittedly the nature of the The milling plant used consisted of a three-roller crusher, impurities also have an effect upon the boiling house recovery, but circumferentially grooved with deep hooked chevrons, and four the computation of the relative values in this respect is difficult mills, the last two in the train having each its own independent to assess in figures. engine. Mill settings were arranged for cane with a fibre content similar to Uba. The sugar manufactured in the factory is rated on a colour basis for customs purposes, the lighter the colour the higher In all tests cold maceration water was applied at approxi­ the duties. Under these circumstances the use of sulphur dioxide mately 150 per cent, fibre behind the third mill, crusher and in clarification is not possible, and juices can be dealt with by first mill juices going together to the mixed juice, second, third the use of lime, phosphoric acid and phosphate of soda only, and fourth mill juices being applied behind the crusher, first and variations in the quantity and the methods of applying and second mills respectively. heat. Actually all clarification carried out during the tests has been by the double-heating, double-liming process, it having The tests of the plant canes covered the period from June to been found that consistently better results have been obtained September ; the first ratoons from July to November, and the by this method in the factory making these tests. second ratoons during November only. Generally speaking, it has been found that the softer cane From the appended tables of milling and sugar production juices required a higher temperature for clarification than do it will be noticed that in all cases of plant and first ratoon tests, the harder canes, thus requiring the use of more steam. As has the tonnage per hour obtained with Uba was below that of the already been mentioned, the softer canes under discussion, seedlings, although fibre per hour in the plants of this cane was P.O.J.2878 and Co.290, produced insufficient steam for factory just a few decimal points higher than Co.281, 0.45 tons higher purposes, and the heat balance of a factory with no auxiliary than P.O.J.2878, and 15 per cent, higher than Co.290. fuel thus finds it more difficult to maiutain the heat balance First ratoon tonnages of fibre per hour were all similar with with extra steam necessary at the juice heaters. the exception of Co.281, which cane, having dried out more It has also been noticed, during these tests at any rate, that than the others towards the end of the tests—thus increasing the softer canes had a lower crusher juice brix than did Co.281, fibre per cent, cane—proved to contain a fibre easily crushed. although Uba juice was also lower than this seedling. This higher This feature of Co.281 has been noticed in all the tests carried brix of Co.281 juice throws less work upon the evaporators, out, and compares to its advantage with the fibre of both which again helps the heat balance of the factory, the softer P.O.J.2878 and Co.290. canes requiring more steam in this department also. 35

Under ordinary circumstances, i.e., clean cane cut during dry weather, the order of difficulty in clarifying the juices from the various canes was as follows, commencing with the most diffi­ cult: Co.290, P.O.J.2878, Uba, Co.281. During wet weather and with trashy cane the first three canes consistently gave trouble in clarification, and necessitated the use of quantities of phosphoric acid. Co.281, even in wet weather, seldom had adhering trash, and there was never any difficulty in clarifying this juice.

P.O.j.2878 generally had a lower Ps05 content in the juice, and although on occasions this proved sufficient for clarification purposes, additional phosphoric acid usually had to be added in order to obtain a well-clarified juice. Clean Co.290 produced a darker coloured juice than any of the other canes and needed the use of phosphoric acid and high temperatures to produce a clear juice. The Pa06 content of this juice was usually up to the recognised minimum standard necessary for good clarification, but with the addition of extra phosphoric acid for lightening the colour of the juice, more lime was necessary to clarify, thus increasing the chemical bill. As already stated, Co.281 gave no trouble at all in the clari­ fication department, and the chemical consumption was no more than that necessary for Uba. In sugar production per hour P.O.J.2878 leads all the other canes, followed respectively by Co.281, Co.290 and Uba. It will be noticed, however, that the comparative speeds of sugar pro­ duction per hour were not in the same ratio as the tons of cane per hour milled. For example, lite crushing rate of Uba plants at 50.30 tons per hour was increased by nearly 9 per cent, to 54.72 tons per hour when crushing P.O.J.2878, whilst the sugar production per hour increase was from 4.30 tons with Uba to 0.30 tons with P.O.J.2878, an increase of 46.5 per cent. It will also be noticed that the respective values of each seedling cane in sugar produced per hour as compared to Uba 100 per cent., was slightly higher in each case than the com­ parative values of sugar produced per 3,000 tons of cane of each respective cane variety. Sugar produced per 1,000 tons of cane increased with each ratoon in all cases except Co.290. In the latter variety first ratoons improved very slightly on the plant canes, but dropped below any other canes in second ratoons. From these figures it would appear that this variety does not ratoon well under our conditions, and, coupled with the factory results already noted, Co.290 does not compare at all favourably with either P.O.J.2878 or Co.281. In the case of P.O. J.2878 the additional necessary fuel, and also the greater difficulty in clarification, necessitating the use of more chemicals as compared to Co.281, more than offsets the increase in sugar content and sugar produced per hour. For this factory's purposes during these tests it would appear that the Co.281 was the most suitable for all our conditions. From the factory capacity point of view, the figures sum­ marised would appear to offer two alternatives when crushing Seedling canes as against Uba. Either the milling speed would have to be reduced to suit the capacity of the manufacturing departments, or else the latter would need to be increased in size, always providing the factory capacity was well balanced when crushing Uba. The amount of this increase is not so evident, as obviously the increase in purity is coupled with a decrease in impurity by a similar amount.

SUMMARY. Milling tests on the varieties Co.281, CQ„290, P.O.J.2878 and Uba were done. These tests were made fortnightly for plant cane and first ratoons and on consecutive days for second ratoons. Co.281. Under the conditions of this experiment Co.281 proved to be the most suitable cane. Not only was it superior to all other varieties for crushing and steam-raising qualities, but it also had a high brix and purity of mixed juice and gave no trouble 36 in clarification. It was second only to P.O.J.2878 in tons sugar Mr. Wheeler referred to clean cane. In this country clean made per hour. In spite of its high fibre it gave a good ex­ cane was a rarity and trash influenced extraction and also traction. eemod to have an effect on boiling house recovery. P.O.J.2878. The effect of fibre on extraction had been discussed by mathe­ While this variety gave the highest tons sugar made per hour, maticians. The factor of mixed supply was very important. In the best sucrose per cent, cane and a very good mill extraction, South Africa fibre varied continuously, not only in quantity as well as a high purity of mixed juice, the clarification was but also in quality, and under those conditions it was impossible rather poor. Although the bagasse burned well, there was always to set the mills to obtain the maximum theoretical extraction. a shortage of fuel when crushing this variety. Mr. WHEELER said that he used the Prinsen Gecrligs formula Co.290. in obtaining the available sucrose. He agreed that we knew Co.290 did not compare favourably with the other two new very little about the non-sucrose composition of juice and that varieties. It gave most trouble in milling. This may partly be this might have an effect on recovery ; but under the conditions due to the poor steaming qualities of its bagasse and to un­ of the experiment available sucrose had to be calculated to suitable mill settings for this low fibre cane. The purity of the serve as a basis for comparison. mixed juice was low and it gave most trouble in clarification. It did not ratoon well either. When cane was burned, as was general practice in Zambesi, the cane supply was clean. In wet weather it was, of course, Uba. impossible to burn the trash, and under those conditions great This variety was used as a basis of comparison. In plant ca.ne difficulties were experienced in clarification. The trash also and first ratoons a lower tonnage of cane per hour was obtained affected the extraction, and this again brought up the fibre question. than was the case with the seedlings. Less sugar was made per hour from Uba than from any other variety, except that in Mr. DODDS asked whether Mr. Wheeler could give the field second ratoons Co.290 gave a lower yield. The purity of mixed performance of Co.290. He had received annual reports from juice was rather low, but no difficulty in clarification was tncomati Estates which showed that Co.290 gave excellent experienced. results in the fields and there were no complaints about its manufacturing qualities. Their milling efficiency had improved since crushing this variety, although no structural improvement The VICE-PRESIDENT, in opening the paper for discussion, in plant was made. said that these experiments had been clone in a neighbouring country. Conditions were not quite the same as ours, but there Mr. WHEELER said that he had no actual figures as regards were many points of similarity. the field performance of Co.290. He pointed out, however, that at Incomati the bulk of the cane supply was Co.290 and their Mr. DYMOND said that Mr. Wheeler had used certain mills were consequently set for this low-fibred cane, with the theoretical formula;. In South Africa there had been considerable result that better results were obtained. doubt in the last few years as to the effect of a few degrees of purity. Mr. Dymond referred to an article by A. R. Ness in a Mr. RAULT said that he had carried out some experiments recent "International Sugar Journal." It was found in Colorado on the effect of trash on extraction. He found that trash did that two beet factories of comparable size, similar equipment carry away some sugar, but not as much as ordinary fibre. and operated under similar conditions gave different results. The result was therefore that the quantity of bagasse increased, The average results for a five-year period were as follows :— but the sucrose per cent, bagasse decreased as a result of trashy cane. It was not correct to say that trash had no sugar either. He had found traces of sugar even in quite dry trash. Mr. VIGER said it was interesting that in these tests all juices clarified easily by the simple defecation method. Mr. Wheeler used the fractional liming and double-heating process Ness investigated this further and found the non-sugars and recommended by J. G. Davies. Davies demonstrated that the the inorganic composition of them almost the same. The reason elimination of non-sugars, colloids, colloid nitrogen, pentosan why factory No. 2 had a greater loss in molasses was due to a and other substances extracted by ether were at a maximum. large amount of nitrogenous compounds which could not be A reduction in mud volume was also noticed. Mr. Viger said eliminated in the juice. he had tried this method with South African juices many a The results obtained by Mr. Wheeler in Portuguese East time. The results were, however, most disappointing. This was Africa, which is far away from South Africa and under different probably due to some peculiar soil and climatic conditions in conditions, might be very different to results in this country. this country. 37 VARIETAL MILLING RESULTS IN NATAL, 1941 By G. C. DYMOND.

1.--METHOD EMPLOYED. Esperanza, and 1.16 per cent, lower at Chakas Kraal, is prob­ In order to determine the practical effect of varietal fibre on ably due to regional peculiarities. This is, however, outside the sucrose extraction in Natal, an examination of available records, objects of this enquiry. relating to the 1941 season, was carried out. Sucrose per cent. Bagasse.—At every mill the sucrose in The method employed consisted of picking out from the Central bagasse is lower in that from Co.281 (despite its higher sucrose Board's daily records of cane testing, those cases when a single in cane) than in Co.MO. variety of cane had boon crushed, for periods comparable with the hourly sucrose and moisture in bagasse figures recorded by the mill laboratories. At ten factories, this procedure was found to be practicable. Two others ran a special series of tests and are included in the general average. The general average difference is 0.38 per cent., with a maxi­ The number of comparable tests of Co.281 and Co.290 at mum difference of 0.70 per cent, at Esperanza, and a minimum these 12 factories was 939 and 070 respectively. of 0.06 per cent, at Illovo. With regard to Uba, only 7 factories had adequate numbers The quantities of these two canes crushed at these two centres of tests, 398 in all. Of these, 344 cases occurred at 4 factories. were not remarkably different:— With P.O.J, varieties, there were only 57 cases, 50 of which occurred at 3 factories. Co.301 yielded 64 tests, of which 45 were found at a single centre. The causes for this great difference in the extraction value must therefore lie in the quality of the canes, or in some un­ The general simple average of figures from the 12 factories is known milling condition. (See moisture in bagasse.) as follows:— Central Board's Laboratory. Factory Laboratory Moisture per cent. Bagasse.—With the exception of Illovo, the moisture in bagasse is higher in Co.290 than in Co.281, the average difference being 1.51 per cent. Individual differences are:—

For detailed list of data see Appendix A.

2.—Co.281 AND Co.290. It is interesting to note that the two factories with the highest The number of cases and the general trend of results consti­ extraction show the greatest difference in moisture, while the tute an outstanding example of the effect of the varietal quality two lowest extraction mills give the lowest, and a reverse differ­ of fibre on sucrose extraction. Thus:— ence. Thus:—

Extraction Values.—From the data available, the sucrose extraction of these two canes, Co.281 and Co.290, can be cal­ culated for any assumed fibre content. The actual fibre content of the individual varieties as supplied to the factories is an unknown ; and therefore constitutes a difficult problem in any attempt to calculate the milling value of canes from the results of this investigation. The Experiment Station found the relative differences in Sucrose per cent. Cane.—With the exception of Amatikulu, fibre in canes grown on experimental plots to be :—- the approximate sucrose in cane is generally appreciably higher in Co.281 than in Co.290. The general average difference is 0.55 per cent. The reason, or reasons, why the sucrose in Co.290 is 0.54 per These figures were no doubt representative of the particular cent, higher than Co.281 at Amatikulu, 0.11 per cent, lower at conditions under which the canes were grown, but may not * Note.—The approximate sucrose figures are those found by the method of represent the yearly cane supply to the mills, which is affected differential Java Ratios. Simple averages have been used throughout. by climatic and regional conditions, physical cleanliness, age, 38 time between cutting and milling, and the changing nature of Co.281 does not take away the same amount of primary juice individual varieties. as does a unit of fibre in Co. 290. The formula used in calculating the following extraction Having established the actual difference in extraction values values of Co.281 and Co.290 will be found in Appendix B of between these two canes, the formula is applicable on the this paper. assumption that canes of 12 per cent, fibre will behave arith­ metically, and entrain the same relative proportion of sucrose. At a basic common fibre content of 15 per cent., the extrac­ tion of these two canes at the 12 mills is as follows:—

If, however, only the extraction of Co. 281 is known and Calculated on tins basis, the difference in extraction between applied to Co.290, the error in the calculated reduced extrac­ a 14 per cent, and a 16 per cent, fibre in Co.281 would be 0.92 tion of Co.290 would be 1.17 per cent, too high. per cent. Assuming, then, that the relative difference in ex­ traction between the two varieties of 1.51 per cent, at 15 per Steam.—From a number of tests conducted at Darnall, the cent, fibre would arithmetically differ at different fibre con­ steaming conditions of Co.290 bagasse is markedly inferior to tents, the question arises, at what level of fibre would Co.290 both Uba and Co.281. After 30 minutes milling the steam give the same extraction as Co.281 ? pressure invariably fell from 100 lbs. to 75 lbs. UBA, P.O.J. AND Co.301 COMPARISONS. Uba.—There are 7 factories at which a fair number of com­ parative tests with Co.281 and Co.290 were found. All these Uba cases, however, represent old ratoons and in some instances canes up to four and five years old. Note.—The calculated extraction at 15 per cent, fibre for Renishaw would appear to be the fairest comparison, as each mill will be found in Appendix A. apart from having 37 per cent, of Uba, this cane is still remark­ Noel Deerr Reduced Extraction.—In the first place the ex­ ably free from streak disease in this area. traction data at the mills demonstrates that a unit of fibre in The comparative data is as follows :—

It is interesting to note that on a basis of 15 per cent, fibre, SUMMARY AND CONCLUSIONS. Uba ranks first in extraction at one mill, second at five mills, and third at one. In the average of the seven factories it ranks 1. This investigation illustrates the fact that certain milling qualities of variety canes can be determined seasonally from second. data which can be made available at each factory. On the assumption that the figures at the Experiment Station are representative of the cane supply, the calculated extrac­ 2. The outstanding difference in milling qualities is that tions would then be as follows :— shown by the variety Co.290, which is markedly inferior in extraction value and in steam-raising qualities. 3. The principal result of this enquiry is the positive proof that the quality of fibre in two specific varieties, Co.281 and Co.290, is a highly significant factor in the milling of sugar canes. This factor has, up to now, been ignored in text-books and papers dealing with the effect of fibre on extraction. Interesting exceptions due to regional effects are : Uba cane grown on alluvial plots (Illovo), and Co.290 grown at high elevations (Illovo, Doornkop). 4. The results obtained from Uba consignments have been recorded, but it must not be overlooked that the quality of present-day Uba is not normal, and that its sucrose content is determined by the differential Java Ratio method. 5. With regard to the P.O.J., Co.301 and Uba results, they are erratic and no absolute conclusions can be drawn as in the case of Co.281 and Co.290. 6. The use of this method for evaluating the milling values of variety canes is impossible without an accurate knowledge of the unknown individual fibre percentages. Should, however, an average table be worked out from a large number of experi­ ments, any evaluation must bear the guarantee that individual consignments will contain the standard percentage of fibre—an obvious impossibility. 39

APPENDIX "A." VARIETAL CANE MILLING RESULTS, 1941. Co. 281. 40

APPENDIX "B."

APPENDIX "C."

OPTIMUM MONTH'S VARIETAL MILLING RESULTS FROM SEVEN FACTORIES DURING 1941.

Factories—Darnall, Felixton, Amatikulu, Empangeni, Gledhow, Renishaw, Chakas Kraal.

The following comment, which really forms a paper by itself, was sent in by Mr. R. M. BECHARD, but was only received after the Conference.

JUICE RETENTION VALUE OF VARIETIES OF CANE. As handled at Amatikulu during seasons 1940 and 1941.

Period Covered. The work was started in 1940. All hourly samples of bagasse used that year in the determination of sucrose and moisture between 21st May, and 21st December, and all those used in 1941 between 10th May, and 23rd November, were examined and classified as to their origin.

Method of Classification. After making the necessary allowance for overlap in the samples, which normally consist of bagasse produced from three to four consignments of cane, the samples were classified as follows:— All samples produced by a single variety, the general average of which is given for 1940 in Table I and for 1941 in Table VI. All samples containing not less than 25 per cent, of one con­ signment of one variety together with another single variety, the results of these are given in Tables II. and VII. All other combinations, these were not made use of.

Number of Samples and Nature of Average. In 1940, 4,283 samples were examined ; there were 744 samples of bagasse from single varieties, also 2,400 samples of straight mixtures of two single varieties, while 1,139 samples of more complex origin. Durin" 1941 the total number of samples was 3,961 ; of these 879 were of single varieties, 2,195 mixtures of two varieties, and 887 of more complex origin. On the assumption that each sample, consisting as it does of one hour's crushing, is of equivalent weights, the averages given in Tables I., II., VI. and VII. are strictly weighted averages. The results for 1940 and for 1941 are given separately as the methods used in the first year are identical to those in the second. 41

Calculation. Thus if we required the value S of a variety, for instance Uba, given:— 2.530 the value of the mixture of this variety with Co.281, 2.757 the value of the mixture of this variety with Co.290, 2.598 the value of Co.281 by itself, 2.940 the value of Co.290 by itself. Y and X, unknown proportion of Co.281 and of Co.290 in the It is evident from this and from an examination of the dis­ mixtures from Uba and these varieties, when the ratio of Y to tribution of samples that only the results obtained in the case X is known. of the varieties Co.281 and Co.290 can be made use of, as these are the only averages yielding significant differences of mean. A gauge to the analysis of the other varieties can be obtained however, from the results of bagasse produced by mixtures of varieties.

The ratio Y to X is eliminated and (3) resolves into a quad­ ratic where the substitutable root of S is the value of sucrose for the samples of the variety required. Proceeding in this manner we get the following values (those for Co.281 and Co.290 having been obtained in the direct way.)

It is again evident that the best and most reliable results are those obtained when the two main varieties Co.281 and Co.290 form one of the constituents of the mixture. It is not possible to translate these values into extraction values, as in order to do this certain totally unwarranted assump­ From this data it is desirable, if found possible, to extract tions would be necessary. the analyses of bagasse from varieties other than Co.281 and Co. 290. From this and other data at our disposal we can, however arrive at the quantity of juice lost per unit of fibre in each of We will discuss this possibility. the varieties. Frequency of Occurrence. This value, which is identical with the coefficient (v) of Noel Consider the results obtained from varieties Co.281 and Co.290, Deerr, will, by differentiation, represent the practical retention taken both singly and in their mixture with one another. We value of each to the different types of fibre. have good evidence, both from the table of. time distribution and from the analysis of variance of samples, that the figures Other Data Used. obtained do represent the analysis value of the bagasse from We have at our disposal for the same period the weighted these varieties. average sucrose content of each of the varieties as determined By means of the law of mixture, we can easily obtain the by the differential Java Ratio method. relative proportion in which the bagasse produced by each of By eliminating this differentiation, it is possible to arrive at these varieties was mixed in the 1,243 samples of bagasse ob­ the weighted average sucrose content of the primary juice de­ tained when these two were mixed. Let the proportion be Y/X, rived from each of the varieties. in which Y is the proportion of Co.281 bagasse and X that of Co. 290. We also have the average purity of the first expressed juice from each variety, by making the unimportant assumption that Again, let Yt be the unknown proportion of bagasse from the purity of residual juice will bear a constant ratio to that of Co.281 when this variety was mixed with another ; for instance the first expressed ; we deduce the solid concentration of each Uba. Let Xx be the corresponding value for variety Co.290. type of bagasse, from which in the usual manner the fibre In order to be able to get the values for the variety Uba, it content of the bagasse can be obtained (1). will be sufficient to know the ratio of Yt to Xj, quite irrespective of the intrinsic values of Y and of X . From the primary juice composition of each variety and the 1 t sucrose content of the bagasse produced, we also arrive at the If in a large number of occurrences, when there is no bias in primary juice content of the bagasse (2). the way in which varieties Co.281 and Co.290 are presented at the mill door for crushing, the ratio in which the bagasse from The ratio of these two quantities (2) and (1) represents the these varieties occur arc in a determinable ratio of Y to X. juice lost per unit of fibre (v), and the relative values of these the retention value of the fibre of each variety. There is every reason to believe that in an equally unbiassed series over a large number of occurrences these varieties will be We obtain the following values :— presented for crushing together with other varieties in fre­ quencies which will maintain the same ratio throughout; in other words, that the ratio of Y! to X! will be substantially the same as the ratio of Y to X. With this single assumption, which appears to be a highly reasonable one, we may proceed to obtain values of average analyses derived from varieties other than Co.281 and Co.290 when these varieties were constituents of mixtures having in the average a significant different value from the straight result obtained from a single variety. 42

If Co.281 is taken as standard (100) the different varieties ences were exceedingly important in the case of varieties Co.281 will have the following relative retention values. and Co.290 ; Co.290 retaining from 24 to 25 per cent, more juice for each unit of fibre than Co.281. Other varieties were inter­ mediate between these two extremes.

Mr. MOBERLY said the method followed by Mr. Dymond in obtaining these results was a very useful one. He thought the work should be extended and the actual extraction should be determined. Mr. Moberly said the author was not correct in stating that the quality of fibre hail been ignored by textbooks and papers dealing with the effect of fibre on extraction. Maxwell and Geerligs clearly recognized the effect of quality of fibre on extraction, while Noel Dcerr showed that pithy fibre and inter- node fibre gave different extractions. In a paper printed in 1938, Mr. Rault acknowledged the effect of quality of fibre on extraction, while Dr. Hedley in 1936 gave some figures on the mechanical quality of fibre. The fact that quality of fibre was an important factor in extraction was well recognized, but it was difficult to measure it quantitatively. Mr. DYMOND, in reply to a further question by Mr. Moberly, It is again evident that only varieties Co.281 and Co.290 said that care had been taken to avoid any after effect of a show differences in analysis which are significant ; there being previous consignment of cane. There was quite an adequate insufficient data from the other varieties. overlap in all cases. We proceed as for 1940, and use those figures obtained from He was well aware that many authors had recognized the analysis of mixtures of two varieties which are significant. importance of fibre quality, and their observations were based P.O.J, is now so scanty that no reliable figures are available. on actual experience. He thought, however, that it was the first time that a large series of figures showed the effect of fibre quality. The VICE-PRESIDENT said that he had often noticed the marked difference in the readiness with which certain varieties would take a stain when a section was examined under a micro­ scope. There was usually a difference in the intensity of the stain as well, and this was obviously due to differences in the chemical composition of the fibres in the various varieties. Prof. STEIN referred to Appendix C and said that in an experiment of that nature the timing was important. The dis­ Again proceeding as in 1940, by eliminating the new ratio of tribution of the samples should be more or less similar. As it Co.281 to Co.290, we obtain values for single varieties. P.O.J, is was, the percentage samples taken from Co.290 during the un­ now not represented. favourable month of June was higher than that for Co.281. The differences between the two varieties were, however, so big as to cover this oversight. One further point was that in the table of distribution, Ap­ pendix C, only part of the data used in Appendix A was given. For Co.290, for example, the distribution of only 340 samples out of a total of 670 was given. Apart from that this number did not seem representative of the whole, the sucrose per cent, bagasse varied from 3.35 to 3.4:8, whereas the average in Appendix A was as low as 3.27. Rather than to take a simple average on these figures it would have been better to take the figures mill by mill and month by month. Prof. Stein also critised the method of taking a standard fibre of 15 per cent. It would have been better if the actual fibre and actual corresponding extraction could have been obtained. Mr. DTJCHENNE pointed out that this paper threw some light on the difference in moisture per cent, bagasse between Co.2Sl and Co.290 and thus their sucrose retention values. It was described as the result of inherent differences in fibre. This physical quality might be attributed to their ratios of rind to pith fibre, which must be higher in Co.281. He pointed out that factory No. 3 crushed the highest proportion of Co.281 and had the lowest moisture per cent, bagasse. Mr. Duchenne gave the following figures for Umfolozi mill, season 1941 :—

SUMMARY. The samples of bagasse analysed at Amatikulu during the years 1940 and 1941 were classified as to their origin. During both seasons marked differences were observed in the juice- holding capacity of the different varieties of fibre. These differ- 43 A REVIEW OF FUEL ALCOHOL PRODUCTION AND DUNDER DISPOSAL.

By G. C. DYMOND.

Gold and petrol are exhaustible products of the earth's crust. price reduction, would balance the loss in revenue, the possi­ Alcohol, while the sun shines and plants grow, is inexhaustible. bilities of fuel alcohol developments from sugarcane surpluses So is charcoal, and it is interesting to note that in Sweden, would appear to be remote in South Africa. for the year ending 30th September, 1041, 8S),000 vehicles operated on producer gas, covering in eight months 312,500,000 SYSTEMS AND RAW MATERIALS. miles. Dealing with the sugar crop only, there are only two major The cost of landed petrol is about 4d. per gallon-—while it raw materials—molasses and the cane itself. lasts; the cost of alcohol from molasses is 7d. or less, and that from sugarcane and molasses about 1/- upwards, according to Molasses may be either the normally exhausted type or quantity and the price paid for cane. "high-test" as produced in Cuba. To-day geographical considerations-- the possession or access Surplus sugarcane can be utilised in a number of ways, for to oil wells with the security of a navy--determine the eco­ example:— nomics of a fuel programme. In South Africa no national policy 1. Crushing the cane entirely for alcohol production, as at has been formulated. Producer gas is on trial ; the cost of Ponta Nova, Brazil. pit-head coal is />/- per ton, from which the Fischer-Tropsch 2. Using the last mill juice for molasses dilution, as at Santa process could produce 40 gallons of petrol per ton of coal ; Thcresina, Pernambuco ; additional imbibition or macera­ and alcohol, it is said, is not an economic proposition. "Eco­ tion water can then be used with higher extractions. nomics" is the most mysterious word of our age. Great Britain would purchase large quantities of alcohol from us at 2/10 per 3. Kliminatirig the filter press department by fermenting the gallon, but our own Government will not consider further pro­ subsidor bottoms, as at Usina, St. Cruz, Campos, Brazil. duction, unless it can he manufactured on a white-labour policy 4. Enriching molasses and thereby simplifying the sugar at (id. per gallon. Mr. J as. Gray1 in his recent presidential manufacturing process. This is general practice. address to the South African Association for the Advancement of Science, pointed out some of the strange manifestations of Utilising molasses only for alcohol infers centralisation and economics. He said : "Within recent months the Maize Hoard consequent limitation of any large fuel programme ; whereas, purchased South African maize at 22/9 per 480 lbs. and sold using molasses with some of the initial products of the cane, the surplus, amounting to approximately five and a half million means production at the sugar mills with attendant benefits bags, in London, where the ruling price was round about 12/-." and lowering of costs (except that of the raw material) and a This procedure is technically termed stabilizing, and numerous production only limited by the capacity of the crushing plants. other instances could be quoted. The case of alcohol works in Associated with this system would be the utilisation of cane the reverse way. Although it is unlikely that the alcohol policy tops. Mechanical harvesting without topping is comparatively will change, a preview of alcohol potentialities is at least of simple, as demonstrated with windrowing machines in Louisiana. general interest. The tops would then either have to be cut off for separate The whole subject can primarily be divided into :— crushing at the mill, a difficult matter ; or the whole canes 1. Economic considerations. could be crushed. In Hawaii no increased difficulties were re­ corded in clarification with this procedure. This method would, 2. Systems and raw materials. however, be best suited when the ratio of quota sugar and 3. Methods of usage. alcohol production is high. Here it is of interest to record the claims made for Jeanite.2 By a special process of fermentation ECONOMIC CONSIDERATIONS. acetone and butyl alcohol are obtained from molasses. The While petrol is available and cheap, there appears little butyl alcohol is then polymerised into a mixture of substances likelihood of any serious development of alcohol production. identical with petrol. The cost is said to be 20 cents per gallon. The reason is primarily very simple. METHODS OF USAGE. The government collects about £5,870,000 in petrol taxes, so There are two systems of utilising alcohol as a fuel. The that the substitution of, say, 20 per cent, of the petrol con­ most general one in vogue is to make absolute alcohol (99.7 sumption by a tax-free fuel, would mean a loss in revenue of per cent.) and mix it with petrol in proportions up to 25 per £1,173,000. cent, (or 50 per cent, in the case of our local Union Spirit). The usual systems are the de Melle, Hiag, Drawinal using ethy- This substitution in terms of quantities would mean the pro­ lene-tri-chloride, and the Marillier process using glycerin. The duction of 35,000,000 gallons of alcohol, which in turn would . latter process is used extensively in the island of Reunion and mean the following requirements in raw materials :— is the basis of the most recent British patent in the production of absolute alcohol. The second method of alcohol usage as a fuel is the system in vogue in Mauritius and the Philippines. This I propose dealing with a little more fully, as there appears to be little in the literature on the subject. All fuel alcohol, or distilled carburant, in Mauritius is a rectified spirits of from 92° to 94° Gay-Lussac. This spirit is mixed with 5 per cent, of petrol. 0.5 per cent, pyridine for At 25 tons of cane per acre, the extra cane required would denaturing purposes, and 0.5 per cent, of castor oil. represent an acreage of 03,760, or 127 farms of 500 acres each. Added to this, there would, be additional employment and the The consumption of petrol in Mauritius in 1940 was 1,312,220 general benefits of a combined sugar and alcohol production, gallons, and that of carburant in 1939, 141,510 gallons. Com­ when sugar is restricted by a quota. The price to be paid for parative costs in drums are : petrol 2/0.4 per gallon and car­ cane would determine the possible payment of a tax, but burant 1/7.0 per gallon. Carburant bears a duty of 6Jd. per assuming a tax-free basis, the loss of £1,173,400 would necessi­ gallon. tate additional taxation in other directions. The unpopularity of such a move is obvious. So while petrol lasts, or until such The development of this fuel is largely due to the peculiarities time as it can be demonstrated that the benefits to sugar, i.e., of Mauritian sugar estates, which are largely self-contained. 44

Thus many estates produce their own fuel requirements for The methods of evaporation are, however, fraught with cane haulage, which include Plymouth type locomotives, a few difficulties. Mr. Alfred L. Webrc, the well-known evaporator tractors, numerous lorries, buses and a few cars. expert, says that the principal troubles are fouling of the tubes and the formation of hydrogen sulphide and carbon dioxide in Experiments carried out at Sans Souci in 1933 gave the the vapours, the former attacking the copper parts and the following comparative costs in fuel per ton-mile :— latter forming a gas film, which affects the heat transmission. At the U.S. Industrial Alcohol Company these problems have been largely overcome by using 20-gauge stainless steel tubes and pretreating the dunder. This is done by spraying the initial liquid, which has a temperature of about 205°F., into an atmosphere of steam at 100 lbs. pres.sure. This causes the heat reaction to take place outside, thereby forcing the libera­ tion of both the carbon dioxide and the hydrogen sulphide before entering the evaporator, and causing a large percentage of the calcium sulphate to be precipitated. This principle of pretrcatment can also be applied to distillery plants with bene­ ficial results, in reduction of scale. Lastly, the untried method on a large scale of composting cane trash with the dunder. In Hawaii, owing to their methods of grab-harvesting, it became imperative to perfect cane-cleaning devices at the mills. This has been accomplished, resulting in huge piles of accumu­ lated trash, which would readily absorb large quantities of dunder. CONCLUSION. This review of a big subject is necessarily brief. The by­ products of sugar have and are engaging the attention of many sugar countries. Sugar men are usually only sugar-minded, but should some day the principle of sugar-alcohol manufacture be accepted, it will, I believe, be the stepping-stone to other by­ products of this important crop, the sugarcane. My own opinions on the relative merits of absolute alcohol used with 75 per cent, to 80 per cent, of petrol, as compared References. with undehydrated alcohol, are that:— 1 Gray, Jas. (1042) : "The Scientist as a Citizen." S.A. Jour, of Sci., 1. 2 Owen, William L. (1041) : "Now a Real Motor Fuel from Molasses." Sugar 36, 1. The use of absolute alcohol needs no engine adjustments No. 11, 21. and in fact improves the performance. On the other hand it requires legislation and the blessing of a government policy. Mr. DYMOND said that since writing this paper he had received the plans of the most recent British patented method 2. The second method neatly slips past the petrol combines of dunder disposal. Briefly, it consisted of a special type of and, provided the government does not burden the pro­ evaporator for evaporating the dunder to a syrupy consistency. duct with excessive excise duties, it has been proved a This was then dried on special roller dryers, using steam or flue successful substitute. Given a fair start at a low price gases. The final product was crushed and bagged. and the right engines, there appears to be a good case for this fuel, when local demand warrants its production. In reply to a question by Dr. Rossouw, Mr. Dymond said that in the same way that Napoleon started the comparatively DUNDER DISPOSAL. uneconomic beet industry through his continental system, so there were many other crops besides sugarcane which could Associated with all alcohol production from sugarcane pro­ and had been used for alcohol. There were, for example, sweet ducts is the disposal of the dunder or distillery slop. The diffi­ and round potatoes, cassava, Jerusalem artichokes, maize, wheat, culties associated with this disposal can be shown by the enor­ etc. In every case, however, there must be a surplus, then mous number of methods, which have either been proposed, or alcohol constituted the social economic method of disposal. In are actually in use. no case, however, could any of them compete economically with The first and simplest are, of course, natural methods of sugarcane under a sugar-alcohol system of manufacture. disposal, such as pumping into the sea and rivers, or into the bottomless hole which occurs at Reunion in Mauritius. Allied There were forty countries which produced alcohol, either on with these methods are those of pumping on to waste lands or a "free" basis or by state monopoly. In Natal, alcohol had large evaporating dams. railage protection, a 5d. protective duty as against petrol, and 3d. per gallon rebate when mixed with petrol for fuel purposes. A method largely used in Mauritius is to lime the dunder In reply to Dr. Fisher, Mr. Dymond stated that very little and dispose of it continuously in the irrigation water. At factory molasses was used for stock feeding. This was principally Medine, Mauritius, the dunder is heavily limed in open concrete due to distribution and transport difficulties. Owing to its high subsiders. After settling the supernatant liquid is run into the sulphur content, this molasses should be fed in small quantities irrigation ditches and the bottoms used for the type of compost until stock became used to it. The refinery had tried to known as sacharogene. In industrial densely populated areas develop this business, but Mr. Dymond said he was unaware natural methods of disposal are naturally prohibited. with what success. In Brazil, since 1884, various commissions have attempted In reply to other questions, Mr. Dymond stated that Mauritius to solve the problem. The result was a flood of numerous and had now standardized their alcohol fuel on a basis of 90 per in. many cases utterly impractical patents. The two most cent, rectified spirits and 10 per cent, of petrol as denaturant. practical methods which I saw in operation, were those used The alcohol had to be 94° G.L. at I5°C. with not more than at Santa Theresina and Usina Catonde, both in Pernambuco. 15 milligrams of acid calculated as acetic acid. At the former the Porion furnace, which burns the dunder to ash, was in successful operation. By this method all the organic The British Improved Motor Spirit, Ltd., had recently matter is destroyed. patented a fuel which should be of interest in this country. It consisted of 70 per cent, methylated spirits (95 per cent.), 3 per At Catcnde, the dunder was first evaporated to 60° brix, cent, benzol, and the balance a petrol extract obtained by a mixed with sun-dried screened bagasse, superphosphates added, narrow cut fraction from petroleum spirit. and the whole dried in an ordinary sugar drier. This product contained 9 per cent, of water and was used as a fertilizer with Mr. P.LATT said that only part of the refinery molasses was excellent results. sold as stock feed. The rest went to the distillery. 45 MANUFACTURE OF GLYCERIN FROM SUGAR BY FERMENTATION.

By J. O. DUCHENNE.

Glycerin has been known to be present amongst the products of ordinary fermentation since Pasteur's time. He established in 1857 his balance of substances formed to sugar consumed and found 3.6 grams of glycerin from 100 grams sugar fer­ mented by his yeast. It was not until 1917 that chemists, studying the mechanism of fermentation, found a method of producing glycerin in large amounts.

Neuberg and Farber in 19.17 found that in presence of alkalis the ethyl alcohol yield decreased, whilst glycerol, acetaldehyde, and acetic acid increased. Then Neuberg and Keinfurth, and also Connstein and .Lüdecke, found that in presence of sodium LARGE-SCALE PRODUCTION OF GLYCEROL AND sulphite, the alcohol and carbon dioxide diminished in favour COMMERCIAL PROCESSES USED. of acetaldehyde and glycerol. These two types of fermentation I.awrie2 describes how Connstein and.Liidecke adapted the became known as Neuberg's third form and second form re­ sulphite process to large-scale production in Germany during spectively, as distinct from the normal or first form. the Great War, 1,000 tons of dynamite grade glycerin being The classical equation due to Gay-Lussac, made per month, lie fined beet sugar in 10 per cent, solutions was fermented with 10 per cent, yeast in large vals of 80,000 C6H12O6 = 222H5OH + 2C02, gallons, with addition of sodium sulphite crystals up to 00 per only shows the final products of fermentation as being alcohol cent, of the sugar present. After a few days fermentation, and carbon dioxide. The intermediate reactions involved have the filtered wash contained 2 to 3 per cent, glycerin, 1 to 2 per been studied extensively by Harden1 and his co-workers, and cent, alcohol, 1 per cent, acetaldehyde, salts, acetic acid and by Neuberg and others. It is now proved that pyruvic acid is other impurities. After distillation of the wash, the residue was concentrated to a syrup containing 14 to 18 per cent, glycerol. formed, together with hydrogen, from some substance, C3H603, derived from glucose. The pyruvic acid is then decomposed by Owing to difficulties in distilling this impure syrup, a purifica­ the yeast enzyme carboxylase into acetaldehyde and carbon tion of the wash was resorted to. This consisted of :— dioxide. The acetaldehyde is reduced by hydrogen from the (1) Filtration and recovery of yeast. first step of transformations, to form ethyl alcohol:— (2) Distillation of alcohol and acetaldehyde. (3) Precipitation of sulphite by calcium chloride and milk of lime, and filtration. (4) Acidification, followed by excess soda to remove lime and iron salts. (5) Re-acidification and concentration to syrup. The losses were around 40 per cent, of the glycerol in the wash. The crude syrup contained 28 to 33 per cent, of glycerin, which was distilled in a Jobbins type still. It was necessary to re­ distil the glycerol in order to obtain dynamite grade glycerol. This contained up to 4 per cent, trimethylene glycol, the sweet water fractions containing 25 per cent. The process of distilla­ tion was carried out in one central factory receiving dunder from 63 fermenting houses. The nett yield of glycerol was around 10 per cent.

THE AMERICAN SODIUM CARBONATE PROCESS. In 1917 Eoff and his co-workers discovered that fermentation in presence of alkalis, such as sodium carbonate, bicarbonate, hydrate, etc., greatly increased glycerol formation. His results, later embodied in his patent, show that 20 to 25 per cent, glycerol was formed apart from alcohol, acetic acid and some acetone, on 100 sugar fermented. The amount of glycerol formed was proportional to the sodium carbonate added. His wash contained 17.5 to 20 grams per cent, sugars, to which he added up to 5 per cent, sodium carbonate in powdered form. The yeast he acclimated was Saccharomyces ellipsoidcus, var. Stcin- burg No. 657, used first in 1 per cent, sodium carbonate culture medium. The soda was added in five doses in such a way as to stop "short of that amount which will inhibit further fer­ mentation." In this way Eoff obtained a wash, after five days fermentation, containing 3.1 per cent, glycerol, 6.75 per cent, alcohol by volume, 3.6 grams alkali as sodium carbonate, and residual sugar 0.86 per cent. On a 425 gallon molasses wash, of 21.2° Bailing containing 16.85 per cent, sugars, he recovered about 100 lbs. of crude glycerin from the purified dunder. This syrup, containing about 33 per cent, glycerol, distilled in a Job- bins-Van Ruymbecke type of still, eventually gave 50 lbs. dynamite glycerol, a nett yield of half a pound per gallon of molasses. Double distillation gave a glycerin nitrating normally. A large plant was put up in Illinois to work the process.3 46

The Cocking and Lilly process was developed in England in F.XIII.—The wash analysed as total S02 = 8.34 grams per 1919. Its object was to obtain glycerol in almost theoretical litre and free S02 = 1.36 grams per litre, leaving 6.48 as yields by using a mixture of acid and normal sodium sulphite, combined to acetaldehyde. As this latter is produced in a in such proportions as to be neutral and relatively non-anti­ ratio of 1 to 2 glycerol, the calculated glycerol from aldehyde septic.8. The advantage was that the acetaldehyde was fixed was 6.48 x 0.69 = 4.S3 grams acetaldehyde = 9.66 gly­ to the bisulphite at an earlier stage previous to the formation cerol. Actual distillation gave alcohol + acetaldehyde = of bisulphite by the normal sulphite reacting with carbon di­ 52.88 grams = 30.7 per cent, sugar. The dunder group oxide. The time of fermentation was shortened and yields up gave glycerol distilled = 8.07 grams = 4.7 per cent. to 43 per cent, glycerol, 21 per cent, aldehyde and 8 per cent, alcohol were obtained on inverted raw sugars; molasses gave It will be noted that the yields in glycerol decrease when 35.5 per cent, yield on sugars fermented. As in the sulphite less sulphite is added, whilst alcohol increases. Also, that the process, the yields are directly proportional to the amount of combined bisulphite is a measure of the glycerol formed. The salts added. reason why calcium sulphite is preferred is that its bisulphite combines with twice as much aldehyde as sodium bisulphite. Recovery is facilitated as solid sulphite is obtained after fer­ menting and distilling of the %vash previously neutralized with lime, thus ensuring enough for re-use. The salt is easily sulphited to desired ratios of the acid salt in the slurry, with existing apparatus in the sugar factory. A large amount could be separated during juice clarification if necessary. On extracting Other patented processes are quoted by Lawrie2, whilst dunder syrup (with alcohol produced during the previous step) Owen, Levy and Owen4 describe some of the fermentation pio- a precipitate of gums, salts, etc., is obtained amounting to 55 cesses and the methods of recovery. These last three writers per cent, of the weight of the syrup. Distilling off the alcohol are of the opinion that:—"Glycerin produced by fermentation leaves a crude glycerin containing 12 to 30 per cent, glycerol, offers by far the greatest promise commercially," and that depending on the yields obtained. The subsequent stage is "there is every indication that fermentation glycerol would soon the most important, as the method of obtaining pure glycerol become a potent factor in glycerin production." must be chosen to give the highest yields and the least decom­ position products, especially in such a biochemical process. In South Africa, glycerin production from molasses on the industrial scale has started.3 The process is an alkaline fer­ Laboratory distillations in a pilot plant during 1940-1941 mentation, followed by distillation, purification, concentraticn have shown that the still has to be carefully designed for the and extraction by a solvent in which glycerin is soluble and type of crude used. It is preferable to purify the crude to the impurities are precipitated. The extract is freed of the solvent, utmost before distillation, to avoid polyglycerols and trimethy- which is recovered for re-use. lene glycol, as well as fatty acids and esters formation at the high temperatures used. The analysis of a sample of once- The process which I developed at Umfolozi when studying distilled glycerin by the above process is included for com­ ethyl alcohol production in 1938 consists of fermentation in parison in the table below, showing the usual composition of presence of calcium sulphite in the powdered form ; later, a commercial samples:— mixture of soluble calcium bisulphite and sulphite was used, the fermentation being kept in the acid range.6 The mixture is added as a slurry with a sulphite to bisulphite ratio of from 15 to 1 to 5 to 1, and in gradually increasing amounts as fer­ mentation proceeds. It is then added in diminishing quantities and the mixture allowed to ferment to the end. Slow stirring of the mixture is necessary. An example of the calcium sulphite fermentation is as fol­ lows : 11 gallons of diluted syrup from old stock containing 139 grams per litre of total sugars and 21° brix were seeded with yeast (S. ellipsoideus acclimated to sulphites) from five consecutive fermentations. The temperature was kept at 35°C. Calcium sulphite slurry, made by sulphiting milk of lime, was added at intervals over a period of 90 hours, and the mixture agitated by hand stirring every 20 minutes. After five days (120 hours) the fermentation was taken as complete. The wash contained a trace of reducing sugars and was of 4.5 pH, with A sugar factory producing 8,000 tons of molasses a year a total sulphite of 13.0 gr. SO., per litre. The wash was allowed could manufacture 6 tons of glycerol and 1,000 gallons of alcohol to settle, the yeast was recovered and also the calcium sulphite, per day, valued at £650. If only alcohol were produced 3,200 of which 16 lbs. 5 ozs. was weighed. It was then neutralized gallons per day, valued at £160. The problem of dunder dis­ with milk of lime (1,200 ml. at 16° brix) containing 2 lbs. of posal would not arise, as the non-glycerol organic matter is a lime. The slurry was again settled and removed. A one-litre solid (containing all the "ash" from the molasses) which would sample gave on distillation 13.6 grams of alcohol and acetalde­ be disposed of with the filter cake. hyde. The dunder, on concentration and extraction with abso­ lute alcohol, gave 154.4 grams of crude glycerin. On distillation in the superheated steam still, 21.2 grams of pure glycerin were collected. The crude syrup contained 13.7 per cent, glycerol. The yields on the basis of sugars present at the start were there­ fore : Alcohol 9.8 per cent., glycerol 15.3 per cent. The rest of the dunder on evaporation gave over 21 lbs. of syrup for ex­ traction. Another test, using the same yeasts and the same calcium sulphite slurry, gave with a wash containing 16.9 per cent, total sugars, alcohol = 13.4 per cent., glycerol = 10.1 per cent, as pure glycerin (distilled).

After seven months continuous fermentations the following Mr. DYMOND asked whether perfectly dry and pulverized results were observed using calcium sulphite and bisulphite dunder as produced by recent plants in Britain using film roller mixtures as aldehyde acceptor :— driers, would not facilitate the distillation of the glycerin ? F.XII, 26-6-40.—1420 ml. of wash: neutralized 1000 ml. and, after distillation, 18 grams calcium sulphite were Mr. DUCHENNE replied that he was at present investigating filtered. Dunder concentrated and distilled : alcohol and the problem. It seemed to him very promising, as the crude acetaldehyde 51.76 grams =20 per cent, yield; glycerol syrup had to be brought nearly to absolute dryness before dis­ 13.13 grams = 10 per cent, yield. tillation of the glycerin. 4:7

Dr. HEDLEY, replying to a question by Mr. Hendry, said • Dr. Hedley did not agree with Mr. Dymond that it would be that the samples of both sulphitation and carbonatation South advisable to dry the dunder before distillation. It simply meant African exhausted molasses sent to America were found to be additional expenses of drying and then wetting it again during distillation. perfectly suitable for acetone and butyl alcohol manufacture. The proportion of these two products could be varied. Mr. DUCHENNE, in reply to a question by Mr. Kault, said that to get the glycerin colourless the acids were first neutralised, He thought Mr. Duchenne had tackled a very difficult problem. the colour then absorbed and the glycerin redistilled. During the last war the Germans made glycerin from pure beet sugar and only obtained a yield of 10 per cent, and about 45 He agreed with Dr. Hedley that it was an arduous task to per cent, of the glycerin could not be recovered. It must be get a good yield of pure glycerin. It was, however, possible to even more difficult to produce glycerin commercially from an get a yield of 16 to 18 per cent, sugars and of 97 per cent, impure product such as molasses. purity. TWO WAR-TIME MEASURES. By C. MARTINDALE, M.Sc, A.M.I.Cert.E.

Owing to the difficulty of maintaining supplies of essential 2. -REVIVIFYING "HYFLO SUPER-CEL." raw materials, a search was made to minimise imports, and in For this purpose the cake from the Vallez filters is washed two instances we have met with very encouraging results. in the normal way and the sludge from the filters is passed through the sedimentation tanks where the mud settles. The 1.—ANIMAL CHAR. supernatant liquid is drawn off at the week-end and the mud Our supplies of this material were imported and arrived at spread out and air-dried. The dry substance, which is quite Bulawayo at a cost of i'.'ifl per ton. Our average yearly con­ friable, is fed into a continuous furnace, where the organic sumption is approximately 30 tons. After some research we matter is partially burnt off. in this manner we recover some have now achieved a satisfactory and easy means of producing (SO per cent, of our "filter-col," and more efficient sedimentation this from degreased bone grit ground and graded to our speci­ would considcrahly increase this proportion. The "filter-eel" fication by the local Cold Storage Commission. This is done by thus revivified lias a higher filtering rate than the original isolating four of the cast-iron retort pipes in our char revivi­ substance. This may be due in part to the addition of spongy fying furnace and passing the bone grit through. carbonaceous matter due to charring the organic matter in the A rough diagrammatical section of the arrangement shows used "filter-eel," and in part to the elimination of the finer the modification necessary in a conventional pipe kiln revivifier. amorphous-like particles in the sedimentation process. We have The hopper through which the grit is fed is provided with a found that the actual ignition of the organic impurities is not baffle and gas vent pipes, and the grit passes through the necessary, although we did attempt this in our original experi­ retorts and cooler pipes to the rocker valve gear and thence mental furnace. to a small bin built into the corner of the main char bin under the furnace. The partially charred grit is returned to the feed Rough diagrammatical sketches of the furnace show the simple hopper and passed through again until its physical appearance working principle. The apparatus consists essentially of a -.{-inch and pH are satisfactory. Two or three passages are required, mild steel plate solidly stiffened to minimise buckling by weld­ depending upon the temperature control of the furnace. Rods ing 12-11). rails longitudinally and transversely to the under of f-inch round iron with kinks every three feet or so are sus­ side. This plate is then secured to two 10-inch by r>-inch K.S. pended from chains above the hopper and pass through the four joists. Two leys 4i> chains connected with slats of 1-inch angle retorts and cooler pipes to within 6 inches of the rocker. It alternating with slats of loosely hanging light, trek chain convey was thought that there might be a tendency for the grit to the material over the J-inch plate at the rate of 1 foot per choke owing to tar liberation, but in actual practice we have minute. The counter-flow principle is used so that the "filter- seldom had cause to use the agitation that can readily be eel" reaches the hottest part of the plate last. The plate is obtained by the use of these suspended bars. maintained at a very low red heat just above the furnace and partial ignition of the organic matter takes place at this point. No attempt is made to recover the gases and tar which issue The hot material then passes through a -J-inch mesh screen to from the hopper vent pipes. This could be readily done with a storage bin, when it is drawn cool. Considerable quantities suitable scrubbers. Slight alterations are necessary at the valve of dust are evolved due to minor explosions which take place rocker to prevent admixture of partially burnt bone grit issuing where the organic matter ignites. The whole apparatus is, from the fourth tube of the isolated bank with normal revivified therefore, closed and so constructed that there is a gentle draught char emerging from the fifth tube of the row. This is a simple through the -J-inch mesh screen at the discharge end to the mechanical alteration that can be made in several ways. Tubes flue at the back end of the furnace. The cost in fuel is almost at the back end of the furnace, i.e., furthest from the actual negligible, and two natives on each shift easily handle the fire, arc more readily isolated than any others, and these tubes whole process from beginning to end. A J-h.p. motor suitably have been selected by us, although the temperature at this geared provides the motive power for the conveyor. point is lower than elsewhere in the furnace. The bone char as produced above is stored until a char Rhodesian Sugar Refinery, filter has been "sweetened off." It is then put on top of the Rhodesia. exhausted char immediately before washing off. In this way the new char gets eight hours washing with hot water before being put into use. It then passes in the normal way into the revivifying furnace together with the old char. The loss in weight from bone grit to finished char is approximately 25 per cent. As stated, above four tubes have been isolated in a standard 80-tube kiln, and this gives us more than enough char for normal make up, so that if we use the apparatus continuously we shall quickly accumulate new stocks of char. We estimate the cost to be £li per ton.

Mr. HENDRY mentioned that during the last war some animal charcoal was made in Madras by heating bones in earthen­ ware pots out of contact with air. About twenty years ago the amount of charcoal required to decolorize the sugar in a refinery was about equal to the sugar itself. To-day very much less was used. This was due to better quality sugars being sent to the refineries and to the use in certain overseas refineries of the carbonatation process. This process consisted of the fractional addition of about 0.4 per cent, cal­ cium oxide on the melt and the passing through of washed and cooled flue gases. The syrup is brought to about pH 9 and then filtered and passed over the charcoal. Animal char­ coal worked better on an alkaline solution, in contrast to most decolorizing carbons, which operated best in slightly acid solu­ tions. 49

According to Lyle, in his book "Technology for Sugar Refinery better part of a week. Even char in circulation was washed Workers," there was a considerable improvement in the quality from 16 to 30 hours. of sugar produced by the charcoal carbonatation process. Less than half the quantity of charcoal was used. This more than Mr. Johnstone pointed out that even at the C. & H. Refinery compensated the slight destruction of invert sugar. in California, where the super-eel was produced and was conse­ quently much cheaper than in Rhodesia, they found it ad­ vantageous to revivify all the super-eel they used. They were, Mr. Hendry said he had tried to apply this process to an of course, doing it on a much bigger scale. ordinary sugar mill, but it was not a success as the carbonate formation was too slow on account of the low carbon dioxide He thought it rather unusual that a faster rate of filtration content of the flue gases. should be obtained from revivified hyflo. Their experience at the refinery was that working with paper pulp a new charge would not give a clear filtrate. As the pulp became contaminated, Mr. JOHNSTONK remarked that the washing period de­ however, a clear filtrate was obtained and old pulp was there* scribed by Mr. Martindale seemed very short. At the South fore preferred, but the rate of filtration was slower than with African Refinery washing of new char was carried out for the fresh filter medium. 50 COMPARISON OF JACKSON AND GSLLIS AND DIRECT POLARIZATIONS.

By G. S. MOBERLY.

I have been requested to prepare a report on the differences between direct polarization and Jackson and Gillis polarization of mixed juice. At the outset i found the available data to be very limited. When carrying out Jackson and Gillis tests it had unfortunately not been a general practice to do a simul­ taneous direct -polarization. My own available figures were very sketchy up to September of last season. I, therefore, circu­ lated an appeal to all chief chemists asking for any relevant figures in their possession. The response was very disappointing, Even during this very limited period of the crop there is no not because of any reluctance to co-operate, but because very agreement in the differences at different factories, positive and few chemists had any information to give. What was available negative differences occurring with equal frequency. was in a great variety of forms, some four-hourly, some daily some weekly and some monthly, and all covering different The question arises as to what are the factors governing these periods of time. However, from the odd mass of assorted data differences, and one naturally supposes that they depend on I have been able to extract a little information. the quality of the juice. The following table shows the annual average difference for The differences shown in the first table are here reproduced, certain factories in recent years, together with the standard together with the purity and reducing sugar ratio of the mixed deviation from the mean of weekly averages (+ indicates juice in each case. Jackson and Gillis polarization higher than direct).

The figures for No. 5 are not strictly comparable as they are for the Herzfeld method, except for one month of 1941, when the Jackson and Gillis method was used.

In the above table the annual differences for the first three factories range from —0.026 to +0.029.

From the very few figures here available it is evident that With the very limited information in the above tables the no average difference applies to any one factory for every year or purity of the mixed juice seems to bear no relationship to the to every factory for any one year. There is a similarity between differences. If we ignore No. 5, where the Herzfeld method the differences for 1940 and 1941, but these are contradicted was used, we can say that the lowest reported reducing sugar by the figures of other years. ratio gave the highest negative difference, and the highest reducing sugar ratio gave the highest positive difference, but At this stage it might be advantageous to consider the value between these extremes there is no sort of correlation. of any difference between the polarizations. With sucrose at £6 per ton each 0.1 difference of polarization is worth about At factory No. 4, where the primary and secondary juices lid. per ton of sucrose in cane, or about £46 per 1,000 tons of are analysed separately, the differences have been recorded for sucrose purchased, or 0.075 per cent, of the price of cane. 254 consecutive four-hourly periods during the latter months of 1941. The average difference in the case of primary juice was The figures for standard deviation from the mean have been + 0.016 and for secondary juice +0.018. given to show the probable degree of accuracy with which annual differences could be applied to individual weeks. A There appears to be a slight and more or less regular change variation equal to twice the S.D.M. might be expected to occur in the sign of the differences throughout the season. For the about once in every 20 weeks, i.e., once or twice a season. factories and years shown in the first table (excluding No. 5) Thus with a S.D.M. of, say, 0.025, the application of an annual we find the following average differences for the various correction to every week is liable to give rise to an error of months:— 0.05 in sucrose per cent, mixed juice in one or two weeks of the season, equivalent to about Jd. per ton of cane, to the advantage or disadvantage of growers delivering more or less than the pro rata quantity of cane during such weeks. An error three times as great as the S.D.M. is liable to occur once every 100 weeks or once every three years.

Fuller figures based on four-hourly tests are available for certain factories, during the months of September, October and November of the 1941-42 season:— 51

The available figures for May and December are too incom­ just been started at that particular factory. He had found, plete to allow of comparable averages, but in both months where staffs were experienced in the use of the method, results there is a marked positive difference. It would seem, therefore, were in very good agreement. that the difference is governed mainly by the degree of maturity or over-maturity of the cane, and not by the other factors The fact that the monthly average differences were small did which affect the purity of the juice. not mean that big variations did not exist. These figures were the averages of a number of years containing both positive In view of all the above, it would hardly seem to be prac­ and negative differences which to a certain extent cancelled ticable to abandon the Jackson and Gillis test and in place out and gave small average differences. thereof to apply a correction to the direct polarization, unless this correction were determined frequently at each factory. As Mr. DUCHENNE gave the following table of differences in a possible method of procedure, I would suggest that the sucrose per cent, mixed juice between the direct, polarization Jackson and Gillis test might be carried out once a day at each method and the baryta method, which was used at Umfolozi :— factory, and that the averages of all the differences for each week might be applied to the average direct polarization for the week. This would, however, cause some inconvenience in cane testing, as it would be necessary to work with a weekly Java Ratio at every factory, instead of with a daily Java Ratio as is now done at many factories.

I would also like to express the view that whereas the present shortage of laboratory staff may justify the adoption of some such expedient as a purely war-time emergency measure, the Jackson and Gillis test should not be abandoned as the standard method of polarization. My experience has convinced me that the more difficult Jackson and Gillis method is carried out with greater care and precision than the direct polarization, and in the case of the latter there is no other figure available with which to check it ami assess its probable accuracy. The baryta method therefore generally gave a slightly higher sucrose per cent, mixed juice than the direct polarization.

Mr. HENDltY said that they tried the Jackson and Gillis Mr. DU TOIT said that this paper had been fully discussed method for one month at his factory, but at the time they had at a meeting of the Chemical Control Committee. It was felt a new cane testing staff and the results were so inaccurate that that the differences were so irregular that it would be pre­ they decided to go back to the Herzfeld method. ferable to accept the value obtained from a direct polarization rather than to apply a doubtful correction factor. The hope He pointed out that the monthly average differences (in was, however, expressed that it would still be possible to carry sucrose per cent, mixed juice) between the direct and Jackson on with the Jackson and Gillis method under present conditions, and Gillis method were so small that there did not seem any as the correctness of this method was not questioned. necessity to do the Jackson and Gillis method. Mr. du Toit read a letter from Dr. Zerban to Mr. Dodds, in Mr. MOBERLY suggested that the difficulty in doing the which the necessity of adhering to a method, once it had been Jackson and Gillis test was probably due to the fact that it had adopted, was stressed. 52 OBSERVATIONS ON THE FERTILIZER VALUE AND WAX CONTENT OF FILTER CAKE. CONTRIBUTION FROM THE CHEMICAL DEPARTMENT, S.A.S.A. EXPERIMENT STATION, MOUNT EDGECOMBE.

The necessity for having more information about filter cakes in this country has been Celt for a long time. The reasons for this investigation become more apparent with the introduction of Oliver Campbell filters, the acute fertilizer shortage in the Union, and the possibilities of putting the cane wax contained in the filter cake to some industrial use, as was done in the last war. Until recent years only two main types of filter cakes were found in the industry, namely, carbonatation cake from the Natal Estates factory, and sulphitation cake from all other factories. As is well known, the carbonatation filter cake is higher in lime, but lower in phosphates and other ingredients than the sulphitation cakes, which themselves vary considerably in chemical composition. The Oliver filter has now introduced further variations in the composition of cakes from the sulphita­ tion factories, owing, of Course, to the dilution with bagacillo. Approximately half of the factories in Natal and Zululand have now installed the Oliver filters, and very little information is available on the comparative qualities of cakes from the old and From the above table it can be seen that the total nitrogen new processes. ranges in the sulphitation factories from 1.17 per cent, to 0.63 per cent., with an average of 0.81 per cent. This figure com­ Regarding the fertilizer value of filter cakes, the present time pares very favourably with the total nitrogen content of Karroo appears to be opportune for an investigation of this nature. manure, which ranges from about 1.4 to 2.0 per cent, nitrogen. With the shortage of artificial fertilizers it is of special import­ It compares still more favourably with the total nitrogen in ance to use additional sources of plant-food. Karroo manure, composts, which ranges from roughly 0.4 to 1.2 per cent. for example, has recently received much attention in the Union, but filter cake has the advantage of being available -within the Available phosphoric oxide (P205) is, as may be expected, industry itself. very high in the filter cakes, the Zululand factories averaging the highest with almost 3 per cent. P 0 . Filter cake has been extensively used for agricultural pur­ 2 5 poses, and has proved itself by field experiments to be a very Potash (K20) is, of course, present in negligible amounts, a useful fertilizer medium on most types of soil. For this reason dressing of 10 tons filter cake per acre supplying only about alone it was felt that a more comprehensive survey of the fer­ 40 lbs. K20. The potash analyses, however, were made by way tilizer ingredients was very desirable. of interest, as questions regarding the potash content of filter cake may occasionally be asked. A further benefit resulting from the work contemplated in this paper is that comparative filter cake analyses from the Available lime (CaO) and available magnesia (MgO) were factories are placed on record for the first time. Not only should estimated also largely by way of interest, as these are not such analyses be of value to the chemical control of each fac­ generally regarded as plant-foods. That calcium and magnesium tory, but should be of interest to chemists and agriculturists are absorbed in considerable quantity by sugarcane has been alike. amply demonstrated from time to time, and it may be that these All the samples analysed below were collected from the fac­ elements do play a more important part in plant nutrition than tories over the month of August, 1941, and were intended to be we expect. While the lime content is far in excess of the plant's representative of that month. requirements, it is useful as a soil rectifier, increasing the pH of The following table gives the available constituents, soluble very acid fields and improving the soil structure of other fields. in 2 per cent, citric acid, as is usual for fertilizers. For con­ It was thought that a more detailed knowledge of the com­ venience total nitrogens are given in the same table. position of filter cake would be instructive, and in consequence four factories were selected at random for a complete analysis. TABLE I. Had time been available it was intended to analyse all the filter Available Constituents and Total Nitrogens (N) of Filter cakes in greater detail. The following four results, however, will Cakes from Natal and Zululand Sugar Factories. serve as a guide to those interested :— (Results on air-dry basis.) 53

These results show that for the four factories a little more than 80 per cent, of the phosphoric oxide, lime and magnesia is soluble in 2 per cent, citric acid, and almost all the potash. As the period of slinking is only 30 minutes, this indicates a high degree of solubility for the plant-foods. The above analyses indicate that we have here in the industry a by-product which should be of great value as a fertilizer. Assuming that some 80,000 tons of dry filter cake are produced each season, then we have at our resources about 700 tons nitro­ gen (N), equivalent in fertilizer value to about 3,000 tons am­ monium sulphate, 2,000 tons phosphoric oxide (P2Os), or 12,000 tons superphosphate, and 150 tons potash (ICO) or 300 tons muriate. These large quantities of valuable fertilizer material, if carefully and judiciously applied to the fields, should go a The average sugarcane wax content from the above table is long way towards solving our fertilizer problems, particularly 4.93 per cent., ranging from a maximum of 12.80 per cent, to a during this period of national emergency. minimum of 0.59 per cent. Apart from about five factories, however, the wax content of the filter cake does not vary con­ There is in filter -cake a relatively high proportion of sugar­ siderably from the mean. It appears that factories with the cane wax which regularly goes to waste. In the present time Oliver filter have lower wax content than the other factories. of need, attention is once more given to this substance, with the Urnfolozi and Sezela are exceptions to this rule. It is interesting result that a number of experiments have been made here to that many factories with complete chemical control give lower ascertain the percentage composition of crude sugarcane wax benzene extracts. in filter cake from the various factories, and the most economic and suitable method of extraction. The sugarcane wax obtained Considerable work has been done in the past on the wax in Natal during the last war was reported to be "sticky, dark in content of sugarcane. Of the various solvents used from time to colour, difficult to bleach and often malodorous." Recently,1 in time (chloroform, acetone, carbon bisulphide, ether, carbon 1040, a survey was made of the wax content of Louisiana filter tetrachloride, paraffin, benzene, alcohol, to name a few), some cakes, with very encouraging results. The sugarcane wax ob­ would not be commercially available. Before continuing this tained there melted at 174"J'\ (the melting point of camauba study it is therefore essential to select the most suitable solvent. wax being I.80"K.), and in many other characteristics it resembled Alcohol was tried and yielded considerably higher results than camauba wax, which in its iinpurified condition is obtained benzene. Examination of the extract, however, revealed the from the leaves, berries and stalks of a palm growing in Brazil presence of much sugar and perhaps some salts, all of which, and other parts of South America. of course, would have to be removed.

The pioneer and largely successful efforts made in Natal SUMMARY. during the last war to extract sugarcane wax from filter cake The need for a systematic study of the fertilizer and wax appear to have attracted much attention. Thus Kingzett's content of filter cake is stressed. Chemical Encyclopaedia defines sugarcane wax as "a by-product extracted in Natal and Java." "Topics and Comments" in the Analyses of available plant-foods of composite filter cake "Manufacturing Chemist" for December last also refers to samples from all the factories are given and discussed. A total sugarcane wax as "a South African innovation of the last war" analysis of four samples is given for comparison, and attention and "hopes that every attempt will be made to 'repatriate' the is drawn to the large amount of plant-food available to the idea." industry. The war has turned attention to this wax and for three seasons The content of wax in sugarcane is discussed and analyses cane wax has been studied in Louisiana and reports have been (benzene extract) are given in support. 8 issued. The American Navy, finding the usual sources of supply The need for further work on the sjbject is stressed. closed, have caused investigations to be undertaken into methods of extraction and refining cane wax, and a pilot plant has been set up for this purpose. Cane wax can also find a market in South Africa for military purposes. The chief obstacle to making the by-product a commercial success is that the filter cakes from many of the factories have now been diluted greatly with bagacillo by the use of the Oliver filter, as mentioned earlier in this paper. The filter cake is consequently more bulky and difficult to handle. Despite this difficulty, it is hoped that the possibility of obtaining the wax commercially will not be abandoned. As a preliminary towards the study, a number of analyses were made in the laboratory at the Experiment Station, using benzene as the solvent, and extracting in a soxhlet for five hours. The results are appended below. Mr. DU TOIT said that he was indebted to the reporter of a local newspaper for the following information : A considerable source of supply of wax was now closed to the United States. At the request of the U.S. Navy a search for new sources was undertaken. The result was that chemists found a way of ex­ tracting sugarcane wax cheaply and a pilot plant was set up to determine the cost under actual manufacturing conditions. Several million pounds could be obtained annually from sugar­ cane processed in the United States. Acotinic acid, too, was essential in the manufacture of many of the plastics vitally needed for war industries. The present process of producing it from citric acid was costly. It consti­ tuted the principal organic acid in sugarcane. The best source to recover it from was molasses. Investigation showed that relatively large quantities occurred in cane tops. The acid occurred" in combination with other substances, and American Government chemists were now working on ways of separating it commercially. Here again it is expected that the available supply would run into millions of pounds. 54

Mr. DYMOND said that when scums were boiled up to ease The VICE-PRESIDENT said that some years ago a seedling filtration, a portion of the cane wax became emulsified and was grown at the Experiment Station that was exceptionally passed into the boiling house. The process used by the Natal rich in wax. There was a thick coating of wax on the outside Cane By-Products at the end of the last war consisted of a of the sticks which made them resemble candlesticks'. The benzene extraction from dried Illovo filter cake. The first wax seedling was discarded, however, as it was thought that it would produced started melting at 50°C. and became totally liquid at not be acceptable to the mills. about 72°C. Buyers who used it for floor and boot polishes, required a harder wax, so it was fractionated with ether to Mr. MOBERLY thought that the use of cold imbibition water remove the fats. The principal trouble, however, was its colour, might account to a certain extent for the lower wax content of and no satisfactory method was ever devised for bleaching it. filter cake. Cane wax in its natural state was white to pale yellow, but the effect of the sugar clarification process caused a black coloration. Mr. DYMOND agreed with Mr. Moberly and said that the He suggested that the only way to obtain this wax in a white Oliver Campbell filters might also be partly responsible for the or light yellow condition would be to extract it from Peck lowering of the wax content of filter cake, as they allowed more strainer cush-cush, or the scums from the old-fashioned wax wax to become emulsified and passed into the boiling house, separators which operated prior to clarification. Such a pro­ where it gave trouble. He would have preferred a low tem­ cedure would, however, be difficult owing to the high sucrose perature filtration. He did not think the new varieties had content of such products. much, if any, effect on these figures. Mr. Dymond recommended that the wax investigation should be continued. Mr. Dymond said that the wax investigation should be con­ tinued and those interested should assist the Experiment Station. Mr. BIJOUX said that he had carried out certain experiments It would be appreciated if Dr. Tromp, Director of War-time and found that a white wax could be extracted from filter cake Research, or any Government officials, could collaborate. with a certain solvent. He could not disclose the solvent, but felt sure that the interests concerned would give the Exepriment Station all the help in this connection if approached. Mr. DODDS said that he had a letter from India in which it was stated that juice was treated with a suitable solvent Mr. Bijoux said that the low percentage of wax in filter cakes before clarification so as to extract the wax. This process en­ coming from factories using the Oliver Campbell type of filter sured the maximum elimination of wax and improved clari­ was probably due to the liberal use of hot water, which dis­ fication. solved precipitated wax formed, and returned it into process. Mr. RAULT said that he had carried out some wax determina­ Mr. VIGER pointed out that low temperature filtration, tions some years ago, using different solvents. He found the especially with the Oliver Campbell filters, would be disastrous. wax content of filter cake much higher. Most factories ranged Deterioration would take place rapidly and the purity of the from 7 to 12 per cent., while Natal Estates had 2 per cent. filtrate would drop. A considerable amount of hydrogen sulphide wax. Factories that were trying to cut chemicals showed a would be formed and this would ruin copper screens in four higher percentage wax in filter cake, but the actual elimination months, and even stainless steel screens would tarnish and was much the same. Mr. Rault thought that an appreciable corrode rapidly. He had found by analysing both mixed and quantity of wax was carried away in the cush-cush where screen clarified juice that 99 per cent, wax was eliminated at the filter filters were used. This might account to a certain extent for the station. Low temperature filtration was therefore dangerous low wax content now obtained. and unnecessary. He was rather surprised that not more magnesium was found Dr. HEDLEY, in reply, said that he did not think that there in Natal Estates filter cake. Not only was more lime used, but would be much profit in wax extraction, but wax was an article being an alkaline process, the magnesium elimination was almost that was urgently needed under present conditions, and the perfect. whole problem should be tackled at once. 55 SOME EXPERIMENTS, ON THE SUGARCANE MEALYBUG. Trionymus (Pseudococcus) sacchari Ckll. By J. DICK. In this experiment, not all the buds in the infested series were covered with mealybugs, but each sett containing about 4 or 5 buds was partially infested. The degree of infestation would affect- the result, so that a more marked effect might be expected from more heavily infested setts.

Effect on Subsequent Growth. Experiments on this question, on a large enough scale for statistically valuable results to be obtained, have teen planned. In the meantime, preliminary trials have been carried out and have given results showing that a very marked deterioration in growth may be expected in cane produced from infested setts. The accompanying photograph, taken towards the end of February, illustrates the difference in growth in Co.331 cane four month? old, from infested and non-infested setts. The mealybugs not only survive planting but, especially when ac­ companied by the Argentine ant, are carried up by the emerging shoots. In this experiment, cane plants produced from infested setts were themselves heavily infested, while plants in the control series, grown from non-infested setts, were free from mealybugs.

Summary. Preliminary experiments indicate the danger of planting sugarcane setts infested by mealybugs, which have a harmful effect on germination and subsequent growth.

Reference. 1 Barber, E. R. (1923): The Sugarcane Mealy Bug and its Control in Louisiana. La. State Univ. Agric. Expt. Sta., Bull. No. 185,16 pp., i pis. Baton Rouge, La.

Experiment Station, South African Sugar Association, Mount Edgecombe. March, 1942.

Co.33l cane four months old ; that on the left grown from setts infested with mealybugs, and that on the right from non-infested setts. 56

The VICE-PRESIDENT, in opening the paper for discussion, that we had an Entomologist at the Station he would like to said that he had once been called out to inspect a field where see this work continued, as he believed that a lot of our clari­ a farmer thought he had an outbreak of gumming disease in the cane; a disease hitherto unknown in this country. He found fication troubles were due to this pest. it was a severe infestation of mealybug. The nodes of the stalks were covered with mealybugs and the wax, which melted on Dr. DICK said that Barber found that controlling the ant hot days, was running down the outsides of the canes. Such a that fostered the mealybug was a satisfactory method of con­ condition would certainly affect the milling quality of the cane. trolling the mealybug. Mealybugs were transported from one Mr. DYMOND said the effect of mealybugs on clarification place to another by the Argentine ant, and the Government had been dealt with in a paper by himself some years ago. Now entomologists had various types of bait for this ant, THE PRESENT FERTILIZER POSITION. By H. H. DODDS.

The last general paper on commercial fertilizers and fertilizer experimental stage, as far as we in this country are concerned, experiments in Natal given to you is that by J. E. Colepeper of which Sesbania macrocarpa, and pigeon pea, Cajanus indicus, and the writer two years ago.3 are of most promise at present. Many profound and far-reaching world changes have taken Sunn hemp and velvet bean are the best of those in common place since then, that have had important repercussions on use because of their rapid growth, adaptability to our special fertilizer supply, especially in those countries, such as South soil conditions, freedom from disease or insect pests, etc. They Africa, which depended largely on imported fertilizers and raw are also excellent for clearing the ground of weeds. materials for fertilizer manufacture. Incidentally, velvet bean is of special value because of its Of phosphatic fertilizers, before the war, nearly two-thirds possible alternative use as food for livestock and may be fed of the total superphosphate used in South Africa were manu­ green, or preserved as hay or silage. Seed is easily raised locally. factured locally from imported rock phosphates and sulphuric acid made partly from imported sulphur and partly from South The amount of nitrogen contributed to the soil by a good African pyrites. leguminous green manure crop is substantial. B. Campbell at the 1940 Conference2 reported an increase of organic matter in Thus in 1937-38 (the last year for which figures are obtain­ a wind-blown sandy soil, six weeks after ploughing-in a good able) there were manufactured in South Africa 172,130 tons of 5 crop of sunn hemp, from 3.93 to 4.14 per cent., or a contribution superphosphate and 82,244 tons of mixed fertilizers, while in of 5,000 lbs. per acre of organic matter. 1938 there were imported 95,724 tons of superphosphate and 109,427 tons of rock phosphates, the latter being used mainly At the same time the nitrogen content of the soil had increased for the manufacture of superphosphate. from 0.216 to 0.231 per cent., corresponding to 375 lbs. of nitrogen per acre. Compared with these figures for superphosphate, the import Recent unpublished analyses by B. E. Beater of sunn hemp and consumption of other phosphatic fertilizers such as basic grown in Mount Edgecombe showed a content of 0.71 per cent. slag, 4,357 tons, and bone manures, 10,821 tons imported and of nitrogen in the tops and 0.36 per cent, of nitrogen in the 9,053 tons produced locally, are of relatively little importance. roots. This corresponds to 15 lbs. of nitrogen from a ton of In the same year (1938) 17,649 tons of ammonium sulphate sunn hemp tops and roots. (sulphate of ammonia) were imported with a negligible amount Since a good crop of sunn hemp can yield 10 or 12 tons or of other nitrogenous fertilizers, while no more than 1,160 tons more of material per acre, it follows that 150 tol80 lbs. or more, of ammonium sulphate were manufactured locally, together with of nitrogen per acre would be contributed. 3,424 tons of blood meal and meat meal, and 6,216 tons of so- called Government guano, obtained from certain coastal islands The nitrogen requirements of an average cane crop are about frequented by sea-birds. 80 lbs. per acre. 7,923 tons of potassic fertilizer were imported in 1938 ; there One serious limitation at present to the cultivation of sunn is no appreciable production of potassic fertilizer from mineral hemp is the restricted local supply of seed. This is a matter that sources within the Union. is being investigated. The position now is that only very limited supplies of low- Unfortunately, it cannot be said that the whole of the nitro­ grade rock phosphate and no superphosphates can be imported ; gen accumulated by the nitrogen-fixing organisms comes from the importation of ammonium sulphate has practically ceased, the atmosphere, since a varying proportion is taken from the and only small quantities of sodium nitrate (nitrate of soda) are soil, especially if the soil is already rich in nitrogen.1 This is obtainable, at a present price of £16 a ton, or £1 per unit of true, of course, of the legume itself, which may take nitrogen nitrogen. from the soil like any plant, as well as of the nitrogen-accumu­ lating bacteria in the root nodules, which may find it easier to The importation of potassic fertilizer has also ceased. take some at least of the nitrogen from the soil rather than from This, then, brings about very serious shortages of all mineral the air. fertilizers. Nevertheless there is, as stated, a valuable net gain of nitrogen The fairly extensive deposits of rock phosphate in South to the soil from a vigorous leguminous green manure crop, Africa are not adaptable to superphosphate manufacture, and especially in soils rather poor in nitrogen. appear to have very limited applicability as fertilizers in other ways, while the other sources of phosphatic fertilizer such Thus the nitrogen requirements of the plant cane crop can as bone, or meat meals are still produced in very limited be met by a previous course of leguminous green manuring, quantities and are in increased demand in animal industry while at the same time the organic material of the soil is being because of the general deficiency of stock feeds, especially of replenished to some extent, a matter which may be at least proteins and minerals. equally important with the fertilizer supply in light or depleted soils. The production of ammonium sulphate in this country cannot be appreciably increased at present, for reasons that I need not The nitrogen supplied in this way does not necessarily last enter upon here, so that we are largely limited to what local longer than the period of the plant cane crop, however, and organic sources of nitrogen can be developed. can hardly be counted on to supply any of the ratoon crop requirements. Let us now examine these possible sources. Weather conditions in this country are such that it is seldom LEGUMINOUS PLANTS (GREEN MANURES). warm and wet enough after harvesting the cane crop to grow These appear to offer most promise of supplying nitrogen. a good green manure crop between the cane lines to fertilize the If our industrial resources are not adequate to fixing atmospheric ratoons without injury to the cane.' nitrogen by chemical engineering means, let us enlist the less Consequently other ways than direct green manuring, must be spectacular nitrogen-fixing bacteria in our aid. There are several found to supply nitrogen to ratoons, of which composting is one species of these minute but beneficent creatures, but the only possible way. one which seems to be of much help to us at present is Bacterium radicicola, which under certain conditions inhabits the root COMPOST. system of leguminous plants and fixes nitrogen from the at­ It should be realised that composting does not contribute mosphere. nitrogen or any fertilizer element, but may help to conserve The legumes which we know can be very useful to us in this such elements, especially nitrogen, in such a way as to facilitate way are sunn hemp, Crotolaria juncea, velvet bean, Siizolobium their eventual application to the cane, while at the same time deeringianum, soya bean, Glycine soja, cowpea, Vigna caijang, converting waste vegetable matter into valuable moisture- and ground-nut, Arachis hypogaa. There are others in the retaining humus. -58

By this means a legume green manure-crop can be harvested resulting •from complete inorganic fertilization including 550 lbs. and so treated, as for example- by compostirig with cane trash sodium nitrate""'(8?> lbs: nitrogen) also applied annually for 74 and tops, as to yield a valuable product for the fertilizing of years. Using ammonium sulphate, 412 lbs. per acre (86 lbs. cane crops, whether ratoon, or plant cane crops which have not nitrogen), in place of sodium nitrate the average yield was only had a green manure crop ploughed in. slightly less. I will not now go further into this matter, which has teen Taking the nitrogen in sodium nitrate as 100, we find that ably dealt with by our Vice-President in a paper given at a recent the nitrogen in ammonium sulphate is worth 90, and that in general meeting of this Association, and which I understand will farmyard manure only 44. be included in the Annual Proceedings. Further, it was shown that farmyard manure took four years to give most of its benefit to the crop, while the maximum FARMYARD MANURES. benefit was obtained from the mineral nitrogenous fertilizers in These are very valuable sources of nitrogen and other fertilizer the first year. elements and of'organic matter, but on the average sugar planta­ tion in this country the supplies of such manures are far below In England, however, there is a considreable annual loss of the demand, though there is a tendency for them to increase nitrogen from the soil by the leaching out of nitrates during the with the increasing development of cattle and pig farming on autumnal rains ; and it is possible that in this country, where sugar plantations. this regular heavy loss of nitrogen does not occur, farmyard manure and similar bulky organic forms of nitrogen may. be Like green manures, they may be used either direct or after relatively more valuable. first using them to make a compost. It may be suggested that' the above comparisons between The composition of such manures varies enormously, not only farmyard manure and inorganic nitrogenous fertilizers is possibly with the content of moisture, which is constantly fluctuating, not fair to the former, since it was always applied in much but with the kind of animal from which the dung was derived, greater quantities of nitrogen per acre, in accordance with and the sort of food it had, the nature and relative quantity of standard English practice. bedding material, the age and conditions of storage, etc. 8 However, the average analysis of a considerable number of However, in another series of experiments at Woburn two samples from various sources tested at Cedara College of Agri­ different quantities, 4 and 8 tons per acre, of farmyard manure culture13 was:— supplying the moderate amounts of 03 lbs. and 105 lbs. of Calculated nitrogen per acre respectively, were applied annually to crops of on dry barley and wheat over a period of ten years (1877-86). Per cent. sample Moisture 60.0 — Results showed substantial increases in yield over control plots without added nitrogen, approximately proportional to Phosphate (P205) 0.2 0.5 Nitrogen 0.6 1.5 the quantity of farmyard manure applied, the larger quantity Potash (K,0) 0.5 1.2 showing slightly better gains per unit of nitrogen applied. Here, also, over a period of 50 years of continuous experi­ It would thus take 6A tons per acre of this farmyard manure to ment (1877-1926) the increments in yield of barley and wheat supply the 80 lbs. of nitrogen required by the cane crop, assuming, per unit of nitrogen supplied were much greater for sodium that all the nitrogen in the manure is available to the sugar­ nitrate than for farmyard manure. While the effectiveness of cane and will be taken up by it, an assumption that is very far the farmyard manure was only 25 per cent, of that of sodium from the truth, as we shall see. nitrate in increasing the yield of barley grain over the first 15 It is indeed a moot point how far nitrogen contained in small years, this proportion had risen to 60 per cent, over the last proportions in bulky organic manures may be considered avail­ 20 years. With wheat, on the other hand, the effectiveness of able to the crop in comparison with nitrogen in concentrated the farmyard manure compared with sodium nitrate averaged nitrogenous fertilizers such as ammonium sulphate and meat 28 per cent, throughout, showing very little increase with the meal. passing of time. This has not yet been worked out systematically under our In both crops, however, there was a tendency for the farmyard conditions, though some experiments with this end in view have manure to increase its relative efficiency in promoting yields of been laid down recently.14 In the past, experiments have been straw. Evidently the soil tended to suffer somewhat after a done to compare inorganic versus organic nitrogen for sugar time by the depletion of some factor that could be supplied by cane, but only with concentrated sources of organic nitrogen farmyard manure and not by artificials. such as whale meal, blood meal, and the like.3 There was rela­ tively little difference in normal seasons in their effect on yields Where sodium nitrate was compared against ammonium per unit of nitrogen applied ; but the tendency appeared to be sulphate the effects on yield per unit of nitrogen were remark­ for inorganic nitrogen to be more effectual per unit in seasons ably similar with both barley and wheat for about the first of adequate rainfall, but decidedly less so in dry seasons. This 12 years; thereafter the yields from the ammonium sulphate question is no doubt complicated by various factors when plots began to fall off, until after 25 years the yields were neg­ moisture supply tends to become more definitely a limiting ligible, due to the increasing acidity of the soil brought about factor. by the ammonium sulphate. Where this acidity was neutralised by the addition of lime, 1 ton per acre, ammonium sulphate main­ In view of its much lower cost per unit of nitrogen, inorganic tained its equality with sodium nitrate. - nitrogen showed much greater profits than organic nitrogen in normal seasons of rainfall and fertilizer prices and supplies. Incidentally the experiments at Woburn, contrary to Rotham­ sted experience, indicated that both sodium nitrate ard am­ monium sulphate could exercise favourable residual effects by LONG-CONTINUED EXPERIMENTS AT ROTHAMSTED leaving something in the soil to benefit the succeeding crop. AND ELSEWHERE. We have had recently some evidence of this in South Africa Systematic experiments on fertilizers for wheat carried out also.15 This "something" may be nitrogen, as it probably partly continuously at Rothamsted since 1843 and recently summarized 8 is at least with farmyard manure, but is hardly likely to be so by Sir J. Russell and D. J. Watson showed that nitrogen from with soluble inorganic nitrogen compounds, whose nitrogen soon sodium nitrate was most fully utilized by the crop, approxi­ becomes oxidised to nitrates which are not fixed in the soil and mately 35 per cent, of the nitrogen applied being recovered in are highly soluble so that they cannot remain long. the plant, but only about 15 per cent, of the nitrogen applied in farmyard manure. The Woburn experiments clearly demonstrate also that for This much greater relative efficiency of concentrated mineral some reason a crop supplied with an adequate complete fertilizer fertilizer as a supplier of nitrogen compared with farmyard does not maintain its yield when grown time after time in the manure is reflected also in the yield figures. same soil, though the deterioration is slower when farmyard manure is applied. This phenomenon has been studied by A. F. Thus farmyard manure applied at the rate of 14 tons per Bell with sugarcane soils in Queensland.1 Whatever the cause acre (200 lbs. nitrogen) annually for 74 years produced an of this deterioration is, it can be temporarily overcome by average gain in yield of grain approximately equal to that fallowing, but not necessarily by crop rotation. 59

Another series of long-continued experiments are recorded One of these is what is known as Karroo manure. This from the New Jersey station.11 These experiments were done on originates from the district known as the Great Karroo, the a small scale in a highly acid Penn loam soil. The crop was a interior portion of the Western Cape Province west of the five-year rotation of maize, oats, oats, wheat, and timothy grass, Sundays River. The rainfall is very low (5 inches or less to and was followed continuously for 40 years. 15 inches annually) and the vegetation consists of drought- resisting scrub which supports herds of sheep and goats. The Here also sodium nitrate (160 lbs. or 320 lbs. per acre) was excreta of these animals dry and accumulate in the kraals in the most effective carrier of nitrogen and gave rise to higher which the stock is folded, the rainfall being insufficient to leach total yields of crops and higher recoveries of nitrogen in the out the material appreciably. crops, per unit of nitrogen applied than any other form of nitrogen. Ammonium sulphate (250 lbs. per acre) and blood This manure received little attention until recently, when two meal were approximately equal, but only superior to farmyard factors intervened ; firstly, very substantial reductions in rates (cattle) manure per unit of nitrogen applied if the acid soil was of freight of fertilizer and similar materials on the national periodically limed. railways made it possible to transport such materials long distances without the cost being prohibitive, and, secondly, the The best results were obtained where both farmyard manure present acute shortage of artificial fertilizers has made con­ and sodium nitrate were used, the former supplying 60 per cent, sumers explore every possible source of fertilizer supply. of the nitrogen applied. The results from each of the 20 different Unfortunately, Karroo manure does not come under the pro­ fertilizer treatments were all greatly improved by a course of visions of the Fertilizer Act, so that there is no guarantee of liming and green manuring (with vetches) twice in each crop composition. Nevertheless it is found in practice that the rotation. chemical analysis does not vary much as a rule. Although the mineral nitrogenous fertilizers and blood meal Thus the average nitrogen content of oven-dried samples of gave the most profitable results, it was noticeable that after six different consignments analysed at the Experiment Station 40 years the only soils that had not diminished in fertility as was 1.70 per cent., ranging from 1.40 to 1.97 per cent. This shown by nitrogen and organic matter content and pH were agrees fairly well with the average nitrogen analysis of a large those that had been systematically treated with 16 tons per acre number of samples at the College of Agriculture, Cedara,10 of farmyard manure annually and periodically limed and green which was also 1.7 per cent, nitrogen, none being higher than manured. 1.95 per cent. The average phosphorus content was 1.36 per The beneficial effects of farmyard manure on the soil were cent., ranging from 1.02 to 2.32 per cent, as PaOB, and the measurable for 16 years after its application was discontinued. potassium averaged 5.52 per cent, as K20, the limits being 3.00 and 7.10 per cent. These tests are somewhat higher than those It appears as though farmyard manure, possibly by initiating recorded at Cedara. certain biochemical and physico-chemical changes in the soil, A large proportion of the phosphorus and potassium contents whether by the agency of its animate or inanimate components, is available, that is to say, soluble in 2 per cent, citric acid. or both, brings about in certain cases permanent beneficial changes in the soil. The manure contains about 50 per cent, of organic matter and may contain from 10 to 50 per cent, of free moisture. It may form a source of some of the growth-stimulating substances for plants, distinct from plant nutrients as ordinarily If purchased in bulk it is a very cheap manure, the present understood. Amongst these are the auxins, or indole-substituted price being about nine shillings per ton delivered in railway lower fatty acids, which are known to occur in urine and can truck loads. There is then no guarantee concerning moisture have a profound effect in stimulating root growth of plants. content or freedom from large lumps, etc., but the limited ex­ perience of the writer is that the material is nevertheless usually Farmyard manure may also benefit the soil by liberating satisfactory in composition and texture, although the moisture large quantities of carbon dioxide, which when dissolved in the content is somewhat higher than in the processed material. soil solution to form carbonic acid will attack insoluble mineral constituents of the soil to make them soluble and available to It is more frequently advertised for sale in bags, after being the plant; the carbon dioxide may also supply green plants with dried, milled and sifted, but the price then may be from 25s. some of their requirements of this tissue-building substance. to 36s. per ton. Even taking the present value of bags into account, it is much cheaper and probably satisfactory as a rule The manure may also promote in some special way the growth to buy it unmilled in bulk. in the soil of certain lower forms of vegetable life such as Sometimes it is burned and the ash offered for sale. The mycorrhizal fungi, a group of soil fungi capable of symbiotic burning, however, destroys the principal value of the manure, relationship with the roots of higher plants, that is to say, they its nitrogen content and organic matter. The ash also is strongly may exist in association with them to their mutual benefit. alkaline from the presence of lime and carbonates of potassium This association, however, is not necessarily beneficial to the and sodium, and also contains chlorides, sometimes in high higher plant, depending on circumstances, and in any case is proportions. It is therefore undesirable for use as a fertilizer. not essential to its normal development.11 Even the unburnt manure may have a pH of over 10, and a Recent evidence from India7 shows that farmyard manure is chloride content of 1 per cent., corresponding to 1.6 per cent, there considered quite inferior for sugarcane to ammonium of common salt, which makes it unsuitable to apply to dry soils sulphate alone or organic concentrated fertilizer such, as oilcake. and to certain crops. It is recognized, however, that farmyard manure is a soil im­ Fortunately, however, sugarcane (more especially Co.281) is prover, but that the nitrogen it contains becomes available too fairly tolerant of brak, our soils are mostly slightly acid and slowly for the sugarcane crop, though it is stated that further are not usually dry for long at times of the year when the long-continued experiments are required, including investiga­ manure would normally be applied. tions into composting with farmyard manure. Experiments are in progress with Karroo manure as a source Green manuring, especially with sunn hemp, is stated to be of nitrogen, but results are not likely to be available for some very beneficial, though it is suggested that heavy applications time.18 of oilcake or a mixture of oilcake and ammonium sulphate may Some planters have reported very good apparent results from be a better economical proposition in some circumstances. its use, and it seems to be a possible source of fertilizer for the sugar industry. KARROO MANURE. Whether Karroo manure will show similar residual values to It may be that the systematic application of some form of fresh farmyard manure remains to be seen, but it seems quite farmyard manure may prove eventually to be necessary to main­ possible that it will be so. tain the productive power of our Natal coastal soils, subject as most of them are to more or less continuous cropping with An application of 3 tons per acre of Karroo manure con­ sugarcane. taining 20 per cent, moisture would, according to our average analyses, contribute to the soil 80 lbs. of nitrogen corresponding Although, as stated, relatively little farmyard manure is pro­ to 400 lbs. of ammonium sulphate, and 65 lbs. of P206 correspond­ duced locally, there are various possible alternatives. ing to 400 lbs. of superphosphate, 16 per cent., and 265 lbs. of 60

Ks0 corresponding to 440 lbs. of potassium chloride. The lime small quantities of them taken up by the sugarcane crop would content of 5 per cent, as CaO implies that the 3 tons of Karroo mostly be retained in the filter cake and so partially returned manure would contribute lime equavilent to 430 lbs. of calcium to the soil ; this is another possible virtue that may be claimed carbonate (agricultural lime). for filter cake. According to the Cedara average analyses, compiled from a The production of filter cake is normally about 5 per cent, of much larger number of samples than ours, the nitrogen from the weight of cane, which means that from a normal crop of 3 tons of Karroo manure would be about the same, but the 5 million tons of cane, 250,000 tons of undried filter cake will phosphorus and potassium would be considerably less, equivalent result. This sounds a substantial amount but will only supply to about 270 lbs. per acre of superphosphate, 10 per cent., and 25,000 acres of land at 10 tons per acre, which is only a small 300 lbs. of potassium chloride. In this case the Karroo manure proportion of the 300,000 acres or more now under cane in this would need to be fortified by the addition of superphosphate, country; consequently the supply is far less than the potential about 150 lbs. to the 3 tons application, to balance the nitrogen demand. so as to make a suitable mixture for ratoon canes. The effective demand is much less than this, however, since it is hardly economical to convey this valuable but bulky material F1LTEB CAKE. to fields far distant from a railway halt and not supplied by Another waste product of value as a fertilizer is filter eake, factory tramlines. sometimes (less accurately) termed filter press mud, scum cake, press cake, milo, or less flattering names. MOLASSES. This is a valuable manure that should be fully exploited at This valuable by-product of sugar manufacture must be men­ the present time. tioned as a possible fertilizer, though its use as such direct has not hitherto proved very successful in this country, for various It consists of precipitated or suspended solid matter filtered reasons. from the cane juice and, like many waste products, is very variable in composition, depending oh the method of filtration, O. VV. Wilcox, years ago, pointed out that sugarcane pro­ the juice clarification system in use, the nature; of the cane and duced more carbohydrate per acre than any other crop, and the soil from which it was derived and its fertilizer treat­ consequently was a greater potential producer of nitrogen for ment, etc. food or fertilizer, because of the possible fermentation of sugars into yeast.12 A large number of filter cake composite samples from different South African factories have recently been analysed at the At present, however, molasses appear to be in great demand Experiment Station, with the following results :— for industrial purposes, so that we need not now consider in detail their use as fertilizer. Even when fermented industrially, however, the inorganic fertilizer elements pass into the (hinder, a matter which I note is to be dealt with in another paper.

SEA-BIRD GUANOS, ETC. These may be mentioned among the natural fertilizer resources of the country. Government guano has been already referred to, and consists mainly of the excreta of sea-birds frequenting certain islands off the Cape coast. The average composition is phosphorus (citric soluble P O ) 10.5 per cent., nitrogen 10.2 per cent., and The 2 per cent, citric acid solution used as solvent in these 2 s potash (KaO) 2 per cent. It is thus not a suitably balanced analyses dissolves out practically all of the potassium and about fertilizer for a plant cane crop but would need an addition of 80 per cent, of the total phosphorus and calcium present. The superphosphate, say 500 lbs. to a ton of guano ; but for ratoon nitrogen was estimated by the usual Kjeldahl method. Further crops it might suffice as it is. details are recorded in a paper prepared by the Chemical Depart­ ment for this Conference. This guano is sold at the remarkably low price of £6 a ton ; The analyses are based on air-dried samples, which normally unfortunately the supply is very limited, only about 5,000 tons contain about 10 per cent, of moisture. The moisture content being produced annually, so that the demand far exceeds the of the filter cake as received from the factory is usually about supply, and the guano is strictly rationed. 50 or 60 per cent., so that if used on the farm in this condition Sea-bird guanos are also sold by certain commercial firms, the above analyses must be reduced by about one-half. ,The but at a considerably higher price than the Government product, cake dries slowly when stored, depending on external moisture the cost of collection being high. Some experiments are under conditions. way in different types of soil at Mount Edgecombe to determine 6 When thoroughly air-dried, an application of 10 tons of filter its performance and value in relation to other fertilizers. cake per acre, which has come to be regarded as an average dressing in normal times, conveys quite a large quantity of Bat guanos are sometimes offered for sale, but are often of fertilizer elements to the soil. relatively little value. Under the Fertilizer Regulations no fertilizet may be sold under the name of bat guano unless it Thus the air-dried 10 tons would contain on the average as contains at least 2.5 per cent, of nitrogen, at least 4.5 rrr cent, much phosphorus as 3,000 lbs. of superphosphate, 16 per cent., of phosphorus as P»06, and at least 8 per cent, of both nitrogen as much nitrogen as 800 lbs. of ammonium sulphate, as much and P205 together. potassium as 60 lbs. of potassium chloride, and as much lime as 2| tons of calcium carbonate (agricultural lime). The moist The so-called whale guanos (more correctly whale meals) material as freshly received from the factory would normally have played an important part as fertilizers for sugarcane in contain about half these quantities. recent years, but are now no longer obtainable as such. Much less whaling has been done of late because of scarcity of suit­ It would appear, therefore, to be advisable to economise in able vessels, there is an increased demand for whale meal for filter cake by using much less than 10 tons per acre of the feeding stock, and I believe what little was available for fertilizer thoroughly air-dried material, say only half as much, thus purposes was bought up by fertilizer firms to put into mixed making it go as far as the original moist product received from the factory. fertilizers. It should be remembered that filter cake is a very complex ARTIFICIAL FERTILIZERS. product and that there are not less than 16 chemical elements The South African Department of Agriculture, in the interests in the soil believed to be essential to the growth of plants. of national economy, has recently laid down formula; for eight While we have had no indication that any of these so-called artificially mixed fertilizers that the fertilizer trade may pre­ minor elements are normally deficient in Natal coastal soils, the pare, no other mixtures being permitted for sale. 61

The position still is, however, that mixed fertilizers of any kind are of little use to the sugar planter, whose main require­ ments are the so-called "straight" fertilizers, or the individual substances supplying separately the elements required. This enables the planter to apply top-dressings of nitrogen when they are needed, without the phosphorus or potassium, which may be applied more profitably at other times. Further, the mixed fertilizers are decidedly more costly per unit of fertilizer elements than the straight fertilizers. It is earnestly to bo hoped, therefore, that straight fertilizers will continue to be available to the sugar industry, if true economy in fertilizer utilization is to be attained.

The phosphates are no longer recorded on water-soluble con­ RESULTS OF RECENT LOCAL EXPERIMENTS. tents, but on citric acid-soluble phosphate, calculated as P2O5. I had hoped to include with this paper a fairly comprehensive Another innovation, which I think is also to be welcomed, is summary of the 22 fertilizer experiments harvested at the that the NPK sequence replaces PNK, thus coming into line Experiment Station and co-operative field stations during the with overseas practice and allocating to nitrogen its rightful past two seasons. This paper has already assumed such dimen­ primary rank. sions, however, that only a brief reference can bo made to the experiments harvested last season. Such mixtures might be compounded as follows, using super­ phosphate, 16 per cent., ammonium sulphate, 20 per cent, nitro­ In the paper contributed by J. E. Colepeper and the writer gen, potassium chloride (muriate) containing 60 per cent, potash two years ago'1 it was pointed out that while a response to as K2O. These are probably still the cheapest and most suitable ammonium sulphate as a fertilizer was found in almost every ingredients with which to make a so-called "complete" fertilizer. case in seasons of normal or excessive rainfall, this was by no means the case in dry seasons. The experiments harvested in 1941 had come through two very dry growing seasons, and it is now possible to classify into soil types the experiments giving positive and negative results respectively. Generally speaking there was no response to ammonium sulphate in heavy soils subject to drought, as at Verida.ni17 (Central Factory) and the Experiment Station, suctions D2I!I and P21B. There was a definite and very profitable response, however, in a sandy loam derived from Table Mountain sandstone at Upper Tongaat,17, and in heavy alluvial soils that were not 20 1 1 It will be seen that mixtures C, E and F do not require 100 per drought-stricken, as at Umfolozi and Illovo. ' cent, of these ingredients, and give the manufacturer an oppor­ There was also a marked profitable response to ammonium tunity to use less concentrated ingredients if he desires. sulphate in coarse sandy soils at Chakas Kraal,21 Kulu19, and in 22 Mixture "A" may be used by the sugar planter in place of a fine loamy soil at Braemar. superphosphate where a response to potassic fertilizer is known During the past season the general level of sxigarcane yields to exist, and where the nitrogen requirements of the sugarcane was the lowest for many years, because of drought, and conse­ crop have been met by leguminous green manuring, or will be quently a relatively high percentage increase in yields from met by top-dressings of mineral nitrogenous fertilizer when the fertilizer treatment meant relatively small actual increase in cane is established. It would be a good mixture also for fer­ tonnage ; this was associated with an increase in cost of fer­ tilizing leguminous green manure crops in poor soils, and for tilizers to approximately double their pre-war unit price. sweet potatoes where the maximum amount of tuber develop­ ment and not too much top is required. It is most remarkable that there was nevertheless a profitable response in so many cases to the use of ammonium sulphate "B" may be used for a similar purpose in those sandy soils and superphosphate. It has to be remembered, of course, that where a light dressing of nitrogenous fertilizer at time of plant­ there has been no increase in value of the product at all corre­ ing is not without use in promoting root formation of cane setts. sponding to the increase in price of fertilizers. This may also be used for sweet potatoes in poor soils. "E" is a mixture that would be of much value for ratoon In order to get the maximum profit per acre of land from the fertilizing in quantities of about 500 lbs. or 600 lbs. per acre fertilizer, it was found from cases where a range of various where it is intended to apply a later application of nitrogenous quantities per acre of fertilizer were applied, the quantity indi­ fertilizer. It would be useful also to balance farmyard manure cated as best in previous experiments had to be reduced. where a mixture of organic and inorganic nitrogen is desired. Thus in some cases where 400 lbs. of ammonium sulphate had "F" could be used for a similar purpose in soils known to be been found the most profitable application in previous crops, deficient in potassium. and would still have been at the old fertilizer prices, 200 lbs. was now the best; in other instances where 800 lbs. had been "H" would be useful for ratoons in cases where it was desired the most profitable, it was now 600 lbs., and so on. to apply larger initial quantities of nitrogen, whether followed by further applications of nitrogen or not. As an example of the remarkable benefit brought about by the use of ammonium sulphate, I may cite the case of an experi­ These fertilizers form a far more rational and useful range of 21 mixtures than the hundreds of registered mixtures, most of ment at Chakas Kraal, harvested as first ratoons in July last. them differing from each other only slightly if at all, that The cane varieties were Co.28.1. and Co.301 in alternate plots resulted from private enterprise, and the Department is to be and the soil an unirrigated coarse sanely loam on an open congratulated on the steps they have taken. hillside. I think we are fortunate at the present critical time to have The ammonium sulphate was applied in top-dressings of 200, a government who are keenly alive to the requirements and to 400, 600, 800 and 1,000 lbs. per acre respectively. Every appli­ the importance of agricultural industry, and to have also in the cation gave a substantial profit except the 1,000.1b. plots, which Union an enterprising superphosphate manufacturing industry could not bear the cost of £8 per acre for the fertilizer. The associated with one of the greatest firms of chemical manufac­ plots without ammonium sulphate yielded 28.47 tons per acre turers in the world. of 15.89 per cent, sucrose content, or 4.52 tons of sucrose per 62

acre, and the highest yield was obtained from the 8001b. plots results ranging from £1 to £2 2s. 9d. per acre, averaging "39.19 tons of cane per acre of 15.93 per cent, sucrose, or 6.24 £1 8s. lOd. tons of sucrose per acre. The most profitable treatment was These positive results were obtained with first ratoons (no the 600 lbs. series, which yielded 39.29 tons cane per acre of plant cane crops were cut) in heavy and medium soils at Verulam 15.82 per cent, sucrose, or 6.22 tons of sucrose per acre. This (Central Factory),17, Upper Tongaat,17 Braemar,22 and Eshowe.14 showed a profit of /4 15s. 9d. per acre over the cost of the The four negative results were in first and second ratoons in a fertilizer, with ammonium sulphate at £16 a ton, and the driest heavy clay alluvial at Illovo,14 a heavy clay (Dl) and a heavy season on record. loam (P2) (sixth ratoons) at the Experiment Station, Mount 17 19 10 In the plant cane crop, similarly fertilized and harvested in Edgecombe, , , and the windblown sand at Kulu. 23 September, 1939, all the applications of ammonium sulphate As with ammonium sulphate, superphosphate suffered from were highly profitable ; the 800 lb. plots gave the best and most the great increase in price, applications that would have shown profitable results, yielding 52.93 tons of cane per acre (com­ a profit at normal prices now failing to do so. pared with 39.30 tons from the controls) of 16.54 per cent, sucrose, or 8.76 tons of sucrose per acre. This represented a net All the experiments had received superphosphate to the plant gain over the controls without ammonium sulphate of £8 lis. lid. cane and first ratoon crops, and in most cases had shown a per acre, the ammonium sulphate then costing £8 a ton. The satisfactory response. The history of the negative experiments percentage increases in yield for each quantity of fertilizer in seems to suggest that sufficient residual phosphates had accu­ the two crops corresponded remarkably closely throughout, mulated in the soil, thus making further applications unnecessary reaching a maximum of 38 per cent, in the first ratoon 800 lb. for the present, the size of the crop being limited by time in the series. Illovo alluvial and by drought at the other places. Another remarkable example of the benefit obtained from The average crop of sugarcane does not remove much phos­ ammonium sulphate is given in an experiment harvested last phorus from the soil, say about the equivalent of 250 lbs. or June at Kulu (C. F. M. Hibberd)19 as second ratoons of Co.290 300 lbs. of superphosphate per acre ; so that once the original cane. phosphorus deficiency of the soil lias been supplied heavy appli­ cations of superphosphate are probably not necessary in most The soil is a windblown light sand, and both the plant cane soils to maintain the available phosphate contents at an ade­ and first ratoons gave highly significant increases to 30 lbs. or quate level. 45 lbs. of nitrogen per acre, whether applied in the form of ammonium sulphate, sodium nitrate, or whale meal. There are certain soils which have the property of fixing phosphates, that is to say converting any phosphates added to Similar results were obtained with the second ratoons, am­ them into relatively unavailable compounds such as iron or monium sulphate, 225 lbs. per acre, increasing the yield of cane aluminium phosphates. To guard against this possibility and from 28.99 tons per acre without nitrogen to 38.95 tons, the to give the plant cane cycle a good start-off, I believe it is value of the increased sucrose after deducting the cost of the advisable to give the plant cane crop a generous dressing of ammonium sulphate at £16 a ton being as much as £6 3s. 7d. 500 lbs. to 700 lbs. of superphosphate or its equivalent in filter per acre. cake ; but after that it may not be necessary to add much In all last season's experiments 200 lbs. to 300 lbs. per acre phosphates (say 200 lbs. to 300 lbs. per acre of superphosphate) of ammonium sulphate yielded a profit in five experiments out to the ratoons. Until more experimental information about our of eight, the average gain being £3 4s. 6d. per acre. 400 lbs. to soils is forthcoming, the planter must still depend largely on his 500 lbs. gave an average net profit of £1 13s. 2d. per acre over own experience of his soils in this matter. four experiments out of seven; and 800 lbs. yielded £3 4s. lid. profit per acre, positive results being obtained in three cases out POTASSIC FERTILIZER RESULTS. of six. The three negative results were obtained in heavy dry In four of the experiments harvested last season at the Ex­ soils. periment Station (Mount Edgecombe), Verulam, Upper Tongaat and Kulu, in widely different types of soil, potassium chloride SUMMARY OF RESULTS WITH AMMONIUM was tested in quantities ranging from 80 lbs. to 160 lbs. per SULPHATE. acre (50 lbs. to 100 lbs. as K20), with negative results in every The jig-saw puzzle of the last fifteen years concerning the case. While we have found occasionally a response to potash, response of local sugarcane soils to inorganic nitrogenous fer­ such cases have been relatively few, and satisfactory yields were tilizers is therefore now largely solved. obtained in practically every case without potassic fertilizer. It would appear to be unnecessary under present conditions, there­ Practically all types of soil show a profitable response to fore, to apply potash, which is fortunate in view of the position sulphate of ammonia in seasons of normal or excessive rainfall. of the supply of such fertilizers. If the soil has had a good leguminous green manure crop ploughed in before planting with sugarcane the nitrogen is already there in sufficient quantity and applications of nitrogenous fertilizer CONCLUSION. will have no effect. Apparently the same may be said of plant We are much better off for fertilizer supplies for the sugar­ cane crops in certain rich soils where a very heavy crop of weeds cane crop than we would have thought possible in pre-war has been ploughed in. times if we had then imagined a total cessation of imports of In such cases a response to nitrogenous fertilizer may be ammonium sulphate and superphosphate and high-grade rock expected in the ratoon crops. phosphates. In seasons of abnormally low rainfall a response to ammonium The extended practice of green manuring, the full utilization sulphate and the like may be expected in open sandy or sandy of waste products such as filter cake and kraal manure, a loam soils. thorough trial of such materials of South African origin as Karroo manure and the like, will probably supplement sufficiently the Heavy soils well provided with moisture, either irrigated soils scanty supplies of superphosphate and sec us through the or alluvials with a high water table, will also respond, but not present difficult times and those still to come. heavy drought-stricken soils. Even in the latter, however, there may be a response to organic nitrogenous fertilizer such as The production of the maximum sugar crop possible with our whale meal or blood meal; in such cases the nitrogen comes present limited resources of fertilizer, soil moisture, cane varieties, into the soil solution only slowly. field equipment, labour, and transport, and the recovery of the greatest possible amount of sugar from the crop, is an urgent national duty that devolves upon each one of us. SUMMARY OF RESULTS WITH SUPERPHOSPHATE. The results last season from superphosphate as a fertilizer SUMMARY. were not so definite and are less easy to interpret. The pre-war South African consumption of certain fertilizers Eight experiments were harvested in which various quantities is noted, especially ammonium sulphate and superphosphate, of superphosphate ranging from 300 lbs. to 1,500 lbs. per acre and possible local supplies of alternative fertilizer materials (mainly 400 lbs.) were applied, and in four there were profitable considered. 63

Those discussed in some detail are leguminous green manure Mr. GARLAND stressed the fact that the price of sunn hemp crops, farmyard manure, Karroo manure, and filter cake. seed had gone up and was now 41/- to 43/- per bag. Natal Long-term experiments with farmyard manure in Britain and Estates had planted 3,000 acres of sunn hemp and it was planted the U.S.A. are also examined. at different times from July to February, yet nowhere was Comment is made on the new fertilizer compositions laid there sufficient seed to justify the collecting of it. He asked down by the Union Department of Agriculture, and the need for what the reason was for sunn hemp not seeding here, and re­ "straight" fertilizers for sugarcane agriculture is stressed. quested the Experiment Station to investigate the problem. Fertilizer experiments harvested by the Experiment Station Mr. DODDS said that a beginning along these lines had already in .1941 are briefly summarised and the effects of drought on been made. He had written to various quarters, but did not the results in various types of soil are pointed out. get much satisfaction. It was possible that the reason for sunn The need for economy in fertilizer use and for maximum hemp not seeding here was due to insect pests or soil and production of sugar at the present time is expressed. climatic conditions. The VICE-PRESIDENT said that very little 'seed had so far Acknowledgments. been collected at the Experiment Station. He had noticed, The writer acknowledges with thanks the help of Dr. A. however, hat sunn hemp planted in February, although not McMartin in some of the subjects discussed, and thanks also growing nearly so well as that planted in November, did form those planters and estates whose co-operation has made possible some seeds. It was also possible that better results might be a wide range of fertilizer experiments in representative soils. obtained further inland. • Mr. FOWLIE said that some ten years ago he saw a plot of sunn hemp that set quite a lot of seed. It had been suggested that there were different strains of sunn hemp and that some strains seeded much more freely than others. Mr. POUGNET wanted to know whether adding lime to a field before an application of fertilizer would not avoid fixation of plant-foods. He also wanted to know what fertilizer elements were to be found in bagasse ashes. Mr. DODDS said that the fixation of phosphate was a difficult and obscure problem. Superphosphate was water soluble, but on application to the soil the phosphate soon became fixed and hardly any further movement took place. Ashes were poor in fertilizer elements and were not usually in available form. Ashes had been used for composting in certain countries, however. Mr. Dodds stated, in reply to further questions, that generally the most profitable quantity of nitrogen to apply was about 80 lbs. per acre, i.e., 400 lbs. sulphate of ammonia or 500 lbs. nitrate of soda. Under present circumstances he would advise a little less, say 300 lbs. and 400 lbs. respectively. PIG MANAGEMENT FOR BEGINNERS. By P. FOWLIE, N.D.A., N.D.D.

For the purposes of this paper it is assumed that the farmer experienced pig breederin making his purchases. In any case, he intends to breed, rear and fatten his own pigs. This being so, ought to inspect the herd from which he is buying as well as the first problem facing the beginner is to decide what breed the individual animals offered to him. All the records of the and type of pigs he intends to keep, and how many breeding herd ought to be inspected to find out whether the herd as a stock he ought to purchase to make a start. whole, and the near relations of the animals offered for sale, breed satisfactory litters at regular intervals. The best time In this country the best market for pigs is usually through to visit a herd is in the morning, as it is easier to form correct the bacon factories. These require pigs between 180 lbs. and impressions in the morning than in the afternoon. 220 lbs. live weight. They should have attained that weight at as early an age as possible, and should be fat but not excessively One should watch out for any signs of bad temper and avoid so, as South Africa prefers bacon without too much fat. Bacon it. It is also advisable to reject animals showing any signs of pigs should be long in the body with deep sides and an even weak pasterns, particularly when looking for a boar, as it is width from shoulder to ham. The pigs should appear very essential that a stud boar should be strong on his legs. Fecundity smooth, with no creases or flabbiness anywhere. Light coloured and stamina are more important than show points. pigs are preferred by bacon factories, other things being equal, and in temperate countries a large percentage of bacon pigs are QUARANTINE PURCHASED STOCK. either white or have white as the predominating colour. This This does not apply when the first stock are bought; but if includes Tamworths; because they have a white skin, although new slock are brought into an existing herd, they ought to be the hair is red. quarantined for at least a fortnight before mixing with the herd. In many parts of South Africa white pigs are at a serious It is advisable to note how purchased stock have been fed disadvantage, because their skins readily suffer from sunburn by the seller, and to feed them as nearly as possible in the when they are allowed outside. For that reason white pigs can same way at first. Change of feed ought always to be made only be recommended if sufficient shade can be provided. gradually.

It is generally considered that the best bacon pigs are first HOUSING. crosses ; that is to say, the progeny of a pure-breel sow of one It will not be possible to deal with the planning and construc­ breed and a pure-bred boar of another breed. The Tamworth tion of piggeries at great length here, but it is hoped that a few comes nearest to the ideal bacon pig of any of the pure breeds. remarks on general principles may be useful. Sows of the Large White, Large Black and Tamworth breeds usually produce large litters and make good mothers. On the Natal coast it is never necessary to provide warm In England the favourite cross for bacon pigs is the Large houses if plenty of bedding is used. It is more necessary to do White sow and the Middle White boar. In parts of South Africa everything possible to have quarters that will be cool in the where white pigs are not considered satisfactory, the favourite warm season. Pigs are naturally clean animals, if given a cross is the Large Black sow and the Berkshire boar. chance. They ought to have a comfortable bed to sleep on and a clean trough to eat out of. Tamworth sows can also be crossed with either a Middle White or Berkshire boar with good results. For anyone intending to breed and fatten large numbers of pigs, a well-laid-out piggery is highly desirable. A plan ought In the sugar belt shade can usually be provided easily, and to be made before commencing to build. The layout should be both Large Whites and Tamworths are giving good results. such as to suit the site, and ought to be arranged so as to allow These two breeds are being crossed with each other both ways it to be built part by part as required. The feed store and and satisfactory bacon pigs are being obtained, but it would mixing house ought to be in a central position, to make the be interesting to see what could be done by using either a work of feeding as easy as possible. In cold countries a boiler Middle White or a Berkshire boar on these breeds. to provide hot water is considered necessary. On the Natal coast it is possible to do without this, but some arrangement At present some of our breeders are keeping a few of their for getting a supply of hot water is very useful, as sows ought cross-breds for sows to be put with a pure-bred boar. to have their feed and water warmed at and just after farrowing time. It is a good plan to have the pens for brood sows a little This cannot be recommended, because the progeny are not apart from those for the growing and fattening pigs. so even in either colour or quality as first crosses. It is generally found that first crosses grow and fatten more economically than A simple form of piggery in use on many South African farms, either pure-breds or the progeny of cross-bred sows and a including those on the Natal coast, is a long shed with a yard pure-bred boar. in front, divided into pens, so that each pen has sleeping quar­ ters under the shed and feeding space in the yard, with a door SELECTION OF BREEDING STOCK. from the yard to a path outside. A good size is 8 feet by 8 feet To start a herd it is a good plan to purchase young sows under the shed and 8 feet by 12 feet at least in the yard. It which have already had at least one litter and which are safely does not add greatly to the cost to make the yards a little longer. pregnant to a boar of the same breed. The progeny of these will then be pure bred and the best females can be selected to Good piggeries of this type are built with walls of hollow keep for breeding purposes. concrete blocks, floors of concrete and roofs of corrugated iron, malthoid, etc. The writer has not seen concrete roofs used, but This may seem an expensive method, as it means paying a he would like to suggest that they would probably be cooler good price for the foundation sows ; but if they are the right and better than corrugated iron and no more expensive, besides class of stock it will pay in the long run. being everlasting if properly cast and reinforced. A -couple of young boar pigs of the breed to be used for The floors inside the sleeping quarters ought to be nearly crossing can be purchased about the same time and reared level, having only enough fall to the yard to allow water to together. If only one of these is required, as will probably be run out when they are washed. There should be a small kerb the case, the best can be selected and the other sold ; but it about one brick high between the sleeping quarters and the may be considered wise to keep both at least until they are yard, except for a short opening to let water out. This is to proved. keep the bedding from spreading outside. The floors of the yards should have a decided slope towards the door. That is the general scheme; now for some details. This selection of foundation stock is so important that the beginner Houses of this class are suitable for six fattening pigs or a is strongly advised to seek the advice and assistance of some larger number of weaners. 65

This type of house is also often used for brood sows, but is right, a pig can make about one pound of live weight gain not ideal for this purpose. from approximately five pounds of dry matter supplied in its feed. The internal organs of the pig resemble those of the Brood sows ought to have a draught-free place when farrow­ human being much more closely than those of the ruminants ing and for some time afterwards. It is very convenient for the and are not capable of dealing with large quantities of bulky attendant if there is a passage under cover, to allow him to foods high in fibre. At the same time a certain amount of watch a farrowing sow in comfort on. a wet night without being roughage is necessary. inside the pen. GREEN FEED. It is better to have the inside part of a sow's quarters with a wall all round and a door to her outside yard. This makes it Pigs ought to have grass or other green feed, preferably of possible to shut her inside when desired. A good size for a a succulent nature, but this ought not to form a large propor­ farrowing pen is 10 feet bv 10 foot if the sows are big, though tion of their feed. In the absence of suitable green feed they 8 feet by 10 feet will do. can be fed a little lucerne or other legume hay which is best chopped fine and moistened. The farrowing pen should be provided with a farrowing rail, with its underside about 9 inches clear of the floor and the same This green feed is important because it helps to keep the distance from the wall, round at least three sides. This is to internal organs working in a healthy normal way. It thus prevent the sow from lying on her young whilst they are small. enables the pigs to make more economical gains from the grain ration. A good house for brood sows can be made with the pens in two rows. Both rows of pens and a centre passage being covered It has also been found that some of the essential vitamins by one roof. are deficient in grain feeds but are present in most green feeds. All pigs benefit greatly from being allowed to graze and have The following are some of the crops which can be grown for a fair amount of exercise, except those thai are in the last two pigs on the Natal coast. months of their fattening period. If suitable paddocks of fair size can be provided, portable houses with strong wooden floors The Legumes, which are valuable for their high protein con­ well off the ground are very good and can be made at a reason­ tent, include soya beans, cowpeas, velvet beans, peanuts, and able cost in normal times. Full details for the construction of beans of the Canadian Wonder type. These can be fed either houses of this type are given in Bulletin No. 7, 1914, by green or as seed. E. Harrison, M.Se., B.Sc, Iale principal, School of Agriculture, Cruciferous crops include such as rape, kale, and chou mollier Cedara. This is known as the colony system and gives good and turnips. results, when the same care is taken in looking after the comfort and well-being of the pigs as would be given if they are shut Sweet Potatoes are one of the easiest crops to grow and both up. The objections are the space required and the extra work the tops and the tubers can be used for pigs. entailed in feeding and looking after the animals. In such paddocks the food troughs should be movable as well Other crops which might be grown are pumpkins, cattle as the houses, and they should be placed some distance from melons, artichokes, mangels, beet and edible cannas. the houses. When grass is not plentiful in the paddocks other green feed should be supplied. When the ground round the house CONCENTRATED FEEDS. or the trough becomes muddy they can be moved. Maize is fed to pigs in considerable quantities in all the principal pig-keeping countries of the world. Where it is pro­ It is essential that the fences of all pig paddocks should duced locally it is usually much cheaper than any other grain. always be kept in repair, as it is dangerous to allow pigs to American experiments have shown that it can be fed whole or break out. even on the cob and gives good results, so the cost of grinding can be saved. In South Africa a considerable number of pigs become infested by the parasite known as pig measles. This is the bladder It is rich in carbonaceous matter, but is low in protein and worm, Cysticercus celluloses, which is one stage in the life-history lime, not very well supplied with phosphates and very deficient of the human tapeworm, TtBnia solium. in some of the vitamins. In fact, it is not a well balanced feed if fed alone or nearly alone. The "measles" are found embedded in the muscles of the pig in various parts of the body. They do not seem to cause the It is generally agreed that it ought not to form more than about pig much inconvenience and mcasily pigs fatten normally. It is half of the dry matter in pig rations. If properly supplemented only when they are killed that the measles are seen in the flesh. by feeds able to correct its deficiencies it is a very valuable feed. Pigs are very fond of it and make good gains in weight from it. The carcases of measly pigs are condemned at the abattoirs and bacon factories and the producers get nothing for them. Wheat middlings and other by-products from the wheat milling industry are highly valued as feed for brood sows and To become measly a pig must be infected with the eggs of for young pigs up to about three months of age. Their protein the tapeworm which have been excreted by a human being. content is higher than that of other cereals, and this makes Tapeworms are not uncommon in natives in South Africa, hence them specially valuable for milk production and for young there is need to take all possible precautions to prevent pigs animals rapidly growing. In the fattening ration they are not becoming infected. quite so good as maize. Unfortunately under present conditions they are not available. Precautions.—Always keep the pigs in piggeries or in properly fenced paddocks. They ought never to be allowed to roam to Wheat hran is sometimes fed to brood sows in small quantities, any place where infection might be picked up. but its feed value is low compared with the usual price and its chief value is as a corrective of constipation. If the other feeds Provide convenient latrines for all natives and see. that they are right it ought not to be necessary. are used. Barley is highly prized as feed for fattening pigs and produces Dose natives with worm medicines such as Areca nut and a high-class bacon, especially if it can be supplemented with Santonin, or extract of male shield fern if considered necessary. milk^ Pound for pound it does not give as much live weight as maize and it requires to be finely ground. Barley can form FEEDS FOR PIGS. a larger part of the fattening ration than maize but cannot be fed alone with profit. This feed, too, is unobtainable or nearly The pig is capable of making use of nearly all kinds of farm so at present. produce as food, but to obtain good results its feed must be mixed so as to supply a balanced ration suitable for its age Oats are also good feed for pigs if ground, but should not and the immediate end in view. It is a much more economical form more than one-quarter of the grain ration unless the rough producer of flesh than the ox or the sheep. If the ration is husk has been sifted out. 66

Other grains such as kaffir corn, rye and buckwheat can be pigs fed largely on grain. If suitable green feed is given, or if used in pig feeds in small quantities, but all should be ground wheat middlings form a considerable part of the ration, much into meal. In fact, maize is the only grain that can be success­ less is necessary. fully fed without grinding, and that only if fed dry. Separated milk, when available, is the ideal thing to supple­ Molasses are not widely used as feed for pigs,' but where ment grain feed, as it is high in protein and bone-forming molasses are cheap, as they are on the Natal coast, they can minerals. It gives best results if fed fresh from the separator be used with great advantage if the necessary precautions are before it is cold, but can be mixed with the feed and fed after taken. The chief food ingredient in molasses is sugar, which may­ standing about twelve hours if care is taken to clean the mixing be as high as 60 per cent., but they also contain all the essential vessels between each feed. Whichever plan is adopted ought to minerals in fair quantity. be adhered to, as pigs are apt to get scours if they are fed fresh milk at one meal and sour milk at the next. Molasses have a laxative tendency, which up to a point is a valuable tendency, but care must be taken not to give too much. Greatest profit is obtained from separated milk if only enough is fed to balance the ration. P'or weaners this is about 4 lbs. of It is advisable to begin with a little and accustom the pigs separated milk for each pound of grain feed. For pigs from gradually to molasses in their feed. As to the amount that can three to six months old about 3 lbs. of separated milk for each be fed, no definite rule can be laid down, but so long as the pound of grain, and for fattening pigs over six months old animals show no signs of purging the amount is not likely to 2 lbs. of separated milk for each pound of grain. Brood sows be too much. As a general rule it can be taken that fattening may have separated milk if it is plentiful. If only limited pigs may be given up to 1 lb. per 100 lbs. of their live weight, quantities of separated milk are available the weaners will give whilst brood sows and young pigs probably ought to have some­ best returns for its use. It ought to be sterilized as a precaution what less. Approximately IJ lbs. of molasses equals 1 lb. of against tuberculosis, unless the dairy herd is free of that disease, maize grain in feeding value. as tuberculosis can cause serious loss in a pig herd. Leguminous seeds, such as beans, peas, cowpeas, soya beans, Cod liver oil is an excellent addition to the ration of brood peanuts and velvet beans are very good for making up the sows and young pigs. The sow can be given up to one table- protein deficiency of the grain ration, if they can be grown on spoonful in each feed, commencing some days before farrowing. the farm or purchased cheaply enough. Perhaps the easiest of Weaners may have up to a tablcspoonful at each feed for a. these to grow on the Natal coast are soya beans and velvet pen of six or eight animals. beans. Soya beans are the more valuable of the two, as they contain a high percentage of fat as well as protein. However, MANAGEMENT. velvet beans are also a suitable pig feed if ground to meal. The sow carries her young for sixteen weeks, and usually Sometimes they are ground in the pods as they are hard to shell farrows within a day or two either way of that period. It has out. They ought not to form more than 15 per cent, to 20 per been claimed that if sows are given service by the boar before cent, of the ration and are not very suitable for weaners. 10 a.m., a large percentage of them will farrow during the Maize germ meal is much richer in protein than mai2e and daylight hours. The writer cannot say whether this is so, but also contains a fairly high percentage of fat. It is good in if the boar is kept in his own pen at night and allowed out to moderate quantities in a mixed ration, but American trials have the sows after having his morning feed, most of his work is likely shown that it is not a satisfactory supplement to a ration con­ to be done in the morning. sisting largely of maize unless something else, such as meat After service the sows should be kept in a paddock, pre­ meal or fish meal is also added. The same authorities give its ferably large enough to provide some grazing. They ought to feeding value as no higher than that of maize. have two feeds a day of grain feed. Enough to keep them in Brewers' grains, which are fairly rich in proteins and which good condition but not too fat. About 6 lbs. of grain per day are an excellent feed for dairy cows, are not suitable for pigs should be about right, with plenty of grass or green feed. except in small quantities, on account of their high fibre content. W;hen the sow is from one to two weeks from farrowing she Peanut cake and soya Bean cake, which are the residues from should be placed in her farrowing pen each night to get accus­ the seeds after they have had most of their oil extracted, are tomed to it, but she may be run out each day till she shows very rich in protein and are excellent for pigs. Peanut cake signs of milk in her teats, when she is best kept in the farrowing can be obtained in Durban ; the price has been reasonable pen. Her grain ration should then be reduced. If she has been recently, but the supply is limited. It ought to form about having dry feed this can be changed to sloppy food. A little one-fifth of the meal ration for brood sows and weaners, and wheat bran is good at this time, and if she is to be fed wheat one-eighth for fattening pigs if it is the only supplement rich middlings whilst suckling her litter this feed can be started in in protein. moderate quantity before farrowing. A tablcspoonful of cod liver oil in each feed is very useful. Such feed is to ensure that she Linseed and linseed cake are very good, but are not usually will not be constipated when she farrows, but will be in the available here. best condition to farrow easily and to nurse her litter. Cotton seed and cotton seed cake are not safe feeds for pigs, When she comes to farrow, a sow can usually manage with­ though good for cattle. They contain something which may act out any assistance, but the attendant she knows ought to stay as a pig poison. around to see that all goes well and to help if necessary. Some­ times young pigs are bom in a bag. These require to be freed 7 PROTEIN-RICH FEEDS OF ANIMAL ORIGIN. at once to allow them to breathe. W hen farrowing is finished Fish meal is made from fish offal and sometimes from fish. and the afterbirth has been delivered it ought to be removed As it is sterilized in the process of manufacture it is a safe feed. to prevent the sow from eating it. White fish meal is the best, but other qualities may be used. Fish meal may cause bacon to taste fishy if fed to fattening Strangers ought not to be allowed near a farrowing sow and animals in the last stages of fattening. It is recommended that she should be kept as quiet as possible. Many young pigs can fish meal be reduced when pigs reach six months of age and be saved by a careful attendant. stopped at least a month before they are sold. The sow should be fed warm sloppy feed in only moderate Meat meal is made at some abattoirs in this country from quantities for the first day or two, increasing gradually for a offal and condemned carcases. It too is thoroughly sterilized in week. It is better to feed a brood sow three times a day than the process of manufacture and is a safe feed. twice. After the first week she should be getting about 9 lbs. of grain feed per day. This is better fed in a pasty condition Both fish meal and meat meal are usually rather expensive than as slop. After each feed she should have about a gallon feeds, but are very useful in small quantities for correcting the of clean water to drink. As the pigs grow larger and make a balance of the ration by bringing up the protein percentage. greater drain on the sow her feed may be increased gradually They are very rich in protein "and 1 part to 9 parts of grain up to 12 lbs., or even a little over, of grain feed per day, but feed is the highest quantity that is required for sows and young not more than she will clean up quickly. 67

The young pigs will begin to take a little of their mother's it as accurate as possible. The paper is quite a long one for a feed when they are about a month old. It is then a good plan conference such as this, so the author hopes that sins of omission to let them have a small trough of sloppy feed to themselves will be dealt with sympathetically by his audience. which the mother cannot get at. If separated milk is available it should be given to the young pigs. Experiment Station, The males should be castrated at about six weeks old. Many South African Sugar Association, pig breeders spay their female pigs intended for baconers at the Mount Edgecombe. same time, as this makes them rest and fatten better. It is a more delicate operation than castration, but any person can do April, 1942. it after a lesson or two. The young pigs are usually weaned at about eight weeks old. The sow can be allowed back to them two or three times to put her off her milk. She is then put with the other dry Mr. DODDS said that planters had found pig-farming a sows and served again at her first heat. Young sows may be profitable sideline up to now. The present scarcity of mealies kept back for a month or two if they are rather run down and might affect this enterprise, but there were other sources of look as if they would be better to grow out a little. food rich in carbohydrates available, such as sweet potatoes and molasses. The wcaners ought to have the same feed as they have had with their mother for the first month. They should take 2 lbs. Mr. Dodds said that he had corresponded with Mr. Montagu of meal within a few days of weaning and increase to 3 lbs. per Simpson and Mr. Simpson stressed the following points : In a day by the time they are three months old. If they are making hot climate such as the Natal coast, good styes with thickly good progress they should require to have their meal feed thatched roofs, as much shade as possible, and good wallows, increased by about .[ lb. each week, so that they ought to be were important. The progeny of a Tamworth sow, especially if eating 4 lbs. per day at four months, 5 lbs. at five months, etc., a I-arge White boar was used, might grow more quickly than in addition to a variety of green feed. If some separated milk that of a Tamworth boar. The resultant progeny in this case is available less meal will be required. As previously stated, the would, however, be a practically white pig and the effect of proportion of protein-rich food can. be reduced as the total sun-scald would have to be borne in mind. The Berkshire breed amount consumed is increased. was suitable only for porkers, and it was baconers that fetched the best prices. The straight-bred Large White usually gained Pigs make most economical gains from their feed whilst they the top price for baconers, if reared and fed under suitable are young, so they ought to be both growing and fattening all conditions, and was therefore popular in Great Britain. A Large the time. White boar and Large Black sow also gave a very excellent type of baconer and was perhaps the most popular with the If pushed along on the rations indicated they ought to reach pig farmer as a whole. A Tamworth boar and Large White 200 lbs. live weight at about eight months old on the average. sow gave a first-class baconer, and was one of the few crosses Some pig breeders feed the grain ration dry to all pigs over recommended by the Estcourt Bacon Factory. The straight-bred six months old, except to sows when rearing their litters. It is Tamworths also made good baconers, but were not quite so fast easier to measure out the proper amount to each lot of pigs growing as the Large Whites or the crosses referred to. and it is claimed that the pigs do better on a dry ration with plenty of water to drink. Mr. WILKINSON sent the following written comments on this paper:— The following is the Morrison Feeding Standards, taken from "Bacon made from all black pigs is apt to suffer from 'seedy- "Feeds and Feeding," by Henry and Morrison. cut,' that is, the roots of the black bristles show up in the fat, especially in the belly pieces ; whereas by crossing with a white breed, this defect is reduced considerably, if not eliminated entirely. "Whilst white pigs are proved to suffer from sunburn in South Africa, frequent access to a mud wallow and the applica­ tion of oil to the pig's skin go a long way towards reducing skin troubles, including parasites, to a minimum in all breeds. A good method of applying oil is to tie an old sack round a post, which should be firmly fixed in a position where the pigs can get at it to rub against at frequent intervals. The sacking should be kept moist with oil, and old motor oil has been found as good as any for this purpose. It certainly saves hand-oiling. It should be borne in mind that pigs do not perspire through their skins, consequently high temperatures affect them more than animals which perspire freely. It is the reason why pigs die so often of apoplexy in heat waves.

"The beginner who intends to go in for pig-farming on any scale at all, should avoid buying weaners to fatten up on his own farm, even if it should mean a considerable set-back in the The important thing to remember is that the young quickly production of his baconers or porkers. There is no surer and growing animal requires more food for its weight than the older quicker way of introducing diseases to his existing stock. Breed one, and that its food also requires to be richer in flesh-forming up your own herd and keep it isolated, except of course for the proteins. introduction of fresh blood from time to time. Tables giving the composition of foodstuffs are given in "If concrete floors are used, movable wooden floors should "Feeds and Feeding." be installed, made with an airspace underneath, in the sleeping quarters. Pigs are very liable to suffer from rheumatism, The author has gleaned information for this paper from a especially sows, if they sleep on bare concrete. good many sources which cannot be mentioned by name, but he gratefully acknowledges his indebtedness to the authors of "When pigs are kept in paddocks, which are ploughed up at two books to which, he is under special obligation. These are intervals, it will be necessary to 'ring' the pigs, otherwise with "Feeds and Feeding," by Henry and Morrison, and "The In­ their 'rooting' the paddocks will soon be full of small craters dividuality of the Pig," by Robert Morrison. which render ploughing most difficult. The matter in a paper such as this is necessarily very con­ "If there is a scarcity of green crops, ensilage is a good densed in form, but every endeavour has been made to make substitute. 68

"When maize is fed whole, very often a big proportion of it The cuts should be swabbed with a solution of permanganate is passed by the pig in its original whole state, which is very of potash, which should also be used by the operator on his wasteful, being of no food value whatsoever. hands and the knife.

"The following method of castration is recommended for the "Bacon factories have often objected to dry-fed pigs if they beginner: Two men are required for this operation. One holds have not been on to wet food (the consistency of thick porridge) the pig upside down by the hind legs and grips its shoulders between his legs, the pig's back facing forward. By this means for fourteen days before killing. If this is not done, the sides the pig is held practically rigid. The blood runs to its head of bacon were found to be hard or 'boardy,' i.e., not filled out and the operator is able to do his job quickly and efficiently. properly." 69 EIGHTH PROGRESS REPORT ON EXPERIMENTS AT UMFOLOZI.

By P. FOWLIE, N.D.A., N.D.D., and F. L. ALMOND.

Four experiments were harvested on Farm 16, Umfolozi, The following tables give the usual data concerning each during the past season. All these were harvested after one experiment, and at the end an attempt is made to indicate season's growth at ages varying from 11½ to 15 months. In some of the general conclusions to be arrived at from a study of addition, an experiment with unreleased varieties at the U.L.O.A. the results as a whole. Estates, Umfolozi, was harvested and the results are included in this report.

UMFOLOZI EXPERIMENTS Nos. 3 and 4.—Now combined as a Fertilizer Trial on Old Ratoons. Variety P.O.J.2725. Third Fertilized Ratoons, harvested at 15 months old, 12th—19th November, 1941. 7.0

UMFOLOZI EXPERIMENT Nos. 7 (A and B).—Variety Trial, Sixth Ratoon Crop. Harvested at 11½ months old, 26th November to 4th December, 1941. 71 72

Summary of Yield of Three Crops in tons Sucrose per acre. 73

Its most objectionable character is its tendency to arrow profusely at an early age in some seasons. When this happens the crop can be considerably reduced, even if it is harvested at approximately .12 months old, and such a crop is quite unsuit­ able to keep over a second growing season.

During the past two or three years there has been a con­ siderable amount of damage done by a eanc borer, Eldana saccharina, on some farms, chiefly in P.O.J.2725 which has teen allowed to stand over for more than one season. It appears that damage from this borer would not be very serious if the cane could be reaped annually.

P.O.J.2878. This variety has been grown only to a very small extent at Umfolozi, chiefly because in the earlier years after their intro­ The sucrose figures given at the mill do not agree with those duction it gave decidedly less promising results than P.O.J.2725. obtained in the experiments recorded in this paper. At the In experiments at Farm 16 the plant cane and first ratoons mill the sucrose per cent, cane for Co.281 and Co.301 is much were decidedly lower than those of P.O.J.2725, but in older nearer to that for P.O.J.2725 than it is in the experiment ratoons there was very little between the two varieties. It does results. It is suggested that this may be because much of the not arrow like P.O.J.2725, has a more upright habit, and a Co.281 and Co.301 sent to the mill was grown on dry hillside tougher rind. These characters make it a more suitable cane lands, whilst nearly all the P.O.J. 2725 was grown on the flats. for carrying over than P.O.J.2725, and it probably deserves to be more widely planted than it has been up to now. If all were grown on the flats the results obtained in the experiments are probably a more correct comparison of the sucrose per cent. cane than those given by the mill for season Co.290. 1941-42. With the exception of Co.301, which has not had very many The difference in yield of tons sucrose per acre from these trials so far, this cane has been second only to P.O.J.2725 in five varieties has not been very great. Of the two P.O.J. these experiments. It is a cane with many advantages and it varieties P.O.J.272C has been better than P.O.J.2878 on the has enjoyed a large run of popularity throughout the South average for two reasons. It has given definitely higher yields African sugar industry, but it was never largely planted at as plant cane and first ratoons in all the experiments where Umfolozi because planters preferred P.O.J.2725 with its higher they have been compared, although in old ratoons there has sucrose per cent. cane and larger size of sticks. It matures been little difference between them, and it has given a some­ early, and this can be either a good or a bad point according what higher average sucrose per cent. cane. to circumstances. It is useful for reaping early in the season, but it does not keep over well for two seasons at Umfolozi, or There has been a very small difference between the three anywhere, if it has attained a fair size in the first year. Co. varieties, but these experiments would place them in the following order : Co.301, Co.290 and Co.281. Co.301 has been Co.281. grown for a much shorter time than the others, so the average for this variety covers fewer seasons and fewer trials than that Although this cane has not shown up so well in these ex­ for the others, which may possibly be to its advantage. All periments as Co.290, it has attained a much greater degree of these varieties have shown themselves to be good growers and popularity at Umfolozi as well as elsewhere. This popularity is capable of ratooning well. Each has got individual characters, probably well deserved as Co.281 is a very hardy cane. It is both good and bad, which have to be taken into account when well suited to stiff soils and can stand very wet conditions and deciding which variety to plant under the varying conditions also drought for a considerable time without serious injury. It found on the Umfolozi flats. is also one of the best canes to stand over for two seasons. In the following notes an attempt is made to set out some of the advantages and disadvantages of each variety. It has been found to be highly resistant to the cane borer, Eldana saccharina, at Umfolozi, and is now being planted on P.OJ.2725. fields where damaged P.O.J.2725 has been ploughed out. As a This variety quickly came into prominence at Umfolozi and measure to try to eradicate the borer this may be necessary, has been more extensively grown there than any of the other but it probably is not a good change over in every respect. new varieties. These experiments show that its sucrose per cent. cane is 0.0 per cent. higher than P.O.J.2878 and about Its very upright growth of rather thin leaves makes it a 1.5 per cent. higher than the Co. varieties. P.O.J.2725 has cane which does not cover the ground quickly. In order to get given very good plant cane and first ratoon crops, easily beating reasonably quick cover close spacing of rows has been resorted all the others. In older ratoons it has given about the same to. This means additional expense in planting and also in hand yield as the others, on the average. weeding the lines in the plant cane crop. 74

Then taking the sucrose per cent. cane of this variety at comparison with P.O.J.2725, and the small experiment reported 13.5 per cent. against 15 per cent, for P.O.J.2725, both the was laid down at the U.L.O.A. Estate. It did not make a very planters and the mill have to deal with 11 tons of Co.281 to good start and many misses had to be supplied, which made get the same return as from 10 tons of P.O.J.2725, which of the plant cane very uneven.. When it was nearly a year old it course reflects extra costs in handling Co.281. was decided to cut it down and plant another larger experi­ ment with the more promising varieties before it was fit to cut These considerations appear to indicate that where P.O. J.2725 for the mill. can be expected to do well it ought still to be planted in pre­ ference to Co.281. The second experiment, which ought to have been fit to harvest at the same time as the first ratoons of the first one Co.301. reported on below, made a good start, but when it was only a It is not proposed to say much about this variety because, few months old it was almost completely destroyed by flood as already stated, the experiments with it are only in com­ water and only a few plots on the higher side of the field sur­ paratively early stages. It is a very vigorous grower and carries vived, so it had to be abandoned as an experiment. a heavy foliage. This makes it very easily blown over, and we already know it ought to be reaped annually on the flats at Experiment No. I consists of four very small plots of each Umfolozi. If that is kept in mind it is well worth a trial. It variety, so these results cannot be regarded as very reliable, should also be said that it is not an early ripener and gives but the plots have made pretty even growth over the area and best results in the second half of the season. may be taken as a reasonably good indication of the comparative value of the varieties. The outstanding feature of the results ONE SEASON VERSUS TWO SEASON CROPS. is the performance of M.P.R.28, which gave slightly better sucrose per cent, cane and sucrose per acre than P.O.J.2725. These experiments show that it is more profitable with any In this crop P.O.J.2725 did not flower very much, it may be of the varieties to harvest them each year rather than to allow said that it had as good a chance as it ever will have. them to go to two seasons. This indicates that only when necessary should crops be held over for two seasons. The best varieties to hold over are Co.281 and P.O.J.2878. M.P.R.28 is in many respects very similar to P.O.J.2725. So far it has shown no sign of flowering in this country, and it has FERTILIZER. a reputation for not flowering readily in Puerto Rico. It seems a very promising variety for Umfolozi and further results are The fertilizer experiments at Farm 16 have shown no response awaited with interest. to fertilizer of any kind on plant cane and first ratoon crops on what was practically new lands. On old ratoons, however, P.R.809 is another very nice looking cane. Its tonnage was definitely profitable results have been obtained from the appli­ very little behind the other two, but its sucrose per cent, cane cation of nitrogen as sulphate of ammonia. was disappointing.

A new experiment has been planted to compare Government The principal index marks of the cane varieties bred in Puerto guano with sulphate of ammonia alone and with a mixture of Rico are:— sulphate of ammonia and superphosphate. This experiment was planted in January, 1941, and will be reaped this year for the M.P.R., P.R., and F.C. first time. M.P.R. designates canes originally raised at the Puerto Rico Agricultural Experiment Station at Mayaguez, at the western It may be that lands at Umfolozi which have carried cane end of the island ; this station is controlled by the U.S. Depart­ for a considerable number of years may respond to fertilizer, ment of Agriculture. although they did not do so when first planted up. The results from this experiment will be watched with interest. P.R. canes are from the agricultural experiment station of the local government of the island (Puerto Rico, of course, VARIETY TRIALS AT U.L.O.A. ESTATE, being a territory of the U.S.A.). This station is located at Rio UMFOLOZI. Piedras, in the north-central part of the island. As is generally known, frequent importations of canes from overseas are received at the Experiment Station. Some years F.C. canes are raised at the experiment station of a com­ ago a number of seedling canes were received from Puerto Rico. mercial sugar manufacturing company operating Fajardo They are mainly crosses of P.O.J.2725 and SC.12/4, a well-known Central, a large factory on the east coast of Puerto Rico. West Indian variety, and belong to the thick (noble) types of canes. It was felt that such canes could not be expected to Climatic and soil conditions vary widely in different parts of give their best returns under conditions at the Experiment Puerto Rico, although the island is only 100 miles long and Station, so as soon as enough planting material had been grown 36 miles wide; hence the development of several independent there arrangements were made to try them out at Umfolozi in experiment stations each with their own sphere of work.

U.L.O.A. EXPERIMENT No. 1.—TRIAL OF UNRELEASED NEW VARIETIES. First Ratoon Crop, harvested at 18 months old, 24th June, 1941. 75

Significant difference between varieties at 19 : 1 odds = 1.82 tons sucrose per acre. Significant difference between varieties at 99 : 1 odds =2.45 tons sucrose per acre. Percentage significant difference between varieties at 19 : 1 odds = 23.94 per cent. of general mean. Percentage significant difference between varieties at 99 : 1 odds = 32.23 per cent. of general mean. Value of significant difference between varieties at 19 : 1 odds — £.10 7s. l1d. per acre. Value of significant difference between varieties at 99 : 1 odds = £13 19s. 9d. per acre.

until it could get at the water reserves below. He would wel­ come an opportunity to carry out irrigation experiments at Umfolozi. Mr. RAULT said that he was struck once more by the dis­ crepancy between sucrose figures obtained at a commercial mill Higgins, also to the staff of the Umfolozi Co-operative Sugar and an experimental mill. He would also have expected a Planters, Ltd., and to Mr. Kirkwood of the Experiment Station higher sucrose per cent, cane in P.O.J.2725. staff, who did the sucrose tests, the authors are deeply in­ Mr. FOWLIE pointed out that sucrose at Umfolozi was always debted. They wish to thank most heartily all who assisted in very much lower than it was for the rest of the industry. The carrying on the work of the experiments. only point he wanted to make in the paper, however, was that figures obtained with the experimental mill were from canes on They also wish to offer their sympathy with Mrs. Dick and the flats, and as such their order was probably more correct her family in their great loss. The kindness, hospitality and help than the mill figures, as the mill handled Co.281, which came extended" by the late Wm. Dick to all members of the Experi­ mostly from the hills, whereas the P.O.J. were from the flats. ment Station staff were unfailing. They were very much appre­ ciated and will be greatly missed. Mr. DYMOND said that the difference in analyses between cane from experimental plots and the normal mill supply was due to the fact that whereas experimental cane was clean and Experiment Station fresh, mill cane was often dirty and affected by factors such as South African Sugar Association, length of time between cutting and milling, old brake cane, etc. Mount Edgecombe Mr. DODDS said that the method of determining sucrose in March, 1942. experimental plots had been carefully scrutinized and no flaws had been found in them. In these tests both the expressed juice and the resulting bagasse were analysed, whereas the cane testing service depended solely on an arbitrary Java Ratio in Mr. FOWLIE explained, in reply to Mr. Pougnet, that at determining sucrose content of consignments. If, therefore, the Umfolozi the usual spacing between lines was from 5 to 6 feet average quality of the cane entering the mill was lower than for P.O.J.2725, but the tendency was to plant Co.281 much that of the plots, the sucrose returns from them would be too closer, often only 4 to 41/2 feet. These experiments showed that low. Mr. Dodds agreed with Mr. Pougnet that it was quite there was very little difference between 4, 5 and 6 feet planting possible for sucrose in cane to increase for a day or two after for all varieties and only a slight falling-off in yield at 7 feet, cutting. which was not significant under the conditions of these experi­ ments. Mr. GARLAND, replying to Mr. Pougnet, said that Co.290 ratooned quite satisfactorily, provided it was cut every year and That being so, he was not in favour of the closer spacings, was grown on suitable soil. Co.290 was essentially a one-year- even for Co.281. Closer spacing meant increased cost in planting old cane. If it were cut as a year or fifteen months' old cane and planting material and also' hand weeding, as it meant more it ratooned very well, and in some cases had given as many as length of line per acre. five and six satisfactory crops, as shown by experiments carried out by the Experiment Station. If it were left to a two-year-old These experiments had only been carried out on a large scale crop, however, so-called "red rot" set in and the cane de­ at Umfolozi, but there were indications that the same com­ teriorated very quickly, and this affected the subsequent parative results would be obtained elsewhere, though the op­ ratooning. timum planting distance would naturally be closer on hillsides than on Umfolozi flats. There was some indication that the Mr. FOWLIE, replying to a question by Mr. Pougnet, said wider spacings tended to increase sucrose per cent. cane. that it was better to cut cane infected by borer every year, as the effect was not so great the first year as when the borer Mr. DODDS said that irrigation experiments had been started was allowed to multiply and continue its work of destruction at Umfolozi some time ago, but it was found impossible to in the second year. continue them at the time. He thought such experiments would be very desirable. Umfolozi had generally a low rainfall. The Dr. DICK, referring to the same question, said that by cutting soil was very fertile, however, and the water table high, with the cane every year a great number of borers were destroyed. the result that cane seldom showed signs of drought. He The development of the borer depended on climatic conditions, thought, however, that irrigation might help a great deal to but in hot weather it probably went through the complete cycle promote the earlier growth of the cane and help it through . in a month. 76 AGRICULTURAL CONDITIONS AND ACHIEVEMENTS OF RURAL POLICY IN GREECE. By Prof. A. J. BOYAZOGLU, D.Sc. (Econ.).

The case of Greece affords a striking example of what can be currants and wines), olive trees, citrus, apricots, pomegranates, achieved by a country with small potentialities and restricted fig trees, carob trees, mulberries, etc. The plains arc cultivated means, toiling under unfavourable conditions, but utilising with field crops and mainly with cereals (wheat, barley, oats, even the slightest possibilities, with a view to building up its maize, sorghums), cotton, sesame, trifoliums, melons, vegetables economy on a sound basis. and other agricultural products. In the basins, where the "terra rossa" is the general rule, field crops are mainly cultivated. On the other hand, the experience acquired during the last Among them maize is of the greatest importance. It may well thirty years by the application of an economy more or less be said that maize is in a large measure responsible for the planned beforehand may provide some interesting criteria con­ maintenance of the population of these districts, because it is cerning the different measures of rural policy. a plant very well adapted to these climatic, soil and other The rural economy of Greece has been of very great im­ conditions. The slopes are, as a general rule, cultivated with portance for her general economy and social welfare. Suffice it vines, trees and drought-resistant field crops, among which to say that over three-fifths of the population have been living tobacco is of the highest economic value. on agriculture, that the agricultural products exported amounted to nine-tenths of the exports of Greece and that agriculture has The mountains, which occupy the greatest part of the central been contributing to the national income by 35 to 40 per cent. belt, are mainly used for grazing and, in some cases, they bear against 15 per cent. to CO per cent. of industry (and this mostly some forests. In places where conditions permit, some field rural) and crafts, 10 per cent. to 11 per cent. of commerce crops, and particularly rye, are obtained. (again mainly of agricultural products), and less than 1 per cent. The succession of vegetation is the following : In the higher of mining industry. parts it generally consists of Fagetum. This is followed by the Greece is situated in the eastern part of the Mediterranean. Picetum (Balkan spruce). Further down we find the Quercetum. The main block of land is a peninsula, not only surrounded by This is succeeded by the Castanetum, and at the lower lower parts — water on three sides but deeply penetrated by it as well. This as far down as the level of the sea—are the; broad-leaved body is enclosed in a system of islands. perennials and the Pinus halepensis zone. The total area of Greece is about 130,000 square kilometres. Twenty per cent, of the entire area of Greece is cultivated, The population is about 8,000,000. There is therefore a density 15 per cent, is covered by forests, and 05 per cent, is more or of population of about 60 inhabitants per square kilometre. less grazed. But if we compare the population to the cultivated area of the The cattle raised in Greece before the war amounted to about land, which is hardly one-fifth of the total area, then we have 1,000,000 head. They were mainly used for draught and for a density of over 300 inhabitants per square kilometre, which milking purposes. Horses, mules and donkeys were also used is very high indeed, and still more so for a country that is for traction and transportation. These numbered altogether predominantly agricultural. approximately 360,000 head. Yet Greece is much more a sheep About four-fifths of the country is mountainous. Between than a cattle or a horse country. The sheep have since time the mountains we have a number of basins. These increase in immemorial been used principally for milking in conjunction number from north to south, while their area decreases in the with the production of meat (lambs and mutton). Their number same direction. We also have several valleys and a few plains. amounted to about 8,500,000. Goats are also raised for similar The plains in the south are very limited, both as regards their purposes. They numbered about 500,000 head at the time number and area. The three biggest plains, those of Thessa- before the war. In addition, there were raised in Greece about lonika in Central Macedonia, of Serres-Drama in Eastern Mace­ 500,000 to 600,000 pigs. donia, and of Thessaly, are all in the north. The most important rural industries were those of wine and The climate of Greece can roughly be described as being spirits, oil and soaps, flour milling, dairying, and textile and divided into three main zones. The central part, extending from silk industries. In this connection we may also mention tobacco north to south, is continental. The coast belt is in principle and currant curing, fruit and vegetable preserving. Mediterranean, i.e., of mild climate with winter rainfall. But The rural economy of Greece as a whole is characterized by the latter can be subdivided into two—that of the westerly exiguity of land and capital, excess of labour and climatic part, which is characterized by a high rainfall, often exceeding difficulties, and erosion handicaps. As regards the size of the 60 inches a year, and that of the eastern part, which is dry, farming units, small holdings have more or less been the general the rainfall varying from 10 to 20 inches a year. Apart from rule in the past. Farming on a large scale was practically non­ these differences, there is also a notable change of humidity and existent at the beginning of the war. The size of the holdings temperature as one goes from north to south or vice versa, the usually varied from 2 to 40 acres, the most common being the north being wetter and cooler. four to six-acre farming units. These small farms were as a The rivers contain a relatively small quantity of water; general rule intensively cultivated, and the intensity was effected owing, on the one hand, to the permeability of their beds, and, by excess of skilled labour, as there has always been a scarcity on the other, to the high degree of evaporation. of capital in the country. The quality of the soil, agriculturally, varies from place to The devotion of the Greek agriculturist to his land and his place. We can say, however, that the soil of the plains is rather industry and perseverance are proverbial. Most noteworthy is fertile, that in the basins is of medium fertility—being mainly also his skilfulness in coping with adverse climatic, soil and the well-known "terra rossa"—and that left on the mountains other agricultural conditions, notwithstanding the deficiency or can hardly bear any grass, shrubs or forest trees. The existing complete lack of vocational education. One simple example vegetation in the highlands is, as a rule, scattered in places may suffice to give you a picture of the situation. It is no un­ where climatic conditions and erosion still permit it. common occurrence on the rocky slopes of the country to come upon a peasant spending his whole day on the task of digging The outstanding characteristic of the soils of Greece is in­ a pit or two in the hard rock, and then carrying soil, often on sufficiency of inorganic matter and phosphorus. his shoulder in a bag to mix it in the pits with the fragments of the rock extracted and plant one or two olive trees, which The natural vegetation varies widely within the country on will only bear fruit in the lifetime of his son or even his grandson. account of the vast differences in climate, configuration of the surface of the soil, its location and nature, and such other con­ Notwithstanding the existing difficulties, the yields per surface ditions on which vegetation depends. Yet it is possible to unit for most of the products have generally been a little higher summarise it in the following: On the coasts it is that of the than those of the Union of South Africa. Among the excep­ Mediterranean. There are vines (for the production of fruit, tions we have to make special mention of the tobacco, for in 77

Greece it gives rather small quantities per acre, but its quality These were settled in Greece in less than three years. This in is excellent indeed. It has a wonderful aroma, an exceptionally a country which, at that time, had a population of four and a good taste and above all, a very small percentage of nicotine half million and small possibilities at first sight, since there was (from about one-third to one-twentieth of the other tobaccos). already a pronounced exiguity of land and lack of capital. Thus to make up for the smallness of the yield, Greek tobaccos The refugees have been colonized under practically the best can be sold so dear that it usually pays to grow them. and the most economical conditions. The farmers not only These have been the main lines of our economy. As regards very soon became self-sufficient, but also began to contribute the nature of the agricultural production of Greece, I may add to the general welfare and shortly constituted a determining that from the most ancient times up to now there has been a factor of the country's economy. specialization in those plants and animals which are particularly The results of the application of the already mentioned rural favoured by local conditions, both physical and social (such as policy and of the establishment of these refugees have really oil, wines, currants and, in modern times, tobacco). This implied been wonderful. Eleven years after the completion of their the necessity of importing considerable quantities of commodities settlement, the agricultural production of Greece was nearly of prime necessity (such as cereals, sugar, etc.), which accounts tripled and the individual income of the farmers tremendously for the fact that agricultural products make up 50 per cent. of increased. the imports of Greece. Needless to say, this amelioration of the situation in the rural Let us see now the measures of rural policy that have been economy has had a very significant betterment in the conditions taken at different times in Greece, since the historic period and of the life of the farming community and a considerable indirect even before. Many politicians, aristocrats, even scientists and influence on the urban districts. The malnutrition of the popu­ philosophers, had their own farms, and when they could spare lation progressively decreased, diseases such as malaria and a few days or even hours they rushed out into the country. A others greatly diminished, and the whole nation visualized a great and wide interest was taken in agriculture ; the rural new era of increasing welfare. problems were studied by the most eminent men and radical Notwithstanding the existing difficulties and limitations we measures were taken by the State in favour of agriculture from have already alluded to, this optimistic foresight must be con­ the earliest times. The rural districts have been provided with sidered as absolutely justified as, with the adequate develop­ credits for the promotion of agriculture, and special measures ment of research and rural education, the influx of capi al and have been taken in favour of marketing agricultural products. the execution of the rest of ameliorations already planned, a It was considered a great honour for a man to be a farmer. Yet further redoubling of the agricultural production is in no way these measures were of local importance on account of the impossible. peculiar State organization that existed at that period. The case of this country may serve, 1 think, as an example A few years before the last war there came into power one of for many others, because the planning and application on such the greatest men Greece has ever had. I speak of Venizelos. a large scale of a modern rural policy, comprising such a wide From the very first moment that Venizelos became prime colonization, may be considered as one of the greatest experi­ minister of the country (1910) he prepared a wide scheme of ments that have ever been made in this field. The results of rural reforms, and in this direction at least he has been followed this compulsory experiment can also give an idea of the possi­ by most of his successors. bilities of better achievements in cases where things can be studied leisurely beforehand and the applications of the pla.ns The first steps taken were the creation of a department of can be carried out under better conditions. In that case, the agriculture and the organization of provincial agricultural imperfections and faults due both to defective planning and services, as well as research and demonstration stations. These deficient application can evidently be considerably reduced. were followed by radical measures concerning the ownership of rural properties. A general redistribution of land took place and the land was given to the people who cultivated it. Then The VICE-PRESIDENT, in opening the paper for discussion, the economic and vocational collaboration of the agriculturists said that Prof. Boyazoglu, who hailed from Greece, had held through the co-operative societies and chambers of agriculture many positions of great distinction, and he was credited with a was organized. This was then followed by the establishment of large number of scientific works. He had to flee from his country the Agricultural Bank, which was a real agricultural bank, and was at present Director of Rural Economics at the Wit- responding to most of the necessities of the country notwith­ watersrand University. He hoped that his stay in our country standing the scarcity of means available. Agricultural insur­ would be a pleasant one. ances were instituted (against hail, frost, fire and all other possible contrarieties). Dr. HEDLEY said that to settle more than 1,500,000 people in Greece was indeed a feat to be proud of. After this war an The marketing of most agricultural products was organized influx of very many people interested in agriculture would take on a large scale and on a sound basis. A special organization place in this country. He hoped Prof. Bcyazoglu would be able was created to deal with the concentration and disposal of to convey to the Government of this country a scheme which cereals and another (head co-operative and vocational organiza­ would provide homes and futures for these worthy men and tion) for currants. Special measures have also been taken for their families. the marketing of wines, tobacco, olive oil, etc. All organiza­ tions and committees have been under the control of the State, Prof. BOYAZOGLU replied that the Government fully appre­ which participated by officials in their administrative boards. ciated the position. He had been appointed to the chair of There was, however, in each case one responsible person. In Rural Economics with this object in view. most cases agricultural dealing was carried on through co­ operative or other organizations. Yet there was no monopoly. Mr. MOBERLY said that Prof. Boyazoglu must have been A farmer could sell, if he liked, to the merchants. struck by the tremendous differences in almost every aspect between this country and Greece. These two countries, how­ To remedy the exiguity of land, important works of soil ever, had some things in common. In both of them there were reclamation, regularization of the beds of torrents and rivers, areas of low rainfall, badly distributed, and soil of poor fertility and the execution of irrigation and anti-erosion schemes have with the inevitable consequence of soil erosion. He hoped that been carried out. But one of the most wonderful achievements this was one of the many things about which Prof. Boyazoglu in Greek rural policy was that of the colonization and settle­ would be able to give us valuable advice. Soil erosion was so ment of the refugees. This was to make up, in a way, for the serious to-day that the individual could no longer be expected failure we have had in our agricultural education, because the to bear the cost of combating it. Such work must be a whole original scheme was unilateral and to a certain extent national responsibility. wrong. It has also been misapplied in practice. I may remind you that, as a result of the last war against Turkey and the Mr. DODDS said that Prof. Boyazoglu was very enthusiastic special arrangements of exchange of populations that were made about his work and had a remarkable penetration and grasp of for our nationals living in Bulgaria, who were constantly and the essential facts of a new set of conditions. He hoped that systematically persecuted by the Bulgarian Government and while the Professor was in Natal the sugar industry would take the population, we received in an incredibly short time in Greece full advantage of his talents in getting him to draw up an more than one and a half million men, women and children. economic survey of the industry. 78 EXPERIMENTS ON THE COMPOSTING OF SUGARCANE TRASH. By A. McMARTIN.

The Indore method was originally designed to convert into Although the fact was demonstrated that a mixture of cane compost mixed residues from crops and habitation wastes, a trash and greenstuff could be rotted down to a finely decom­ process which presented little difficulty as long as the materials posed product, the cost of doing so could not be evaluated, an used were such mixtures. Greater difficulty was experienced, item which would largely determine the value of the process to however, when the attempt was made to apply this process to the planter. single materials, such as the by-products of plantation crops, Accordingly a series of experiments was carried out on a e.g., sugarcane trash and cotton stalks. much larger scale, involving the handling of some tons of trash, In a paper by Tambe and Wad on "Humus Manufactured which it was felt would provide data from which an estimate of from Cane Trash," reproduced in the "S.A. Sugar Journal" in the cost of production could be derived. March, 1937, the authors record that using cane trash alone, In carrying out these experiments the attempt was made to the standard technique—i.e., composting by means of dung, put into them as little labour as possible, provided that the slurry (urine-earth, wood ash and dung), urine-earth and Adco— end was being achieved, i.e., the heaps were decomposing. It failed to give results. They noted, however, that cane trash in was realised that quicker results could probably be obtained if small quantities in mixed residues decomposed readily, and also more work, in the way of turning the heaps, was performed, that if molasses were added to an old but undecomposed heap, and also that if the rainfall was deficient the addition of water the trash crumbled and produced good compost; the addition would hasten the process ; these items, however, would all of molasses to fresh trash, however, left the latter largely un­ increase the cost. Moreover, it is questionable if speed is of affected. vital importance, as probably in actual practice the compost derived from the trash from this year's crop would not in the The conclusions the authors came to were that cane trash bulk of cases be required till next season's planting. must be kept in contact with an actively fermenting mass until it became capable of carrying on the decomposition by itself, In making the heaps, also, variations of the constituent a condition which they finally achieved by making heaps of materials were tried, principally to see if the addition of ex­ alternating layers of green material (grass, weeds or leaves) and traneous green matter was essential, or could be replaced by cane trash. other materials, e.g., by filter cake. Weights were kept of all the materials used, and chemical analyses were also carried out The heaps were turned four or five times, and to some of on them both before use, and when the compost was ready, in them fresh green stuff was added at each turn, while in others order to determine the changes in plant-food occurring during no more such material was added at the turns; the latter, they the process. found, decomposed to a greater degree of fineness. These authors found that by this means, compost could be made in FIRST SERIES. 140 days or earlier, with intermittent rainfall. It should be The first series, consisting of eight heaps, were started on noted from their time-table of operations, however, given in the the 7th May, 1940. These heaps were made on a field close to paper, that this rainfall amounted to 57 inches. that in which the trash was lying, and were made immediately the cane was cut. (In a second series the trash was used after PRELIMINARY EXPERIMENTS AT THE it had been lying on the ground for some time.) EXPERIMENT STATION. The heaps were built about 8 feet broad, 3 to 4 feet high, The first attempt to produce compost from cane trash here and as long as the material allowed (the amount of material was made on a very small scale, and was intended merely to was largely determined by the amount of trash available from try the process, and to provide some material with which to one day's cutting ; as this was from a number of small experi­ make, when mixed with soil, a suitable seed-sowing medium for mental plots, all the cane of which had to be individually raising sugarcane from seed in tins in the glasshouse. weighed, the amount of trash was considerably smaller than In this trial, layers of trash, about 4 inches deep, were would be produced on a day's cutting of commercial cane.) alternated with layers of lawn grass clippings, and instead of a The trash was laid in layers 4 to 6 inches deep, alternating slurry,' the heap watered with one per cent. molasses solution. with layers of greenstuff (where used) about 2 inches deep. The heap was periodically turned, and when crumbling began, After each two layers were laid down the material was watered, sunn hemp was sown on the top, and turned in at the last in some heaps with 1 per cent. molasses, in others with 10 per turning. The heap rotted well, and was allowed to decompose cent. molasses. till it had the consistency of earth, a stage of decomposition The watering presented some difficulty and is a factor which which is usually considered too far gone for field application, would have to be contended with wherever compost is being but which was wanted for the purpose in view. This took five made in the field, especially during seasons or years of deficient months to accomplish, at which time it had the following rainfall, unless the planter is in the fortunate position of having analysis, supplied by Dr. E. R. Orchard of the Division of a supply at hand. Chemical Services, who was interested at the time in compost In this case the water had to be carted from the laboratory ; manufacture:— it was applied at the start with bucket pumps, in an attempt Analysis of Air-dry Material. to soak the material as thoroughly as possible. This method, Moisture 5.60 per cent. however, was found too slow and ineffectual, and was discon­ tinued in favour of watering cans, or even open tins. Loss on ignition 37.40 per cent. In building the heaps the centres were kept lower than the Available P205 0.16 per cent. sides, to prevent the liquid running off ; the bottom and the top layers were of trash. Available K20 0.05 per cent. Total nitrogen 1.30 per cent. It was soon discovered that the particular site chosen for these heaps was an unfortunate one, however, in that it was Dr. Orchard stated that "the analysis reveals a compost rich in too exopsed to wind, which caused too great a drying-out of nitrogen and with a high organic matter content, but, like most the material, and also that it prevented the rise in temperature composts not treated with phosphate, the P2O5 content is very which should accompany the decomposition process. The heaps low. The K2O content is also lower than is usually the case." barely heated during a great part of the time they were lying in the field, and only after the trash had weathered very slowly A similar heap was later made with bagasse, which, although did the breaking-down begin. it appeared more resistant to decomposition and took longer, eventually rotted to a fine state of decomposition. The heaps were first turned after six weeks. After three months very little change was noticed in most of the heaps, It was realised, of course, that the making of composit in such and it was decided to see whether a further watering, with the small heaps bore no resemblance to field practice. provision of some means of retaining moisture, would hasten 79

the process. For this purpose a portion of about one-third of The percentage analyses are as follows :— each heap was cut off, turned, watered (with water alone), and had earth thrown over it. It was realised that this would upset our final weights from the experimental point of view, but it was hoped this would be compensated for by any additional information gained of an observational character. Very soon a difference between those portions of the heaps with this treat­ ment and the remainder of the heaps was noticed, in that decomposition was proceeding more quickly, in some cases markedly so. After another three months, however, the process appeared to have stopped, and all the heaps received another turning (after a soaking with rain), so that in each heap one portion had three turnings, and one only two turnings. Heap No. 3. There was considerable difference in the manner in which the Here the additional green matter was replaced by filter cake, heaps rotted, the first ones being ready by the beginning of January, 1941. At this stage all the heaps were weighed, com­ supplied by Messrs. Natal Estates, Ltd. pared and analysed. The materials used were :— The length of time taken to decompose may be attributed to the fact that fresh trash was used, that the heaps were built during the cooler months, and largely to the drying-out which took place. The fact nevertheless remains that compost was made in some cases with only two turnings, and with no addi­ tional artificial watering after the first when the heap was made. The following are the details of the different heaps made :—

Heap No. 1. If it is necessary to have the material to be decomposed, i.e., trash, in contact with green material, the question occurred, This heap rotted fairly well, but not so well as No. 2. It was would the green tops of the crop be sufficient in quantity and barely ready for use when the latter was. of the right nature to effect this process ? This heap therefore The percentage analyses were :— consistedl merely of trash and fresh tops, watered with I per cent. molasses. The quantities were :—

4,121 lbs. dry matter. Heap No. 4. Decomposition here was practically nil. The tops simply dried In this heap sunn hemp was used in addition to the cane without fermenting, and when the heaps were finally weighed material. The quantities used were :— this one was dry and of almost the same consistency as when made. The portion split off and covered was, however, moist and more decomposed. The following are the percentage analyses of the material:—

In opening up this heap it was found that decomposition had not proceeded evenly throughout, and while in part rotting had The total dry matter in the heap when finished was 2,790 lbs. been satisfactory and good compost made, in other parts the It was clearly demonstrated, then, that under the conditions heap was dry and only slightly decomposed. It was felt that of this experiment, at any rate, the green tops of the cane itself this was due probably to bad building of the heap, and not to were not effectual in promoting decomposition. the fault of the materials, as where rotting had proceeded it was as good as heap No. 2. Heap No. 2. The percentage analyses are as follows :— In this heap velvet beans were added to the mixed cane tops and trash. The materials used were :—

Heap No. 5. Here, in addition to sunn hemp, molasses of 10 per cent, This heap rotted down well, and produced a compost ready for strength was used, and lime (burned lime) was also added. The use at the time of weighing. quantities were:— 80

This heap, when opened, was fairly moist, and decomposition was proceeding; it was not, however, nearly so well broken down as some of the heaps. The percentage analyses were as follows :—

This heap was moist when opened up, but not very well rotted. The percentage analyses were :— Heap No. 8. This heap consisted of cane tops and trash, sunn hemp, and 1 per cent. molasses, but differed from the others in the method of building. With the object in view of spending loss time in making the heap, the materials were dumped in broader layers and built higher, a boy standing on top to whom the others pitched up the material when the heap got too high to build from the ground. The quantities used were :—

Heap No. 6. This heap had the same constituents as the last one, except that the lime was replaced by filter cake. The composition was :— On opening up this heap is was found to be very patchy inside. Decomposition had only proceeded in parts, and there were large parts which were dry and not rotted. The percentage analyses were :—

This heap decomposed better than any other, producing a good friable compost ready for use at the time of weighing. The percentage analyses were :— From these experiments, then, it was seen that the cane materials in themselves were insufficient to produce compost— at any rate, as quickly as when mixed with other materials. It may be that, if left long enough and kept watered, a compost might be produced, but the process would be stow. The addition of extraneous fermentable material is desirable, e.g., filter cake or green material. It should be noted here that the filter cake used here was from the carbonatation process; that from the sulphitation process might have given different, perhaps better results. As far as green matter is concerned, either velvet beans or sunn hemp appeared equally effective ; the latter, however, appeared more easily handled. The addition of filter cake as well as greenstuff produced the most decom­ posed compost, but as the heap without filter cake but with Heap No. 7. green matter was in a condition to use, it did not seem that the former was necessary. Here the heap was made of cane material and sunn hemp, but instead of watering with molasses, a slurry of cowdung, On the whole, it was shown that compost could be made soil and wood ashes was used. The quantities were :— simply with cane trash and green matter, provided the proper conditions were supplied. It should be noted, in examining the analyses given, that they are presented only on the percentage basis, of the dry material. The total weights of plant-food materials in the heaps before and after making are not given, as due to the addition of some soil to one portion of the heaps, the weights were altered. Examining the figures we did obtain, however, it was clear that in the process of making the compost a considerable loss in total plant-food had occurred ; although, e.g., the percentage of N in many cases had increased, the total amount of this material had decreased. 81

SECOND SERIES. Heap 1A. From experience gained in the experiments just described, both in the making of the heaps and in the materials to use, it was decided to start a second series of experiments, to confirm these points and, further, to test the action of molasses ; it will be recalled that in the last series all the heaps except one had molasses. In this series, the intention was to make as simple a mixture as possible, such as could be made on a plantation. It was also intended to omit the addition of water after the first wetting when the heaps were made, and to leave the wetting to the rainfall. Unfortunately, the rainfall that materialised was so much less than could be expected in normal seasons that water had to be applied. In doing so, however, the amount added was calculated to make up the deficit in rainfall between what had been re­ ceived and the average for past years. These heaps were built in February, with trash from a crop that had been cut about the same time as that which provided the trash for the first series ; it had therefore lain on the field for some months, and having weathered considerably Heap IB.—With extra velvet beans added. was much less resistant than the first trash used. The heaps were built as in the first series, with a layer of trash about 6 inches deep alternating with a 2-inch layer of velvet beans. The latter were wilted for a clay or more before using, as is now usually recommenced in the literature on com­ post making. In making these heaps, however, they were packed more firmly by having a boy on top tramping them down. Only two heaps were made ; one was watered with water alone, while the other had 1 per cent. molasses solution applied. After the heaps were built, the two sides exposed to the prevailing wind were covered by having cane tops laid up against them, and the tops of the heaps were covered over with a layer of dry trash, in an attempt to prevent drying out. This proved quite effective, as the heaps remained moist and heated immediately. Daily records of the temperatures were kept and showed a considerable rise in temperature, followed by a decline. The heap without the molasses showed the highest temperature. At the end of a month the heaps were turned. At this point it was decided to see whether the further addition of velvet beans would appreciably affect the process; each heap was therefore split in two, and re-weighed, and to one-half of each heap the green matter was added. The heaps were also watered, Heap 2. as mentioned, although it was not intended to do so originally. The heaps were covered as before, and again a considerable rise The materials used were:— in temperature was recorded. Higher temperatures were recorded by those with the extra green stuff, the highest being that which also had no molasses. After another six weeks the heaps were again turned, no water being added this time, and again after another month, when water was added. This was in May, after which they were left. Decomposition was much better in this series than during the first, the quickest being in the heaps without molasses, and of these in the one with extra green material added. At the beginning of September, thirty weeks after making the heaps, they were weighed and analysed. At this date they were ready At the first turn, when dividing, the materials used in making for use. The details are as follows :— were:— Heap 2A. Heap 1. The materials used were :—•

At the first turn, when divided into two, the materials used for each heap were :— 82

CONCLUSION. The conclusions one would draw, then, from all these experi­ ments are, that it is possible to decompose cane trash, and at the same time utilize other by-products, e.g., filter cake ; but compost can also be made with trash and green stuff alone. For use in September, as in this case, the best compost was that made in February from old trash. On a farm scale this might involve collecting trash from the field into heaps till it is required for making the compost heaps, or till green stuff was available. It is doubtful if, without a good deal of expense, trash from one crop could be converted into compost for use in the same season's planting. Finally, whether the whole procedure of making compost is economically sound is a debatable point; it would require further experimentation to determine whether, for example, any advantage is gained by collecting the trash oil the ground, These heaps, then, made compost of nitrogen content varying mixing it with green stuff, and after spending 6/6 per ton for from 0.7 per cent. to 0.9 per cent.; it will be noted, however, labour on it, putting it back again, compared with ploughing-in by examining the figures, that during the process of manufacture the trash and sowing the green stuff to be ploughed-in later there has been a loss in total nitrogen. The highest nitrogen on. There might be some justification for the process, however, heaps, of course, were those with the two additions of velvet if the compost is made from trash from good fields and put back beans. into the poorer ones, or into poor spots in the same field, although even this docs appear somewhat like robbing Peter to pay Paul. This series, then, showed that compost could be made from cane trash and green matter alone, provided they are kept damp ; it seemed also that weathered trash was better than SUMMARY. fresh trash. Another advantage of allowing the trash to lie for Experiments are described in which sugarcane trash was some time before using it in this case was, the fact that it decomposed into compost by means of the addition of green had not decomposed so far before being used, as the compost material, either as velvet beans or sunn hemp, with or without made earlier. It is generally recognised that the material should the addition of filter cake, or molasses. be bulky, and not earthy, the latter condition being that now It was found that trash and green material alone made a of the first-made heaps. After these latter had been analysed, good compost, when built into heaps consisting of alternate they were all heaped together to lie till they could bo used. At layers of the two materials, and kept clamp. this stage, in September, the percentage analysis of this compost heap was:— It was found that decomposition was greatly facilitated when the heaps were provided with shelter against wind, and when Dry matter. Ash. N. K-O. P20 . trash which had been lying in the field for some time was used. 60.1 83.0 0.40 0.34 o". 19 It was also found that if the compost is left too long in the Thus the compost from the second series was very much better. heap once it had been made, it breaks down to a material of the consistency of earth, with a loss of organic matter, and a COST OF MANUFACTURE. resulting increase in the cost per ton by the time it is used. Account was kept of the labour used in collecting the trash, The labour costs of making the compost amounted to about carting it to the site of the heaps by means of a wagon and 6/6 per ton. eight mules, building the heaps, cutting the green matter, carting it and other materials, and turning the heaps. This Chemical analyses are given of the materials used, and of the worked out at about 6/6 per ton of compost when ready to use. resulting composts. These show that while there may be an On a plantation scale this would probably be reduced somewhat. increase in the percentage of the various plant-foods resulting It should be pointed out here that the longer the compost lies from the process, there is a loss in the total plant-food. after it is ready for use, however, the lighter it gets, and there­ These investigations were carried out by members of the for the cost per ton increases—another point in favour of not botanical, agricultural and chemical staffs of the Experiment making the material too early. Station.

Experiment Station, South African Sugar Association, Mount Edgecombe. April, 1942 83 ORGANIC MANURES IN MAURITIUS. By G. C. DYMOND.

For more than 100 years, the production and return of COMPOST MANURES. organic residues has been a tradition and a basic principle of It can be truly said that "compost manures" form' the basis agriculture in Mauritius. There is little doubt that this age-old of all manurial treatment of the plant cane crop in Mauritius. practice has played an important part in maintaining that general level of fertility, so noticeable in the heavily cropped Two main types of this material are recognised, "fumier," cane lands of this tropical island 1,500 miles from Durban. which is made from cane trash, grass and weeds, rotted with cattle droppings, and "saccharogene," which is a mixture of Before dealing with this specific subject, I should like to filter cake, molasses, ashes and bagasse, with a variable quantity give you a few descriptive notes on this 720 square miles of land of coral sand. in the Tropic of Capricorn. With regard to the former, fumier varies considerably in its Mauritius has a mixed population of about 410,000. Out of a quality. Thus Indian smallholders with one or two oxen, pro­ total acreage of 400,800, there are 143,497 under sugarcane ; duce what is called "long manure," a compost in which the for sugar constitutes 97 per cent, of the potential wealth of the original materials are low in plant food and only partially rotted, island. I say "potential," because the value of their primary owing to exposure to heavy rain without catchment facilities. product has varied from an extreme high of over £90 per ton, to an extreme low of under £5. At some of the estates the manufacture of both fumier and saccharogene is a highly developed business. At Benares, for The conditions of sugarcane agriculture and sugar manufacture example, 1,500 tons of compost are made under cover each differ considerably from those existing in Natal and Zululand, year. This requires the carting in single ox-carts of 750 tons of due primarily to peculiarities of soil, climate and rainfall. trash and weeds, and involves the use of 11,905 labour days per year. At an average labour cost of 55 cents per day, the The soil is of volcanic origin, its rocks consisting almost labour bill amounts to approximately £500. Costs are carefully entirely of basalt and its varieties trap, trachyte, lava, etc. kept, the total cost per ton working out at 6/6. The number of The rocky nature of some of: their cane fields is something that cattle required to produce this 1,500 tons is 140, or roughly has to bo seen to be believed. In consequence, the use of 11 tons of compost per head. All of these animals are kept mechanical implements is restricted. specifically for this purpose and live their lives as manurial An incredible amount of labour is expended in collecting the machines in specially constructed stables. stones and rocks, and packing them into walls, which separate At Mon Tresor, 5,000 tons of compost are made from 300 every second cane row. These ramparts are moved every five cattle and 500 sheep and goats. The costs here were approxi­ or six years, when the cane is replanted in fresh holes between mately the same as at Benares. the remaining rocks. The resulting aspect of the cane fields, before they become covered over, is something that must be The trash used at these estates is from cane which is to be unique in the history of sugar production. replanted ; all other canes are stripped and the trash banked between the cane rows. Weeds and grass, such as the variety The rainfall, though usually abundant, is unevenly distributed, called "chindent" or "dogs teeth," on account of its tenacity, as it ranges from 50 inches per annum in the coastal areas to are all collected from the brakes and roadside and laboriously 175 inches and over up country. The soil is porous, and despite brought to the composting site. In Natal cane cleaning devices, the good rainfall irrigation is extensively practised. such as have been developed in Hawaii, would provide all the trash required for any compost programme. The principal canes being grown to-day are BH. 10/12 and a Mauritian seedling M.134/32, which is a cross between P.O.J.2878 In most cases the compost is made in large rectangular blocks and D.109. above the level of the ground. Concrete ditches surround these In the north of the island, planting takes place between May sites and various devices are used for the return of drainage. and June, while in the cooler uplands (about 1,800 feet) it is In all cases I saw, there appeared a lack of aeration, while the done between September and December. Five ratoons are the mass was kept too wet. Another method consists of a deep general limit and the cane is harvested each year, when it is covered excavation adjacent to the stables, where the cattle are 12 to 16 months old. The standing cane in each field is hand- fed and gradually raise themselves to ground level, by alternate trashed once and often twice before cutting, the trash being layers of trash and their own excreta. placed in alternate cane lines. This old-established custom costs The following is the composition of fumier and goat manure, from four shillings to six shillings per acre. This practice, it is as recorded by N. Craig Bulletin No. 11. said, prevents the growth of aerial roots and side shoots behind the dead leaf sheaths common in humid climates. It also assists the cutters in reaping and sending only clean cane to the mills, an important condition not observed in this country. The average yield of cane per acre per year is about 22 tons. This figure is, however, affected by low yielding native areas, as on well controlled estates yields up to 50 tons are obtained. The price paid for cane varies from 11/- to 13/- per ton, from which the planter normally makes 3/- profit. Sugar production during the last three years was :— 1939.

Saccharogene is a variable mixture of filter cake, molasses, ashes, bagasse and coral sand. At Medine, the dunder from the There are 30 sugar factories operating at present in Mauritius. distillery is heavily limed in concrete tanks and allowed to Owing to the short crushing season (about ninety days) a great settle. The supernatant liquid is run into the irrigation water deal more care is paid to the agricultural side than is the case and the sludge added to the saccharogene beds. in Natal. Thus planting is always done during the most favour­ able period and from selected material. The top portion of the It is stated that differences in the composition of this material cane only is used and this is soaked for ten days in lime water arc not only due to varying factory processes of clarification, prior to planting. but also by "differences in the cane supply." So varietal canes 84

grown under identical conditions show varying quantities of physical condition and excessive air penetration. The following P205 in the juice. Thus :— are the analyses of composts made with various sunn hemp Grms. P206 in admixtures :•—- 100 ml. Juice. Sunn hemp, Sunn hemp Sunn hemp, trash and White Tanna 0.025 Sunn hemp and kraal trash and kraal R.P.8 0.015 only. manure. filter cake. manure. R.P.73 0.006 Moisture ... 76.00 54.25 60.00 66.75 Loss on ignition ... 48.80 31.35 33.85 38.55 BH.10/12 is stated to contain very much less P206 than "White Tanna. It is regrettable that similar investigations started by Nitrogen 1.78 1.28 1.55 1.44 the Clarification Committee in this country some years ago were Total P205 0.44 0.44 0.57 0.67 not continued. Available P 2O 5 . ... 0.20 0.23 0.25 0.27 In regard to molasses, V. Olivier, Sans Souci, found a distinct Total K 2O ... 0.70 0.41 0.75 0.44 relationship between the potash content and the rainfall—the Available K2O... 0.45 0.14 0.54 0.17 potash increasing as the rainfall decreased. This is an interest­ ing point that might be investigated in this country. I am not prepared to venture an opinion, at this stage, into the relative merits of ploughing-in the green crop or composting The average analysis of saccharogene is :— if off the field. Pot tests by either method give excellent results, Water. Nitrogen. Pa06. KsO. but costs can only be ascertained by careful measurements. 39.0 0.98 2.87 1.64 As is to be expected, composts made from sunn hemp give Composting is laborious, costly and primitive. Artificials are better nitrogen results than that from trash only. Thus :•— very costly, simple of application, and a gamble. The effect of Garden the first is long-term, the effects of the latter are to be found Trash, kraal refuse with in a million conflicting reports. It is probable, in my opinion, Trash and manure and inoculated Trash and kraal molasses kraal that they would not be so conflicting if their use were based, filter cake. manure. inoculated. manure. as in Mauritius, on a basic policy of organic composted manures. Moisture ... 58.60 56.90 56.10 51.30 One of the reasons against the more popular development of Organic matter ... 26.05 24.00 26.00 18.35 composting, is the costly and laborious routine of turning the Nitrogen 0.87 1.05 1 .08 0.84 heaps. This, I have found, can be obviated by the use of a crowbar, which not only can be made to provide the necessary Total P 205 ... 1.54 0.45 0.42 0.45 aeration during the first two months, but enables the minimum Available P205 . 0.25 0.24 0.25 0.31 quantity of water to be used effectively. In this way, the heaps Total K20 0.31 0.52 0.67 0.93 can be protected by adequate coverings of earth, or other suit­ able material, without excessive heat or moisture loss. Owing to the war and the consequent lack and high price of artificials, interest in composts has increased, though practice The methods of application of composts vary in Mauritius. in this country will doubtless wait upon the blessing of the In general—-that is in those districts where the rainfall is between Experiment Station. 60 and 100 inches per annum, a comparatively small amount is applied with the setts on planting, and the remainder when the The subject has, however, been very well reviewed in the cane is from four to six months old (about 17 tons per acre is November issue of the International Sugar Journal.1 This is the the total average application). The second application is made concluding paragraph :— in small furrows around each stool. The breaking of the surface roots is said to cause the plant to tiller and so send out fresh "It is no longer sufficient to consider it (soil fertility) in its roots. The beneficial result is said to be visually apparent. purely physical and chemical aspects, a problem of soil texture in which the role assigned to humus is the simple one of In the drier districts—that is those with less than 60 inches affecting texture, or of amounts of available plant-food, par­ per annum—all the manure is applied at planting. This en­ ticularly nitrogen, phosphorus and potash. Humus undoubt­ courages germination and assists in the conservation of moisture. edly plays a far more subtle role, the details of which have yet to be worked out. In a recent paper R. J. Borden writes : Conversely, where the rainfall is over 100 inches, composts 'It is quite apparent from the data presented herein that soil are only applied after the cane is from four to six months old. fertility includes something else besides N, P and K. It is our No further additions of pen manures are made until the third feeling that this "something else" is largely the relationship ratoon, which conforms with Turner's observations in Trinidad, between the soil organic matter and its rate of decomposi­ that organic manures have a residual effect up to the second tion. . . . Its (organic matter) rate of decomposition will be ratoon. governed by the number and kind of micro-organisms.' Considering the rocky nature of the island, it is not surprising "May not the key which will provide an answer to this that the growing and ploughing-in of green crops, such as sunn questioning, be found in the mycorrhiza associated with the hemp, is not practised. cane plant ?'' At Maidstone, Natal, sunn hemp has been gathered and com­ In conclusion, I hope that these;. notes will add to the sum- posted. Following this method, I find that a normal crop of total of knowledge on an age-old method, and that practice will sunn hemp (roots and stalks), approximately 4 feet 6 inches not wait upon the slow scientific final proof, but will rapidly high, means 9.9 tons of green material per acre. Of this, 6.4 develop along the long-view policy of making and keeping our tons is water and 3.5 tons dry matter. The nitrogen amounts land fertile for the centuries ahead. to 150 lbs. per acre and the total ash 240 lbs. Sunn hemp can be composted with trash, kraal manure or Reference. filter cake, but by itself rotting is delayed, due probably to its 1 H. M. L. (1941): "Specialization, Susceptibility and Symbiosis." I.S.J., 43, 330. COMPOSTING GARDEN REFUSE. By P. ROBERTSHAW, F.R.H.S., F.I.P.A., Director, Parks and Gardens, Durban.

When I received an invitation to speak at this Conference I labour for us in town and in the country. I will be fair and deal was rather reluctant to accept, as I felt that the subjects you with our town-dwellers first. We have, in Durban, a city of are most interested in were of such a nature that I could offer which we should be proud, but, like every city and town in very little information likely to be of value, but after considera­ the world, it has features which require to be changed. We tion I decided to place before you a few points concerned with have our slums and we have under-nourished people, both the disposal and use of garden refuse and the benefits to be Europeans as well as non-Europeans. Charity and relief work obtained as the result of its use. is not the solution of the problem. When we are at war we spend sums of money, far too large to appreciate their size, on The actual operations concerned with composting have destruction in order that we might survive. When war is over received world-wide attention and books have been written on wo are faced with all kinds of problems, and many of them are the subject. Care has been taken to analyse the resulting set aside because we cannot afford them—at least, that is material to find the value as a moans of supplying plant-food. usually the reason given. At your meeting last year interesting facts and figures were put forward dealing with the manurial values and the cost of In a vast country like South Africa there should be no need production in comparison with fertilizers. for the overcrowding and terrible conditions in which people live, if we tackled the job in the same costly way as we do a I realise the tremendous difficulties experienced where large war. If we want war material a large sum is collected in a few areas have to be considered. The cost in labour and transport days. If we want a housing scheme we talk about if for years. is enormous, and this alone makes the process impossible to This may seem to be getting away from my main topic, but it manage on such a scale. It is not my intention, to-day, to enter illustrates what I have to suggest. into any details upon the phases of the work which have been covered in books or at previous meetings. I would like to attract Unless we consider the health and living conditions of our your interest from an entirely different point of view. labourers, then the labour is certain to suffer and the output is lessened. In recent years housing schemes have been commenced You will agree with me that healthy labour is half the battle and plots of ground have been allocated to the tenants. At the in any job. For some time I have been taking an interest in Lamont Native Location, situated near the Umlaas River on the study of the health and welfare of non-European labour, the South Coast road, steps have been taken to encourage the studying the conditions in which they live and their manner tenants to produce vegetables for their own use. A lecture was of feeding. As there is a large population of such labour em­ given to a large audience of women a few days ago and interest ployed in the production of sugar, I feel that the subject might was aroused. be considered here. Demonstrations have been arranged to teach the composting As you are aware, the health of many of these people is in process and practical assistance will be given to produce a a state which is causing alarm to many eminent authorities who routine system of cropping to overcome the present method of are making a close study of it, and who are devoting their lives putting in a crop and waiting until that is finished before putting to attempt to improve the conditions. An example of what has in the next. been achieved in an area near Bulwer is an illustration of what There are numerous compounds in the country areas, many I am going to propose. of which I have not visited, and it would be interesting to know what has been achieved in the way of cultivation of crops to Dr. S. Kark, of the Polela Health Unit at Bulwer, has been be used by the workers. Certain foods are issued out as rations, making a close study of the Native in his home conditions. but the home production of green produce encourages thrift Among other studies the question of foods and the materials and economy. used have been observed and recorded. It was noticed that the women walked miles to collect various plants used in their The Indian is, by habit, a cultivator, but, if spoon-fed, soon foods. becomes lazy and is inclined to rely upon others to supply him, and I favour the provision of plots and the encouragement to Specimens were collected and identified as being numerous cultivate his own requirements as much as possible. I know forms of wild spinach. Dr. Kark set out to demonstrate a method this does not apply to the Indian alone, and it might do a lot to maintain a source of supply close at hand. He collected all of good to do half-an-hour in the garden every morning and waste vegetable matter and put it through a composting process evening. and fed this to the land immediately adjacent to his house. He collected seeds of these various forms of spinach and grew I would like to see the establishment of a training centre these successfully. where non-European instructors could be trained on the same lines as the European instructors are trained. They could be Calling the women together, he pointed out how unnecessary responsible for certain areas to train their own people in the it was to search for miles around for a few plants when it was correct methods of culitvation. Their services might be useful possible to cultivate them at the door and have a stock on hand in the commercial gardens which supply our markets. which could be obtained in all weathers without discomfort. When I came to Durban I was disappointed to find the soil Interest was aroused and this led to greater progress. He in such a poor condition after hearing such wonderful reports gave a woman one shilling to buy vegetable seeds at the local of the beautiful flora. When I say poor, I mean that it seemed store and she returned with two packets of vetegable seeds. Dr. to have no power to retain water. Soon after a rain or after Kark obtained a quantity of seeds at wholesale rates and made watering it dried out quickly and became hard and young plants this up into packages valued at one shilling. struggled for existence. This illustrated the value of community work. Lessons were Lack of humus was the cause, and steps were taken to remedy given in composting all forms of refuse and plots started near this. The first place to be tackled was the Botanic Gardens, the homes. Vegetables were grown and used by the families. which dried out very quickly. The effect of using humus for a The records of individual weights were recorded and health few years has improved the ground, and to-day we find it records were kept. The results have proved most satisfactory. difficult to keep the grass in order. No water is applied to the grass other than that supplied by natural rainfall and seepage You will have realised by this time that I have been dealing from the upper areas of the Berea. with the work being carried out to combat the rapid progress made by tuberculosis in this country, and I have brought with Other parks have received similar treatment. One of the me some records made of the forms of plants used as food, their most outstanding examples is seen at Fynnland, where Lieutenant preparation and the results of the work being carried out. King Park is situated. The soil is of a light sandy nature, and when the earthworks were completed the levelled area consisted Before dealing further with the life of these people in their of a sandy subsoil. Liberal application of humus has resulted in reserves, I want to deal for a few minutes with those who a prolific growth of grass, thus forming a first-class sports area. 86

The methods employed in composting have been simple : 75 I realise the value of fertilizers, but feel that it is a waste per cent, garden refuse is sprinkled with urinated earth and to of material to apply fertilizers to a soil which is incapable of this is added 25 per cent, stable manure. The stacks are formed holding moisture. If the growers would get the mechanical on level ground up to a height of four feet and 24 feet in length. state of their soils in order the chemical applications would After a week the material is turned and lime and wood ash is have better chance of achieving success. added. Subsequent turnings take place and the material is available for use in three months. On the other hand, when we consider the Indian and the Native in their small plots we have to study expense, and they By means of broadcast talks and practical demonstration3 are not always keen to spend money on fertilizers. In the illus­ interest has been aroused to get more people to use humus tration I gave of the successes at Bulwer, I omitted one im­ Usually I find people more willing to purchase the finished portant point. Humus alone was added to the ground and no article than to be bothered to supervise the composting process fertilizers were used. I am not going to suggest that this is in their own gardens. ideal or even a correct procedure, but the results obtained were enough to justify the addition of humus, without which there The enormous amount of available material in Durban and would have been little to show for the efforts. the open spaces, parks and recreation grounds has led me to consider the proposition on more extensive lines, and it has been As time goes on we shall have to take a keener interest in suggested that central stations be formed where composting can what is being done and what remains to be done to provide be undertaken to supply large quantities for these areas. an ample supply of fresh vegetables at reasonable cost to ensure all families of all races a chance to combat the scourge of diseases The question of supply for private gardens has not been which are prevalent to-day. It is going to be a continuous job, decided, but f can well imagine that there will be numerous and if responsible people who know the needs of the people and requests for supplies. If we can stop the burning of garden the soil get together, much can be achieved within a short space refuse we shall at least earn the gratitude of the neighbours of of time. the offenders. I have omitted one important point in my remarks about Apart from the recreational and floral areas which require the cultivation of vegetables by the Natives at Lamont Location. humus, we can give consideration to the cultivation of vege­ Their own efforts appear to consist of the growing of mealies tables. Prices are high, and I know many families are not in a only, and it has been felt that the ground could produce vege­ position to provide the quantity and variety which should be in tables of greater variety and value and the amount of mealies every home. It is a. simple matter to give up part of a flower produced could be bought for a few pence. garden or lawn for the growing of a few lettuce, beans, cabbage, spinach and other valuable fresh foods, and these would make a It is with combined interest in view that I have ventured to great difference in helping to keep a family fit. present to you a case for the furtherance of the proper treat­ ment of waste vegetable material, in order that the soil may As I said at the outset, I was somewhat reluctant to speak produce the best results and that the health of the people may to-day as I could not enter into a scientific discussion on the be raised to a standard of high quality. To produce the best value of humus versus fertilizers without dragging out all well- results we must have the best type of labour. Health is the worn facts with little to add. secret, and feeding is the means to this end. 87

INSTRUCTIONS TO AUTHORS.

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