IAEA-120

ISOTOPES AND RADIATION N INVESTIGATIONI FERTILIZEF O S D AN R WATE E EFFICIENCUS R Y R EASCOUNTRIEFA T E TH F ASID O S AN A

PROCEEDINGS OF A STUDY GROUP MEETING CONVENED BY THE JOINT FAO/IAEA DIVISION OF ATOMIC ENERGY , IN FOOD AND AGRICULTURE AND HELD IN BANGKOK, THAILAND 21-25 APRIL 1969

A TECHNICAL REPORT PUBLISHEE TH Y DB INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1970 The IAEA does not maintain stocks of reports in this series. However, microfiche copies of these reports can be obtained from INIS Microfiche Clearinghouse International Atomic Energy Agency Kbmtner Ring 11 0 59 P.Ox Bo . A-1011 Vienna, Austria on prepayment of US $0.65 or against one lAEAmicroficheservice coupon. PLEAS AWARE EB E THAT ALL OF THE MISSING PAGES IN THIS DOCUMENT WERE ORIGINALLY BLANK ISOTOPE RADIATIOD SAN INVESTIGATIONN NI F SO FERTILIZE WATED EFFICIENCE RAN RUS Y- COUNTRIES OF ASIA AND THE FAR EAST.

Proceedings of a Study Group Meeting convened by the Joint FAO/IAEA Division of Atomic Energ Foon Agricultureyd i dan , held in Bangkok, Thailand April 21-25, 1969.

IAE Vienna- A , 1970 CONTENTS

OPENING ADDRESSES H.E. M.R. Chakratong Tongyai ...... 1 D.A. Rennie ...... *...... 3

RICE: PHYSIOLOGY, NUTRITION, FERTILIZATION A review of the co-ordinated research programme on the application of isotopes to rice fertilization studies, 1962-1968 ...... 6 P.B. Vose Studies on the efficiency of time and method of fertilizer applicatio ricr nfo e using N-1 P-3d 5an 2 ...... 5 1 M.W. Thenabadu Studie comparative th n so e nutrient requirementd an w lo f so high yielding varieties of rice ...... 29 A.B. Khan, L. Rahtnan, S.I. Chowdhury, S.M. A lam, i Al . Y d an P.K b .De A study on the efficiency of shallow and surface placement of nitroge phosphorud nan s fertilizers applied separateld yan chemically combined for usiny mb g isotope technique ...... 0 5 S.. SuwanHaong, P. Sanitwongse and P. Sawatdee Recent soil, fertilize physiologicad ran l studies with P-32 on high yielding varietie paddf so y ...... 1 6 B.V. Subbiah and J.C. Katyal The effect of osmotic pressure on P-32 phosphate absorption d leakagan excisey eb d ric adaptatioee th root d san ricf no e root varyino st g osmotic pressures ...... 2 8 Yuh-Jang Shieh Effec silicof absorptioe to th n no manganesf no phosphorud ean s in rice seedlings ...... 97 S.C. Shim Jang-Kirl. U , Hyong-Koe Le , o

NUTRITION STUDIES: PHOSPHORUS Evaluation of pyro- and metaphosphates as sources of phosphorus for plants Uptak. I , e studie waten si r culture ...... 4 .10 A.K. Sinha and K.B. Mistry Report on the use of radioisotope P-32 for fertilizer studies in Indonesia ...... 2 .12 Nazir Abdullah CONTENTS ctd.

The significance of the 'A value concept in field fertilizer studies ...... 1 . 132 D.A. Rennie Fat fertilizef eo r nitrogen applie soilo dt s ...... 6 .14 J.O. Legg N-1tracea f o s 5Tha e fertilizen ri eus ? efficienc' y study in Japan ...... 1 .16 Nishigak. S i

NUTRITION STUDIES: MOISTURE RELATIONSHIPS Radiation techniques as means of improving the efficiency of wate e ...... »rus . 168. Barrad. Y a Hater and ion movement in soils ...... 179 W.R. Gardner i effecte Th asphalf ,o t barrier moisture th n nutrientsd o ean s retention in rice and sugarcane fields of sand soils ...... 183 C.C. Wang, K.Y. Li, C.C. Yang, P.W. Ho and J.T. Wang

RECOMMENDATIONS ...... 2 .19

LIS PARTICIPANTP TO S ...... 4 .19 FOREWORD

The Study Group Meeting on the Use of Isotopes and Radiation in Investigation Fertilizef so Wated Efficience ran rUs s conveneywa d jointly by the Food and Agriculture Organization of the United Nations Internationae anth d l Atomic Energy Agency sessione ;th s were held in Bangkok, Thailand generoue th t ,a s invitatio Governmene th f no f to Thailand. Approximately thirtyfive participants from the countries of Asia and the Far East presented papers or contributed to the discussions.

purpose meetin e brino Th t th s f geo gwa together firse th tr ,fo time since the termination of the IAEA's six year co-ordinated rice fertilization programme, specialist soin si l scienc d planean t physiology to discuss recent developments in the physiology, nutrition, and ferti- lization of rice; the programme also included reports by regional scientist d lecturesan authoritiey sb arean i s s other than rice; this proceeding includes the 16 technical papers presented during the meeting.

While the informal study group atmosphere stimulated a full exchange of experience and information on current developments in the application of isotope radiatiod san soi o ncrod t lan p production studies ,recora d of these discussion bees sha n excluded from these proceedings; however, the meeting's formal recommendations, which constitut esummara ^ th f yo discussions, are included; these focus on such areas as Rice, Other Crops, Soil Chemistr Related yan d Studies, Wate Fundingd ran . OPENING ADDRESS

H.E. M.R. Chakratong Tongyai Minister of Agriculture , Government of Thailand 21-25 April 1969

Honoured guests, distinguished Delegates, Ladies and Gentlemen?

It gives me great pleasure to be present at this opening session of the meeting of the Study Group on the Use of Isotopes and Radiation in Investigation Fertilizef so Wated Efficiencye ran rUs . recalI f I l correctl thirye th thi ds i smeetin g sponsoree th y db Joint Divisio Pooe Agriculturd th dan f no e Organizatio Internationae th d nan l Atomic Energy Agency to be held in Bangkok. The first meeting for which Thailand had the honor of being the meeting place, was the panel meeting of expert Inducen so d Mutatio Ricf no e Breedin 1965n gi secone .Th d meeting, also held in 19&5* was on Rice Fertiliser Research using Isotopes. It is indeed reassuring to know that atomic energy has been harnessed to serve useful purpose mankinr sfo d and, especiall fiele th f o dn yi agriculture, has resulted in more food so essential to human life, instead of deat destructiod han durin s Thana e behaln O th i . gf o fII Worl r dWa people Jniteo wis,I tw expreso e ht d th Nation o st s Agencies IAEAd an ,O ,FA our sincere appreciation for promoting the application of atomic energy fiel e peacr th agriculturef fo o dn ei . We are all aware that, in many countries, tremendous advances have bee pasne madth t n fifteeei n year researcn si fertilizen ho wated re an rus applyiny b g isotope radiatiod san n techniques. But mosn ,i t Asian countries, scatterew onlfe ya d research projects have been carried out. Since fertilizer wated an r requirements vary witsoile th h , climacic conditio cropd nan , first- hand knowledg needes ei r eacdfo h particular localitr eacfo h d cropyan .

- 1 - This meeting provides an opportunity for the exchange of experiences among Asian countries to help promote wider application of radio-isotopes and radiation techniques in fertilizer and water use researches in this worlde th par f .to From persone.1 acquaintance among scientist variouf so s countries made during this meeting, I believe further "bilateral and multi- lateral contacts wil maintainee lb exchange future th th r n ei dfo f eo ideas and research results. All these will eventually lead to a better and more exact knowledg fertilizef eo r uptak r increasin watefo d ean e rus g the crop yield and will result in the efficient application of inputs and resource ensuro st e increas production ei maximud nan m r profiou r tfo farmers. thin I worle s th par df o t wit majorite th hpeople th f yeo engaged in agricultur future th d eean rapid growt populationn hi , increasn ei crop production efficienc maximuy yb m lanwated dan r utilization is'vital e solutiot th ofooe th d f nprobleo economio t d an m c development. Though crop production depends mainl seen yo d variety, soil fertility, protection, and cultural practice, soil fertility is the main factor in increasing the yield. Hence knowledge of proper and efficient application of fertilizer crop.a th extremels 1i so t y important for agriculturae .th l developmen countriesr ou f to . By further researches in the application of isotopes-and atomic energy techniques, scientists will understan nature d th mord f ean o e behavior of nutrient elements in relation to various crops under various environmental conditions 30 that they can advise farmers as to the kind and the amounts of fertilizer, and t3 3 time and the methods of application to various crops in various localities in order to ensure the effective and economica fertilizerf o e lus waterd san . Distinguished delegates meetine ar u ,gyo her sharo et exchangd ean e knowledge among your colleagues, I hope that this meeting will give new impetu moro st e intensiv extensivd ean e researc countriesr ' ou y n hi ma u .Yo be sure that your contribution future th o est developmen agriculturf o t e will benefit your fellow men. On behalf of the Government of Thailand, I wish to extend a very warns welcome to each and every one of you. May your stay in Thailand be pleasing and rewarding. I wish you success in all your deliberations. - 2 - OPENING ADDRESS D.A. RENNIE Joint PAO/IAEA DIVISION VIENNA, AUSTRIA.

Distinguished colleagues,

Public attention has "been drawn in various reports during the past year abou revolutionare th t y development agriculturan i s l productiod nan the highly encouraging yield statistics, implying thaworle th t d food crisiapproachine b y sma least ga partiata l solution indees i t .I d true that we may be on the verge of a break-through in agriculture production; years of patient activity in research are at last beginning to bear fruit. y tha ablw sa tno o e t there ar reas i ee lW hope, give righe nth t conditions, and providing the right steps are taken in the right sequence, that the food situatio transformee b n nca arean di s such as.in Southern Asia from where frequentlo faminon e to e th l eal y stalke lane whero th dt d least ea t a subsistence level can be guaranteed for all.

We must not, however, become complacent on the basis of the last few years' statistic agriculturan so l production relao . T effortr xou n si research, having just see majoe nth r dividends suc f thaariso n hca t eou effort, could lead to the disaster that we have been struggling to avoid. criticaf o s Ii t l importance that those involve researcn i d h grase pth complexit challenge th f yo e facing them. It is for these reasons that the Agencies sponsoring this Study Group Meeting Internationae ,th l Atomic Energy Agency .anPoo e Agriculturd th ddan e Organizatio Unitee th f dno Nations programmed this meeting tak.I e great pleasure on behalf of these sponsoring organizations to welcome you, I am sure that I put into words the feeling of all of you as well as the sponsoring organization alsI thit f oa si s time expres sincerr sou e gratitud Governmene th o et Thailanf to havinr dfo g kine extendeth d s u o t d invitation to meet here in this ancient city of Bangkok and in our spare time to bask in the beautiful surroundings of this fair city.

- 5 - I also want to extend to Dr. Sala Dasananda, Director General, Rice Department Conferencs ,hi e Committee particularn i d ,an hard-workinr ,ou g conference secretary, Mrs. Patoom Sanitwongse my sincere thanks and appreciatio lookinr nfo g afte local ral l arrangements. The Joint PAO/IAEA Division has "been instrumental in the past in holding Symposia, Panels, etc. at various localities throughout the world. This is the first Study Group Meeting that has been held, and we trust that durin nexe gth t fiv attendancen i day l sal e will hav opportunitn ea o yt enjoy and benefit from what might be termed "the informal study group atmosphere", i.e. a full exchange of experience and information on current development applicatioe th n si isotopef no radiatiod san soio nt l and crop production studies. You will recall that the.sponsoring i.' - Organization supported unde IAEA'e rth s Research Contract Programmea six year co-ordinated rice fertilization stud twelvn yi e countries using

isotopioally labelled fertilizers. This Stud y:firse Grouth ts pi follow-up to this programme and you will note that a significant portion of our discussions is devoted to the physiology, nutrition and fertilization of rice. We trust that at the end of this Study Group Meeting .guidelines continuee th o t s da attentio suppord nan t that shoul e givee db th o nt applicatio isotopif no c technique ricn si e physiolog fertilizatiod yan n studies wil formalizede lb tente .eleventd Th han h session Workine th f so g Part Ricn yo e Soils Wate Fertilised ran r Practice Internationae th f so l Rice Commission recommended active programme thin Agencye i s th s n areai ,, .We await your recommendations. Rice is not the only crop grown in the countries of Asia a'nd the r East Pa thud ,an s rightly programme ,th e includes reports offerey db participants and lectures by acknowledged authorities in areas other, than rice. I trust you will find this portion of the programme, as stimulating as the initial lectures devoted to rice production. wit, so h d thiAn s brief reviescope th topic f covereeo e f w b o o t s d in this Study Group Meeting I trust that all in attendance will find, in this forum, an opportunity not only to further their knowledge but also throug medie hth fruitfuf ao l debat discussiond ean , leave these meetings

- 4 - "better armed with the tools that will enable each and everyone of us, on our return home, to more effectively attack the .problems restricting yields of agricultural crops.

I wish you a most successful meeting and I herewith declare this Study Group Meeting on the Use of Isotopes and Radiation in Investigations of Fertilizer and Water Use Efficiency formally opened.

- 5 - A Review of the Coordinated Research Programme on the Application of Isotopes to Rice Fertilization Studies, 1962-1968

Vos. B eB. yP

I. INTRODUCTION

The results of the Coordinated Research Programme were communicated as they were obtained to the meetings of the Working Party on Rioe Soils, Water and Fertilizer Practices of the International Rioe Commission (Manila, 1964$ Lake Charles, 196 Kandyd 6an , 1968) detailee .Th d results of the experiments have thus already been widely disseminated, and the present paper attempts to review in general terms the overall significance programmee ofth appreciation ;a isotopf no e technique fertilizen si r efficiency studies; some possible indications for the future. For those who may not be familiar with the detailed organization, objective resultd programmee san th f so ,summara year6 y e reporsth f to of work is available.

Researc. II h Achievement Programme th f so e

broae Th d research achievement programme th briefle b f s o n eca y summarise followss da : clearl) (i y definin optimue gth m condition placemenf so f to phosphorus and nitrogen fertilizers; (ii) clearly defining the relative efficiency of the major nitrogen sources; (iii) achieving a better understanding of the effect of time of applicatio efficience th n no nitrogef yo phosphorud nan s utilization ricy b e;

- 6 - (iv) obtaining "by direct measurement precise information on the proportion of applied fertilizer actually taken up "by the crop; (v) obtaining a clear - numerate - understanding of the penalty paid in terms of fertilizer wastage, if inefficient placement or incorrect nitrogen source is adopted? (vi) demonstrating that "che basic factors concerned with the efficienc fertilizef yo r utilizatio ricy nb e grown under lowland, i.e. flooded, conditions hol dver a goor ydfo wide rang soi f egeographio d lan c conditions, from Ital Koreao yt *

time programme Ath teth s starteewa lace generallf th dko y accepted theoretical and practical bases for the efficient nitrogen and phosphorus fertilization of rice was clearly indicated by the standard texts, though Mitsui and his co-workers were pointing the way. Furthermore, the concept of efficient fertilizer utilization i.eefficiene th . t fertilize uptake beet th cropno e n f ed o th ,ha y b r greatly stressed in those countries with long-established traditions of fertilizer research. Thibecauss swa thesn i e e developed countries fertilize relativels ri y cheap. However mann ,i y developing countries where rice is grown fertilizers are expensive and may require scarce foreign exchange. How important is the need for efficient fertilizer use can be deduced from a study of the overall experimental results. Thus even under the best condition nitrogef so n fertilizer application i.e* ammonium fertilizer ploughed-in, the amount of fortilizev taken up by the rice crop seldom exceeds 50-3 cenr thaf 5pe o t t applieoftes i d n an dless , even where there isignificansa t yield respons kg/h0 6 nitrogenf o aeo t . Unde worse rth t possible conditions, nitrate fertilizer applie plantint a d g time, only fertilizee cenr lesth r pe o t f 5 so r applie actualls i d e yth takey b p nu crop isotopf o . o Beforus e e -techniqueeth s such estimates involve larga d e measur guessworkf eo case phosphoruf th eo n .I s about 5-1 cenr 0y pe tma be mos e utilize th caste f efficienth eo n di surfac- t e applicatio- n treatments cenr lesr pe littls deptr o t a 2 sfo plantinr d s o h,ea an g point treatments.

- 7 - Efficiency of phosphate fertilization In general the very low efficiency of phosphorus fertilizers is usually explained by the nature of the soil-fertilizer-interactions. The equilibrium concentratio phosphorue th soie f no th l n ssolutioi n often falls within the conoertration-limiiod part of the phosphorus uptake curv thef eo - crop. Thu highee sth r concentratio f phosphoruno s around the fertilizer particles may help explain the response to phosphorus application by the crop. Th?.s effect is of a temporary nature and the bulk of the phosphate gets eventually bovnd to the solid soil complex, necessitating yearly applications of phosphorus fertilizer to maintain an e.d equate supply to the crop.

Comparatively little wor beed kha n carriefertilizen o t dou r phosphorus placemen ricer tfo mucd ,thaf an hcontradictorys o twa . The common custom, is to broadcast phosphate fertilizer, but the practice had been based more on expediency than on facts. In India, early work suggested that placemen 5 inche2- t s belo plante wth s betteswa r than broadcast application, but a later series of experiments reported that ' broadcasting was superior to 3 and 6" daep placement. A Louisiana experiment indicated .that banding gav consistentlea y higher yield than broadcasting, "bur. studies in Texas showed no significant difference, between a series of band deptdan h placement broadcastingd san . LLL Under lowland conditions, phosphate fertilizer applied on the e soith l f o ensure ., ratfacm c e mosw sth r hoefe to e p efficiendto int, e th o t utiliRp.tio fertilizee th rice f no th e y rplantb . Placemen plantint ta g point v;,->,s ineffective. TrUning generaln ^I , phosphate applicatio single croon e n th ep i o nt dos t ea tne tins of transplanting is at least as efficient as at other times. Late timin splittind gan phosphoruf o p gu s applications result sligha n si t inductio utilizatioe th n ni froP fertilizere f th mno reductioe .Th s ni ho?/3ver smal doed precludt lan sno e later application fertilizee th f si s ri not available at transplanting time. Nursery applications of phosphate do not result in either increased incorporation of phosphate in the plant or increas 'relativn ei e efficienc latsf yo r application fertilizerf so .

- 8 - mixinP K- combined gan d sources; Mixing ammonium sulphat superd ean - phosphate stimulate uptaksP e from fertilizer place shalloa t da w depth "but not on the surface. Phosphorus utilization was found to "be little influenced "by the nitrogen component of combined N-P sources. Although placemen combinef to sourceP dN- deptt sa h reducee sth efficiency of P uptake, there is nevertheless an increase in P efficiency obtaine mixinP d N- froe gmth effect. This suggests tha practicn i t e the application of a combined N-P source at a depth of 5 cm at transplanting time gives nearl efficiens ya t utilizatio phosphoruf no separats sa e applications of ammonium sulphate at 5 cm depth with superphosphate on the surface.

Phosphate sources: Pot experiments carried out at the Seibersdorf Laboratory of I.A.E.A, compared natural phosphate fertilizers such as Olinda, Araxa, Araxa Thermo, Tunis Rock, Florida Rock, Basic Slag and Bone Meal. It was found that on acid soils availability was generally high, but that on alkaline soils only Araxa Thermo and Basic Slag had an availability similar to superphosphate. In a comparison of commercial fertilizer founs wa dt si that K-metaphosphat Magnesiue+ m Sulphatd ean K-orthophosphate were more available than superphosphate on all soil types tested. K-syrophosphate and K-metaphosphate were less available than superphosphate on all soil types. The striking effect of MgSO in increasing the availabilit froP f myo K-metaphosphate remains unexplained.

Efficiency of nitrogen fertilization Consideration of nitrogen placement and timing for rice must take into account the peculiar physico-chemical properties of flooded soils and the transformation of nitrogen compounds under these conditions. Thus in flooded paddy soils there is an aerobic layer a few cm thick in contact with the thin i wate sd layeran processee th r primarile sar y oxidative. Below this laye conditione rth anaerobie sar reductiod can n processes prevail. The early Japanese work indicated that nitrification of ammonium nitrogen occurre oxidisine th n i d g layer, resultin loss nitrogens it sa n gi t ,bu that ammonium in the reduced zone is stable. Similarly, although nitrate is theoretically shallostable th n ei w oxidise dleaches i layer t i df ,i

- 9 - into the reduced zone it is denitrified and lost as- gas"; Althouign~dTep placemen ammoniuf to widels mwa y recommende Japann i d successfud ,an l results were .obtaine Californin i d elsewhered aan e value th ,th f o e practia s not.eha , been universally recognized broae .Th d geographid can edaphic presene scopth f eo t programm permiw eno numbeta broaf o r d generalizations.

Placemen tThert apparentls ei y neve y penaltran r placinyfo g ammonium fertilizer at depth, nevertheless the generally beneficial effects of depth placement vary accordin soio gt l type greatese .Th t benefit is obtained on acid soils of low organic matter content, and depth placement is most essential on these soils, immediately followed by soils of intermediate pH. With soils of low pH and high organic-mat'tear """~ conten effece th t shallof o t w placemen efficience th n o tfertilizeN f yo r uptake is only slightly higher than for surface placement. On soils with high pH containing Ca CO, the difference between surface and depth placement efficience th n o utilizatioN f yo smals ni non-existentr lo . Although 5 ons depth placement of ammonium sulphate at transplanting time usually increase uptake froN sth fertilizere f mth o e , compared with surface application, 'no decrease in uptake of fertilizer N is found with e optimuTh placemen . mcm dept5 dees 1 ta placemenf s o pha y therefortma e be greater than 5 orc» and there were small but not statistically significant indication thi.o st s effect.

Timing> The late application of nitrogen as a. singTe"dose often.results vera n yi significant increas utilizatioe th n i e f fertilizer^nitrogenno . •- , There is little advantage in splitting the nitrogen betwee.n several applications - assuming that nitrogen is not very deficient. Exce.pt. where soil phosphorus is very deficient the timing of nitrogen application has no- • utilizatioe effecth n o t phosphorusf no . When soil phosphoru vers si y deficient higher fertilizer phosphorus utilization may occur with late nitrogen applications.

- 10 - Nitrate fertilizer muce sar h more efficiently used when give latea s na r top dressing than when applied at planting time. Under certain conditions of medium pH with not too high organic matter content, top-dressing of all fertilizers may result in slightly more efficient utilization than application at planting time. As far as investigated, a time 2 weeks "before primordial initiation appears to "be the most appropriate time for a single top-dressing, and with ammonium sulphat ured ean a applie thit da s time ther comparativels ei y little difference in effectiveness of utilization, compared with 5 cn> depth placemen transplantingt ta .

Sourcesi Ammonium sulphate and urea are about equal in effectiveness; sodium nitrate is very ineffective in supplying nitrogen to rice, when give "basia s na c dressin transplantingt ga ; under these conditions ammonium nitrat intermediats ei valuen i e . Compariso Ammophof no nitrid an sB c phosphate with ammonium sulphate plus superphosphate showed that the efficiency of nitrogen utilization from the two sources is about the same. Nitric phosphate is a much less efficient supplier of nitrogen than either Ammophos B or ammonium sulphate.

III. Appreciation of the isotope technique for fertilizer utilization efficiency studies

Fertilizer use efficiency can be studied by (i) direct measurement of ho fertilizewe th muc f ho usiny takes b i r , gn up isotopically labelled fertilizers,(ii) indirect measuremen amounte th f fertilizef to so r takep nu by calculating the difference between the yield of nutrient from a treated non-fertilizea plod an t d control plot, (iii) indirectly observiny ,b g yield responses to the various methods and times of fertilizer application.

- 11 - isotope th s i e y methoWh d inherently superiort no t alsi y ?Wh s oi ' • j possibl equivalent ge o et t results from classical techniques using yield or nutrient content as the criteria? The .basic advantage of the . isotope method is that the fertilizer actually taken up by the crop can be detecte measuredd dan enablet .I straightforwarsa d quantitative compariso amoune th fertilizef f tno o r element eacr takefo h p nexperimentau l treatment. wels Iti l understood that under certain conditions yield techniques can indeed be used to determine indirectly the efficiency of fertilizer utilization. Thi particularls si soiln o extremelf o so ys fertilitw ylo y where yield respons fertilizeo et vers ri y high. However frequene ,th t absence of consistent results where only yield response and the content of a nutrient are used to compare placement, source and.time of fertilizer application is not hard to understand. As the yield of the various treatment placemenf so t trial usualls si y approaching maximue th d man difference smale sfirsar e lth t requiremen sucf to experimenn ha thas ti t the level fertilizef so r application shoul adjustee db thao e s d tth treatment responses are within the steep part of the yield response curve. In practice it is difficult to select such levels. Furthermore, on soils fertilitw oflo resulte yth confoundee sar vero t ye markedu d d increases in root growth from fertilizatio exploitinn- glargea r volum soilf eo , hence acquiring more nutrients from the soil, changing the whole environment of the roo confusind tan subsequene gth t interpr§t.at.ip_n..o.£.fertilizer utilization. Such yield experiment necessarilye sar - larg includo et e several levels of fertilizer applicatio provide•adequato t d nan e replication requird ,an e repeatin numbea n gi successivf o r e years. Such desiderata 'have seldom been adequately met. The isotope procedure is valid for virtually every experiment regardless of soil or location, and the ability of the technique t& give in the vast majorit oasef yo spositiva e experimentaanswee th o rt l objectives, is one of its .jnost valuable practical features. The expense of labelled fertilizers has been put forward as an objection to fiel n theii e d rus experiments comparisoa f .I mads ni e cosmerele th t f yo of labelle unlabelled dan d fertilizers this vie soms wha e validity. However, true ifth e cos obtaininf to samge th date f reliabilitao y from yield techniques if computed, i.e. the increased labour costs for carrying out - 12 - the necessarily larger experiment d theisan r neerepetitior dfo n ni successive years, then isotope techniques compare very favourable. factn I , wit cose N-1f hth o t 5$10t a grar 0pe m N-15 atom excesn a d san average cosP-3r tfo 2$1.50.pef o (plue rm s preparation chargr efo superphosphate) there is no need for a properly designed field experiment to cost more than $10 r labelle0fo d fertilizer. Thi coursf so e assumes that labelled fertilize subplousea s i rn di unlabelled tan d fertilizers e applieyiele ar th do t dsub-plots . Finally, isotope technique uniquele sar y suite r determinindfo bese gth t method gettinf o s fertilizee gth r intplante oth , i.e r investigatin.fo e gth most efficient source, placemen timr o tapplicationf o e t . no The e yar suite r indicatindfo amoune gth fertilizef to appio t roptimur yfo m yield. When the most efficient means of application has been found then the optimum amoun fertilisef to muse determinee us tb o rt d using normal commercial fertilizers. The 6-year rice fertilization programme has surely given a clear demonstration of the value of isotope techniques. The programme originated i ndesira settlo et differencee th e propee opiniof th so o rt placemens na t of phosphorus fertilizers this problem was in fact cleared up in the first year of the programme. In each subsequent year it was possible to attack a different problems showing both the economy of the technique and the advantage of cooperative work.

IV Possible future work

Withi'i the context of the complete 6-year programme there are probaly two areas of work which would repay further attention: the timing of nitrogen fertilizer application confirmatioe th d wore san placemenn th ko f no d tan timing with the new varieties. The 1964 experiments studied the time of nitrogen application but it seems possible that efficient utilization might occur from even later applications than were trie that a d t s timei t .I probable thaexistine tth fertilizeP gd resultan N r r sfo placemen d tan timing are directly applicable to the new high yielding varieties. Nevertheless, these varieties hav considerablea y different growth habit and also a much higher fertilizer requirement than most of the varieties hitherto grown in the programme. Sources: further work with slow-release nitrogen sources wile lb required soon, though this will availabilite depenth n o d materiaf yo l suitably labelled with N-15. From time to time further work with P sources may be necessary but can be effectively carried out in pot experiments. Also of value might be studies on the comparative nitrogen nutrition of japonio d indioaan a varieties, particularl relation yi differeno nt t plant spacinlattere th f go neede . W , too, -further knowledg microelemenf eo t problems and the development and evaluation of foliar spray techniques.

... ' • - - - . . \» e objectivTh programme th studo t f mose eo s yth t ewa efficient.sources meand an applicationf so man n appropriate i b y d w countrie,an no y ma e t si to determine the best level of fertilizer application. Isotopes are not necessar suiter yo thio dt co-ordinate a s s worki r ,no d approache th s ,a optimum levels mus determinee tb countra n o d country yb arer yo arey ab a basis. ' e typ Th experimentaf eo l wor programme ke th carrieth n i d t ean ou d principles on which it was based are equally suited to other crops: e.g. soybeans, sweet potato, pea-nut, cassava etc.

- 14 - StudieEfficience th n so Tim f Methoyd o ean Fertilizef do r Application for 2 Ric5 P od Usinan 5 1 gK Mervyn W. Thenabadu

Central Agricultural Research Institute, Fere.clBri.iya, Ceylon.

Introduction

Oils of the "best joe'Irhcds fcr incieasing agricultural production is "by the increase fertilisersf o e dus moderatf o e Ceylon .I us ee napplicationth s of fertilizers, particularly nitrogen and phosphorus, has resulted in appreciable yield responses with rice (l,2) alss i ot . I noteworth y that there has "been a steady inoreaco in fertilizer consumption .in Ceylon since 1956 (3). Good management practices, like placement of fertilizers and fertilizer applications synchronised to meet the demands of the crop, are important loefficiene rth t utilisatio fertilizerf no labellef o e riceus y de s"b .Th r«rtilizevs has enabled studies en the efficiency of different fertilizers, time method th e an r.ir n o applyinf do d g fertilizer r ricesfo .

Under, the Co-ordinated Contract Programme sponsored by the Joint PAD/IAEA Division of Atomic Energy in ?ood ir>d Agriculture, five experiments were conducted in Ceylor be-'-T^n IfM "-"d 196? to study the efficiency of time rind method of fe'ctiliz^r application /or rice (4, 5, 6, 7, 8). This paper .juniiaarize resulte th s s s,nd inclusion f thesso e experiments. Experimental

Experimental techniques were carrie accordint dou instructiono gt s from the Joint FAO/IAEA Division of Atomic Energy in Pood and Agriculture, Vienna, Austria detaile .Th procedurf so describee ear d elsewhere (4, 5, 6, 7, 8). The objectives of the experiments were as follows:

Experiment 1 (1964) To determine the efficiency of fertilizer nitrogen applied to lowland ripe as affected "by time and rate of application using ammonium sulphatej efficience th d an fertilizef yo r phosphoru affectes sa tim y ratd d"b ean e of nitrogen application using superphosphate.

Experiment 2 (1965-66) To determine the efficiency of fertilizer nitrogen applied to lowland ric affectes ea placemeny interactioe d"b th d tan n with phosphorus placement} efficience th d an fertilizef yo affectes ra placemeny intere d"b th d -tan action with nitrogen placement.

Experiment 3 (1966) comparo T efficience eth differenf yo t form nitrogenouf so s fertilizers as affecte shalloy db w placemen transplantint ta surfacd gan e placement at primordial initiation determino t d ; an efficienc e eth fertilizef yo r phosphorus as affected by form and method of nitrogen application.

Experimen (1966-67t4 ) To study the efficiency of utilization of ammonium sulphate by different placement methods; and to study the interaction between nitrogen placement utilizatioe th d an superphosphatef no , applied broadcas transplantingt ta .

- 6 1 - Experimen (1967t5 ) To compar efficience eth differenf yo t combined nitrogen/phosphorus sources wf bh ammonium sulphate plus superphosphate; and to compare the efficienc differenf yo t combined nitrogen/phosphorus source influences sa d shalloy b w placemen t transplantinta d surfacgan e placement -few> weeks before primordial initiation.

firse Th t experimen s conductet wa locationo tw t da se vizth t :a Agricultural Research Station, Maha Illuppallam Centrae th t a l d Researcaan h Station (Gannoruwa) Peradeniya. All the other experiments were conducted at the Agricultural Research Station, Maha Illuppallama.

Maha Illuppallam y zon Ceylof dr situates eo ai e th nn whici d h includes the lowland plains of the north and east. The mean annual rainfall is 1403 mm. The mean annual temperature is 27.3 C, (9)*

The soi Maht la a Illuppallama where these experiments were conducted ranges from sandy loam to sandy clay loam in texture and is slightly acid to neutra reactionn li contene .Th totaf o t l nitroge thin ni s soil varies fronuO.09 to 0.15 percent while the content of available phosphorus (Olsen's) per acre The varies from 6.96 to 38.74 lb P2N * content of organic metter in this soil varies between 1.10 and 2.39 percent.

Gannoruw situates ai mid-countre th n i d t zon yCeylowe f eo d nan receives a mean annual rainfall of approximately 2131 mm. The mean . annual temperatur approximatels ei y 24.5°C, (9).

The soil at Gannoruwa where the first experiment was conducted is a sandy clay loam which is moderately acid. The content of total nitrogen is 0.15 percent and that of available phosphorus (°lsen's) is 13.6 lb PgO_ per acre. The organic matter content of this soil is 2.30 percent.

- 17 - Results and Discussions

'• '*. . * Fro resultfirse e mth th tf so experimen whic) t II s (Tablhd wa an eI conducte zony dr e botn e i d(Mah hth a t eonIlluppallamawe ee th n i d )an (Gannoruwa'; Peradeniya) by Nagarajah and Al-Abbas (4)» it was found that the greatest uptake of fertilizer nitrogen at both locations was from the treatments where a single dose of 60 kg N/ha was applied two weeks before primordial initiation. Ther s littlewa e advantag applyinn ei g thi. s nitrogen in two or three split doses. At the wet zone Station, (Gannoruwa, Peradeniya) it was ob'served that applying the fertilizer at transplanting or halfway between transplantin weeko tw sd beforgan e primordial initiation resulted in relatively less nitrogen being derived from fertilizer.by plants than when the fertilizer was applied two weeks before primordial ^ :. initiation. This could be due to loss of applied nitrogen from ,.the root zon plantf eo s especially since this station experience totada f lo rainfal564.f o m 5m l durin firse monthexperimene o gth th ttw f so t (October and November 1964) in contrast to 280.1 mm at the dry zone station during 'this period.' At the wet zone station Gannoruwa, time of nitrogen application-had no uptakeffece th phosphoruf n eto o s from fertilizer y aondr , ee whilth t ea ' ' i . •- . station Maha Illuppallama a single application of nitrogenous fertilizer two weeks after transplanting resulted in the most efficient uptake of phosphorus from fertilize plants.y rb • The result secone th f dso experiment conducte Maht da a Illuppallamy ab Nagaraja Al-Abbad han s showe benefite th d deef so p placemen nitrogef to n on plant uptake (5). Ther greates ewa r uptak botf eo h nitroged nan phosphorus'by plants from fertilizers when ammonium sulphat applies ewa d itham nc deptrowa n5 t whef sa ho n this fertilize applies rwa rown i dn so the surface (Table III). Placemen superphosphatf to mixinr eo g with ammonium sulphat influenct no d uptakedi e eth nitrogef eo plantsy nb .

- 8 1 - The results of the third experiment conducted at Maha Illuppallama by Kathirgamathaiyah, Thenabadu and Al-Abbas (6) showed that there is greater uptak fertilizef eo r nitroge planty nb s when ammonium sulphate, urea, ammonium nitrat d sodiuean m nitrate were "broadcas surface th n o te weeko tw s "before primordial initiation than when they were applien i d rows at a depth of 5 cm at transplanting (Table IV). These results are in agreement with firs e thosth tf eo experimen t whic s conductehwa t a d two locations (4). It was found that plants absorbed the greatest amount of nitrogen from urea when applie eithet da r stage. Thi followes swa d by ammonium sulphate, ammonium nitrat sodiud ean m nitrat descendinn i e g order. The efficiency of the nitrate containing fertilizers was significantly greater when applied as a top dressing than dressing at 5cm depth at transplanting.

The efficiency of phosphorus uptake by plants was highest when urea applies wa weeko dtw s before primordial initiation.

Although ther s increaseewa d uptak nitrogef eo phosphorud nan planty sb s which were fertilized with urea, there was no significant increase in grain yielconsequencea s a d yielde .Th plotf so s that received nitrate fertilizers were relatively lower than those of the other fertilizers. Among these plots, those that received top dressings of nitrate fertilizers yielded better than those that received basal application.

There was a highly significant correlation (r = 0.98l) between nitrogen derived from fertilizer in the straw and that in the grain at final harvest. If nitroge grai e indicatioa th s i n ni proteis it f no n content then time of fertilizer nitrogen application could be a significant factor in improving qualit ricf yo e althoug significano hn t quantitative effecto t e sdu treatments were observed.

- 19 - The results of the fourth experiment conducted at Maha Illuppallaina by Thenabadu, Jauffer and Willenberg revealed the benefits of deep placement of ammonium sulphat grain eo n yield ricf so e (7)« Sub-surface placement of this fertilizer at 5, 10 and 15 cm at transplanting produced significantly higher yields over surface applications, broadcasn i r to rows (Table V)..The highest yiel obtaines dwa d whe fertilizee nth s rwa placed 15 cm below the surface and the yield was lowest when fertilizer was applied in rows on the surface. When fertilizer was placed at 16 cm depth the yield .increase was intermediate. The yield responses to ammonium sulphate treatments were generally associated with higher percentages' of nitrogen derived from fertilize highed ran r concentration elemene th f so t plant e i0 daynth 4 st sa from transplanting.

thin I s experimen methoe tth nitrogef o d n applicatio significano n d nha t percentage effecth n to phosphoruf eo s derived from fertilize planty rb r so on the content of phosphorus in plants.

The efficiency of utilization of four combined nitrogen/phosphorus source influences sa shalloy db w placemen transplanting..ant ta d surface, placemen weeko ttw s before primordial initiation was. compare lase th t n di experiment in the series, (8), conducted at Maha Illuppallama. .

Due to an error.in manufacture all treatments did not receive equivalent quantitie nitrogef so n (lO) ratee . Th applicatiof so foue th r f nitrogeno n sources were as follows*- Treatments A and E received 62.5 kg N/haj B..D,E and H received 55-4 kg N/ha and C and G received 2J.9 Kg N/ha. The percentage nitrogen derived from fertilizer shown in Table VI are the corrected

.percentage standare th r sfo d rat 62.f eo 5N/hg K a calculated accordin; g A-Value tth o e transformation, assuming tharate f soitth eo l nitrogen fertilizere affectet suppl ratth e no f th s eo yi y db highese .Th t percentage of fertilizer derived nitroge botn ni h grai strad nan s foun w wa plant n di s receiving ammo-pho deptm c transplantingt 5 ha whict sB a s appliew hwa ro n i d .

- 20 - Where fertilize applies rwa d later (broadcas surface th weeko n to etw s "before primordial initiation) ammonium sulphat superphosphatd an e e resulted in the highest uptake of fertilizer derived nitrogen. The effect of treatment percentagn o s phosphoruf o e s derived from fertilizer indicates that auano-phos B was the most efficient form of phosphorus.

Conclusions

The conclusions from these five experiments are as follows:

1. Deep placement of nitrogen at transplanting promotes "better utilization of fertilizer "by plants than surface applications at transplanting "bettes .i Placemen m c r 5 1 tha t nta shallower placement depthm c 0 1 . r o at5

application A . 2 nitrogef no weeko ntw s "before primordial initiation promotes more efficient utilization of nitrogen than one at transplanting, althoug formee surfaca th h s i r e applicatio depta lattee t a th h s d i r nan of 5 cm.

3. Nitrate containing fertilizers are not efficient sources of nitrogen for rice grown under submergence.

utilizatioe Th . 4 phosphoruf no ricy sb e doe appeat affectee b no s o t r d methoy b applicatiof o d nitrogenf no .

References 1. Ponnamperuma, F. N. "Fertilizer experiments in cultivators' fields in Ceylon". Tropical Agriculturist, CXVI, (i960), 253.

Constable. 2 . "FertilizeH . ,D r evaluatio ricn o ncultivatorsn ei ' fields in Ceylon". Research and Production of Rice in Ceylon. - Proc. Symp. of Ceylon Association for the Advancement of Science. D.V.W. Abeygunawardena (Ed). (1966),71 " The Colombo Apothecaries Ltd. Co . Colomb Ceylon, 2 o .

- 21 - 3. Kalpage P. S. C. P. "Fertilizer use on rice in Ceylon". Research and Production of Rice in Ceylon. — Proc. Symp.of Ceylon Associatio Advancemene th r nfo Sciencef to . Abeygunawarden. W . V . D a (Ed). (1966), 61,Colombe .Th o Apothecaries Ltd. Co . Colomb Ceylon, o2 .

4. Nagarajah, S. and Al-Abbas, A.H. "Co-ordinated contract programme on the application of isotopes and radiation in rice cultivation in Ceylon". Tropical Agriculturist, CXXI, (1965), 1.

5. Kagarajah, S. and Al-Abbas, A. H. "Nitrogen and phosphorus fertilizer placement studies on rice usin2 3 g N 15 and P ".. Tropical Agriculturist, CXXI, (1965), 89.

6. Kathirgamathaiyah, S., Thenabadu, M.W. and Al-Abbas, A. H. "Utilizatio nitrogef o n d phosphorunan ricy saffecteb - eas d fory b d tim man applicatiof o e fertilizef no r using N-- and P52". Tropical Agriculturist, CXXIV, (1968). ,1

Willenberg d . Thenabadu7 an Jauffer, . M . W. M . . M . M ,S ,. , M "Studie placemene th n so ammoniuf to m sulphat r lowlanefo d rice using isotopically labelled fertilizers", -Tropica. • l Agriculturist, (in Press).

Thenabadu. Willenbergd 8 an Jauffer, . M W. . . M . M ,M . ,. S , M "Efficiency of combined nitrogen and phosphorus sources for rice as influenced by time and method of application (Unpublished data).

9. Mueller-Dombois, P., "Climate Map of Ceylon. (1968). • Smithsonian Ecology. Project, Departmen Botanyf to , University of Ceylon, Peradeniya, Ceylon.

10. Vose, P. B. (1968). Personal communication.

- 22 - Table I - Effect \f time !iii;?fiS.ll -CJL. --e'•'• ^ and- •bt£1^ ^.gpjLgf. Nitroge Phosj>horud nan s Utilizatio P.icy nb e Plants. (Experimen Mah- t1 a Illuppallama) Nagai•ajah and Al-Abbas. 1964 (4)

Treatments* Grain Yield Percentage Nitrogen Percentage Phosphorus derivet f - d in .plants P derived in plants -./haN/ha. g K Kg . timet .a s from from a b c fertilizer fertilizer by plants by plants 60 0 0 3141 32.1 1.30 39.7 0.191 0 60 0 2998 28.2 1.56 46.4 0.189

0 if 60 2963 35.1 1.67 33.8 0.195 30 30 0 3136 31.7 1.22 42.3 0.187 30 0 30 3437 31.5 1.74 43.3 0.193 0 30 30 3111 32.5 1.45 39-7^ 0.190 20 20 20 3003 28.8 1.38 35-8 0.201 L. S. D. at leve5% l 663 n.s. 0.29 7.9 n.s. I... S. D. at 1leve% l 887 - - 10.6 - plotl Al 0 s/ha2 * ? receive . . Kg 0 6 d and 60 Kg. KgO/ha. as superphosphate and muriate of potash respectively, a s> Time > at transplanting. b = Time, halfway between the time of transplanting and two weeks before primordial initiation. Prinordial initiation is defined as the time the ear can first be felt at the base of the shoot. Time= c weeko ,tw s before primordial initiation. TablEffec- I eI Timf Ratd to Applicatiof ean eo Ammoniuf no m Sulphat Yieln eo Efficiencd dan f yo Nitrogen and Phosphorus Utilization by Rice Plants. (Experiment 1 - Gannoruwa} Nagaraja Al-Abbasd han , 196) 4(4 • «

Treatnents* Grain Yield Percentage Nitrogen Percentage Phosphorus deriveN d Kg.w/ /ha. Kg . nat time«a- s in plants P derived in plants from w from - (<£\ , . c b a ...... - fertilizer . fertilizer _ by plants . y plantb " s - ...

v •» 60 0 0 . 4291 13.8 1.88 20.4 0.172 i 0 ro 0 6 0 3911 20.8 2.01 21.8 0.168 0 0 60 4296 27.4 2.35 30.0 0.150 30 30 o 4291 18.7 2.09 21.9 0.161 0 3 0 30 3634 23.2 1.99 29.7 0.158 0 3 0 3 0 4336 24.1 2.35 23.9 0-.174 ^0 20 20 4410 25.4 1.99 26.7 0.133 L. o. D- .• • - at-£ • >3 $71 •-level 7.7 0.29 n.s. n.s. L. 8. D. at l.fo level 953 10.3 •» — —

* All plotB-rwelved €0 Kg.' P_0-/haVan'd 60 Kg. K^/ ha. as superphosphate and muriate of potash respectively. a = Time, at transplanting b a Time, ha];fway"b"e~twee e timnth e i of transplante we o tw d !nan e iks before orimordia]L initiation. Primordial initiation is defined as the time the ear can first be felt at the base of the shoot, Time weeko ,tw s before primordial initiation. Table III - Effect of Fertilizer Placement on Yield and Efficiency of Nitrogen and Phosphorus Utilization "by Rice Plants (Experiment 31 Nagarajah and Al -Abbas, 1965/6) 6(5

Treatment .s Grain $age N Nitrogen $ageP Phosphorus N Yield derived in derived 'in Fertilizer Fertilizer. Fertilisers mixed .... /, from plants ($) from plants . or separate Kg./ha. fertilizer . fertilizer (ft by plants by plants Irow nn Fertilizer. I rowson n so s mixed 6073 18.2 2,59 38.9 0.189 the surface the surface before application I rownn I n rowFertilizeso n so r applied 6688 20.6 2.77 37.1 0.185 the surface the surface separately in rows ro In rows at In rows on- Fertilizers applied 6692 31.2 2.81 49.7 0.197 dept m surfacc e th 5 h e separatel rown yi s Fertilizerrown . I rown t sI a t sa s mixed 6611 55.9 2.96 50.3 0.215

deptm c 5 5 h depth before application m

rown I rowt n oFertilizersa I t sa s applied 6705 31.6 2.76 37.7 :.201 5 cm depth 5 cm depth separately in rows The N ahdP Fertilizers mixed, broadcast on 6542 19.4 2.59 50.8 0.198 the f surfaco m c mixe d 5 ean p d to inte th o soil (puddled) L.S.D. at 5 $ level 537 6.2 n.s. 9.9 n.s. 1 72 L.S.Dleve^ 1 lt . a 8.4 13.3 NOTEi All tieatments received 60 Kg.N/ha. 60 Kg. PgC /ha. and 60 Kg KpO/ha. as Ammonium Sulphate, Superjhosphate and Muriate of Potash respectively. (60 Kg./ha. = 53.52 Its/acre) Table IV - Effect of Form and Time of Application of Fertilizer Nitrocen on Yield, and isff-io-ior,™ of Nitrogen and Phosphorus Utilization by Rice Plants (Experimen^ t

: Kathirgamathaiyah, Thenabadd uan Al -Abbas, 196} 6(6

Grain Percentag ederiveN d Percentage.? derived .from Treatments- , Yield from fertilizet ra fertilizer by plants (Straw) Kg/ha. maturity Straw Grain 2 weeks before At primordial primordial initiation e • * '. initiation Ammcniusa sulphate at transplanting . 6621 17.0 17.2 21.2 19.1 ideptm nc row5 ht sa Ure transplantint aa rown g i t sa 7140 18.8 20.2 5 cm depth 16.2 16.3 ra Ammonium nitrat t transplantinea g 5917 8.9 8.4 *p in rows at 5 cm depth 19.7 18.4 Sodium nitrat transplantint ea g 5961 3.6 . . 5 4. 18.1 16.8 ide'ptm nc row5 ht sa Ammonium sulfhat week2 t ea s before 7212 19.0 19.0 19.8 primordial iritiation broadcast on the surface ~" — " ... - weekUre2 t aa s before primordial 6834 22.4 24.8 initiation bioadcas surface th n to e Ammonium nitrate at 2 -weeks before 6742 13.6 12.8 primordial iritiation broadcasn to the surface- ...... _.„...._ Sodium nitral week2 t ea s before 6108 9.8 6.9 primordial iritiation broadcast surface onth e L.S.D $_leve5 t .a L- 63. 8... .- 3.3 L.S.D. at 1 % level 859 : •me rare or nitrogen was 60 Kg.W/ha, All trratments receive Kg.Pg0 6 d O Kg.K 0 /ha6 d ?0/ha.an Superphosphats .a Muriatd ean Potasf eo h respectively, broadcas surface th n transplantingo t e a . Effec- Y Ammoniuf to m Sulphate Placemen Yieldn o t Efficiencd ,an Nitrogef yo Phosphorud nan s Utilization by Rice Plants (Experiment 4) Thenabadu, Jauffe Willenberd ran g 1966-6) 7(7 _ e m t a e r T s t n Grain Yield PercentageN Nitrogen Percentage Phosphorus /ha derived from in plants** P derived in plants P-Fertilizer **' N-Fertilizer fertilizer ?o\7>)A from Fertilizer by plants** by plants** Broadcast on Applied at trans- 5233 a* 54.7 2.68 71.1 0.135 the surface planting broadcast surface ohth e In row- s o od n - tie 4652a 49.0 2.77 72.6 0.186 surface In rows at f - do - 5956b 54.5 3.30 71.6 C.189 cm depth C row1 n I t sa - o d - 6061b 65.0 2.98 75.1 0.185 cm depth 3 rown 1 I t sa - do - * 6555 b 67.9 3.44 67.8 0.197 cm depth L.£ .D. at 1 $ level 13.8 0.68 n.s. n.s. * Duncan's iultiple Range Test at 5 i° level of significance. Mean "followet sno samy db e lette significantle rar y different from each other. Plant* * s sanple day0 d4 s after transplanting. NOTE't The rate of nitrogen was 60 Kg,/ha. All treatments received 60 Kg.P2o5/ha. and 60 Kg.KgO/ha. as Superphosphate and liariate of Potash respectively, broadcast on the surface at -transplanting. Table VI - Effect of Separate and Combined Sources of Nitrogen and Phosphorus on Yield and Efficiency of Nitrogen and Phosphorus Utilization by Rice Plants as Affected by Method of Application (Experiment 5) Thenabadu, Jauffer and Willenberg, 1967 (8)

Treatments Percentage N derived Percentage P P in plants ($) from fertilizet ra N-Fertilizer P-Fertilizer derived from at Primordial maturity______fertilizer at Initiation Straw Grain Primordial Initiation A-Ammonium Sulphate Superphosphate "L.") at transplanting in t .transplantina g 21.20 17 02 deptm c rowc ht sa broadcase th n o t 37.4. 0.208 B-Ammo-phot a , sB surface transplanting in Phosphate applied 55.39 24.77 44.8 0.183 deptm c row5 h t sa combined withN C-Nitric Phosphate - do - 15.55 3-6.2 (75 $ soluble?) at 0.213 transplantin rown gi s m c dept a5 t h D-Nitric Phosphate - do: - 10.49 15.33 (25$ solublt a ) eP 35.1 0.193 transplanting in rows at 5 O|B depth E-Amronium .sulphate,2 Superphosphate at 14.70 18.32 25.4 0.213 weeks before P.I.stage, week2 s before broadcast on the surface P. I. stage, broad- ;. - . cast on the surface P-Ammopfeoa B>a t2 Phosphate applied 12.45 15.45 28.7 .weeks before P.I. stage combined withN 0.229 broadcas surface th n to e G-Nitric photphat- eo d (75- ^ 10.09 7.28 18.6 week2 solubl t a s ) e? 0.245 before P.I.stage, broad- -rurface casth n to e H-Nitrio phosphat ••o e—d (25- ^ 10.37 9.09 17.4 0.218 soluble P)a tweek2 s before P.I.stage, broadcas surface th n to e STUDIE COMPARATIVE TH N SO E NUTRIENT REQUIREMENTS OP LOW AND HIGH YIELDING VARIETIES OF RICE

A.B. Khan Rahma. L , n S.I. Chowdhury, S.M. Alam l Al . Y d an P.K b .De Atomic Energy Centre, Dacca, East Pakistan

ABSTRACT? A series of glass house and field experiments on nutrition and physiolog ricf o y e were conducted wit withour ho applicatioe tth f no radioisotopes. This paper -contains information, in a summarised form, covering the significantly important aspects of the research findings.

Analytical dat variouf ao s grai d stranan w sample ricef so , collected from fields revealed that grain N, P and K contents of different kinds of decreasine th n i ric e gear orde Borf ro o (Summer rice), Aman (Winter rice), Aus (Autum rice) and for Ca content, the order is Aus, Boro, Aman. Aus straw contain thaa C nd Amas an Bor d morK nan o , eP straw Born ,i o straw th econtenN higheste th s ti . •xp Placement of P' labelled superphosphate at various depth and with continuous and intermittent flooding did show variation in the uptake and drymatter yield. Absence of fertilizer K apparently reduces the uptake of froN m urea sourc muct bu eh from ammonium sulphates .wa Uptak P f o e 32 more when N was applied as urea than as ammonium sulphate. Low yielding local Aman rice (Naizersail) does not respond beyond the dose of 60 Ibs N/acre while high yielding IRRI variety (IR8-288-5) showed progressive increase of yield up to 180 Ibs. Chlorophyl contenb d an leaf o tla f increased with highe applicatiorN n upto 90 Ibs N/acre in local and 120 Ibs N/acre in IRRI varieties and with more chlorophyl IRRIn i l . Crop logging (5rd leaf analysis at 65 days) showed nearly maximum N content in local varieties with 60 Ibs N/acre application while that of IRRI increased progressively up4;o 240 Ibs N/acre.

- 29 - N, P and K content of low yielding varieties, are 2.2, 0.2 and 2.0 $ while those of high yielding varieties are 2.5, 0.25 and 2.5 $ respectively. inden a useAnalytica e r leaved s "b dxa fo ol y sma y da l 5 dat2 f ao correcting the deficiency level of nutrients for ultimate higher yield.

In Boro season "both low and high yielding varieties showed increased N and K uptake with higher rates of applied fertilizers, more progressive being with IEBI varieties. For IBRI, grain yield and N content was more and P content was less in Boro season than those in Aroan season, K-content remaining same. In IRRI (Aman) leaf Ca-content (3rd leaf at 65 days) decreased very sharply and consistently with increased N-applioation, "but -that was not applicable with local varieties.

Total and applied Fe^5 9 content of rice plants was more at earlier stage daysO s(J IRRn )i I tha Naizersain ni l (local) ..late. at rt ;bu stag e • t the Fe-concentration increases in the local variety, both from foliar spray and soil application. Plant Hn concentration increases with higher doses, more being in local varieties, than in IRRI. Higher concentration reducen M d an d oe D.MfF . yield.

- 30 - .. Introduction* World population is increasing at a fantastic rate and the Agricultural Scientists are putting their efforts to meet the food situation created "by over population. Naturally, the ultimate aim of the workers in all fields is to produce more and more food "by better fertilisation, cultural practices, introductio evolutior no w ne f no varieties and controlling pests and diseases. Agricultural practices adopted in a country or region, based on the existing varieties of a usuallt crono o pd y hol newle d th gooyr introducedfo evolver o d d varieties, having the capability of higher productivity. Rice, a major cereal crop is grow varien ni d climatic, topographica soid lan l conditions. Keeping this in view, an attempt will be made in this paper to discuss the fertilizer requiremenhigd an h w yieldinlo f to g varieties only.

The requirement of various nutrients by rice plants depends on the variety, soil condition, yield-target, seasonal variation, cultural practices and many other interrelated factors- JJo...variety,, low or .high yielding, is likely to produce the maximum unless it does or can absorb and assimilate the optimum nutrients either from the soil or from the applied fertilizers Japanese .Th e agricultural scientist presentle sar y aimin produco gt mor% 0 e5 yield fro uni: ma t area than what thee yar producing now. In order to obtain a target yield from the high yielding varieties scientiste ,th workine optimue sar th fino gt t mdou fertilizer rate, instead of seeking the yield-target by increasing the rates. Islam (1965) reported -chat 50-10 0yiel% d increase b ricf n eo eca achieved onl applyiny yb g fertilizers judiciour fo t .Bu s applicatione ,on must know the varietal characteristic in respect of nutrient absorption capacit yield yan thaf do t strain. Standard fertilizer recommendationr sfo common East Pakistan varieties are about half of those used for the high yielding IRR Japonicr Io a varieties. Over 10 tons/ha of rice was produced in Japan by applying N P K § of approximately 200, 150, 250 kg/ha in a loamy soil (1966). Karim et.al (1968) found that application of lime in the acid soils of Sava Tongid ran , Dacc equivalena8 $ lim40 e609o d t saturatio5an n showed 2&fo and 2jfo yield increase. The changes in pH were from 4.8 to Savat a Tongid 5 ran 6. ,o t respectively 0 5. d an likels i 5 t 6. .I y that alsa C o serve nutriena s da t other tha nsoia l amendment.

The problem of micronutrient is also important when high yielding varieties are cultivated with higher rates of fertilizer, under flooded conditio acin calcareoud no dan s soils. Tanaka (1966), reported remedial measur irof o e n toxicit applyiny yb g manganes certaia o et n extent.

It is, therefore, apparent that cultivation of high yielding rice varieties needs closer attention frocornersl al m , keepin vien gi w the factors prevailing in the region they are grown.

SHORT DESCRIPTION OF THE EXPERIMENTS: Experimen1 . tHo Nutrient uptak matury eb e rice crops. In order to assess the loss of some major nutrients (N,P,K and Ca) from the soils of East Pakistan by cropping, plant samples of Rice, Jute Sugarcand an e were collected from various place analysedd san analyticae .Th l data of rice straw and grain revealed some very valuable information about their nutrient contents. The table given below will show the exact position in this respect othee .Th rconsideret cropno e sar d here.

- 32 - Table - 1

Chemical composition of unhusked grain and straw.

Type of rice S$ P$ K$ Ca$

Aus (Autumn). Grain 0.98 0.25 0.32 0.22 Straw 0.58 0.10 1.55 0.41

Aman (Winter) ' Grain 1.25 0.29 0.43 "O.O? Straw 0.58 0.04 1.09 6.31

Boro (Summer) Grain 1.40 0.32 0.53 0.09 Straw •--- 0.90 0.08 • ' 1.5-- 3 0.19

Resul discussiond tan » • Pro above inferrede mth "b e y (tablma - t thai e t Boro grains contain more nutrients (N, P, K) than either Aus or Aman grains while the Ca 'content is the highest in Aus grains. In Aus straw, P, K and Ca contents were more than those in Aman and Boro varieties; but the N-content was the highest in Boro. This provide wit e opportunitiee son hth think.thao st t .different high yielding varieties of IRRI grown in East Pakistan in all the three seasons will require variable rate fertilisef so r dependin croe th p n go season.

' . >. Experimen2 . tNo Effect of continuous and intermittent flooding on.the uptake of applied phosphoru ricy sb e plants.______' Red soils of Dacca (pH-5.5 to 6.0) collected in layers of 0-10, 10-20 and 20-25 cm deep, were used in pots for experiments under 'continuous and intermittent flooding. In one series the soils were placed layer by layer

- 33 - and in another they were mixed. Superphosphate was placed on the surface, at

10 cm depth "before transplanting, rate in all oases "being 80 Ibs P20 /acre, except the control. Rice plants, harvested at an interval of 20 days from transplanting, were analysed. Data are given in Table-2.

Result and discussiont • Dry matter yield, grain yield, 73 2 uptake were the highest with surface ajpplication. Mixing or non-mixing of soils had little difference on mattey dr r yiel d graidan n production, "but uptak P^O,f eo mors .wa e from surface d 5 applicatio mixen no d soils tha non-mixedn no .

Experiment No. 2 "Effect of continuous and intermittent flooding on the uptake of applied phosphorus by rice plants".

Table show mattery sdr , stra graid wan d phosphoru an n m yielg n i ds conten hills(underlinedg 3 m f n o i t . t po r )pe

Mixed soil Non-mix«d soil Treatments D.M. D.M. 1 D.M. D.M. | 1st 2nd Straw Grain 1st 2nd } Straw Grain cutt. $ cutt. ' cutt. °utt. (j |Control 2.33 7.32 17.74 12.96 2.20 7.65 20.34 14.69 1} Conti Sur5 -e fac i 3.04 10.88 23.28 17.65 j 3.08 9.53 25.29 16.34 nuou. f s I 6.24 22.40 14.63 21.66.0| 77 16.04 12.13 F!oo- * !2±!1 axn ———— * flO on 1| 2.94 7.82 25.54 15.20 3.03 10.67 20.90 15.49 y depth 0.88 5.16 6.27 5.82 400 13.85 6.88 8.61

OControl 2.49 6.61 13.36 8.87 ' 2.1 J 06.0 1 14.94 8.53 Inter- -K ——————— mitt- Or, * 2.82 „.»+ ^Surface 9.84 13.77 I 10.53 2.3i 9.2f 7 0 13 ..30 11.59 X 4.77 15.65 5.^8 j 11-95 4.41 |l4.Q9 5.65 •f", or,- J) •12.7i • i- 3' ~- m c d?ngo jK , 2.57 1 7.93. 14.3I 10.4- 9 4 8.5? -'284 .0 .14.49 11.18 Idepth '• 2.06 6.27 3.56 j 8.15 ' 3.006 9.15 i —— —— t —— *• J i-22 • 8.71

- 34 - Experiment No* 3

The effect of rates and forms of nitrogen fertilizers on the uptake of P and N by rice plants.______

A glass house experiment wit soid Dacchf re lo a applyins It 0 g4 and 80 Its N/acre, separately from ammonium sulphate (A/S) and ure s conducteawa studo t d y theiN d r an uptake effec P th f n eo o t and alsyielde o th level o .Ibs/acre0 Tw 4 _ sd 0 an eacP o f h( )o and KgO were applied with both the forms of nitrogen. Three hills was harvested, at 50 days after transplanting, for analyses and the remaining 3 hills at maturity.

Result discussiod san n

Table-3 shows that P and K influenced D. M. and grain yield. 32 Uptak P increasef eo d applies whewa n N ure s a d a than whes na ammonium sulphate. Subsequently, a field trial on lateritic soils of Savar, Dacc conducteds awa , usin sourceg2 nitrogef so thret na e levels (0,40 and'80 Ibs N/acre) with basic phosphorus and potassium

(60 Ibs/acre of P20 and K20). Data showed that 80 Ibs N/acre as urea wassuperior to A/S in acid soils, 'producing 32$ and e$0 more yield over the control (NQ) respectively. With lower N rates, both sources were equally effective. It can reasonably be expected that high yielding varietie difficule b y sma groo t acin wo d soils with higher rates of A/S.

- 35 - Table - 3 Experimen3 . tNo "Effec ratef to formd san nitrogef so n fertilizern s,o the uptake of phosphorus and nitrogen by rice plants" ______(glass house experiments^______Table shows matter y yieldr f o d , grain_i and..FQr.t.Tm ng P a.nd total-N in mg per pot (three hiUs).

Treatments D.M. . Grain Fert-P Total-N in Ibs/acre t harves1s t yield ig nm ig nm in gm m g n i . .0*70 .• W4o . 2.45 3.07 Control Wo 1.11 2.22 0.53 5.62

N0P40K40 1.23 3.02 0.68 6.16 •— -~-g— ---• N40P0K40 1.36 2.27 -

Wo . 1.7' 7 2.56 0.81 . 8.77 Ammon Sulphate N40P40K40 2,31 2.84 1.04" 12.68

H80P0*40 1.99 2.68 - ' • 13.45

N80P40K0 2.98 1.07 0.83 18.19

W80P40K40 3.27 2.0y 1.01 14.55

>i N40P0K40 1.20 2.53 - 7.90

W40K0 1.61 2.51 0.92 7.84

N P K 1.91 3-37 1.30 9.44 Urea 40 40 40 N80P0K40 1.83 2.85 - 15.49

N80P40K0 2.11 3.16 1.22 10.61 N80P40K40 { 2.39 , 2.57 1.15 10.95 N.B. Straw: Grain Ration Contro- s 2.50 - 1.66 l- S ,,A/ Ure 1.75a- , - 36 - Experimen 4 ...... tNo

A comparative study of local Aman and IREI varieties on their H-tQlerano yieldd ean , wit withour ho t potassium.______

Standard recommendation of the Department of Agriculture, East Pakistan is 40-40-40 Its/acre of N, PgO and K^O. It is assumed that if "balanced P and K fertilizers are applied with N, even the local varieties can absorb and assimilate more nitrogen and yield more grain to a certain extent. The intention was also to study the performance of newly introduced IRRI varieties, well known for iheir high nitrogen absorption capacity, with more grain yield.

The Aman experiment was carried out on red soil of Tongi,

Ite'jca, based on :the information obtained through the earlier isotopio axp3riments. Latisail (local),and IRQ (high yielding) varieties were N/acrs 120, Ib 60 locar , 0 ed fo 16 lan d an 0 teste12 , d80 wit, 60 h N/acrs Ib IRRIr 0 eratfo e 24 potas.f Th eo d .0,60,12s an hwa 0 18 0 Ibs/acr

of K«0 and P2°c was applied § 80 Ibs/acre. N as urea was applied in three splits viztransplantingt a .- day0 5 day5 s,d 2 aftesan r trans- planting. Sufficient irrigation was provided as and when needed.

P.nsult discussiond san ; Field and analytical data are given in Table-4 and 5 for Latisail d IR8an , respectively observes i t .I d that Latisail produce highese dth t yi3ld with 60-80-60 Ibs/aci erespectively0 P-0,rate, K« N d f .so an e .Th result confir mearlier ou som f eo r finding nullified san idee sth a that local varieties cannot stand higher rates of N and produce good yield. Nitrogen beyond 60 Ibs N/acre did neither increase yield nor the plant IT-content of the local variety appreciably or proportionably, indicating limited requirement of the variety. Such N rates induced more lodging with loss of yield.

- 37 - The highes obtaines wa t8 yielIR d f wito d h 240-80-60 ratd ean a reasonably high yield with 180-80-0 or 180-80-80 rates. Potash had no effec yieldn o t sufficien,e th probabl o t e tydu soi contentlK . Nitrogen conten8 increaseIR f o t N/acrs dIb upt0 e o24 rat applicationf eo .

Leaf N, P, K content of 65 days old plants were 2.2, 0.2 and 2.0$ for loca 2.5d lan , 0.2 2.5d 5an THRr $ fo I varietie thesd san e levele sar considered to be adequate. However, it is also expected that the N, P, K content of whole plant at about 25 days may serve as an index for correcting the deficiency standine anyf ,i th n ,o g crops.

Leaf samples from 65 days old plant showed that both in local and IRRI varieties contena C e ,th t progressively decreased with higher rates of N application;. ov»n with liming §0.35 ton/acre. The reduction s sharwa casn pi IHRf eo I J;ha locan ni l varieties. Treatment wito hn nitrogen had 0.15$ plant Ca which went down to 0.08$ with 180 Ibs N/acre for IRRI and that for Latisail v/ent down from 0.11$ to 0.10$. This may be from the shortage of soil Ca~supply and the dilution effect due to more dry matter production. However, the competition between N H* and Cations can not be ruled out. Karimet alfound increased Ca uptake and yield due to higher rat liminf eo acidin gi c rice fiel. d Tabl4 e-

"Effec highef to r level Nitrogef so n wit withoud han t Potassium on nutrient content and grain yield of T. Aman rice (Latisail) grown at Tongi, Dacca". treatmentj plan. . ^ y -tda 5 2 s% 1 65 days 3rd leaf j Grain yield Ibs/acre Ibs/acre N% 0 P% 0 K% i1 < N $° F? 1 ( 6 B ) ( N K 1.90 0.2? | - 0 2.30.11 7 I 1.98 8 3374" 60 0 : 1 —— — f —— ¥* ————— ' i— — rt ———— ——— — ; 0.22 < »*fto 1.90 0.30 •1.3 2.2" | 83 : I 2.7 "3538| 9 i 2.50 5 3210 N60K120 1.89 0.27 2.03 0 2.37i 0,17 1 1.70 N80K0 1.85 0.23 2.05 I °'14 296<32.2| 5 vr ir 1 0.22, NftOK60 1.80 0.27 2.15 2.22 1.90 (j 3045 17/ } . W V 2.10 ! 1.90 3210 W80K120 1,27 0.23 2.18 i °- 1 i N120K0 2.03 0.29 1.83 2.31 i 0.19I 1.58 3374 ———— i— ———— — —— - — • * ( 1.38 3210 N120K60 1.48 0.30 2.03 j 2.39I 0.19 y . ir "" !• 1.32 0.30 2.1 I 2.45 2 i 0.15 2.05 3045 N120K120 —— 1 K 2.02 0.27 2.65 'j 0.19 1.65 3374 »6o o ) « N160K60 "l.34 0.27 2.27 0.1| 5, i 2.17 3210 ' v . ... | 2.38 | 2880 N160K120 1.99 0.29 2.20 | 2.420.19; 1. Replicates were composited for plant analysis. 2« A-basal rate of 80 Its PgO /acre was applied in all the plots. N and K were calculated as N and KLO respectively. Fertilizer used were urea, triple super phosphat muriatd ean f potasheo .

- 39 - Table - 5

"Effec highef to r level Nitrogef so n wit withoud han t * Potassium on nutrient content and grain yield of T. Aman rice (IR8-288-3) grown at Tongi, Dacca".

Treatments 25 days plant days 3rd leaf Grain yield Ibs/aore 1 65 1 bs/acre N?6 » P% J) K$ P Wfc 0 P^ 1 Kf5 N60K0 1.34 0.37 2.03 2.02 0.19 1.78 3127

N60K60 1.62 0.40 2.20 2.22 0.21 2.10 ! 2963 , N60K120 1.51 0.3i 2.19 0 2.05 0.20 j 2.0- 5 2880

N K 1.44 0.42 1.98 2.48 0.26 2.58 3374 120 0 .

N120K60 1.68 0.45 2.20 2.53 0.28 2.70 3374 ————— N120K120 1.66 0.46 2.33 2.25 0.25 , 2.05 3374

N180K0 1.61 0.40 2.03 2.86 0.28 2.58 3621 ™^^~^^™^^— 1 ——— N180K60 1.56 0.48 2.20 2.89 0.30 2.43 5621

N180K120 1.66 0.45 2.20 2.72 0.33 2.63 : 3374

N240K0 1.86 0.46 2.03 3.05 0.34 2.98 I 3703

N240K60 ... 1.77 0.53 1.60 2.09 0.29 2.6 j 3 3868

N240K120 1.53 0.49 2.10 3.02 0.31 1.80 3457

Replicates were composited for plant analysis.

- 40 - Experiment No.. 3

Respons yieldinw lo higf eo d han g Boro rice to higher nitrogen rates.____ .

This experiment was conducted in Boro season at Mirpur, Dacca, with the same idea and objective as that in Aman season, except with slight changes in the fertilizer rates for the low yielding local variety. For IR8, th« fertilizer rates were 60, 120, 180 and 240 Ibs N/acre in combination with 0, 60 and 120 Ibs KpO/acre. For Habiganj-VIII the rates of Ibs/acre0 12 d an ,0 N9 K-treatment wer, 60 e s remainin samee basige th .Th c rat^ Ibs/acr Pp^ f s eo c wa e from superphosphate.

After 65 days of transplanting, third leaves were analysed for N, P and K contents.

Results and discussions The analytical dat graid aan n yiel showe dar Table-6n ni . Highest grain yield was recorded with 120-80-60 treatment in case of IR8 while He/biganj-VIII responded mor lesr eo s equall N-treatmentsl al o yt , irrespective 01" K-application. Wit decreaso hn mor o yielt n e i e e vegetativddu e growth out of higher N-rates it may be observed with interest that if properly balanced, eve locae nth l varietie stann sca N/acres dIb upt0 .o12 This •';rend was also observed in case of local Aman varieties.

Nitrogen application increased leaf N-content of IR8 almost consistaatly with increase yieldinw dlo ratese th g n .varietI yalonN e increased the leaf N-oontentj but the difference was not pronounced.

If the leaf N-contents of plants grown in Aman and Boro seasons are compared, it may be observed that N-contents was 40$ higher in Boro season resulting proportionately higher yield. Potash application was ineffective i

- 1 4 - It may also "be mentioned here that the concentration of chlorophyll a and to in leaf increased with higher rates of N-application upto 90 Ibs.IT/acre in local and upto 120 Its N/acre in IRRI varieties. However, the concentration of both a and "b were more in case of high yielder.

Application of K tended to increase the chlorophyll concentration yieldinw inlo g varieties whil causet ei d reduction hign ,i h yielding variet N/acrs Ib y 0 upt elevee 12 application oth f lo , with again na increasing tendency at higher levels.

- 2 4 - i'aole - 6

Experimen5 . tNo "Response of high and low yielding Boro rice to higher nitrogen rates (Varietys IRRI-8 and Habiganj - VIII)"

Treatments Nutrient contents of 65 days leaved 'ol yiel d s an grai f do n in Acs/acre in Its/acre ' i Habigan VIIj- IRR8 I I- N# P# K$ Its/aciB 1 n£ * K$ Its/acre

N60K0 2.92 0.24 2.50 4789 2.98 '0.29 2.40 3288 N60K60 2.87 0.22 2.37 4961 2.84 0.30 2.23 3436 1I60K120 2.57 0.26 2.85 4690 3.15 0.36 2.38 3387 *90K0 - - - - • 3.02 0.38 2.40 3313 N90K60 - - - - 3.31 0.34 2.55 1 3378 N90K120 - - - . 2.93 0.33 2.52 I 3469 N120K0 3.46 0.23 2.30 4551 3.33 0.35 2.60 3411 N120K60 3.20 0.27 i 2.37 5223 2.68 0.29 3.10 3469 H120K120 3.54 0.24 2.42 5002 5.25 !0.34 2.50 3674 N180K0 3.48 ; 0.26 2.50 5215 N180K60 3.60 0.26 2.43 ' 5199 N180K120 3.55 0.24 2.78 5109 N240K0 3.4; 2 0.24 2.30 4805 N240K60 3.48 0.24 2.43 4124 N240K120 3.82 | 0.24 2.53 4485

- 43 - Experimen6 . tNo

Effect of Fe and Mn application on the D.M. yield, Fe and Mn contents of local and IRRI rice._____

5 wer Mh culturt d epo an usea en di e experimen P studo t y their nutritional behaviour on two varieties of rice namely, "IR-8 and Naizersail. T-he mode of application -of the nutrients were foliar spray and soil application with various concentrations' (Tables 7 and 8) having vje-fold replications. An alkaline soil (pTJ-7*.4) was used for the experiment. Five weeks old seedling .pe,4 wert rpo e transplanted. Plant samples were collecte anad dan - lyse day0 6 dsd -aaftefstagee an tth 0 3 rs - transplanting .'

lUsult and discussion:

Columns 4 and 10 of Table-7 show that Fe content of JO days IRRI plant sample mors si e than thos Naizersailf eo latet a t r, bu stage eth concentratio locae th ln i variet e F f no y increased boto t he "du typ f eo applications. It appears that in general, total Fe concentration slightly decreased beyon p.p.m5 1 dose f dth boto en . i h varieties wit foliae hth r "spray whereas the concentration increased from soil application.

Both total and applied Mn concentration in plant increases with - increased dose of application, more being in the local varieties (Table-8, and"8"col" 5 " tha.) 4i ,"9 n IR-8.

The dry matter yield in both varieties decreased with increased. - plant manganese and iron concentration (Table-7 and 8).

- 44 - Tabl7 e- Experiment No*6 . Effec application'oe P f to D.Me lead nth contenan e f.F ) P.P.M.n gm yiel (i tn d(i f )o

_ _. ____ — -_ . .- •' ..._*__ i _ ___ — ^* -1» •• i . • j rt- a.-A- I 7 rt n Why) £if\ A ft tm r% f 4* SN4* 4» Y*A Wm V\l O V»^ •! **l n» 1

1 j • • - 9 5 Fe„ ^ applied IRRI (IR - 8) . _„' Local (Naizersail) 7 ^m oi fQjy in P. P.M. Tota mattey dr l r Total Fe(PPM) •PPM of Fe? Total ^.r yj 1'otal ^©(PPM) matter 3C 60 30 0 6 0 0 3 300 3 60 60 30 j 60 206 - 0.655 4.561 - 24! 3 - 223 Control 1.330 3.592 315 i t Foliar 10 0.717 3.591 298 0 5 21 i 0 9 5 0.741 4.204 485 317 58 ' 61 1 Spray 15 0,725 3.310 342 169 65 108 0.252 7.037 243 j 270 13 6 j 9 11 Y 25 0.620 4.800 469 226 168 158 0.432 5.846 419 165- 84 85 ! 50 ! 0.350 3.876 374 198 126- 84 0.4605 22 3,99- ( • 3 1 31 253 i 56 , 0.956 310 280 4 77 J 0.766 5.260 ! 272 151 26 I 62 , Soil 10 4.775 ' i 5.479 382 195 IS 159 0.866 3. 9H 377 280 20 1 80 Appli- 0.649 catiol ge n 0.820 I 3.548 398 232 30 146 0.629 5.657 367 226 57 | 133 50 0.636 5.50. ' 2 432 265 88 321 0.5492 27 1.64 4j ' 7 6 451 8 30 Tatl8 e- Experiment Ho• 6 Effect of Mn application on the D.M. yield (in gm) and leaf Mn content (in P.P.M.) of loca d IRRlan I ric variout ea sday0 6 day sd harvesf so aftean 0 r(3 t transplanting).

Mn54 appll«*. ) 8 - IRRR (I I Local (Naizersail) 1 54 in P.P.k. Tota f Mn'y o mattedr M l HPP j r Tota mattey dr l r PPM of Mn54 30 60 30 j 60 50 60 •30 60 Control 1.330 I 3.592 - - 0.655 4.561 - - Foliar 20 1.065 3.50 ! 86 84 0.480 6.315 146 109 Spray 30 '0,625 3.635 228 175 1.15 4.754 155 109 60 0,922 2.268 j 300 380 0.435 3.850 390 421 100 . 0.350 4.338 608 .644 0.355 5.753 523 519 20 . 0.454 2.220 37 101 0.402 2. -696 - 58 75 30 0.595 1.560 58 243 0.365 2.524 89 236 Soil • appli- 60 0.429 1.672 170 440 0.405 2.770 281 219 cation 100 0.364 2.063 218 840 0.588 • 1.105 216 692 ! Summary* ultimate Th eagricultural goaal f lo l experiment achievo t s si e increased productio witd nan h this poin vien ti attempn wa bees tha n made to summarise some of the experiments with valuable information. This is only an attempt to throw some light on the performance and nutrient requiremenhigd an h w yieldinlo f to g rice definitelt ,bu t yno a chapter closed for discussion.

Experiments conducted in various seasons with different varieties Ticf o e using majo minod ran r Mf , elementsetoc. Pe , . Ca , ,K i.e, P , .N are summarised here.

The following conclusio drawe b y m- nma

1. Nutrient contents of rice plants vary depending on the crop season, even in the same variety. Boro (Summer) appears to be the richest in respect (Autumns Au d respecan n ) i K P Ca-contento f tfo N . 2. The phorphorus uptake was the highest from the surface application of superphosphate under water-logged condition and also from mixing of surfac subsurfacd ean e experiments t soilpo n si . 3P « uptak32 e increases whe source nth nitrogef eo ures ni a as-ffompared to ammonium sulphate. '. 4* Field trial showe bettea d e ureb ro at sourc nitrogef eo n than ammonium sulphate in lateritic-soils in respect of grain production. Low yielding local Aman rice (var - Naizersail) does not respond beyond 60 Ibs N/acre while in the same season IR-8 showed progressively increased yield N/aores Ib upt0 .o18 Potassium non-responsivseeme b o st clan ei y soils.

- 47 - 5. N P K content of 65 day old leaves were more in IRRI varieties tha locan ni l varietie Aman si nseasono r seasoP n weli .s na s la

6* Overall nutrient content of the same IRRI variety in Boro season is much more higher than that in Aman season resulting in higher grain production,

Lea. 7 f N-content Born si od tha n wer& Aman 5 i t e3« n foune b o dt 5 percent2. s i ' indicating that increased N-conten relates ti higheo t d r yield.

8. Higher rate of N-application decreases the Ca-content of 65 days d lea botel n fi h varieties, decline being shar IRRIn pi . Liming improves the crop yield effecting both soil reactio Ca-nutrltiond nan .

Chlorophyl. 9 l conten leaf o t f increased with higher N-applioation upto 90 Ibs N/acre in local and 120 Ibs N/acre in IRRI varieties, being more chlorophyll content in IRRI.

. Thir10 d leaf analysi prt sa e -primordial stag epromisina seeme b o st g tool for adequate fertilization of rice crops like many other short duration crops .

Acknowledgement The authors wish to record their gratitude to the members of the Plant Physiology technicae Sectioth r nfo l assistance rendere connection i d n with this work. They also express their sincere gratitud otheo t e r member thif so s Centre for their co-operation.

- -48 References

1. Agri. Asia 1966 (English Edition). Association of Agricultural Relations in Asia, pp 275-276.

2. Islam, M. A., (1965), Fertilizer problem of Eaat Pakistan, unpublished, 1 pp- .

3. Karim, M., Rahman, M., Sandhu, M.S., Patwary, S. and Bashir, M. (1969). Liming of acidic rice soils (unpublished),

Ric. 4 e production manual, Universit Philippinee th f yo s (1967) . 60 - p3 p4

5. Tanaka, A., Novasero, S.A. (1966) Soil Soi. P3. Nutr. 12_ (5). 197 - 201.

- 49 - INTERNATIONAL ATOMIC ENERGY AGENCY in cooperation with the FOO AGRICULTURD DAN E ORGANIZATIO UNITEE TH F NDO NATIONS CountrieEasr Fa te Studth Asi f sd o y aan Group Meeting on the Use of Isotopes and Radiation in Investigations of Fertilizer and Water Use Efficiency

Bangkok, Thailand 21-25 April 1969

A Study on the Efficiency of Shallow and Surface Placement of Nitroge Phosphorud nan s Fertilizers Applied Separateld yan Chemically Combined For Usiny mb g Isotope Technique--'

. - ' • Sombhot Suwanwaong, Patoom Sanitwongs Prayood ean n Sawatdee Technical Division, Rice Department, Ministr Agriculturef yo , Bangkok, Thailand

OBJECTIVES comparo T . efficience 1 eth differenf yo t chemically combined nitrogen/phosphorus sources with ammonium sulphate plus super- phosphate .

I/ Report of experiments conducted in Thailand under a research contrac IAEe th A n coordinateti d prograapplicatioe th n mo n of isotopes and radiation in rice cultivation (1967-1968).

- 50 - 2. To compare the efficiency of ammonium sulphate plus superphosphate and different chemically combined nitrogen/phosphorous sources as influenced by shallow placement at transplanting and surface placement two weeks before initiation of panicle primordia.

MATERIAL METHODD SAN S

Experimenta. 1 l site experimene ;Th conductes twa Rangsit da t Rice Experiment Station, Pathum Tani Province located abou kilometerO tJ s north of Bangkok.

2. Soil at experimental site;The soil at experimental site is a moderately acid sulphate soil formerly part of the tidal flats with heavy clay texture developed from brackish water alluvium belongin Rangsie th o gt t series (Rs), The chemical properties of this soil at the experimental site are given in tabl Kaoli. 1 e n mineral prevalene sar t throughou profile th t e while vermiculite, illite and montmorillonite are sub-species. The details of the clay mineral composition reporte Kawaguchi. K y db , Kyoto University, Japan are as follows?

Composition of clay Composition of next minerals left, column nui •j.&uu Kaolin Illite intergrade, Mont. Verm. Al-Verm. ^t^11^ mixed layer

+ 1 + 4 5+ + 20+ 35 + + 3 + + 45 + 15 0 4 5 40 20 40 -i- ++ + . ± froapproximate e ar figuree th m 4 Th d Note columnn an si . 1 3 e: , amouns2 t of crystalline minerals in percent, deduced from the measurement of the heigh ared X-ratan f a o y diffraction peaks.

2. "Mont-Verm intergrade, mixed layers" include montmorillonite, vermiculite, their intergrade and mixed layer minerals. Bic. 3 e variet rice yTh e variety employe experimente th n i d s swa characterize e whicb 4 Nahnn S- hca n gMo talla s da , medium-late, non-glutinous, photo period sensitive variety, normally maturing abou November0 t2 typicas Indice i th t .I f alo type th use n i d lowland transplanted areas of the Central Plain.

Experimenta. 4 l Method experimene desige :th Th same f thas th ; nea s ttwa suggeste IAEy consisted db Aan Randomizea f o d d Complete Block with4 replications. Each replication contained a total of 10 main plots or treatments herein designate dthrougA treatmente Eigh. th hJ f to s (A through H) were concerned with (l) sources of N and P, (2) placement of the fertilizer and (3) time of application. Plots A through D had fertilizer applie plantint da g centimete5 tim rowa n i et sa r depth while treatments E through H had fertilizer applied broadcast on the soil surface two weeks before panicle initiation. The treatments A and E received superphosphate broadcas transplantint ta weeko tw sd gprioan r to panicle initiation, respectively, sinc ephosphorouo n ther s ewa s chemically combined with the nitrogen. All 8 treatments received 60 Kg. of N per hectare using the different sources of nitrogen applied as previously stated with spacing of 25 x 25 centimeters.

Treatment I was a maximum yield response plot using 120 Kg. N per hectare in the form of ammonium sulphate applied in rows at a 5 centimeter depth at transplanting time. The treatment was subdivided

into two equal plots referred to here as I, and I2 in which plant spacing was 25 x 25 and 25 x 34 centimeters respectively.

-Treatmen alss wa otJ subdivided equally int ploto2 s calle, dJ absence Thi. th N n sf i o e als K compar Jo 2d t d o an an effece P eth f to

serve experimente controa th s da r lfo ? receive.J fertilizeo n d r wherea receive, . eacsJ. P^O Kg f hectareo hr 0 c6 pe d an<° *KO .

- 52 - All plot shectarr exceppe O e2 Kg receivetJ "broadcas, Kg 0 6 d t immediately after applicatlon-of •the" nitroge phosphoroud nan s treat- ment justjbefore transplanting ...... • . .

•' 'Both radioactiv d non-radioactivean e superphosphate wels ,a s la the N-15 labelled and non-labelled nitrogen fertilizer were applied at the same rate and same -time according to the fertilizer treatments. The following outline gives a description of each treatment in detail.

Treatment. Placement and Timing N - Fertilizer P - Fertilizer ammonium sulphate applied at superphosphate applied at transplantin. cm 5 rown gi t sa transplanting broadcast on depth. the surface. E ammopho applies3 transt da - phosphate applied combined plantin row°n»5 n g i t .sa with y. depth.

nitric phosphate (75 fo soluble phosphate applied combined applie) P transplantint da g wit. hN cni5 rown i «t sa depth .

nitric phosphat% 5 (2 e phosphate applied combined soluble P) applied at wit. hH transplanting in rows at 5 cro depth.

E Ammonium sulphate applied superphosphate applied 2 weeks before primordial 2 weeks before panicle initiation, broadcast on initiation, broadcasn to the surface. the surface.

' - 53 - Treatment Placemen Timind tan g N - Fertilizer P - Fertilizer P Ammo-Phos B applied two phosphate applied combined weeks before primordial with N. initiation, "before primordial initiation, broadcast on the surface

nitric phosphate (75 % phosphate applied combined solubl applie) eP d with N. week2 s before primor- dial initiation, broad- surfacee th oas n to *

H nitric phosphat% 5 e(2 phosphate applied combined soluble P) applied 2 with H. weeks before primordial initiation, broadcast on the surface.

yiele Thith ds s i respons e plot and N in the form of ammonium sulphat applies ei d transplantint a rown gi t sa 5 cm. depth and at the rate of 120 Kg. N per hectare. Superphosphate at the rate of r P. 62hectar°0Kg c Pe s ei applied at transplanting, broadcast on the surface. This plos dividetwa d into two equal sub-plotd an , sI

- 54 - Treatment Placement and Timing

N-Fertilizer P - Fertilizer J zere Thith o s fertilizesi r control plot (yield check) and was divided equally into two sub-plots J, .a.nd Jg.

Note: Rice was transplanted July 15, 1967 and harvested November 26, 196?.

SUMMARY; A study on the efficiency of shallow and surface placement of nitrogen and phosphorous fertilizer applied separatel chemicalln i d yan y combined form by using isotope techniques was conducted in 1967-1968 at the Ringsit Rice Experiment Station, Pathum Tani province. The soil at experimental moderatela sit s i e y acid sulphate soil with heavy clay texture prevalene .Th t clay mineral is kaolin with low pH and base saturation but high in organic matter. This soil belongs to the Rangsit series (R_). The results of the 5 experimen summarizee b y tma followss da :

1. According to the.results of the experiment on the yield and yield components founs wa t d,i that both ammonium sulphate plus superphosphate and chemically combined nitrogen/phosphorous fertilizers, when appliet da transplantin weeko tw sr g o befor e initiatio paniclf no e primordia gave significantly higher numbe tillersf ro , height, numbe paniclesf ro , grain and straw than those of check plots (Table 2, 3 and 5).

Considerin. 2 g applicatio fertilizef no transplantint ra yiele gth d components wer significantlt eno y different regardles fertilizef so r sources. However, grain yield obtained from ammonium sulphate plus superphosphate and from ammo-pho significantls swa y higher than those from both nitric phosphate sources.

- 55 - Whe . fou3 e nth r kind fertilizerf so s were applieweeko tw st da befor e initiation of panicle primordia, it was found that there was no significant difference among yield components and grain yield but there was a tendency toward lower yield in treatments using nitric phosphate fertilizer.

4. When the two methods of fertilizer application were compared, it showed that in general the fertilizer application at transplanting time gave more number of tillers, number of panicles, grain yield, straw yield, straw-grain ratio and total dry matter production than the later fertilizer application. On the other hand, the later application gave higher panicle weight and number of grains per panicle.

Analyse. 5 recovere th n s o nitroge f yo phosphoroud nan s derived from fertilizer were performed on the 8 treatments (A through H) using leaf sample differen3 t sa t graistagee th d stra nan n growtf si o t w a d han harvest time (table 4). Prom the data obtained it was revealed that when the fertilizer was applied at transplanting (A through D) in rows at a 5 centimeter depth the plant recovery of nitrogen derived from nitric phosphate, 25 percent soluble P, was lower than those of the other fertilizer treatment stagel al t leaf sa o f growt grain weli s straw d ha s nan la , whil othee eth r three fertilizers showe differenco dn thin ei s respect. othee Onth r hand, when these source fertilizef so r were applied broadcast on the surface at two weeks before initiation of panicle primordial (E through H) it was observed that there was not much difference in percent of nitrogen derived from the different fertilizer sources. However it can be noted that nitrogen derived fromammo-phos was consistently higher at all stages even though statistical analysis did not indicate significant differences.' When both stage fertilizef so r applications were comparede ,th percentag nitrogef eo n derived from fertilizer applie transplantint a d g was slightly higher than the later application. It is interesting to note that regardless of fertilizer sources, there was a very high positive asso- ciation between uptake of nitrogen and phosphorous at both first and second harvesting of the leaves. Fro. yiele 6 th m d obtaine percentagee dth (.Tabld an ) enitroge5 f ' o n phosphoroud an s derived from fertilize cleas r wa (Tablt ri tha) e4 t nitric phosphate, 25 percent soluble P, was inferior to: both the' ammonium sulphate plus superphosphate and amroophos, although there was practically rio difference in efficiency between these two latter fertilizers. In Comparing nitric phosphate sources, the 75 percent soluble bettes i P r than 'nitric phsophat percen5 e2 t solubl althougeP s i t hli lower than the other two sources. . . . . :

ACKNOWLEDGEMENT The authors wish to express* their sincere gratitude |to Dr. Ben R.Jackson, Takahash. J Saro. . Dr Dr td Montrakuian their lfo r correction helpfud san l advise in preparing this paper.

Special acknowledgement is due to IAEA for the material and academic supports. Warm appreciation is extended to fellow workers of the Rice Department especially to the staff of the Rangsit Experiment Station for their helpful cooperation! 1 , in this experiment.

- 57 - Tabl . Analysie1 experimentae soif th s o t la l site*

Exch Exoh. Cation me./lOOg. i pH s O.M.: Available! *°lal, mei/lOOg.: Base Base Texture ***'' * ! cm P K H Sat Sand H20 1 H A me./100{5. K+ •.** Sitl Clay KC1 ppm. ppm._ * *** I 4.2 5.4 0.8 3-59 7.9 65.6 0.16 28.38 13.74 0.63 7.17 8.02 2.00 48.09 11.3 16.1 72i6 II 4-5 5.4 0.9 3.48 9.2 59.6 0.16 28.69 14.18 0.60 6.58 8.86 2.04 49.77 10.5 18.2 71.3 0-20 IIl 4.2 5.4 0.8 5.22 7.1 61.6 0.16 28.70 14.44 0.66 6.61 9.20 1.99 49.55 11.5 15.4 73.1 IV 4.2 5.4 0.8 5.17 7.6 65.6 0.15 28.58 14.44 0.60 7.47 8.91 2.00 50.10 9.2 16.3 74.5

Averages 4.2 5.4 0.8 5.57 7.9 65.1 0.16 28.59 14.20 0.62 6.96 8.75 2.01 49.38 10.6 16.5 72.9 i ? I 4.0 3.2 0.8 1.72 2.6 46.0 0.10 25.72 9.75 0.41 5.18 8.06 2.17 38.00 11.5 16.1 72.4 II 4.0 3.2 0.8 2.08 5.0 53.6 0.11 26.95 10.65 0.58 5-45 8.52 2.24 39.42 11.2 16.1 72.7 20-40 ra 4.0 3.2 0.8 1.72 2.5 57.6 0.10 27.20 12.49 0.45 5-73 8.87 2.16 46.64 11.4 16.1 72.5 IV 4.0 0.8 0.8 1.61 1.7 61.6 0.09 27.05 12.58 0.58 5-75 8.62 2.55 46.11 11.2 12.2 76.6

Averagft 4.0 3.2 0.8 1.78 2.4 54.7 0.10 26.73 11.37 0.41 5-53 8.47 2.28 42.54 11.3 15.1 73.6 Table 2. Tillering of Bioe Plants at Various Stage

Treatment Average Number of Tiller per hill 30 days^/ 57 days^/ 71 days^/ 131 days^/

A 11.96 12.51 9.84 9.19 B 10.84 11.60 9.25 9.02 C 10.72 11.63 9.11 8.32 D 10.45 11.12 8.95 7.93 E 3.34 3.36 10.66 6.47 P 3.30 3.41 10.37 5-83 G 3 .'09 3.30 •9.52 5.65 H 3.08 3.30 9.43 5.91 I 10.15 13.80 10.95 9.82 I . 11.21 18.05 14.07 12.13 3.64 3.45 Jl 3.56 3-57 3.79 3.47 J2 3.29 -3.74

O.t>5- D HS ~ -1.&4 - 1-.-48- - 1-.3-2 1.25

l/ Mean of four replications. 2/ Tillering of rice plants at the time of half way between transplanting weeko antw d s before primordial initiatio Augus4 n(1 t 1967).., Tillerin ricf go weekeo tw timplante sf th eo befor t sa e primordial initiation (11 Sept. 1967). . . Tillering of rice plants at the time of the intermediate harvest at primordial initiation (25 September. 1967).. Tillerin ricf go e timplante harvestin. th eof t sa Novembe6 g(2 r 1967).

- 59 - Tabl . Heighe5 Ricf to e Plant Variout sa s Stages^/

Treatment Average Heigh Ricf to e Plants (cms) 2J 30 days=^ 57 days^/ 71 days^/ 131 days^/

A 74.54 114.36 132.85 176.47 B 75.76 111.74 126.98 166.58 C 77.02 107.10 121.53 159.68 D 70.90 96.12 107.89 151.48 £ 51.94 69.57 114.03 171.81 P 52.93 69.79 112.26 165.54 a 53.34 69.23 106.90 160.22 H 52.06 70.10 109.65 160.66

Ix 74.64 131.06 154.58 209 1.0

I2 74.40 136.00 159.82 208.17 Jl 55.43 70.66 81.41 133.69 J2 53.57" 69.60 80.15" "132.2" 1

HSD 0.0- 5 '4.67 • 7.88 8.91 6.79

Mean of four replications. n Height of rice plants at the time half way between transplanting and two weeks before primordial initiation (14 August 1967) u Height of rice plants at the time of two weeks before primordial initiatio Septembel n(l r 1967) Height of rice plants at the time of the intermediate harvest at primordial initiatio Septembe5 n(2 r 1967) Heigh ricf to e planttime harvestinf th eo t sa 6 Novembeg(2 r 1967)

- 60 - Table 4. Height of leaf cample grain and straw and percentage of total nitrogen, phosphoru percene th d tsan derived from fertilize variout ra s stagef so growth in Isotope-plots.

First Harvesting*/ Second Harvest ing£/ Third Harvesting^'. / Fourth Harvesting-^ Grf3jj,p Rt-T .=» W _ Tr. Dr. ywt Nitrogen Phosphorus Dry wt^ Nitrogen Phosphorus Dry wl/ Nitrogsn Nitrogen Ifi tropen e Total DFF Total DFF S Total DFF Total DFF g Total IFF "Total br r TotaJ

A 7.80 1.90 74.2 .141 61.9 7.67 1.54 72.1 .099 70.0 7.90 1.06 63.2 0.89 52.5 0.29 41.0 B 7.03 1.76 78.6 .115 61.9 7.23 1.40 76.6 .094 51.3 7.12 1.01 66.4 0.87 52.8 0.27 49.0 C 6.79 1.67 77.9 .119 61.2 6.32 1.28 76.1 .091 54.5 6.56 0.94 66.1 0.82 49.6 0.28 47.0 D 6.05 1.58 59.9 .135 53.8 5.75 1.34 58.1 .115 47.9 5.72 1.02 48.8 0.85 33.5 0.31 33.3 E 3.72 - - - - 5.10 2.71 61.7 .246 50.3 6.96 1.61 49.2 0.88 39.8 0.30 41.5 F 3.70 - - - - 5.63 3.03 79-5 .217 58.2 6.98 1.55 64.4 0.85 47.7 0.30 47.9 G 3.58 - - - - 4.30 2.30 56.6 .216 56.0 6.62 1.56 59.2 0.86 42.7 0.29 46.8 H 3.50 - - - - 4.24 2.14 48.0 .174 50.8 6.71 1.44 48.9 0.87 33.0 0.31 35.9 & - 1.91 - - - - - — — - — — — — — — —

HSD - 0.05 0.71 0.15 5.0 .02 6.7 1.27 0.65 14.0 .04 16.8 1.28 0.17 10.0 NS 10.0 0.03 ND

week2 t A s Ibefor/ e primordial initiatio Septe2 (1 n . 1967). 2/ At primordial initiation (26 Sept. 1967). flowerint A IJ Oct6 (2 g . 1967). harvestint A / Kov6 4 g(2 . 1967). 5_/ Mean of four replications of twenty sev n leaves. 6/ Composite sample of treatment E F G H. Tabl . Yiele'§ d component ricf so e plant harvestt sa .

j No. of :f Paniclo . No e : : wt./lOOO :Grain Yield : Straw Yield : Rati: o Total dry matt' anicle wt. grain/ grain production Treatment P / Kg./Ha. Kg./Ha. straw/grain : Hill : gra. : panicle : gnu : Kg./Ha.

A 9.193.18 84.47 33.13 3,904.18 10,222.35 2.62 14,271.32 B 9.022.85 79.15 32.93 3,533.11 9, 416.41 2.66 13,069,99 C 8.322.89 80.36 33.16 3,088.90 7,313.43 2.37 10,505.50 D 7.932.86 79.20 32.99 2,762.41 5,911.93 2.14 8,773.99 E 6.474.02 107.79 34.27 3,264.99 4,663.02 1.43 8,039.74 P 5.834.51 120.77 34.12 3,067.71 4,372.65 1.42 7,551.25 G 5-654.42 122.58 33.99 2,855.78 3,896.35 1.36 6,805.39 H 5.914.63 124.57 34.06 2,909.05 4,048,65 1.39 7,055.09

Ix 9.823.58 98.83 33.32 4,955.66 13,077.94 2.64 18,218.15

2 I 12.13 3.85 107.58 32.74 4,799.87 13,002.38 2.71 17,996.90

Jx 3.^53.46 98.75 31.62 1,551.71 1,864.77 1.20 3,475.88

l tt^9 J *^ mj 3.18 92.13 31.57 1,518.66 1,77^.84 1.17 3,347.06

US 0.0D- 5 1.25 0.90 24.70 0.90 493il8 1,909;09 0.36 2,238.55

Mea fouf no r replication from yield plots. RECENT SOIL, FERTIBIZER AND PHYSIOLOGICAL STUDIES WITH 32p ON HIGH YIELDING VARIETIES OP PADDY

B.V. Subbia J.Cd han . Katyal Nuclear Research Laboratory, Indian Agricultural Research Institute, Delhi, India

ABSTRACT A knowledge of the rooting pattern of high yielding paddy varieties is of considerable importance in soil,water and fertilizer management problems. Studies wer applicabilite e th planp carrien ^2 o te t th injectiodou f o y n techniqur efo paddy, comparison of the results of root activity obtained by,the placement of P in different soil zones and root distribution pattern by P plant injection technique rooe ,th t distribution patter hige th somf h no f yieldineo g dwarf paddy varieties as compared to local ones, and effect of nitrogen fertilization on the rooting patter dwara f no f variety resulte Th .followsss briea n s i e far - (a) T* plant injection technique was found to be applicable for paddy for evaluation of root distribution and injecting ^^p into the plant with sucrose was found to result in increased transport of the activity from the stem to the roots. (b) The root activity data by P placement (in capsules) gave statistically reproducible results whic highle har y correlated wit rooe hth t distribution pattern obtained by i2p plant injection technique. (c) The high yielding dwarf varieties (viz. IH-8 and Taichung Native l) were found to have more intensity of root distribution in lower depths as compared to local tall variety (Vi 130)P zN . (d) Effect of increasing levels of nitrogen fertilization was found to result greatea n i r intensit roof yo t distributio lowen ni r depths.

- 61 - RECENT SOIL, FERTILIZE PHYSIOLOGICAD RAN L STUDIT3S WITH OF- HIGH YIELDING .VARIETIE PADDF SO Y

B.V. Subbia J.Cd .han Katyal Nuclear Research Laboratory Indian Agricultural Research Institute Delhi India

1. INTRODUCTION !*fith the recent introduction of high-yielding varieties which are being further crossed with local varietie brino st g about certain desirable characters, new problems in soil fertility and water management are coming up for sblution. Since the roots are principal organs of a plant through which nutrients and water e absorbedar , .the knowledg characteristie th f eo c rooting habit relativd san e activit -|;hf o ye root differenn si t soil zone f thesso e high yielding varieties is essentia bringinr lfo g about efficient ssoil, wate fertilized ran r management. Very littl knows ei n abou exace tth t rooting patter thesf no e recently introduced paddy'varieties, because of difficulties involved in such-studies. In the present paper (a) the applicability and standardization -of •* P plant injection technique paddyr fo compariso ) ) ,(b ? , (6 resultf no s obtaine thiy db s technique with those ptakep oactivity f32 ,b y placemen capsulesn (i t differenn )i t soil zones) ,(c

U evaluation of the rooting pattern of some high yielding paddy varieties, and (d) effect of different levels of nitrogen fertilization on root distribution of a dwarf paddy variety have been studie resultd an d s discussed.

MATERIAL. 2 METHODD SAN S 2.1 Standardization of T* plant injection technique: Plant paddf so y variety Taichung Nativ e(dwarfI ) were grow solution ni n culture using standard Hoagland's nutrient solution, using 0.5$ Ferric ammonium thif o citrate sl m iro e nOn . solutio s alsnwa o added dail eaco yt h porcelait npo of one litre capacity. One plant was grown in each pot. Nutrient solution was changed once or twice a week. Nutrient solution in the pots was aerated for 5-6 hours each day using a compresser and glass tubing with multiple openings. Due to synchronized tillering habit of the variety used, a suite.ftle tiller at ,

flowering stage was selected for injection. Ten microcuries of carrier-free p P in 0.0? ml. in the form of E^PO2 . (in HCl) was injected in the second internode using a micro syringe (6, 7). In order to study if there is a beneficial effect of injecting carrier-fre P wite^ h sucrosmovemene th distribution d eo an t f no plante th treatment*2o n ,pi tw s namely wit withoud sucrosM han 1 t0. e were included seconA . d micro syring uses creato ewa t d e suctiosame th e n internodni e atra point about 3-4 cm. above the first syringe. Root and shoot samples were separated by cutting the plant at the base of the stem at time intervals of 1,3 an day6 d s after injection. Roots were washed thoroughl removo yt e nutrient solution sticking to them. Roots were divided depending upon the length, into 3 or 4 parts of about 5 cm. length and each used separately for specific activity determination. Injected tille eacn ri h cas s separatedewa . Uninjected tillers were separate d eacdan h used individuall specifir yfo c activity determination. tiller2 y da sd werHowever3r d e an combiner samplet ,fo 1s f orden so i d reduco t r e the numbe samplesf ro . - 62 - 2 Estimatio2. specifif no c activit planf yo t samples: Both rood shooan t t sample r eacwery sfo hda e oven dried a ove y an n n i dr d weight recorded. Dried samples were groun Wilea n di y micro mill, total phospho- rus determined by "Vanado molybdo phosphatic yellow colour method" (l). One mg - P equivalent solutio precipitateP s take d nwa nan magnesius a d m ammonium phosphate wit) modificatioe (5 hth n usin $ triammoniug50 m citrate whic bees hha n founo t d be. equally suitable in place of 50$ ammonium citrate. The precipitate was filtered under identicall conditions using demountable' falteration set. The dried and mounted precipitat countes ewa d usinwindod en gG.Ka .w decade sealer counter. Specific activity data were calculated after making necessary corrections. 3 Fiel2. d Studies 2.3.1 Assessment of root activity pattern by 32P placement. ° In this experiment carrier-fre mixes wa dP wite 3 2hKgSO.) . KgSOmg uc/10 2.(5 . / / \ K/jSO. was dissolved in minimum amount of water in a mortar and carrier-free K^SO.f o . .mg 2 Thi1 tddep r s 32 pe correspono active t dc u 0 5 , o solutiot d s nwa thoroughly stirre dried an d d under infra-rod lamp with intermittent mixine th f go material. After dryingrouns wa t gdi thoroughl glova n yi e box. Twelvf o . emg this material was weighed accurately (using a percision balance) each time and put in the gelatinous capsules. Capsules were closed carefully with their caps. One month old nursery of variety Taichung Native I (dwarf) was transplanted in the plots of dimensions 6m x 6m. 12.5 cm from plant to plant and 20 cm. from row to row distance was given. Two healthy seedlings were transplanted each hill. A basal dose of 100 kg. of N (half at the time of transplanting and half after one month of transplanting) as urea and $0 kg. P00K as super phosphate per hectare were added before puddlin ured gan a fcfter Afte day5 r 1 transplantin f so g four capsules wer arount epu d each plant ta equal distances on the periphery of a circle. The different lateral distances from the plants were 2.5 cm (L,). 12.5 (Lp) and 22.5 cm. (L,) and depths were 4 cm (d,), 12 cm (d?), 20 cm (a,) and 28 cm (d,). The holes were made at these lateral distances and depths by a thick and sharp iron rod and after placing the capsules the holes were closed completely by filling with soil. Plants where capsules were placed were labelled. flowerine Ath t g stage above ground capsule partth f so e placed plants were harveste used specifir dan dfo c activity determinatio describes (a n d above). Specific activity dat r threafo e replicates after necessary corrections were used for calculating the percentage root activity in each zone. 2.3.2 Root distribution pattern by 32P plant injection technique: 2.3.2.1 1967 Studies: During this year two varieties of paddy viz IR-8 (dwarf) and Taichung Native I (dwarf) were grown in the fields (15 Main Block, Agronomy Farm, I.A.R.I.Delhi) using the same distances as mentioned earlier. Ten rows of each variety were transplanted in a plot of about 2.5 m x 6 m. Two plants were put per hill. Fertilizer dosage and method of application were same as above. At flowering stage wheabou t soila e nth s t !wa fiel d capacit suitable yon e tillef ro a healthy plant was injected with carrier-free ^2P using 5*0 uc in 0.125 ml. Three plants of each variety were injected. After giving six days for ^2p ^o "equilibrate in whole of the plant body, above ground parts of the plant were cut soid an l f sampleof s were take laterat na l (L,m distancec 5 )(Lm 2. c 12.?f )5so an(dj) m c (Ljdm ,c depthd 8 22.(dg)m c 5)an 0- ,9-1 (d,)6m f sc o , 17-24 25-3m 2c (d.) using a tube auger. Four samples were taken at each lateral distance - 63 - and depth aroun plane mixedd th d an te sample Th . s were taken whe surface nth e soil was below field capacity. Each composite sample was labelled (showing the lateral distance and depth) and kept in polythene bag. These soil samples with roots wer r drie d groundeai an d eacf .o h® Abou S sampl 0 5 ts ignite ewa a n i d muffle hoursfurnaco ashetw e Th r .500t d ea fo °sampleC s were ground thoroughly to ensure the uniform mixing of the activity with soil and filled in cupped planchets (0.625 cra depth). The surf an-, was levelled by using a steel spatula. The weight of the soil in each planchet was recorded. (This weight was found to be almost constant. 0 secondcounte 5^ Th )r sfo were taken usin windod gen w G.M. Counter. After makin necessare gth y correction percentage sth e root distri- butio county nb s calculatedswa . g.3.2.2 1968 Studies: During this year four padd y 0 (tallvarietie13 P ,N z svi local variety) Taichung Native I (dwarf), BC 5 and 5C 6 (both obtained by crossing Taichung Nativ locaX eI l tall variety botd basmatan h 0 thes 37 idwarfse ar e ) transplanted afte monte ron sowinf hMaio 5 1 nn g i Bloc Agronomf o k y Farm. Method of transplanting, dat transplantingf eo , spacing used, fertilizers applied were. previoue exactlth n i same ss yth ea year' s experiment flowerint A . g stage three plants were injected and collection of coil samples at various depths and lateral distance, ignition, counting etc. were exactl same aboves th ya o . 2.3.2.3 During this year another experiment was set up to study the effect of different levels of N fertilization on root distribution of variety Taichung Native I. Levels of N used were 0, 70, 140 and 210 kg N/ha. This experiment was laid out according tc randomized block design using three replications. Rest of the conditions were exactly the same as above, and root distribution was made at the flowering stage as in other experiments.

importane th Som f eo t soil character summarizee sar varietad an tabln i da I el characteristics in table Ib.

The soils of the fields where experiments were carried out as can be seen from silte tablar yeI clay loams buld wit ranginan H kh p 5 densit8. g- froy0 8. m1.1 - 8 depthe th l s al wher 1.3n i 2 e root distribution studie madee soile sar Th e . sar fairly rich in total nitrogen and available phosphorus and are known to have good amounts of potassium.

3. RTOULTS 3.1 Standardization of 32P plant injection technique: The results obtained on the 32P distribution in different parts of paddy plant day6 injectiof d so an afte3 presentee , r1 nar tabln i d. II e The data in table II show that more than 88$ of the activity has remained in the injected tiller even afte dayx injectionsi rf so , although trena ther s dewa of slow decreas activite injectee th th n i en i y d tiller with time. Howevern ,i the uninjected.tillers the amount of activity moved, increased with time. But one very striking featurdate thas th i a f fairla teo y good amoun activitf o t y moved firse roote th i th ntn so n casday I suoros.f .eo - treatme.it ther s abouewa t 2.9$ of the total injected activity in the routs on the first day, 1.9$ on the third day and 3.4$ on the sixth day, while in case of no sucrose treatment the corre- sponding figures were 2.7$, 1.2$ and 1.4$ respectively. In general the sucrose treatment resulted in a greater amount of activity aft^r 3rd and 6th day in roots. From the point ' of view of applicability of the technique for the estimation of the root distribution, it is essential to have uniform specific activity in the entire root system. From this point of view the data obtained on the specific - 64 - activity in the different parts of the roots is presented in table III. It shows that there are big variations in the specific activity of different root parts on the first and third day but tend to become more uniform after the sixth day. Thus this method for the estimation of the root system will be applicable in the light of these findings. Hence this period of six days was choosen for collection of soil root cores in the subsequent field studies. 3.C Studies on root activity by 32P placement: One of the main difficulties in soil 32P injection technique for assessment of roo hige tth h activit s coefficieni fiele ) th (3 dn yi variatiof to n between the replicates (2). Subsequent developmen placinf to g tagged super phosphatn ei different soil zone alss overcomt sha o no e these difficulties.e Thuth n si present work an attempt has been made to bring about uniformity in application of activity in different soil locations by preparing a solid adsorbed phase of KpSO. (as per details given in materials and methods) at the time of application but carryintaggin e liquie th th t n dgi gou phase. Each capsule containeg m 2 1 d 2 of K2SO. carrying 50 uc of ^ P. Four capsules were placed around the plant at the lateral distance depthd san s mentioned above. Placemen sucf o t h capsulet sa each location will ensure uniform distribution of applied carrier free *2p without disturbin contenP zonee e th gth .f o t The specific activity data obtaine differenr dfo t depth d laterasan l

distances averaged for three replicates is given in table IV. These results show that for variety Taichung Native I the root activity at d,L, representing the ^P2 uptake from a depth of 4 cm and lateral distance of 2.5 cm as highest and forms more than one third of the total uptake. The total intensity of root activity

horizontae th P e l 5 icent th nal • n 7 O 5 l. s distancei ) cm 4 deptt ( sa , hd

r e othedepth_ d combinee , r sar d, han f firsr di laterao fo d ttw l distances i.e. up to 12.5 cm it is about 79$. Hence it can be said that the intensity of feeding is higher at a depth of 12 cm and up to lateral distance of 12.5 cm. 3 Varieta3. l difference roon si t distribution patterplanP ty nb injectio n 32 method: The percentage root distributio varietief no s TN-1, (1967-68 (196?)0 13 P )N , IR-8 (1967) (19686 (19685 C B give e C ,casn B ) d ar I tabln )f an ni eo . V e variety Taichung Native I the bulk of the root distribution is up to d2L, (i.e. up to a depth of 16 cm and lateral distance of 2.5 cm) and d-jLp (i.e. up to a depth of 8 cm and lateral distance of 2.5 cm). The same pattern is obtained in the second moryeaa lesr n o ero s similar soil. However, in case of variety NP 130, a local basmati tall variety, bulk of the root distribution is confined to d,Lp (i.e. up to a depth of 8 cm and lateral distanc 12.f eo 5 cro). Showin mora gt ethereby go shallo s ha t ,wi root systes ma compared to variety Taichung Native I. In case of variety IR-8 the pattern is somewhat similar to that of Taichung Native I. In case of BC5 and TJC6 which are basmati dwarfs, the root distribution pattern is confined to surface like NP130.

- 65 - 4 Compariso3. resultf no s obtaine capsuly db eplanP metho td injectioan d n 32 method: It will be of interest to compare the results obtained by 32P plant injection technique with thos capsulf eo e seto method tw resultf s o e Th . s gave mor lesr eo s similar pattern, except that from the point of view of root activity the d? showt deptno ns valuehha value e th higs s a s sha reveale date rooth f ao y tdb distribution pattern generan i t Bu l. significana ther s wa e t correlation (r=0.98) between these two sets of values, showing thereby that *2p plant injection ••» technique which gives root distribution pattern also correlated well wite hth uptak phosphorusf eo . 5 Effec3. differenf to t level: N f so As Nitrogen is one of the main yield increasing components, study was made to assess the effect of different levels of N (0,70,140)and 210 Kg. N/ha) on the rooting patter Taichunf no evidens i g s NativA t . froeI date th taftlmn ai I V e the effec increasinf to bees gbrino ha nt leve N gf lo abou greateta r feedinn gi d« zone at the expense of d, zone. This in this variety increased level of N fertilizatio resultes nha greaten i d r subsoil feeding which importan n wila e lb t factor in the areas where assured water supply does not exist.

4. DISCUSSION From the point of view of applicability of 32P plant injection technique for padd resulte yth s clearly indicate thaunifore th t m specific activit obtaines i y d afte dayx rinjectionsi f so particulaf o s i t I .r interes noto t e thate bulth f ko injected 32p still remained in the injected tiller. For increasing the accuracy of the technique it is desirable to bring about a greater transport of the injected P int2 rootse 3 th o . Earlier attempt usin) (4 s g indole acetic acin'os t ha dtme with any good' succ'ess in bringing about the greater proportion of the injected 32p in the root system.. In the present investigation, use of 0.1 M ducroso roote th s sa n i movemene effece solutioP th th -^ n e i tf s se mado t nka o et compared to one without sucrose. While more work is necessary to find out the other means of increasing this transport, at present sucrose appears to bo the most promising carrie bringinr rfo g about greater activity into roots, thus increasing the accuracy of the subsequent estimation of root distribution pattern under field conditions. While 32P plant injection technique appears to be most promising method for assessment of root distribution of cereals, the method at best gives the amount of roots presendifferene th n i t t rooe soith t l t activity.,_Izoneno d san s ti desirable, to assess how far the rpojb distribution data obtained by P plant injection technique give pictur sa nutriene th f eo t uptake from different soil ones n thiI . s respec comparative th t e dat amethodso obtainetw e th ,y dnamelb y placemen n capsules(i t differenn )i t soil zones agreed remarkablye ,th correlation coefficient being 0.98 whic highls hi y significant. Thus, similar information coul obtainee db methodse eithey db th f o r . The'only consideratior nfo the choice being ease ,techniquf th eo laboue th d r ean involved . From this point of vie planp w32 t injection technique offer uniqusa d eleganean t meanf so obtaining the rooting pattern in soils under natural field conditions for cereal crops. Using P plant injection technique the root distribution pattern of some of the high yielding varieties, currently being cultivate Indian i d bees ,ha n esti- mated. These results clearly show that although, padd generaln i y shalloa s ,i w - 6 6 - rooted crop, the dwarf varieties are comparatively more deep rooted as compared to local tall varieties. This character confer distincsa t advantage froe th m poin vief to droughf wo t resistanc d lodgingean . Althoug rootine hth g pattern of the new crosses "HC5 and BC6 is like that of NP130, but BC5 is comparatively deep rooted than the BC6 variety.

interesf o s Ii t note'tho t e effec highef o t r level nitrogef so n fertili- rootine zatioth n no g patterhige th h f yieldinno g dwarf variety, Taichung Native I. The increased fertilization gave deeper rooting pattern. This finding may be of significance during the seasons of uncertain water supply. r exampleFo , recently when ther droughs padde ewa th yn i tareas-Taichun g NativeI survived much better than local varieties.

5. SUMMARY

A knowledg rooting-pattere th f eo higf no h yielding paddy varietief o s si considerable importance in soil water and fertilizer management problems. Studies were carried out on the applicability of the "p.plant injection techni- que for paddy, comparison of the results of root activity obtained by the ,_ placemen i differen p *2 f o t t soil zone rood san t distribution patterP y nb

nplant'injection technique, the root distribution pattern of the some of the high yielding dwarf paddy varietie s comparesa locao t d l ones d effec,an f o t nitrogen fertilization on the rooting pattern of a dwarf variety. The results i nfollows:s briea e far - planP t) injectio(a n techniqu applicable founs b ewa o t d paddr efo r yfo evaluatio roof no t distributio d injectinnan p intplano g^2 th o t with sucrose was found to result in increased transport of the activity from the stem to the roots. (b) The root activity data by P placement (in capsules) gave statistically reproducible results whic highle har y correlated witrooe hth t distribution pattern obtained by ^2p plant injection technique. hige Th h ) yieldin(c g dwarf varieties (viz. IR- Taichund 8an g Nativ) el were foun havo t d e more intensit roof yo t distributio lowen i n r depths sa compared to local tall variety (viz NP 130). (d) The effect of increasing levels of nitrogen fertilization was found to resul greatea n ti r intensit roof o y t distributio lowen ni r depths.

ACKNOWLEDGMEN. 6 T

Gratefu Indiae th o nt l Councie thankdu e Agriculturaf o lsar l Researca r hfo grant of a Fellowship for one of the authors (j.C. Katyal) during the period of study. The authors also wish to thank Dr. N.P. Datta, Head of the Division of Soil Scienc Agriculturad ean l Chemistry, Indian Agricultural Research Institute, Delhi, for the facilities kindly made available. The authors also are deeply indebte . M.SDr .o t d Swaminathan , Director, Indian Agricultural Research Institute, keee Delhith n r interes,fo thin i t s work.

- 6? - REFERENCES

(1) BABTON, C.F., Ind.andlng.Chem.Anal. 20 (1948) 1068-73

(2) BURTON, G.W., Rol f tracero e n rooi s t development investigations. Atomic Energy and Agriculture Hi. Comer, C.L. Publi.49, Amer.Assoc. for Advance- ment of Sci. Washington B.C. (1957)

) (3 HALL, N.S., CHANDLT5R. W.F., VAN BAVEL, C.H.M., REID, P.H d ANDERSONan . , J.H., Tech.Bull., (1953) N. Carol.Agric. Sxp.Sta. 101

) (4 HALSTEAD, E.H d RSNNIE.an , D.A., Can^..J.Bot (1965_ 43 . ) 1359-67

) (5 MACKENZIE, A.J d D*1ANan . , L.A. 0 (1948,2 ) Anal.Chem. 559-60

(6) RACZ,'G.J., RWIE, D.A. and HUTCHEON, W.L., Cand.J.Soil 801.44 (1964) 100-8 32 (7) REHNIE, D.A. and HALSTTSD, E.H., "A P injection method for quantitative estimatio f the-no ! distributio d extennan cereaf o t l grain roots" Proc. Symp. IAEA/FAO Ankara (June/July 1965) IAEA Vienna (1965) 489-504

- 68 - Tabl* eI

£h«aioa1 sa

Soil Characteristics 15 No. 14

n •*2 3 4 1 ' 2 3 Siity Silty SUly Silty Silty Silty Silty Silty Textural Class ?1ay clay ct%;/ clay clay clay 61 ay loam }*>vn loan loam Bulk density 1.18 1.32 1.21 1.18 1.22 J.29 :.r. PK 8.00 . - o.Ot) 8.1 5.7 8.0 31*cttloal conductivity 4» 1 (» ohos/cm) •» «• ^. 2.05 1.12 i.87 $ 0.108 o.oo/r o.o?>? 0.0^5 0.03? 0.031 1 JTitrogon (<£) 0.089

AvaUahl* ?J)C 91A.0 O 7. 20.0 2.0 ?7.^ :3.4 *3.0

8 c nr..C- -1^ cw, d, « 17-24 25-32 cm Table To. Some of the characters of the varieties used for root distribution studies.

Pedigree Plant type Duration Yield Grain Character Disease r«»siatsr»3e 1 ——— TJT— *——— — ' 3 " 4 5 f> Ig-8 Introduction Semi-dwarf Photoinsensitive, averOn na - 3o2d, chalky, Susceptible to bias1 from IRHI, hybrid (80 cm) 130-135. days age yields tolerable and tungro moderate?? selection from« upright and about 6500 cocking susceptible to blight. cross between dark green kg/ha (with quali fcy. Pet Dee-geeax - leaves 100 kg/fr/ha) wu-gen Taichun* NativeI Introduction from Semi-dwarf Photoinsens itive, averOn na - K«?diura-, non- Highly sus^eptiol* T«iw»m, Cross pro- little reduced 120-125 yielde ag s chalky cooking to bacterial bligir duct using dwarf- height as aon- about 5000 quality better twufr d mod:>ratran y !l ing g«ne dcn.ir, par«» o T3-t d 8 kg (with 100 than IR-3 susceptible tc and lees .lark kg N/ha) -ohun X green foliage 3 t 130

selectio« s Ti t n 7«ry. t«'-ltmnr*» Photosensi n\ve, On an aver- frrra th«» local s?lender tc He n i m c tha 0 n14 120 d5;;s age yields non-chalky, three dise33»s. variety in T?rrth height, loss about 3000 translucent, India (selection kg/ha (with good cooking o at synchronized 60 kg/R/ha) quality. head ing, lodging, Tabl b continuedI e ,

Moderately Selection from Semi-dwarf Photoingensitive, n Oaveraga n e Medium selend»r, 120-125 days. yields 5500 kg/ non-chalky,having susceptible the selfed ^ 7ver5c y to blight. population from upright, dark ha (with 100 aroma, good five successful green N/hag k ) oooking quality back crosses of Taichung Native I X Basmati 370 where Basinati- 3?0 was uso'3 as a recurrent parent 3C 6 Same as BC 5 Same as BC 5 Same as 3C 5 5 C 3 Sam s a e Photoinsensitivfi, On averaga n e 0 day11 s yields about 5000 kg/ha (with 100 kg N/ha) Percent injecte differenn i P d t 3 plan2e day6 th -vrtinjectiof d so tf an o s afte injecteP 3 " , r1 ( n d witd an h 3? without sucrose)

Cays after Injected Dhxnject-nd Foots Injection tiller tillers Sucrose No sucrose o sucrosSucrosN ee sucroseo ?T Sucros- e

7 2. 1 89.9 2. 5 90, 2 7. 1 6 7.

3 89.3 88.8 8.8 10.0 1.9 3.2

4 1. 6 4 88.3. 0 9 9. 88.7 6 8. i —to4 1 Tnblc Til

Spf.-aifin n c fcivity (<™nts /:.-•* ?/••«' ".ut-. } of :iiff"r«nt r-H.-r. part P injec( s t '•<\ wir.ti and. witncul

Root length 1 doiy 3 days 6 days (with sucroao) rj D "D T5 TJ (in om) H R2 "3 Ri 32 R3 Bl

0-5 2396 1706 1363 972 "i6r>8 434 . 3267 748 2740 5-1 D 121.7 442 41 fi 50] 1489136 4498 767 2877 10-15 873 /387 296 22'i 452 67 3699 872 2912 >5 2.1 (without sucroso) 0-5 • 1530 18M' 8.508 60 . 5 41 1370 124'•15765 1938

5-10 278 604 282 189 370 893 11714864 1711 >10 106 285 187 223 2SO 832 12813882 1962

B s re ca e L = replicate 1, R- » replicate 2, : 3 Pl^ * 3. Table IV: Per cent root activity (by P uptake) of paddy variety Taichung Nativ different a eI t depth laterad san l distance flowerint sa g stage (by^2p placement in capsules) Dat transplantingf eo : July 31, 1968 placementP Dat f eo :32 Augus 196, t15 8 Leve activityf lo : 200 uc/plant (placed at four pointcircle th n seo aroune th d concernee planth n i t d zone). Location: 14, Main Block, Agronomy Farm, I.A.R.I. Delhi. A Specific activity data (^punts/rag P/Se eacr cfo h zone)

L1(2.5 cm) L2 (12.5 cmi ) L^(22.) 5cm Total d-j^ (4 cm) 125.3 52.8 14.0 192.1

d2 (12 cm) 30.4 29.7 13.7 73,8 d, (20 cm) 19.7 16.0 5.0 40.7 d (28 cm) 11.3 11.3 2.3 24.9 Total 186.7 109.8 35.0 331.5 L = Lateral distance from the plant where capsule was put. d = Depth, where the capsule was placed. io root activity

I\ (2.5 cm) 2 (12.L ) 5cm 3 (22.L ) 5cm Total ) cm 4 ( d-j^ 37.5 15.8 4.2 57.5

dg (12 cm) 9.1 8.9 4.1 22.1 ) cm 0 d(2 , 5.9 4.8 1.5 12.2

) cm 8 (C 4 d 3.4 3.4 0.7 8.0 Total 56.4 32.9 10.5 99.8 tesF t significan$ 1 t ta Lateral distance (L) Depths (d) Interaction

S.Bn 0.57 0.69 1.14 C,D. at 5$ 1.17 1.81 2.35

- 74 - Tabl : PercentageV e root distributio counts).oy (b n f some paddy varietie different sa t depth d laterasan l distances at flowering stage. (Using carrier-fre injectioP e n technique). Year 196? Year 1966 Date of transplanting: July 31, 1967 July 31, and August 1, 1968 injectionp Dat32 f eo : Octobe 196, r27 7 Octobe 196, r25 8 Leve uc/plan0 activitf 5° lo ty used uc/plan0 :5° t Location: 14 and 15 Main Block, Agronomy Division Farm, I.A.R.I., Delhi. Taichung Native I (196?) A. Percentage root distribution by counts. B. Net counts per 500 seconds. L,(2.) 5cm L?] (12. ) 5cm L, (22.) 5cm Total L.. (2.5 cm) L (12.5 cm) L, (22.5cm) Total dl [0-8 cm) 45.7 9.9 9 2.4 58.0 ^62.3 165.0 40.0 967.3 fj£(9-l6ctri) 20.4 3.3 1.1 24.8 340.5 55.0 18.5 414.0 (17-24 cm ) 6.3 1.7 1.1 9.1 105.0 28.5 18.5 152.0 "3 28.5 0 a4(25-32 cm ) 5.6 1.7 0.9 8.2 93.5 15. 137.0 Total 78.0 16.6 5.5 100.0 1301.3 277.0 92.0 1670.3 F test significant t I**a ? Lateral distances depths Interaction s.m 1.6 1.9 3.1 C.D at 5& 3.2 3.9 6.5 Taichung Native I (1968) A. Percentage root distribution by counts. B. Net 0 count50 r spe seconds. T., (2.5 cm) LJ12.5 cm) L^ (22.5cm) Tota~ ~ l L,(2.} 5cm 1 L?(12.5 cm) L,(22. 5) Totacm l d (0-m c 8 ) 1 41.8 2 16.6 " 3.0 61.4 1491.0 592.0 107.0 2190.0 d2(9-1) cm 6 14.7 5.9 1.6 22.2 524.5 210.0 57.1 792.1 d.(l7-24ci 3.5 4.4 2.3 10.2 125.0 15f.O 82.0 364.0 'V(25-32cim) 2.0 1.8 2.3 6.1 71.5 64.0 82.0 217.5 Total 62.0 28.7 9.2 99.9 2212.0 1023.0 328.1 3563.6 F test significant at 1% Lateral distances depths Interaction S.Sd 1.90 2.29 3.80 C.D at 5<£ 3.92 4.73 7.84 Table V. continued (19680 HP13 )

!• Percentage root distributio countsy (b n ) B* Net counts per 500 seconds. L, L^ Total Li Total (2.5cm) (I2?5cn) (22.5cm) (2.5cm) (I2.fcm) (22^) 5cm di 0-8cm) 61.9 4.9 3.1 69.9 d,(0-8cm) 1933.0 153.0 97.0 2183. 0 d9 9-l6cm) 10.7 4.6 1.6 16.9 d2(9-l6cm) 334.0 143.5 50.0 527.5 d* 17-24cm) 3.8 5 7. 2.1 6 1. d^(17-24cm) 118.5 65.5 50.0 234. 0 d4 25-32cm) 2.8 1.6 1.4 5.8 d^(25-32cm) 87.5 50.0 43.5 1.8 1.0 To1Sal 79.2 15.2 7.7 100.1 Total 2473.0 412.0 240.5 3125.5 'P* test significant at 1^ Lateral distances Depths Interaction S.Hi 1.03 1.24 2.06 C.D. at 556 2.13 2.57 4.26 IR 8 (1967) A« Percentage root distribution (by counts) 0 secondcountt B_50 Ne . r spe s L L.J Total L i L2 l L? Total (2.5cm) (1275cm) (2275cm) (2.5cm) (12.5cm) (22.5*em) d. (0-8cm) 44.6 11.2 5.3 61.1 d1(0-8cm) 266.5 67.0 31.5 365.0 d^(9-l6cm) 11.7 5-6 8 2. 20.1 d«(9-l6cm) 70.0 37.5 16.5 120.0 d*(!7-24cra) 4.3 3.8 3.3 11.4 df(\7-24cm) 25.5 22.5 19.5 67.5 d^(25-32cm) 3.8 1.54 7. 2.1 d^(25-32cm) 22.5 9.0 13.0 44.5 Total 64.4 22.1 13.5 100.0 Total 384.5 132.0 80.5 597.0 »P» test significant at V& Lateral distances Depths Interaction S.Ed 1.40 1.77 2.90 ^ 5 C.Dt a . 2.90 3.60 5.90 Tabl continue. eV d T"? 5 (1968) .A. Percentage root distribution by counts. 0 secondscountt B_50 .Ne r spe . L,(2.) 5cm 12(12. 5cm) L^(22«5cm) Total L,(2.5cm) L (l2.5cro) L (22.5cro) Total 0C, j> d.(0-8cm) 36.4 20.0 7.6 64.0 936.4 514.5 195.5 1646.0 6.2 6.2 3.6 16.0 159.5 159.5 92.5 411. C df(17-24cra) 5.8 4.1 2.9 12.8 149.2 105.5 74.5 329.2 d^( 25-3 2cm) 2.0 3.0 2.2 7.2 51.3 77.0 56.5 184.8 Total 50.4 33.3 16.3 100.0 1296.4 856..5 419.0 2571.9 •F* test significant at 1$ Lateral distances depths interactions S.Sd 1.50 1.81 2.99 at- *Wt \ C.D. Cl U V/v 3 •09 3.73 6.18 B(1968C6 ) A- Percentage root distribution by counts. B. Ne t 0 secondscount50 r spe . L (22.5cm) Total ~" L (2.5cm) L (l2.5cm) L.J'22.5cm) Total h(2.5cro) L2(l2.5on) 3 1 2 di(0-8cm) 45.5 14.99.0 69.4 1625.0 532.0 321.5 2478.5 (9-l6cm) 4.3 5.3 4.1 13.7 153.0 189.0 146.5 489.0 d*3 fl7-24cm3. ) 8 1. 2.0 7.1 64.0 118.0 71.5 253.5 6 3. 4 4. 1.8 9.8 157.0 128.5 64.5 350.0 Total 56.0 27.1 16.9 100.0 1999.5 987.5 604.0 3571.0 ' tes•P t significant ta 1* Lateral distances depths interactions S.Bd 1.72 2.07 3.43 C0£ C.D at• s 3.54 4.27 7.08 L » Lateral distance from the plant d « depth of sampling Table TI. Percentage r-'Ot attribution pattern (by counts) of ?:iichung Hative I variety of paddy affectes a differeny r, d t level Nitrogef so s trrt?'./(A n , (Using corrier-frer planp 32 > t injection technique). Dat transplantingf eo ! July 31, 1967 injectionP 2 Dat* f eo s Octobe 196, r27 7 Level of activity injected* 500 uc/plant 'Locations 15, Main Block, Agronomy Division Farm, IARI, New Delhi. CONTROL A.. Percentage root distribution by counts. sec-nds0 countt 50 Ne r . spe B .

L2 (2.5cm) L2(l2.5cni) Lj (22.5cm ) Total Lx(2.5cm) L2(l2.5om) L3 (22.5cro) Total

1Lj (2.5cm) L2(l2.5cn) L.(22.5om) Total L1(2.5cm) L2(!2.5cm) L3(22.5cm) Total d-. i 0-8om) 36.0 6.4 5-3 47.7 402.0 71.5 59.2 532.? dv 9-l6cm) 13.8 6.1 3.8 23.7 154.2 68.2 42.5 264.9 17-24cm) 5.8 4.6 4.7 15.1 64.8 51.3 52.5 168.6 d*(25-32cm) 4.5 4.1 4.9 13.5 50.2 45.8 54.7 150.7 Total 60.1 21.2 18.7 100.0 671.2 236.8 208.9 U16.9 •P' test significant at Lateral distances depths Interactions » - 1.57 1.89 * 5 C. t Da 3.24 3.91 d « depth t Latera- L l distance Table VI. continupd 140 Kg N/ha A* Percentage root distribution by counts. t count5 Ne r . p» B s iOO seconds •

1^(2.5cm) L?(12.5om) L-,(22.5om) Total L3 (2.5cm) L?(12.5cm) L,(22.5 Total 2.2 5 35.0 dl (0-8cm) 42.0 7.2 5^ .4 667.8 114. 817, d?(9-7 !1 6cm) .0 4.5 4.2 25.7 . 71 270.3 5 66.8 408. df (17-24CK;3 ) .4 .1.5 3.7 11.6 54.0 71. 5 56.8 184. (25-2 3 2cm) 3.4 31.3 . 82 42.8 7 54.0 179. d4 2 5. .7 Total 65.1 2? .4 13.5 100.0 103/1.9 3402 . 214.61589.7 »?• test signif ic.-int at 1< Later?.! distances Des pth Interactions S.W 0.89 1.07 1.78 C.P at 5"5 1.83 2.21 3.67 - ddept h = LLat < L-r«l dista.nces. 21.0 !fc IT/ha A- Percentage root distribution by counts. . Nt-B t0 second count50 r po s 5cn) L.j(22.5cTn) Total L (2.5cm) L (12. Total L'l^2*'5cm) L2(12.' 1 ? 5r:m) 1^(22. 5< d (0-8cm) 35.4 9.9 4.6 49.9 923.3 258.2 120.0 1301.5 'it>-(9-l6otn) 31.8 2.8 3.2 37.8 829.5 73.0 88.5 986.Q ri?(l7-24em? 2. ) 2.0 2.4 6.6 57.3 52.2 62.7 172.2 (25-32cm4 1. ) 2.2 2.0 5.6 52.2 146.? d4 36.5 57.5 Total 70.8 16.9 12.2 99.9 1846.6 440.9 318.4 2605.9 •F« ten* signif A cant at 1^ Lateral distances Depths Interactions S. Sri 0.86 1.04 1.72 C.D. ft 5^ 1.78 2.14 3.55 d = depth : L= Lateral distances. SCHEMATIC SKETCH SHOWING THE PERCENT ROOT DISTRIBUTION (BY COUNTS) IN DIFFERENT SOIL ZONES OF SOME OF THE PADDY VARIETIES AT FLOWERING STAGE. (CARRIER FREE P32 PLANT INJECTION TECHNIQUE)

I96T 1968 DAT F TRANSPLANTINO E G JULY 31 AU6D I .JUL AN 1 Y3 DATfci OF P32 INJECTION OCT.27 OCT. 25 LEVE ACTIVITF LO Y USED JJC/PLANO 50 T SOO .DC/PLANT LOCATION 10 MAIN BLOCK 14 MAIN BLOCK AGRONOMY DIVISION FAR . A.R.II M . DELHI

TNI1967 TNI1968 IR-8 1967

«•« aa-e •»•« 22 5 22-9 tt-9

su> a PERCENTAGE g TOTAL ACTIVITY 0-5% LATERAL DISTANCEStem) LATERAL DlSTANCESl cm.) LATERAL DlSTANCEStem.)

NPI30 1968 B C5 196 8 BC 6 1968

22-9 12-9 tt-9 aa-9 22-9 12-9

LATERAL DISTANCES! cm) LlfTERAL DISTANCES (em) LATERAL WSTANCESCcm.) t ROOT DENSITY SHOWN IS APPROXIMATELY PROPORTIONAL TO THE PERCENTAGE OF TOTAL ACTIVITY )

- 80 - SCHEMATIC SKETCH SHOWIN E PERCENGTH T ROOT DISTRIBUTION (BY COUNTS) IN DIFFERENT SOIL ZONES AS AFFECTED BY DIFFERENT LEVEL NITROGEF O S PADDF O N Y VARIETY TAICHUNG NATIVT A EI FLOWERING STAGE (BY CARRIER FREF P** PLANT INJECTION TECHNIQUE)

DATE OF TRANSPLATING—— JUL , 196Y31 8 DATE OF P32 INJECTION — OCT. 27, I960 LEVE ACTIVITF O L Y USED- 500 pC/ PL ANT

LOCATION 14MAIN BLOCK,AGRONOMY DIVISION FARM I. A. R. I. DELHI.

CONTROL K0 G7 N/ho PERCENTAGE TOTAL ACTIVITY 5 122 52

JO-5%

5-10%

10-15%

LATERAL OISTANCES(em.) LATERAL DISTANCES(cmJ 15-25%

25-35%

WO KG N/ho N/hG K o O at 95-45%

B-522-0

LATERAL DISTANCESfCm.) LATERAL DISTANCES (em.)

(ROOT DENSITY SHOWN IS APPROXIMATELY PROPORTIONAL TO THE PERCENTAGE OF TOTAL ACTIVITY)

- 81 - EFFECE TH OSMOTIF TO C PRESSUR N EO P-PHOSPHAT E ABSORPTION AND LEAKAG EXCISEY EB D RIC ADAPTATIOEE ROOTTH D SAN N OF RICE ROOTS TO VARYING OSMOTIC PRESSURES SMeh, Yuh-Jang, Institute of Botany, Academia Sinica, Nankang, Taipei, Taiwan, Rep. of China

ABSTRACT

The amount of 32P-phosphate absorbed by excised upland rice roots decreased with increasing osmotic pressure of the solutions. This trend was less marked for paddy rice roots. If active absorption was expressed by the amount of ions take intp ncelle u maintaineth od san d therein against loss abilite n ,th io f yo accumulation of both paddy and upland rice roots was greatly reduced by high osmotic pressur solutione th f eo . Rice roots adapte higo t d h external osmotic pressur increasiny eb g internal osmotic pressur mattey dr d rean content. This adaptation enabled rice rooto st accumulate phosphate from solutions of high osmotic pressure as well as from hypotonic solutions. Plasmolyzing rice roots absorbed phosphate activel wels ya turgis la d roots. absorptioe Th effectivele b n nca y suppressed with 2,4-dinitrophenol. Large amount of phosphate exosmosis was induced by immersing plasmolyzed rice roots into solution osmotiw lo f so c pressur waterr e o e amounth Th .d an t rate of phosphate leakage were proportionately related to the rate of water entry introoe oth t during deplasmolysis. This leakag consideres ewa essentialle b o dt y procesa temperature th diffusiof n so i 3 20-4f 1. eo nf . o 0C havin Q Q, ga roomattey e dr th t e f alwayro Losth f so s accompanied phosphate exosmosis. Afte perioe rth exosmosisf o d ,deplasmolyzea d rice root reabsorbe accumud an d - lated phosphat steada t ea lowet ybu r rate thanormae nth l root. A new method for determining the osmotic pressure of plant tissues by detecting solute leakag suggesteds ewa .

- 82 - THE EFFEC OSMOTIF TO C PRESSUH 3 P^PHOSPHATN EO E ABSORPTIOD NAN LEAKAGE BY EXCISED RICE ROOTS AND THE ADAPTATION OF RICE ROOTS TO VARYING OSMOTIC PRESSURES Yuh-Jang Shieh and Teh-Chien Shen Institute of Botany, Academia Sinica, Taipci, Rep. of China

1. INTRODUCTION

forcee Th s involve transfee th n i dwatef ro r from soi plano lt t rooty sma be attributed mainly to the hydrostatic pressure and the osmotic potential of soil water (Day, 1942). In general, plant growth is retarded by a high moisture potentia soile th .f lo Successful crop productio founs n wa soil n do s whicd hha the osmotic pressur lessr o m e. at (OP4 f )o The major factors whic planf o h P affectO tissuee th t s were soil moisture and humidity (Stoddard, 1953 and Herrick, 1933). Increased drought conditions resulted in an increasing osmotic value throughout the aerial parts of the plants. A measurement of the osmotic values was a reliable index of the relative potential ability of a plant to compete for water under conditions of stress and due to a deficiency of water. The requirement of metabolic energy for the accumulation of ions by plant roots is well documented in published literature. Anaerobiosis, uncorplers of energy transfer, and inhibitors of respiration have all been shown to inhibit ion uptake* It has generally bcf-n considered that metabolic energy is required transpore th r fo ionf to s across cell membranes. All plant parts and especially thin sections derived from them have been observed to leach solute upon immersion in water or rinse under water. In recent years evidence thapermeabilite tth f celyo l membrane modifiee b y sma d unfavourably b e condition bens sha n presented ,largA e amoun exosmosif o t f so cell constituents was found to be induced by inorganic salts and organic sub- stances. Helder (1956) mentioned that phosphate and other inorganic salts were usually present in the exduate of roots and other plant tissues along with easily diffusible parts of the cell constituents as the consequence of increased permeability of cell membranes induced by salts, toxic materials or metabolic inhibitors. This paper present datae sth , concernin absorptioe gth - P d los nan f so 32 phosphate of excised rice roots as affected by the tonicity of, the external solutions and the adaptability in nutrient absorption of rice roots to the osmotic pressure of external solutions.

MATERIAL. 2 METHODD SAN S 1 Preparatio2. roof no t materials. Seedpadda f so y rice variety, Taichun wer, 65 e . watep soakegNo ta t ra n i d dayso tw .28-3r fo Whe semina0e C nth l roots starte emergo t d e frohuske th m , the seeds were sprea layea n cheeseclotf o dro h whic supportes hwa n a y db aluminularga diametern n i o e m t petrc m se fram e 5 fram1 Th s i. ewa f dishe o . e corner cheeseclote Th th f so h were dipped dishe intwatee th A th o.n r i second cheeseclot s spreahwa d oveseedse rth roote Th . s wore grow 28-3t na 0C in the water underneath the cheesecloth. Roots were excised just below the cheesecloth when they attained the length of 2-3 cm. - 83 - 2.2. Absorption experiments. Two mM KHpPO. solution was prepared for the absorption experiments. The OP of solution s idjusteswa d with mannitol. Excised roots were rinsed with distilled water, and gently blotted on dry soft lintless paper. One gram samples were weighed out and transferred to a 250 ml Erlenmoyer flask. Ono hundred ml of the experimental solution was then poured in. Radioactive phosphate was added into the beginninflaske th absorptioe t sth a f go n f periodo H solutioe p Th a . d nha about 4.2-4.5- The solution was vigorously nerated and was kept at 30 C. After the absorption period, root samples were separated from solution with a copper screen, rinsed with 300 ml of water, spread evenly in planchets and dried at 40 C. 2.3. Exosmosis experiments. o gramTw f exciseso d rice roots wore allowe absoro t d b phosphat hour3 r sefo in 2 mM KH0PO. solution which was labelled with radioactive phosphate. The roots were then treated with solution differenf so t osmotic pressures. Pbcosmosif o s phosphate remaining in the root after the treatment or by the amount of radio- active phosphat rooe th et f leake o intexternae t th o ou d l solutions lattee th n rI . case, 0.1 ml aliquot of the external solution was drawn at different times dmring the treatmen radioactivitr tfo y counting. 2.4. Paper chromatography. Qualitative studie phosphate th n so e compound ricn i s e rood thosan t e leaked frorooe mth t were carrie witt ou dpapeha r chromatographic technique$ 80 e Th . ethanol extract ricf so e leakag s rootit spottes r so ewa Whatman o dfilte1 . nNo r paper. The chromatograms were developed one-dimensionally using butanol-propionic acid-water (10:5:7 v/v).

SHORT-TER. 3 M ACCUMULATIO 32F P-PHOSPHATNO EXCISEY EB D RICE ROOTS

Plant roots absorb ions in two phases: the initial rapid absorption and followe lineaa y db r stable uptake secone Th . d phas defines ei activs a d e uptake which is ai energy require process. Rice roots absorbed phosphate in the similar manner. Figure 1 shows that excised rice roots absorbed 32P-phosphate in a series of external osmotic solutions adjuste mannitoly db . Mannito e s choselth wa s na osmotic agent. Ferguso , (1958al t ne ) reported that mannitol coul classifiee db d as unabl functioo et carboa s na n sourc r tomatefo o root culture s founwa dt I . that little externally-applied mannitol .-;ntered into potato discus (Thimann et al., I960). Roots which only washti with 300-m second5 watef lo r fo r s after absorption absorbed phosphate as the same in all osmotic pressures while roots which soaked x changeisi n 200-mf so wat&f ono-houn lo a n ri r poriod cause groaa d t decreasn ei phosphate absorption at higher osmotic pressures. "Burg ct al. (1964) reported that a high concentration of glyccrcl or other osmotic agents prevented exosmosis from those tissues shows i t nI .tha t rice roots maintaine greaa d t portioe th f o n absorbed phosphate during plasmolysis. Dut when plasmolyzed rice roots were immerse watern i d ,greaa t portio f theno - absorbed phosphat e rootsth e f leakeo . t ou d e phosphatTh e uptak s decrease ewa externae th s a d l osmotic pressure increased- . Mere interest was in the uptake of phosphate- by both turgid and plasmolyzing rice roots (Fig. 2). During the first 30 minutes, rice root absorbed more phosphate in the solutions containing 0.4M cf mannitol regardless of the presence or absenc DNPf eo . This increased rat phosphatf eo e absorptio plasmoe th y nb - lyzed root:', may be attributed to the increased volume of free space. Plasmolyzing rice root accumulated phosphate ions metabolically, though at a lower rate than turgie th tha f do t root, Active accumulatio s effectivelnwa y inhibitee th y b d presenc absorptioe th lxlO~4}f eo n i P inDN solution.

- 84 - 4. LEAKAGE OP 32P-PHOSPHATE AS AFFECTED BY SALTS, OSMOTIC AGENT, AND METABOLIC INHIBITOR

When rice roots wore treated with consecutive soakings in water and 0.4 M mannitol solution ,greaa t portioabsorbee th f o n d phosphat s losewa t froe th m roots if the roots were plasmolyzed first in 0.4M mannitol solution and wore then transferre witco t d r (Tabl . Measurementel) radioactivite th f so e th n yi external solutions showed that a small amount of absorbed phosphate was present mannitoe th n i l solution whil greaa e t amoun phosphatf o t presens o ewa th n i t water whe plasmolyzee nth d ro--ts were transferre Furthe. it o t dr work showed that rice root plasmolyzed in the hypertonic solution of inorganic salts (NeCl+Na2SO.) resulted in a great loss of its phosphate when it was transferred to water. Polyethylene glyool (C20M) solutio concentratioe th f no 22.8f o n weighy $b t which would have an osmotic pressure of about 10 atm. as determined with thermocouple psychrometer method by Lagcrwerff et al. (1961) induced neither appreciable plasmolysi grear sno t phosphate leakag ricf ec e root. notices Itwa d thay matte dr lose t f so r frorooe th mt always accompanied the leakage of phosphate (Table II). .The data which did not list also showed that high concentratio P (5xlO~^MDN f no ) cause mattery losdr a d f so . The data presente Tabln i dI shoeII w that rice roots plasmolyze 0.5n i d M mannitol solution lost more phosphate when they were subsequently soake waten i d r (M5-0). Plasmolyzed rice roots lost more phosphate into the water (M5-0, M3-0) than into 0.2M mannitol solution (M5-2, M3-2). These data suggest that the leakag phosphatf eo s proportionalli e y relatedegreo th plasmolysif o eo t d f so the root and the rapidity of water entry during deplasmolysis. The experimental results summarize Tabln i d indicateV I e d that wheconcentratioe th n e th f no external solutio firss nwa t gradually diluted fro0.4e th mM solutio 0.2Mo nt e ,th plasmolyzed root lost less phosphates than when it was directly transferred from the 0.2M solutio watero nt . An exampltime th e f eo cours phosphatf eo e leakage from plasmolyzed root into water is shown in figure 3. In all of the cases studied, the initial rate of phosphate time leakagth e d needeean r reachinfo d g equilibrium were affectey b d the difference betwee osmotie nth c pressure solutione th f so consecutivf so e soakingamoune th f absorbed o t san d phosphat roote th .n ei The phenomenon of the leakage was furthor studied by measuring the rate of phosphate exosmosi different sa t temperature range th en si fro freezine th m g point tc 40 C and in the solution^of different non-radioactive phosphate concentrations (Fig. 4). In the temperature range of 20-40 C, the rate of phosphate leakage was a linear function of temperature with a temperature coefficient of about 1.3, typica diffusioa f lo n process. However rate ,th e curve flattened betweed an 0 n1 20.C, and rose when the temperature was approaching the freezing point. The rato phosphatf o e affectet leakag presence no same th s n specie th y ewa eio db f eo t sa low concentrations in the external solution. However,, it was somewhat increased when the concentration of phosphate in the external solution reached 2-20 mM. It speculates i d thaphosphate tth e leakag essentialls ei diffusioya n processs It . rat s enhanceewa d nea freezine rth g changee pointh y b tcertain si n physical propertie consistence th r scytoplaso o th f yo m (Seifriz, 1936) increasee Th . d rate of phosphate leakage observed in 2 and 20 mM KH^PO, solution may be due to the isotopic exchange facilitate hige th h y concentratiodb non-radioactivf no e phosphat oxtee th rn ei solution .

* -85- Paper chromatographs (Pig. 5) showed that after ther three hour period of absorption ,larga e portioabsorbee th f o n d phosphate remaine fore f th o m n i d inorganic phosphate. Six other labelled unknown compounds were found. Radio- isotope labelled phosphate compounds which leake frot ou ddeplasmolyzinma g rice root were mainly inorganic phosphate and four othor unknown It was evident that solute leakage.- induced by dcpiasmolysis was not n result of complete disorga- nization of the proplasm or the membranes.

5. ADAPTATION OF RICE ROOTS TO VARYING OSMOTIC PRESSURE

f The degree of the damage that a rico root was subjected to during deplasmo- lysi studies swa observiny db recovere phosphatgs th it f yo e absorption ability. One-gram samples of rice- root were plasmolyzod in 0.4M mannitol solution for 1 hour, rinsed to remove the mannitol adhering on the root surface, and then trans- KHpPOM m ferre 2 .o t dsolutio n containing radioactive phosphate. Different samples were taken f?oabsorptioe mth n solutio givet na n times, soaked with4 changes of 200 ml of water within one hour to remove the phosphate which was not actively absorbed by the roots. The results (Pig. 6) showed that after the first minute0 3 houn a immersiof ro o st absorptioe th n i n n solution, deplasmolyzing roots started to accumulate phosphate at a steady but lower rate than that of th<= normal rice root. This steady phase of absorption continued to the 12th hour at the end of the experiment while the absorption of a normal root was a linear function of time for about 7 hours and continued to absorb phosphate at a declinin 12te th gho t rathour h e7t . froe th m Further experiments wei^e conducted with roots grown in solutions of different OPs. Roots designated as RMO were gr»wn in water. R,^ roots were grown in water first, then transferred to-a mannito day1 r .4.9f fo o lm P 7 O solutioat e th f no root. RM s were further transferre mannitoo t d r 9.9f fo o l m P 4solutioO at e th f no another day. R..^ roots acted similarl roote th figurf so o t y . R.,1 e R.,d -an . roots absorbed considerable amoun ^'•P-phosphatf o t e froexternae th m l solutions of the OPs of 9*94 and 12.43 atm (Fig. 7). RMQ started to plasmolyze in the test solutions of the OP of 7«46 atm. P-.p roots plasmolyzod only slightly in the test solution . f 12.4sR.,o OP m .3 at roots kept turgi riln thesf i do l e test solutions. Roots grown in solutions of high OP had more dry matter in the one-gram fresh root

samples than those grow waten ni . Averagsolutionr OP ro w weighy lo e da f f so to

e Wer s roo the samples of RMQ >64.9 ^M2»^* '%I61.7an< 4 , and 93.7 rog respectively.

d R.. an .setR o Tw f rooso t samples wore prefed with P-phosphatn ei 32 Q

KHrtPOM m 2 .M solution samplee Th . s wei-fc washe watef o thed l dm ran n wit 0 h30 immerse raanniton i d l solution hourso tw differenrootf e so r Th . fo s s wertOP e again soaked in wat^r for^an hour before drying and counting. It was found that greaa t samplee amounth n prefef i to s P treated d with mannitol solutionf so high concentrations was lost from RMQ roots during the soaking period. The amount of 32p remained in these roots (Fig. 8) was closely similar to the accumulation curv othee f R...th eo rn -figurn O i hand . amoune e7 , th prefef ^ o t- ap 32 droot s

was not afrooten d by the immersion into mannitol solutions. It was evident that rice roots acquired the adaptability of growth and absorptio ison ni hypcrtonir -o c media adaptatioe Th . manifestes nwa e th y db increase in dry weight and 32p accumulation from solutions of high tonicity. In the intact rice roots, reserve materials from seods might serve as a source f osmotio c active materials i'n<•• additio o thost n e release e rooth t y db cells . The increased OP of protoplasm enabled the cells to keep turgid in solutions of high tonicity. Thi believes si essentiae b accumulation o io t d r lfo ricn i n e roots. - 86 - 6. A NEW METHOD FOR DETERMINING THE OSMOTIC PRESSURE OP PLANT TISSUES Experimental evidence showed that phosphate exosmosis accompanied the depla- smolysis of the cells. It offers a possibility of determining the osmotic pressur planf eo t tissue detectiny sb g solute leakage when incipient plasmolysis cannot be seen clearly in the plant tissues such as rice roots. Rice root samples prefed with radioactive phosphate were soaked in mannitol solutions of different concentration for one hour and then transferred to water. It was found that the roots which had been treated with mannitol solutions of the concentration higher than 0.22M lost appreci'.'ole amount of phosphate. The amount of phosphate loss increased sharplconcentratioe th s ya mannitof no l solution increased from rice th e f rooo 0.23s 0.40celo e p 0.2t twa th s sa 4l Ma M f o (Pig.9) P O e Th . determined" wit cryoscopiha c method value verTh s .e wa y mucsame thas hth a e t indicate transitioe th y db ncurve poin th figurn ei f o t » e9 REFERENCES

(1) BURG, S.P. et al., Relationship of solute leakage to solution tonioity in fruits and other plant tissues, Plant Physiol. 39 (1964) 185. BURG) (2 , S.P., THIMANN, K.V., Studieethylene th n so e productio applf no e tissue, Plant Physiol. 3_5_ (i960. )24 DAY) (3 , P.R. moisture ,Th e potentia soilf o l , Soil Sci 4 (1942.£ ) 391. (4) FERGUSON, J.D. et al., The carbohydrate nutrition of tomato roots. promotioe Th . V inhibitiod nan excisef no d root growt variouy hb s sugar and sugar alcohols, Ann. Bot. 22_ (1958) 513. HELDER) (5 , R.J. lose ,substancef Th so celly sb tissued san s (salt glands). In: Ruhland, W. (ed) Ency. Plant Physiol. 2_ (1956) 468. (6) HERRICK, E.M., Seasonal and diurnal variations in the osmotic values and suction tension values in the aerial portions of .Ambrosia trifida, Amer Bot. .J .(19330 2 . )18 ) LAGERWSEFF(? , J.V al.t .e , Contro osmotif lo c pressur culturf eo e solution with polyethylene glycol, Sci. 133 (l96l) I486. SEIPRIZ) (8 Protoplasm, ,W. . McGraw-Hill Yorw ,Ne k (1936). (9) STODDARD, L.A., Osmotic pressure and water content of prairie plants, Plant Physiol. 10 (1953) 661. (10) THIMANN, K.V. et al.. Penetration of mcinnitol into potato disks, Plant Physiol. 3£ (i960) 848. Table I. The /«.«.< of absorbed fhasphalc /»»»» rice n»'ts MX cauwl by n Hsrralirc suaAi'n#s I'M water an-l O.IM »;tinntl»l st

|»l;<>s)»hat* 1* r rein:;ii>>ni Tr«-atmci«* l «-<>ntr*rn i ri-«.t«> « ;• . l

* out roi t t«t.O

A

B i**nzifc"***T 97.5

C i_ _..)

D t- z/.r,

P L. ...rrrm:x:r_r..: t ato<>rptiu i I * n •••• m*nninti.

tnatttry dr absorbtdd / < an n /o phosphate« r* L I info wattr fiont ttct roots ptosmatyted previously in different hypertmic solutions

Dry wt. of rixit after >'" phosphate remaining in Treatment treat m«nl, •. at iiouirol controf rooto i f , l

control loao 100.0 •»lt» a4M 902 &4£ mannitot tt4M 8a9 33.4 C20M ZZ»% 102L7 87.1 ' ..fole ill. The lass t>f abstwhcil phosphate frf Jifi'frrnt hmtrilirs

Treatments* in r«v.t. ".,' of roritn.l

11)0.0

M5-0

34.3

M3-0 »—— — -! —— 1 ——- ^ —y ^ - ^ I^ S \ *.•. »- ! M3-2 <——— — •*— •

W t J- - ( | —— — .r: _~ ~~i 01 \

1 1 in:uinit» 1 I 1 i I —— 1 .ih:i>rj)li

Table IV. The loss of alwrbrd phosphate from >ifc tmt as aflecttd fatebythe of Di'iicaSe th 1 11 ' Perio r rlianRinfo d c Intfrva! between ioni'«'iitirt(ion of 1 down from C.-1 to O.^M successive additions mantiitiil solution P* - phosphate mannitol solution of water rnusc eaiy Ub h remainine th n Ri (hr.) (min.) additio f wateo n r root (';i f cuntrolo ) (M) " '" ' " 1st experiment 8 60 0.025 45.9 4 30 0.025 39.2 2 ir» 0.025 35.6 0*» — 23.9 2nd experiment " 4 15 0-0125 56.1 4 30 0.025 53.8 4 60 0.05 48.7 4 120 0.1 43.3 0" m~ 28.4 ~ * Kice roots were prefed with phosphate and then soakrd in 0.4M mannitol solution for 1 hour. Afterward, the concentration of (he niunnitnl solution was diluted at different rate from P.4 to 0.2M by ir.eans of adding water as indicated in the table. e rootTh s were transferred from 0.2M mannitol solutio o wate nt werd an re staked therei hour1 r nfa . *• Kcots directly transferred from 0.4M mannitol solution to water.

_ or, _ 3000

9 O t. 2000 JSm o> o»>.

1000

oft 01

8 10 Osmotic Pressure (atin) Fig . Absorptio1 . -phosphat^ P f no rooty eb solutionn si differenf so t OPs. x , roots washed with 300 ml of water for 5 seconds after absorptionr t rootwa , f ,c o s l soakem change6 0 n 20 di f so in one hour period.

- PI -

"3^, co tfO> (-4,> fc.Orx - or o ciL l^-ol Ju^> II iO 0

120 i8C Tim minn ei . Pig. 2» The absorption of phosphate by excised rice roots in 2 mM KHgPO/j solution wit withour ho d an presence F tth DW f eo jnannitol.* , without mannitol; x, with 0.4 M mannitol; -, without DNP; •••, with 10"^f DNP. Roots which were used for the DNP t.»atments were pretreated with lxlO"*M DNP for 30 minutes before the absorption period. 60 12U 100 Tine In min. leal-cage Th Fig f absorbe» o e3 . d phosphate into eacternal water from roots plasiaolyzed previousl n -lifferenyi t hypertonic solutions.

g 8C a*o 60 Si

20

o 0 3 0 2 0 1 0 2 40 £ 2 0. O.C2 TemperaturO C e KHjPO, concentrationM m .

Fig. /». The rate of leakage of absorbed phosphate from plaamolyzecL rice root as affected by temperature (left) and the concentration oi phosphat externae th n ei l solution (right) rate leakaf Th .ep g expresses wa amoune th phosphatf y to db e leaked froroote mth ; int externae oth l wate KHr ro 2 ^0^ solution durin firse gth 0 t1 minutes of soakjng. o o

0 0 0 o o Q

Origin Re R E 5» Autoradiograp papea f ho r chromatograp- K. e th f ho compound ricn si e roo leakaged -labelle" P tan R,;d , an K . d compound roon si t befor afted leakage en rth e inducey b d plasBolysis-deplasmolyais treatment. .The roots were ground extractod 4 ethanol " -labellean 80 i" h , dt B r. d corapounds leakagen i leakage ni ,evaporates ewa drynes- o dt re d sfn dissolved in BQi ethanol for paper chrooatographing. »0,COO

Is 8.00C 6,000 • Vi +» O

CM 2,000 XL--.- t _ - i— 2 1 0 .1 • « 4 2 Time in hour absorptioe Th . P Figphosphatf .no untreatey eb ^MM^rid dan M ric. roots were plasnolyzed In 0.4 M mannitol solution and th n transferred to 2 mH KHoPO^ solution for absorption. Samples were rinsed in water for 1 hour after they were taken from the absorption solution to remove the diffusible phospnaj in the outer space. Untreated rice roots were used as th control. • , control; O , plasmolywd roots.

4000 ^

t 3000

2000 Is. ?Sa& 1000; I

02466 10 12 Osmotic Pressure (ata)

7. Absorption of P3 -phosphate by R«Q (•)» *nd roots in solutions of different DPs. Roof were soak 'with houi r r wafo afte tr r absorption period. 4000

3000 -

2000 -

100- 0

0 1 8 6 4 12 Osmotic Pressure (atm)

Pig. 8. The loss of prefed P* -phosphate from H..Q (•) and 1L., (*) roots caused by 2-hour immersion in mannitol solutions of different OPs. The samples were soaked in 6 changes of «<• ml of water for one hour before drying.

M.OOO

30.000

»,coo

ao»ooo

r& M 0 k OJ 0 0 2 0. ! «• Concentratio mannitof no l solution,M Pig. 9. The loss of absorbed phosphate from rice roots which had U immersed in mannitol solution of different concentrations •: on hour before being transferr d to water.

- 6 9 - EFFEC SILICO P TABSORPTIOO E TH N NO N MANGANESP O PHOSPHORUD EAN RICN SI E SEEDLINGS

Shim, Sang Chilj IT., Jang-Kirl} Lee, Hyong-Koo Radiation Research "Institute in Agriculture Offic Atomif eo c Energy Seoul, Korea 1968

INTRODUCTIO. I N

Recent studies on silicon fertilizer have shown that application of silicates under certain conditions, have resulte increasen di d yiel ricf o d e crops (12, 13, 19)« On the other hand, the close relationship of silicate application with increasing resistanc inseco et t pests, pathogenic fung lodgingd ian s ,ha long been recognized* Although a considerable attention has been -paid to an increased yield, comparatively little is understood about its unique nutritional aspect. previoue Inth s paper (20)shows wa nt ,i tha t silicon affect absorptioe sth n of both manganese and phosphorus by rice plants. At the low concentrations of sodium silicate sourca s ,a siliconf eo absorptioe ,th nmanganese peakth f so e and phosphorus were found at the silicon concentration of 50 ppm. In the present paper, effects of silicon, at low concentrations, on the elementabsorptioo tw e th s f havno e been re-examined r thiFo .s .study, .sodium silicat m-silicid ean c acid have been utilize source th siliconf s eo a d .

EXPERIMEN. II T

A) Material Ric) 1 e varieties rico :Tw e varieties were chosenKwanos a wa s e ka ; on lodging othee varietth rd Jinhunyan lodging-tolerabla s ga e one. 2) Seedlings: Test plants were obtained as follows: a) Rice was germinated and grown in distilled water for 20 days in a growth-cabinet, mod. YGC-125, controlled at 20°C, at the relative humidity of 65-80$ and illuminance of 4,500 Lx. Ric) b e plants wer) growa es na transplante 5 litr2. o et d plasti t cpo filled wit completha e culture solution* growd )an n abou monta ta n hi green house until just before tillering. Treatmen) B Mn-5, P-3d Si 4an f 2to Silicon) a : Water glass NapSiO m-silicid ,an c acid**) were used. Solution e th f weri o S l ef m o prepare0 m 50 pp d 0 an d20 d an 0 10 0 5 o f, 0,525 , ,10 solutio uses treatmenr nwa dfo t Mn-5) b P-32d 4an : Mn-5 micro-curie2 MnCls 4 a P-33. , ; gml s 2 a 0 50 s/ EjPO. j 7.4 micro -curies / 500 ml. c) Culture solution: 9 test plants, either 20 days or 50 days old, were beakerl m hoursimplante3 0 lefd r 50 , an fo t a . o t dEac h treatmens twa made 3 replications.

- 97 - C) Measurement of radioactivities hour3 f o s d incubatioen e Ath t n period, tissues were burne ashed dan s were uniformly sprea countinn o d g planchet. Activitie Mn-5e th 4f so wer e measured with scintillation detector, type P-20P and P-32 with end-window (1.8 rag/cm^) Geiger tube.

*; The chemical constituents of the complete culture solution (the amounts of nutrient" litre5 n si fuls sa l strength) Major elements Minor elements in Z-solution (pelitr1 r e solution)

Ca(N03)2 mol l m 12.55 ZnSO. 0.2 gm it 25 » 0.18 » tt 10 " 01130475^0 0.1 » (i 8 " H^BO, 0.5 ft ft 0.05 " KI J 0.03 tt ti n. 5 Co(N03) o.i Pe-EDTA mol 0.5 " **) m-silicic acid, H«SiO, could be obtained from water glass, NapSiO,, which was decationized with Amberlite LH-120 cation exchange resin.

-98- III. RESULTS AND DISCUSSION

Figure 1,2,3 and 4 show the effects of silicates with sodium silicate and m-silicic acid on the absorption and translocation of manganese and phosphorus. In Pig. 1 and 4, it can be readily seen that those effects differ according to the component culturf so e solution resultse Th . , however shot y no wan d ,di remarkable difference between varieties, Kwanok and Jinhung, or ages of test day0 5 plants sd oldan 0 ,2 . There exist sconsiderabla e degre correspondencf eo e between present results and other investigations (12, 13, 19, 20) on that the absorption of manganese and phosphorus decreased with increasing silicon concentration. However, one has to draw attention to tho following facts: Physico-chemical differences between NapSiO, and HpSiO, solution 1} Chemical interactio silicatf no . P e r wito n hM f therI e wer appareno en t difference experimentae th n so l conditions except chemical forms, the properties of silicate media could be only influenced concentratio. pH s bit y silicatef no d othesan r mineral constituents. Earlier, Rolle ; reporte(2 r d that m-silicic aci hydrolyzes i d foro t d m o-silicio acid. quits Ii t e probable that such o-silicic acid availablmighn a e tb e forf o m silicon subsequently propose Yoshidy b d a (13 Whittenberged )an r (?). Chemical properties of Na-SiO-j and H^SiO, have been believed extremely critical: colloidal behaviou d coagulo.tioran etc.g M d , an alway ne F wit , shMn anionic reaction d commonl,an y inorganic existence. Although bearin minn gi d the behaviour silicatf so culturn ei e solution, these important properties would seem to have littls ecological value here, because, in this experiment, low • concentration and controlled pH were carried out before absorption. Eaton et al (10) have recently reported that the reaction of maaganese with silicate is dependent upon tho degree of alkalinity and that a representative valu irrigatior efo n wate soid ran l solutio SiOf o m arouns ,ni pp (imeq0 d3 r .pe 1 litre). In addition, the solubilities of several metals in the presence of Na-SiC-j at high pH condition were shown: Cu-^Zn vMn • -"JCd-c'-'Pt--Mo

- 99 - a) sodium as a main component of the osmotic pressure and tra-nslocation with transpiration flow through vascular system in plant, b) increase in the ratio of alkalinity to silicate, c) interaction of sodium cations with manganese or phosphoru solutionn si . Absorptio) A n from nutrient solution Hunter (8) and others (5,6) thought that silicates applied to soils promote, either directl indirectlyr yo , availabilit phosphoruf yo prevenr so s tit

fixation, simila anion a o nrt exchange mechanism same th e t timeA . , Okud) 7 (1 a and Yoshida (13) convinced thg--1 solubl^ r.ilicatessBelectively absorbed by roots prior to phosphorus absorption, is likely to convert into insoluble form, which in turn. obstruct simultaneous absorption of phosphorus. But this conception has t alwayno s been cleapostulatioe th wels ra s a l n that plann ,i t nutrition, silicon can perfor functionme th som f eo phosphoruf so partialld san y substitutr efo phosphoru 14), (6 s . s evideni t i Pign I t» 4 . tha absorptioe th t manganesf no phosphorur o e s si dependent upon the sources of silicon in the nutrient solutions. Halstead 2nd Barber (9) reported that availably manganese was supplied into seedling f croso p plants mainl diffusioy yb n mechanis solutione th e n th i m n O . manganese absorptio soil-roon ni t phase, Mulder (22), Piper (23)Waid an ,n (24) demonstrated .that change valencn si manganesf o e ironr eo e relate,ar 'tho t d e availabilitia elemente th f planr ?o sfo t growth. Subsequently, Brow Joned nan s (25)* assuming these results, e.g. ion conversion of available Mn to insoluble neutran i d alkalin . lan n M r eo solution n M , possibilitiee pointeth t ou d s of reductio manganif no c oxides into manganou rooe th t t surfacsa e before eth manganes absorbede b n eca . Her (18) once wrote about colloidal silicates like this: 11 Colloidal silicates may vary from rather homogeneous colloidal aggregates to extremely small ultimate unit polysilicif so c acid metad san l hydroxideo st heterogeneous masse whicn si h eithe motne silice th rth lr ao hydroxide e sar present as discrete colioid.il units held together by the other component-s." Referring to the previous study (20 ), the amount of absorbed manganese in sodium silicates and phosphorus in m-silicic. acid increa-sod with the concentration

of silico thereafted nan untiPP 0 l5 r decreased. m To speak briefly, effec sodiuf o t m silicate, relativ m-silicio et c acidn ,o

the absorption of the two nutrients is more pronounced. Now, it seems quite probable that at the high concentrations of sodium silicates, the mobility of: manganese in the solution would be significantly influenced by the discrete colloidal units presen oxidizee th alsd y tan ob d manganic strona for n i m g alkaline medium. On- the other hand, Jinhung has absorbed manganese and phosphorus much more tha ntranslocatioe Kwanoth d kan elemento tw day0 n2 o d sth ol ratn s i f eo seedling greates swa r tha nday ° seedlings5 d tha sol f o t , thougn M h d amountan P f so absorbed by root .-. were greater in the latter.

- 100 - B) Translocation from root to shoot Translccation of nutrients in biological system would depend upon the physiological functions. Effect silico f scroo e th p n yieldno d resistancsan e to diseases are well known. However, the physiological role of silicon has clearede b yeo t naturee .Th f silicoo - plann i n t tissue, existin aiinsolubls ga e cellulose-silica membran silicifion i e d cel cuticle-silicr o l ae layeth n ro surface of leaves, makes it difficult to reveal its organic function. Added to the problem are 1) partial substitution of silicon for phosphorus, and 2) organic rol siliconf eo , e.g. cationic reaction with certain organic compound organd san o silicon properties. On the contrary, Kosower (26), Kessler (3), and others have proved that manganese and phosphorus indispensiv&ly take pnrt in the activation of various essential enzymes. Disregardin chemicae gth l form silicof so n source, phosphoru Kwanon si k which absorbs much less phosphorus than Jinhung, was readily translocated in Jinhung. contene th f phosphoruf I o t Kwanon si less kwa s than tha Jinhungf o t , Kwanok appears less influenced than Jinhung by silicon concentration and absorbs much more phosphorus than Jinhung. Thi contrars si r expectationou o t y thio S .s result apparently indicates tharelatioe th t phosphoruf no d silicosan n appears specifia s a c propert croa f pyo plant. The curves in Fig. 3 and 4 show that there is a similar tendency on trans- location of manganese and phosphorus between sampling stages, 20 days old and day 0 seedlings5 d sol , unde same rth e conditions. To conclude, present results have an interesting bearing on 'the characteristic effects of the different chemical forms of silicon sources, viz. alkaline compo- nent silicon si n fertilizers absorptioe th n ,o d translocatioan n manganesf no e and phosphorus.

SUMMARY

Effect silicatef so absorptioe th n so d translocationan manganesf no d ean phosphoru ricy sb eday 0 seedlings5 d plants sol d an 0 ,2 , have boen investigated. resulte Th s obtaine summarizee ai d followss a d : 1) The absorption and translocation of Mn and P dependent upon the chemical form silicatf so e sources e effec;Th Nfi^SiOf o t , being more pronounced than HpSiO^. 2) Absorption of Mn reached maximum at the Na-SiO-j concentration of 50ppm Si while that of P decreased considerably at the same concentration. 3) The effect of sodium silicates on the absorption of nutrients is difficult to evaluate due to the presence of alkaline sodium. One has to take into account the colloidal behaviour, salt concentratio transpiration ni n flow distributiod ,an n of sodium and silicate in plant tissues.

- 101 - R13FEREHCES

(1) WILLIAMS, D.F. and VLAMIS, J. 1962. The effects of silicon on yield .-.nd manganese-54 uptake and distribution in the leaves of barley plants grown, Plant Physio 404: .32 . (2) ROLLER, P.S. and ERVIN, G. Jr. 1940, J.A.C.S. 62:468. KE3SLER) (3 195. ,E 7 "Researc Photosynthesisn hi Interscicnc. ed t "1s e Publ.Inc., N.Y.: 243:249. (4) JACOBY, B. 1963. Function of bean roots and stem in sodium retention, Plant Physiol. 38:445-449. LETTERMAN) (5 , WEISSMAN ,0. SAMMETd an , 1925. ,H. K . Actio silicf no n ai increasing the yield of plants. Z. Pflanzonernahr., Dung 4A; 265-315. (6) BRENCHLEY, W.E., MASKELL, E.J. and WARINGTON, K. 1927. The interrelation between silico d othenan r element plann si t nutrition. Ann. Appl. Biol. 14,: 45-82.

(7) WHITT3J3ERGER, R.T. 1945. Am. J. Bot., 3_2:539. (8) HUNTER, A.S. 1965. Effects of silicate on uptake of phosphorus from soil by four crops. Soi100(6);391-396. lSc . (9) HALSTEAD, E.H. and BARBT2R, S.A. 1968. Manganese, uptake attributed to diffusion from soil. SoiSoc . Proc. lSc . Am . 32:540-542.

(10) EATON, F.A., McLEAN, G.W., BREDALL, G.S., and DONNER, H.E. 1968. Significance o ffro g losM silice mf th so irrigatio n ai n waters. Soil Sci. 165:260-280. (11) ALEXANDER, G.B., HESTON, ¥.M. and ILER, R.K. 1954. The solubility of amorphous silic watern ai Phys. .J . Chem. 58:453-455. (12) OKUDA, A. and TAKAHASHI, E. 1964. The mineral nutrition of the rice plant. (iRRl) John Hopkins Press:123. (13) YOSHTDA 1965. ,S . Chemical aspectrole silicof th eo f so physiologn ni e th f yo rice plant. Nationa e Bullth f ,o l Institut Agriculturaf eo l Sciences series: B. No. 15_:l-58. (14) OOKAWA 1936. ,K . Physiological functio silicof no plantn ni . e Jourth f ,o Scienc Soif eManureo d lan . 10;445«' (15) KAWANQ, Z. 1961. "A study on resistance for breakage of rice culm". (16) SAMOTO, K. I960. "Rice crops and protection of lodging". (17) OKUDA, A. 1958. Bull, of the National Institute of Agricultural Sciences, 48:194. (18) ILER, R.K. 1955. "The colloid chemistry of silica and silicates". Cornell Univ. Press, N.Y., 324. (19) PARK, Y.D. 1967 effecte .Th silicof so ricn no e growing, Annual Reporf o t O.R.D. 10:55-61. Nutrition uptake of rice in Akiochi. Ibid:23-35.

- 2 10 - (20) SHIM, S.C. and U, J.K. 196?. The effects of silica on the absorption of Mn-5 P-32d 4an . Bull Atomif o , c Energy Research J_:45-49. (21) SHIM, S.C. 1968. Physical properties and chemical constituents of rice culm. Bull, of Atomic Energy Research 8/1-2):55-62. (22) MUL2ER, E.G. and GERRSTEEN, F.C. 1952. Soil manganese in relation to pl

(25) BROWN, J.C JONESd .d an an ,. W.ERb . Ca 1962 . .Zn Absorptio. Mn . Pe f no Phosphate ion y soybeasb n roots that diffe thein ri r reductive capacity. Soi24:173-180. lSo .

(26) KOSOWER. 1962. "Molecular Biochemistry". McGraw Hill Book Comp.Inc. N.Y.: 198.

- 103 - EVALUATION OP PYRO AND METAPHOSPHATSS AS SOURCES OP PHOSPHORUS FOR PLANTS I. UPTAKE STUDIES IN WATT3R CULTURE

A.K. Sinh K.Bd aan . Mistry Biology Division Bhabha Atomic Research Centre Trombay, Bombay, India

ABSTRACT

Pyro and metaphosphatcs are the chief non-orthophcsphate constituents of the condensed or polyphosphate fertilizers which are -being developed -over recent yea'rs. While numerous tests have bee utilizatioe nth carrien o t thesf ou dno e phosphates added to soil, little quantitative data are available .on the question absorptiof o pyrf nmetaphosphatd o oan o th specien d io c an planty e sb s r spe extent to which utilization of these phosphates is influenced by their hydrolysis to orthophosphate forms*

The present paper reports the results of short-term water culture studies on uptak phosphoruf eo maizy sb bead ean n plants from ^P-labelled pyrd an o metaphosphate relation si thao nt t from orthophosphate norma e whicth s lhi sourc phosphoruf eo plann si t nutrition. Concurrent measurement hydrolysif so s pyrf metaphosphated o oan s have been made. Over uptake periods ranging from 1 to 6 days pyro and metaphosphates are slightly less efficiently utilized thaorthophosphatee nth differencee th t sbu s are not significant. Similar results are obtained from yield data. In the very short treatment periods of 1 to 12 hours, however, the uptake of phosphorus from the pyro and metaphosphates is significantly lower than from orthophosphate. At each uptake period, fro dayshou6 1 m quantito e rt , th orthophosphatf yo e formed in solution, as a result of hydrolysis of pyrophosphate, is higher than the total quantity of fertilizer phosphorus absorbed by plant. This is also true for metaphosphate over periods of .1 day or more. The extent of hydrolysis increases with time and is significantly enhanced in the presence of roots of intact plants. markedle Th y lower uptak phosphoruf eo s from pyrmetaphosphated oan s over correlatee hour2 b period 1 n relativelo o st ca th p o su t d orthophosphatw lo y e concentrations present in solution. The present results suggest that phosphorus is absorbed by plants chiefly as the orthophosphate ion and the efficiency of non-orthophosphate compounds as sources of phosphorus for plants growing in solution cultures is largely dependent on their conversion to orthophosphate*

- 104 - EVALUATION OF PYRO AND METAPHOSPHATES AS SOURCES OF PHOSPHORUS FOR PLANTS, UPTAK. I E STUDIE WATEN SI R CULTURE. A.K. Sinh K.Bd aan . Mistry Biology Division Bhabha Atomic Research Centre Trombay, Bombay, India

INTRODUCTION

Pyro and metaphosphatos are the chief non-orthophosphate constituents of the condensed or polyphosphate fertilizers which are being developed over the recent years. A numbe greenhousf ro d fielean d efficience testth f so pyrophosphatef yo s (1,2,3,4) and metaphosphates (5,6,7,8,9,10) added to the soil have been carried out. Recently attempts have been mad elucidato et factore eth s affectine gth conversion of pyrophosphate to orthophosphate in soil (l,2,ll) and studies made at the Tennessee Valley Authority (TVA) have examined the chemistry of reaction condensee ofth d phosphate aqueoun si soie sth l system n i (12,13,14) d san . However, very little quantitative informatio availabls ni questioe th n eo n whether pyrophosphat metaphosphatd ean e ion e absorbesar o t planty e db s r spe y significanan extene tth whico n extent o utilizatio e d hth tan f thesno e phosphate influences si y theidb r hydrolysi orthophosphate th o st e forms (l?). consideres Itwa d worthwhile, therefore examino ,t plane th e t uptakf eo phosphorus added as pyro and metaphosphates under the controlled conditions of water culture. Only water-soluble compounds were selected for this study and since orthophosphat normae th s lei sourc phosphoruf eo plann si t nutritiot ni was decided to evaluate the efficiency of the condensed phosphates in relation tcorrespondine o th tha f o t g orthophosphates hydrolysie Th . pyrf metasd o oan - phosphates under conditions of the water culture experiments was concurrently examined. This paper reports the results of relatively short-term studies on these aspects.

EXPERIMENTAL METHODS

For the present study a number of pyro, meta and orthophosphates were prepared in the laboratory and labelled with '^P at specific activity levels ranging from 0.3-0.5 mC./g.P. The compounds were: Potassium pyrophosphate K.PgO-, sodium pyrophosphate Na.ppO-, ammonium tetrametaphosphate NH.H^PO., pdtassium orthophosphate KHpPO. and sodium orthophosphate NaHoPO.. Sodium and potassium pyrophosphates and sodium and potassium metaphosphates were prepared accordin methode th o gt s describe l (15)Leha y db t re . Ammonium metaphosphate was prepared by the method supplied by TVA 1[l6T~which is essentially that of Thilo and Ratz (17). The orthophosphates were prepared by dissolving the saltminimua n si m quantit waterf yo , adding carrier-fred an P e recrystallizing unde heara t lamp. Total phosphorus contencompounde th n ti s estimate swa methoe th f y o ddb Barton (18). The pyro and metaphosphates were hydrolyzed to orthophosphate by

- 105 « boiling with mineral acid before assay. Chemical labellepurite th f yo d compounds, especiall condensee yth d phosphates checkes papee ,wa th ry db ohromatographi c procedur Karl-Kroupf eo a (19)resultine Th . g radiochromatograms were scannen i d a Nuclear Chicago Actigraph Scanner. The chemical species for each compound was assigne basie th thei f so n d o r total P.conten chromatographid tan c data. For water culture experiments maize (Zekidned re a d maysyan K ) 5 var6 P .N beans (Phaseolus vulgaris) var. Local were used as experimental plants. The seeds were germinate purifien di d quart whed plante zan nth s wer daye8 thed sol y were transferred to polythene culture jars containing deionised water for a 48 hour period. Subsequently plante ,th s were treated witlabellee hth d phosphate sources dissolve deionisen di d wate culturn ri e jar solutione sth containinf o l .m 0 g90 Normally two plants were grown in ..each jar and five replications were maintained r eacfo h treatment quantite Th . phosphatef yo periodo s th adde d f treatmenso an d t which varied in different experiments are indicated under TSxrperimental Results. The experiments were carried out in a growth room which permitted reproducible en- vironmental conditions. The temperature was maintained at 23 +_ 2 C, relative plante th cenr d s pe an twer 5 humidite^ illuminate5 6 t ya hou 2 1 rn i dperiod s at 600 footcandTes. Since preliminary experiment nutrienn si t solutions indicated marked an d variable effectdifferene th f so t nutrien hydrolysite th ion n so condensef so d phosphate decides wa experimente t th carrso i t dt ou y deionisen si d water systems. plante Th s day6 wer f longese so e th whicd observe s en thealthe hwa e b th o t dt a y treatment period employed. After treatment the plants were sacrificed and separated into shoots and roots. Roots were given a 10 second rinse in distilled water to remove superficially retained solution tissuee Th . s were oven drie a 105°Ct na n di , weighe wetd dan - ashed with concentrated nitric acid till clear extracts were obtained. TotalP in the extracts was estimated by the method of Barton (18) and 32p assayed by countintubaliquotM . G- ml e a 0 afte n g1. si r drying unde heara t lamp. Radio- chemical data were processed to compute- the plant uptake of phosphorus and percent utilization of the added phosphates. r measurementFo hydrolysie th f so pyrf sd o metaphosphate oan intervalt sa v - s corresponding to those of plant uptake identical jars containing the labelled phosphate solutions but without plants were set up. At different periods suitable aliquots were withdrawn from thes quantite e th jar d orthophosphatsf an yo e formed was estimated by the method of Dickman and Bray (20), which is highly specific for orthophosphate. Parallel estimations on solutions in which plants were grown were made to study the influence of root activity on the hydrolytic process.

EXPSRIMSNTAL RESULTS

a. Studies on pyrophosphate Dat utilization ao potassiuf no m pyrophosphat potassiud ean m orthophosphaty eb intact maize plants over uptake periods ranging from 1 to 6 days are presented in table I. evidens Ii t t that whil orthophosphate eth marginalls ei y more efficiently utilized than pyrophosphato over-all treatment period differenceo sth s betweee nth two sources are not significant except for the shoot values after 1 day. Data on - 106 - mattey yieldr f do r (tabl ) alseII o show generaln ,i significano ,n t difference betwee growte nth plantf ho s under pyrorthophosphatd oan e treatments ovee rth short uptake periods employed. hydrolysie Datth n ao potassiuf so m pyrophosphat solution ei reportee nar d in table IIIapparens i .t I t that potassium pyrophosphate undergoes hydrolysis and measurable quantities of orthophosphate were present after 1 day; the extent of hydrolysis increased with time and was enhanced in solutions in which plants were grown. It is of interest to note that the amount of orthophosphate P present in solution resula s ,a hydrolysif to pyrophosphatee th f so mors ,wa e thaamoune nth t of fertilizer P absorbed by plants over each treatment period. influence Datth n ao planf eo t specieuptak& froP th f n meo so pyrorthod oan - phosphates are reported in table IV. It is seen that for both phosphate sources the fertilizer phosphorus uptak eweighty (computedr . g beany )b r s dpe si markedly higher than tha maizey tb . However, relatively greater fractioe th f no absorbed P is translocated to tho shoots in maize resulting in significantly higher value transporf so t indexj thi trus si botf eo h pyrophosphat orthod ean - phosphate treatments. Studio. b metaphosphatn so e Data on the,.comparative utilization of ammonium meta and orthophosphates by maize are presented in table V. Data show increased utilization of metaphosphate with time and over tho relatively short uptake periods employed accumulation of rootn i considerablo sees b P si o nt y more thatranspors nit aeriae th o lt tissues. Comparison with the data on uptake of ammonium orthophosphate reveals relatively greater utilization of the orthophosphate over each treatment period. However differencee ,th s betweesourcestatisticallt o no tw e e snth ar y significant. Similar effect y matte yiele dr e evidendatth e f sar o rdn th ao (tabl n i t ) eVl which indicate marginally higher yields with orthophosphate. Data on the hydrolysis of ammonium metaphosphate at concentrations identical to those in the uptake experiments are reported in table VII. It is seen that significant quantities of orthophosphate were formed in 1 day and the extent of hydrolysis increased with time. As in the case of pyrophosphate (Sec. a) the hydrolysis is markedly influenced by roots of intact plants and the amount of orthophosphat eformeP solution i d n over successive treatment periods si significantly greater than the quantity of fertilizer P absorbed by plints under condition r experimentsou f so . Comparative uptake of P from ammonium meta and orthophosphates by maize and beans is reported in table VIII. Over identical duration of growth the accumu- lation of fertilizer P by roots is greater in bean plants while its upward trans- location is higher in maize. Similar interspecific differences are observed with both phosphate sources.

c« Very short-term studie plann so t uptak hydrolysid ean pyrf mctaphosphateasd o oan . Data reporte earlien di r sections showed that even afte dayr1 ,e whicth s hwa shortest perio treatmenf do thesn i t e experiments, orthophosphat formeds ewa s ,a a result of hydrolysis of the pyro and metaphosphates in solution, in concentra- tions high enoug planty uptakb e accouno ht P th sf r e o growin tfo thesn gi e solutions. Since these results do not permit definite conclusions on the question whether phosphate ions other than the orthophosphate are absorbed by plants very

- 7 10 - short-term studies with experimental periods ranging from 1 to 12 hours were undertaken. Dat maiz y uptakb n ao P e f eplano s from solution sodiuf so m pyro, metd aan orthophcsphates after hour2 1,3, 1 s reporte e i d sar 6t an I tabln i d. IX e observed that over these extremely short uptake period absorptioe th s P f o n from orthophosphate was significantly greater than that from the other sources. This findin contrasn i situatio e s gth i o t n over relatively longer periodf so sees i morer o nt I y tha.difference uptakda th t1 f eo e between phosphorus uptake from orthophosphat othee th rd ean source greatess si shortese th t ta t perio uptakef o d , i.e . hou1 tendd ran narroo t s w over increasing treatment periods. Data show thauptake P (expresseth t f eo ug.P/jars da ) from sodium metaphosphat significantls ei y less than that fropyrophosphatee mth . However, the differences between meta and pyrophosphate may, at least in part, be due to the smaller quantity of metaphosphate added to the uptake solution. This is evident whe uptake nth e dat recalculatee aar cenr pe t s utilizatioa d e th f no phosphates. Concurrent measurements of hydrolysis of the condensed phosphates (table X) reveal measurable, though very low, concentrations of orthophosphate in solution. After 1 hour about 0.6 per cent of the pyrophosphate and 0.3 per cent of the metaphosphate were hydrolysed. The extent of hydrolysis.increased with time and after 12 hours per cent hydrolysis values of 5»® and 4.0 were obtained for the pyro and metaphosphate, respectively. It is noteworthy that the presence of plant roots in solution appeared to enhance the rate of hydrolysis of the pyrophosphate even over very short periods. Comparative data on hydrolysis of the condensed phosphates and plant uptake ofrofP m these source hou2 1 s ro ove t period 1 r presentee ar s tabln di . XI e s evideni t I t tha textremele th eve t na y short uptake period amoune th sf o t orthophosphate forme solution i d hydrolysie resula th s na f to sodiuf so m pyro- phosphat greates i e r thaquantite th n fertilizef o y absorberP plantsy db . In contrast, plant uptak froP f mo e sodium metaphosphat marginalls i e y higher thaquantite nth fertilizef yo absorberP plantsy b d contrastn I . , plant uptake of P from sodium metaphosphate is marginally higher than the quantity of ortho- phosphate P formed in solution at each of the four uptake periods.

DISCUSSIOH

Our findings on relative uptake of phosphorus from pyrophosphate and ortho- phosphate over very short periods are similar to the results of Sutton and Larsen (l),whp found tha waiter-culturn i t e experiment 5 phosphoru6. H p t a ss uptaky eb intact barley plants from sodium orthophosphate was more than twice that from sodium pyrophosphate houoveJ 3- r uptake period. hydrolysie Th s dat pyrophosphaten ao s indicate tha eact a t h uptake period, from 1 hour to 6 days, the concentration of orthophosphate formed in solution is higher than the total quantity of fertilizer phosphorus absorbed "by•plant. This is also true for metaphosphates over the relatively longer periods of 1 day and more. However amoune ,th orthophosphatf to e forme solutionn i d metaphosf so - phat hour 2 period1 n ei lowes o st wa rp s u thaquantite nth fertilizef yo r phosphorus absorbed by plant over the corresponding period suggesting the possible absorptio phosphatf o n specien io e s other than orthophosphate (i.e. metaphosphate). - 108 - The present data on hydrolysis of pyrophosphate are not in agreement with thos Buttof eo Larsod nan n (l) havo ,wh e reporte hydrolysio dn sodiuf so m pyro- phosphate (Na2BLP207) at pE 6.5 in 3-g- hours. While the pyrophosphate species

used in our experiments (P0 ~) and the initial pH of solution (pH 8.8) are not

2 strictly comparable with tnos4 e of Sutton and Larsen, it is stressed that under r experimentaou l conditions the.exten hydrolysif o t orthophosphato st e occurring over 1 to 12 hour periods could account for the phosphorus uptake by plants. r datOu a indicate thahydrolysie th t pyrf metaphosphatesd so an o , especially over longer periods considerabls ,i y enhance presence th n i dplanf o e t roots. bees Itha n reported that hydrolysi pyrophosphatf so influences ei , pH y db enzymatic activity and ionic environment in the solution (l, 11, 21). It is con- ceivable that as a result of the metabolic activity associated with roots of intact plants changes in pH and the ionic composition of the external solution can occur which may lead to an increased rate of hydrolysis. Activity of the microorganisms associated with roots in the non-sterile conditions such as those prevailing in our experiments (22) are also likely to influence the conversion of pyrophosphate at least in the close proximity of the roots. While the possible influence of these factorhydrolysie th n so metaphosphatf so beet no ns reportesha s i t i d likely that similar effects may occur. The markedly lower uptake oi phosphorus from pyro and metaphosphaxe as compared to that from crthophosphate over periods up to 12 hours can be correlated to the relatively low concentrations of orthophosphate present in solutions of the non-orthophosphate sourcevere th y t sshora t treatment periods. The present findings suggest that phosphorus is absorbed by plants chiefly orthophosphate as th efficienc e th d an non-orthophosphatf n yo eio e compounds sa source phosphoruf so plantr sfo s growin solution gi n culture 'largels si y dependent on their conversion to orthophosphate.

- 9 10 - REFERENCES

STJTTON) (1 , C.D., L/.HSW Soi. ,3 l Sci (1964. .9J ) 196. LEHR) (2 , J.R., HJGELSTAD, P.O., BROWN, E.H. Proc. Soil Sci. Soc. Amer (19648 .2 ) 396. SAMPLE) (3 , E.D., M.S. Thesis, Universit Nortf o y h Carolina, Raleigh (1965). SUTTON) (4 , C.D., GUNARY LARSPN, ,D. Soi. ,S l Sci (19661 .10 ) 199. STANFORD) (5 HIGNETT, ,G. , T.P. Proc. SoiCrod lan p Sci. Soc. Florida 1J_ (1957) 161. TERMAN) (6 , G.L., DEMENT, J.D. Agro(19624 ^ . nJ ) 433. HAGIN) (7 Soi. ,J l Sci (19662 .10 ) 373. (8) DATTA, N.P., MISTRY, K.B. Proc. 2nd UN Int. Conf. PUAE 27_ (1958) 182.

(9) MISTRY, K.B., IAEA/FAO Symp. Radioisotopes in Soil-Plant Nutrition Studies, IAEA, Vienna (1962) 427. (10) SINHA, ThesisA.K.. D . ,Ph , Indian Agricultural Research Institutew ,Ne Delhi (1967). (11) GILLIAM, J.W., SAMPLE, E.G., $oil Sci. 106 (1968) 352. (12) HUFFMAN, E.O., FLEMING, J.D Phys. .J . Chem (i9604 .6 ) 240.' (13) PHILEN, O.D., Jr. LEHR, J.R. Proc. Soil Sci. Soc. Amer. 31. (1967) 196, (14) HUFFMAN, E.O. Outlook on Agriculture £ (1968) 202. (15) LEHR ,Chem. J.Ral .t . e Engng. Tennesse, Bull6 . .No e Valley Authority (1967). (16) HIGNETT, T.P. Personal Communication. (17) THILO RATZAnorg, . Z , E. . ,R . Allgem. Chem (19490 .26 ) 260. (18) BARTON, G. Anal. Chem. 20 (1948) 1066 (19) KARL-EROUPA /nal. ,E . Chem (19568 .2 ) 1091. (20) DICKMANN, S.R., BRAY, R.H. Ind. Engng. Chem. (1940 2 Anal1 . ).Ed 665. (21) WAZER, J.R. Van. Phosphoru Compoundss it d san Chemistry. .I , Interscience Publishers Yorw ,Ne k (1958). (22) BARBER, D.A. Ann. Rev. Plant Physiol. !£ (1968) 71.

- 0 11 - TABL3 I

Comparative utilization of pyro and orthophosphates by maize plants in water culture

Phosphate Initial Quantity Utilization of fertilizer phosphorus (^ of added) H p source added 1 day 3 days 6 days (mg.P/jar) Shoot Root Total Shoot Root Total Shoot Root Total plan. . t planplant t Potassium 8.8 20.2 0.07 0.33 0.40 0.42 1.11 1.53 1.46 1.15 2.6l pyrophosphat e

3 Potassiu5* m 20.5 0.1? 0.60 0.75 0.55 0.99 1-54 1.14 1.75 2.89 orthopho sphat e

Significancf eo S N . S N differencS N ) (F e S 5 S N S N S N S N 0.05 TABLT? II

Comparative.effec pyr f torthophosphateo d oan growtn so maizf ho e plant waten si r culture

Phosphate Initial Quantity Yield of dry matter (g/jar) source pH added 1 day 3 days 6 daya (mg.P/jar) Shoot Boot Shoot _ Root______Shoot____Root

Potassium 8.8 20.2 0.132 0.090 0.174 0.113 0.213 0.133 pyropho sphate

Potassium o rthopho spha t e 5*3 20.5 0.144 0.100 0.187 0.097 0.173 0.122

0 1 Significancf eo • differenc) e(? 0.05 TABLE III

Hydrolysis of pyrophosphate in water culture Quantity added t 20.2 nig.P/jar Initial pH t 8.8

a.b. Days Orthophosphate in solution Uptak fertilizef eo r phosphoru plany sb t (mp.P/iar} (mg.P/jar) a Ko. With plant plant 1 1.01 1.23 0.08

1 1.36 0.33 t-* 3 1.15 u»-** t 6 1.24 1.39 0.53

) Wit maizi o a htw e r plantja r spe correctet no ) fertilizer ii dfo r phosphorus uptake by plants. Total plant (shoot •«• root) value*. TABLV EI

Effect of giant species on jphosphgrua uptake and translooation from py™ a«n n>.+.h»rv>ffT,ha+fr ^^"^^™^^™^^™^^™^^™^^"^^^"^^™^^™^^™^^™^^™^^™^^™^^™^^"^^^"^^™^^™^^™^^^^^"^^^"^^™^^™^^™^^^^^^^^^I^^™^^™^^™^^™^^™^^™^^™^^™^^^^^™^^^^^'^^^"^^^^^^^^^^^^^^^^™^^^"^^^^^I^SE^^^^^J*^^^^^*^^ sources, in water culture Duration of treatment t 6 days

Phosphate Fertilizer phosphorus uptake (mg/g dry wt) Transport index8 source Shoot Root Maize Bean Maize Bean Maize Bean

Potassium 1.43 1.83 1.77 7.26 Pyrophosphate 45 20

,_ Potassium 1.53 2.19 3.25 32 £ orthophosphate 7.55 22

transport inde x- Shoot , content ———— Total plant content TABLEV

Comparative utilization of meta and orthophosphates b^ maize plant waten si r culture

Phosphate Initial Quantity Utilizatio fertilizef no r phosphoru addedf o $ s( ) source pH added 1 day 3 days 6 days (mg.P/^ar) Shoot Root Total Shoot Hoot Total Shoot Boot Total ______.^sia_l______.______. ______Plant______plant______plant

Ammonium 6.6 1.86 1.32 3.40 4.72 4.86 7.34 12.20 13.76 11.60 25.36 metaphosphate

i Ammonium 5.0 1.89 1.94 4.46 6.40 6.64 8.44 15.08 13.SO 11.94 25.44 H- orthophosphate VJl I S N S F S N S F S IT S U S N S IT S U Significanc f o e differen) (? e TABLI EV Comparative effec met f torthophoaphateo d aan growtn so maiaef ho ^ plant waten si r culture

Phosphate Initial Quantity Yield of dry matter (g/jar) source pH added 1 day 3 days 6 days (mg.P/j.ar) Shoot Root Shoot Root Shoot Roc.t

Ammonium 6.6 1.86 0.115 0.083 0.131 0.084 0.164 0.088 metaphosphate

Ammonium 1.89 0.145 0.089 0.156 0.092 0.150 0.099 orthopho sphat e

Significancf o e differenc) (? e NS ira S3 TtS ns NS TABLI EVI

Hydrolysis of metaphosphate in water culture Quantity added s 1.86 mg.P/jar 6 6. : Initia H lp

a.b. Days Orthcphosphate in solution Uptake of fertilizer phosphorus by plant (mg.P/jar) (mg.P/jar) a No with plant plant

1 0.14 0.22 0.09

3 0.18 1.20 0.23

6 0.27 1.26 0.47 ai) With two maize plants per jar ii) Not corrected for fertilizer phosphorus uptake by plants, 0 Total plant (shoo rootd tan ) values. TABLg VIII Sffcot^of j>lant specie phoophorun so s uptak d translocrtti-'ean n frc^m mota and[ orthnphnsphatft source waten si r culiurg Duratio treatmenf no day6 = ts

Phosphate Fertilizer phosphorus uptake (mg/g dry wt.) Transport index source Shoot Root Maize Bean Maize Bean Maize Bonn

Ammonium metaphosphate 1.63 1.03 2.44 2.78 40 27 i Ammonium »-; orthophosphate 1.80 0.88 2.60 3.18 41 18 oo

Sh00 content "Transport index Tota-l plant content x 100 TA3LX EI

Phosphorus uptake from ofvro1 meta and orthophosphate by maize plants over very, short periods in water culture

Phosphate Initial Quantity of fertilizer phosphorus (ug.P/jar) source pH added Shoots Roots h 6 h 3 h I (mg.P/jar h 2 1 ) h 16 h h 3 12 h

Sod ixim 8.8 25.4 0.8 15.8 71.4 199-5 B5.9 182,7 299.7 436.0 pyrophosphatr

4 6. Sodium 7. 02 3. 24. 32 0. 55-1 .O 65.2 139.1 247.7 mf> phosphata t e

2 5* ^ Sod iun 26.4 3.7 58.8 226.1 342.3 183.3 400.4 648.8 840.7 1 orthophosphate

L.e.d 0.05= P ( .) 8 1. 11.8 36.5 70. 3 7. 38.7 7 62.3 82.9

aWit planto htw jarr spe . TABL3 X

flydrolysi pyr f snrntaphogphated o oan s over very short ~

' ~" _ - Phosphate Initial lty source pH - 2£ ,h Hydrolysis (me. orthophosphate P/jar) (mg.P/oar) No awith No aWith v** a iiin No aWith No aWith ——— ^— . plant plant plant Dlant —— Plant . ——— plant ——— ^lant —— plant

Sod iura 8*8 25.4 0.16 0.96 1.17 pyrophosphate 0.89 0.87 1.20 1.29

Sodium 6.4 7 02 me tphosphata e ° * °- 0.04 0.03 0.14 0.08 0.26 0.26

. * i - • - "

Wit) maizo i htw e plant jarr spe . ii) Not corrected for fertilizer phosphorus uptake by plants. TABLE XI

Comparative data on hydrolysis of pyro and metnjshoaphates and plant uptakf__of phosphorus'from these sources over short 'treatment periods

Phosphate Initial Quantity Hydrolysis bUptake of fertilizer phosphorus by plant source pH added (mg orthophosphate P/jar) (mg.P/jar) h 2 1 h 6 h 3 h 1 h 2 1 h 6 h 3 (mg.P/jar h 1 )

Som diu pyrophosphate 8.8 25.4 0.1* 0.96 0.89 1*20 0.09 0.20 0.3? 0.64

Som diu g metaphosphate 6.4 7.0 0.02 0.04 6.14 0.26 0.03 0.07 0.16 0.30 l Sodium orthophosphat 2 5. ? 26.4 26.4 26.4 26.4 26.4 0.19 0.46 0.87 1.18

In absenc plantf eo s Total plant (shoo roott+ ) values witmaizo tw h e plant jarr spe . EEPORT ON THE USE OP RADIOISOTOPB'.' 32P FOR FERTILIZER STUDIES IN INDONESIA

Nazir Abdullah

The applicatio radioisotopef no agriculturan si l research Indonesin ,i a has been limited by the existing facilities and urgency of the problems faced. Up workw til onlw beed fe lno syha a n conducted using radioisotopr o f p e32 fertilizer studies. Experiment technique th n so phosphatf eo e fertilizer placement were carried out with rice at Pasar Djumat Research Centre of the National Atomic Energy Agency, while work on maize was done at Bogor Institute of 'Agricultural Sciences. From the data collected, it appears that with respect to placement on rice, broadcas bese th t uptake s methoth twa phosphorusf r eo fo d , while mixin parga t of phosphate fertilize maize th eo r t seeds , resulte betten di r growt earlt ha y stage of development. Mixing the fertilizer with seeds was especially recommen- ded for small seeded maize. An experiment was also carried out using 32P to study the effect of ferti- lizer and liming in field conditions for areas planted with kidney beans (Phaseolus lunatus L.). Results from this experimental work showed that this soil gav greaea tfertilizationK responsNP e th o et . Limin soie gth l witha dose of 4 - 6 tons of lime per hectare increased the efficiency of NPK fertili- zation. This efficiency increas e mighth partlo e t b phosphoru f eo e ydu s availability for the plants and by the decrease of P fixation by the soil. Some other experiment stile sar l Pasagoint a n rgo Djumat Research Centre on the use of radio£hb.sphorus for fertilizer studies in rice.

- 122 - REPORT ON THE USE OP RADIOISOTOPE 32P FOR.FERTILIZER STUDIE INDONESIN SI A Nazir Abdullah 4t^f '\ Pasar Djumat Research Centre The National Atomic Energy Agency Djakarta, Indonesia

1. INTRODUCTION

The application of radioisotopes in agricultural research in Indonesia has been limited by the existing facilities and urgency of the problems faced. Radio- isotope techniqu widelt no s eagriculturai yn i use t dye l researc Indonesian hi . Research on the use of radiophosphorus in the tracer technique has been initiated just afte Trige rth a Mark Reacto Bandunt ra g starte produco t d e several kindf so radioisotopes (10). Up till the present QQly few experimental work has been done in the field of fertilizer studies using ^P. Lack of research workers who are familiar with this new technique and also lac certaif ko n electronic equipmen severan ti l agricultural research institutes maie th n e handicaar p which explainradioisotope th y swh e techniques have been developed slowly. However, this does not mean that the use of radioisotopes in several fields of agricultural studies are unacceptable by the research workers. Some activitie beed verse ha n th y carrie y limiteb t dou d well trained staft fa Pasar Djumat Research Centre additionn I . experimentaw fe ,a l work beed sha n undertake co-operation ni n Bogoe wit stafe th hth rf f o Institut Agriculturaf eo l Sciences at Bogor. Other problems faced by the research workers in the past was the unregularity radioisotope ofth e productio limitee th d dnan quantity whic availables hi . Although these problems cause discontinuita d "thf yo e experimentale worth n ki past, we always believe that the intensity of work in this new field of study will be increased in the coming years. purpose Th thif eo s summarizpapeo t s ri resulte eth s obtained from research don Indonesin ei a radioiaotopconcerninf o B US n fertilizei e gp th e*^ r experiments.

papeA r Eas) * Fa r t e presenteStudth Asi e d yth aan n Groudo e p Us Meetin e th n go of Isotope Radiatiod san Investigationn ni Fertilizef so Wated ran e rUs Efficiency, held in Bangkok, Thailand, 21-25 April 1969. Contribution of the National Atomic Energy Agency, Djakarta, Indonesia. Technica) ** l Staff Membe Pasat ra r Djumat Research Centr Nationaf eo l Atomic Energy Agency, Djakarta, Indonesia.

- 3 12 - 2. EXPERIMENTAL WORKS AT PASAR DJUMAT RESEARCH CENTRE

WIDJANG ^ al_. (13) studied the uptake of phosphorus in rice for three different methods of fertilizer application, namely (i) surface broadcast, (ii) band application belom c seed e fro m 7 seede d c (iiiwth d th ms,an 5 san ) mixed

witsoile hth . Phosphorus (Po^c s ) wa applie fore Doublf th o m n i de Superphosphate

f o k 10 n additio n at the rate of 100 kg per hectare (3&°8 per cent P°5^*I

alss wa cenr o ) pe appliedN t Ure 5 (4 a . 2 The experiment was conducted in pots containing 2 kg of soil. The amount of fertilizer used per pot was 100 rag each of Double Superphosphate and Urea. Twenty seed f "Sigadisso 11 rice variety were planterowo r eactw s fo n hi d pot. The plant day6 5 s sd wer an froe e2 th m4 harveste , 28 intervan a , t 14 a d f lo dat plantingf o e . Fifteen plants were harveste firse th tt a dinterval r Fo . succeeding interval numbee sth plantf ro t spo harvester pe 2 d dan wer2 » e5 respectively. The determination of the P uptake by the plants, derived from fertilizer was done by means of a comparison between the specific activity of specifie plante th th d n san i c P activit applieP soile * • th f .o yo t d Phospho- rus uptake from fertilizer was determined by bioassays. Tabl treatmente showeeI th l d al that s tno wit h surface broadcast gave eth highest quantit shoult mattey i dr d f dyro an als mentionee ob d thahighese tth t quantity of dry matter does not always yield the highest phosphorus content in the plant.

TABLE I. AVERAGE DRY MATTER YIELD AND PHOSPHORUS CONTEST OF THE PLANT

plante Ageth f so TREATMENT 14 28 42 56 D.M. P.C. D.M. P.C. D.M. P.C. D.M P.C.

Control 400.'.55 - 743. y - 1200.0 - 1J5B.O Broadcast 388,..0 2.85xlO~4 755.9 6.00xlO"4103l.4 1.65xlO~3 1438.9 1.17xlO~3 Band __.0 6.15xlO~6 846.0 8.25xlO~4ll02.3 1.35xlO~3 1395.0 l.60xlO~3

Mixed 358.5 4.35xlO~ 610.6 3.05xlO~ 897.0 0.69xlO~ 1219.5 0.88xlO~

5 4 3 3 Legcnda: D.M. dry matter (mg) P.C. phosphorus content (mg) The results obtained from different methods of phosphate fertilizer placement thin i s experimental work wer followss ea j (i) The highest uptake of phosphorus by rice plants harvested 14 days after plantin s derivegwa d from surface broadcas followed an t mixey db d treatment. This migh takee b t n into .consideration, that during this perio growtf o d h phosphorus was not well spread yet into the soil.

- 4 12 - (ii) The plants harvested 28 days after planting showed that the highest, phosphorus uptake obtained was by-hand treatm-ent, followed by surface broadcast. It migh understooe tb d that during this perio growtf o d h phosphorus moved already vertical into the soil and spread to the top-layer of the soil and reached the root topis; - • ••••• - ••" ••--••••--•••-•••• ...... -•(iii- plante )Th s harveste ari2 d4 d -56-days-aflrer planting gav highese eth tP uptake-by "surface broadcast-and band treatment-respectively ."The• " 'lower"P fixing capacity may explain the higher P uptake in band treatment. This experimen s conductetWa d under supervisio IAEAn a f ,nd o experha o twh been employe Pasat a d r Djumat Research.Centr r severaefo l montho 1968t n s i e Du . insufficient suppl- radioisotopf y-o recep e^2 ive d -from Bandung Reactor, this" experimental worconductes kwa d only witreplicationso htw might I .consideree tb d as a preliminary investigation for the basic experiences of this new technique for future works. ! Another experiment was_carrie 196n i ) witt 6(8 ou dratheha r .differen, t. techniqu methode th n placemenf e 'i so forme th fertilizef so d an t r t usedpo A . experiment was conducted to study the different methods of placement of phosphate fertilize meany rb s of.labelling with ^2P. Plastic pots witm c diameteha 8 2 f o r soilfillep to ,f dfroo witg mk Pasah7 r Djumat Experimental Gardebasia d cnan dose of fertilizer applied at a rate of 100 kg per. hec.tare Potassium Sulphate--and Ammonium "Sulphate, equal to 200 mg each fertilizer per pot. Labelled NaH^ PO. was used as labelled fertilizer. Seven rice seeds of "Bengawan" variety planted in . Fiv eacwitt cm ehpo distanc9 ha differenx 9 f o e t method placemenf so t with four replications wer followss ea : *' Control," without" phosphate fertilizer Placemen surfacn to e broadcast Placemen from surface c depta th m3 t f a to h e directly belo seee wth d Placement at a depth of 3 cm from the surface and 3 cm below the seed Placemen belom from c surface c seee dept a 6 mth 3 wth d t d f ta ho ean .Placement just above the seed and under the 'surface The plants were harvested at 14, 28 and 42 days after planting. The characters studied were plant height, fresh weight weighty ,dr , counting yiel percentagd an d e uptakeP surface Th . e broadcast gavhighese echaracterth e th tl resulal r s tfo studied for all ages except for plant height at 42 days after planting (table II). It shoul notee db d that therpositiva s i e e relationship betwee weighy ndr wels a t l as percentage P uptake with the ages of plants harvested. In case of dry matter yield obtained from this experimen resulte tth s confirm KHAN's ^Ua^. report (?), participatinl al tha n ti g countrie PAO/IAEe th f so A Co-ordinated Research Programme, the highest dry matter yield was obtained from surface treatment, except in Pakistan.

- 125 - TABLE II. THE EFFECTS OF FERTILIZER PLAC^-MENT ON PLANT HEIGHT, FRESH WEIGHT, DRY WEIGHT, COUNTING YIELD AND PERCENTAGE OF P UPTAKE IN RICE

TREATMENT REMARKS CSARACT. AGES OF STUDIES PLANT(SA ) B C D IS F PLANT 14 33.6 36,-1 34.9 32.8 31.4 31.3 HEIGHT 28 72.2 76, 69.1 71.3 67 .6 67 .9 (cm) • 5 42 106.0 104, .5 110.0 108.5 105.2 93.3

FRESH 14 164.3 218.0 164.5 197 .3 177 .7 153.0 WEIGHT 28 3,041 3,889 2 ,651 3,240 2 ,747 2,781 (mg) 42 9,866 16,227 11,450 10,922 6,747 5,424 ^^^^^^^H DRY 14 29.1 38.8 25.6 34.3 30.5 26 .8 WEIGHT 28 515.5 646. 6 461.1 540 .4 499.6 550.6 42 3,119 4,005 2 2,829 ,931 2,211 2,572 COUNTING 14 - 9,616 9,498 4,170 538 9,491 YIELD 28 - 26,466 15 ,500. 6,550 10 ,800 23 ,692 (cpm) 42 - 15,753 13 ,359 8,491 4,405 10 ,066 H 14 •'' 0. 076 fr.075 0.033 0.005 0.075 UPTAKE 28 - 0.722 0.423 0.179 C.267 0.646 (#) 42 - 7.50 6.35 4.04 2.48 5.28

Legenda: A : Control,without phosphate fertilizer PlacemenB: surfacn to e "broadcast Ct: Placement at a depth of 3 cm from the surface and directly belo e seewth d D : Placement at a depth of 3 cm from the surface and 3 cm below the seed E s Placement at a depth of 3 cm from the surface and 6 cm belo e seewth d Placemen: F t just abov seeundee d surface th ean d rth e

- 126 - 3. ACTIVITIES IN CO-OPTSRATION WITH OTHER INSTITUTES

Fertilizer studies on maize plant was done in co-operation with the staff of the Bogor Institute of Agricultural Sciences at Bogor (9). To minimize the P fixatio soiy n"b l components, phosphate fertilize placeo b n drca localizeo dt prevent more contact wit soile hth . Such metho s recommendedwa solublr fo d e phosphate fertilizer on maize plant grown on acidic soils (4). In this case fertilizer was placed at a distance of 7*5 cm side way the seed and 5 cm below. It has been mentioned in the literature that placing a part of phosphate ferti- lizer together with maize seeds, will stimulat growte eth younf ho g plant) (5 s and the yield will also be increased. The study was intended to compare the effect of several methods of placement P olabellef^ d Double Superphosphat growtn eo uptakd han phosphoruf eo y sb plants. Pot experiment was carried out in greenhouse using 3 kg of "Tjidjantung" fixinP d an g soi G capacitl6. witH p abous h$ a (14)ywa t94 .s wa Eact hpo planted with 10 seeds and harvesting took place at the ages of 11, 16, 22 and 27 days after planting. Bioassays were made according to the methods used by G'O BAN HONG (l) and the activity measured with G.M. Counter. The results obtaine thin i d s experimen presentee tar tabln i d e Ilia. The results indicate that the dry weight was affected by fertilizer placement, (9). Randomized block desig uses nwa d with three replications soio Tw l. samples were use thin i d s experiment Botanie ,th c Garden's Latosol (BGL) rich with nutrient and another soil sample Tjibinong Latosol (TBL) poor with nutrient. Th 0 respectivelyvalueH ep 5. d san wer 2 resulte e6. Th . s obtaine thin i d s experiment - are .shown in tabl& Illb. '

TABLE Ilia. AVERAG MATTEY EDR R (mg /plants2 MEAD )AN N PLANT ACTIVITY (counts/ min/ 2 plants) AS AFFECTED BY DOSIS AND PLACEMENT OF PHOSPHATE ...... - FERTILIZER ......

TREATMENT Ages of plants Spec, 11 16 2:? 27 activ. D.W. C. . C D.W. D.W. C. D.W. C. at d ' 7 2 CDm/nu? A. e.p. 247 - 579 - 1321 - 2132 - - B. i.p- i 231 a 585 15 1652 134 2685 149 0.06 ' 1 hill C. l.P- 272 19 537 33 1225 133 2635 493 0.19 hill2 s D. 2.P- 258 15 546 32 1452 98 2410 582 0.24 -' hill2 s E. l.P-Mixed 243 17 642 19;i. 1213 6 2225 46 0.02

F. 1/3 P- 240 54 690 33 : 1728 84 2745 322 0.12 ' r . mixed . . t 2/3 P- 1 hill . Legend weigh D.Wy : a dr .t: (mg) C. : counting (counts/min.) l.P i 1 g Double Superphosphate per pot plus 1 uc 32P. Each pot contained 3 kg "Tjidjantung" soil introduced with Nitrogen (l g Urea) and Potassium oxide (l g Potassium Sulphate) Fertilizer and planted with 10 maize seeds of "Harapan" variety. - 127 - The data indicated that the Botanic Garden's soil gave better growth and th uptakeP highes ewa r than that derived from Tjibinong's soil. Furthermore small seeded maize gave the;. highes uptaktP botr efo h type f soilso mixiny B . g para fertilizef to r wit seedse uptakP hth e increaseds ,th e wa resulte Th . s mentioned above indicated thar smaltfo l seeded maize, mixin parga phosphatf o t e fertilizer with the seeds was recommended since; it would increase the efficiency of P uptake by the plants. An experimen alss twa o conducte dstudo t usineffece P yth gfertilizef to r32 and liming in field conditions by using kidney beans (Phasoolus lunatus L.) and the effec availabilite liminf o tth n go phosphoruf o y fixatioP soie d th san l y nb (3). This investigatio resulte bases th nwa n do s obtaine fiela n i dd experiment done at "Panumbangan" Sukabumi, using NPK fertilizers and liming. The main plots were treated with NPK fertilizers and without any fertilizer, while tbo sub plots consiste level5 f o dliminf so g namely 0,2,4,6, ton0 1 limf hectarer so d epe 8an . Results obtained in this experiment showed that fertilization with NPK fertilizers y dr n increasea to h ton6 anr 1 - d so pe yiel e t 4 rate limin th dp f th du eo t ga seeds per hectare. Liming alone was not much effective (table IV). The determi- nation of available phosphorus was done by extraction method according to STANFOR MEWE D TD& (ll) .fixatioP determines nwa d accordin SUWADJo . gt al t Ie (U). TABLE Illb. THE EFFECT OF SOIL SAMPLE, SIZE OF MAIZE SEEDS, METHODS OF FERTILIZER PLACEMEN MATTEY DR N RTO (mg/pot SEEDLINGY B UPTAKT p )AR 32 F T ESO A 12 DAYS OLD

TREATMENT Plant Plant P P weight activity 2°5 2°5 (rag) (cpm) w A. O.P- largeL seeBG - d 423.0 - - - B. 1/3 P- with seod- 2/31 Pn i hill 390.0 88.0 0.18 0.05 large seed - BGL C. l.P in hill1 - large seodL -BG 416.0 50.0 0.10 0.02 D. 1/3 P- with seed- 2/3 P in 1 hill sipall seed - BGL 383.0 312.0 0.65 0.17 E. l.P in 1 hill- small seed- BGL 313.0 125.0 0.26 0.08 F. 1/3 P- 1 wit n i h P seed 3 -2/ hill large seed - TBL 273.0 38.0 0.08 0.03 a. l.P in hill1 - largo see- d TBL 226.0 38.0 0.08 C.03 H. 1/3 P- with seed- 2/3 P in 1 hill smallL seeTB - d 190.0 300. 0 0.64 0.34 J. l.P in hill1 - small see- d TBL 170.0 63.0 0.13 C.08 LegendaBotani: L cBG : Garden's Latosol, rich in nutrient, pH 6.2 TBTjibinong': L s Latosol, poor in nutrient5 H ,p l.P : 1 g Double Superphosphate per pot plus 6 uc•§2p "Harapan" variety : late maturity, large seeded maize "Pendjalinan" variety, early maturity, small seeded maize

- 128 - EFFECE TH FERTILIZER K TablLIMINF TQ NP , D eIV GAN SEEN SO DE YIELTH D DAN INFLUENC LIMINF EO .pHN GO , PHOSPHORUS AVAILABILIT FIXATIOP D YAN N IN PHASEOLPS LUNATU. SL

TfiEATMENT Field experiment Soil analysis by means of tracer Lime, (tons/ha) Yield- • - technique (NPK Lim& e Fertilization) pH (H^O) Activit fixatioP y n (cpm) 0 3.4 12.9 4.8 8 84 2 3.6 10.4 5.2 35 75 . 4 . 4.9 14.8 6.1 38 68 6 4.8 17.5 6.9 45 69 8 4.5 . 12.0 7.8 33 72 10 4.1 ' 12.9 7.8 . 2? 81 Mean 4.1 13.4

L*S.D. 0.05 : . for meanmaia npl 3 1. itj s . for mean sub pints » 4.1 same th ploeb fo n mairsu i t n plo: t 5.9 The samples used for measurement were made in forms of briquets according -to the method done by MacKMZIE jst.al. (6).

availabilite Th phosphoruf yo meany sb liminf so closels gwa y relateP o t d fixatio soile th .y nb Frodate th ma collecte sees i nt i tabln tha o d" , tP eIV fixation decreased when liming was increased up to 4 - 6 tons por hectare and the fixation was increased again as lime application was increased.*) This is in agreemen generao t l opinio , phosphoruH nP w tha lo soin i tf alss lo s wa o lacking

due to fixation by iron and aluminum (12). The data showed that liming with

1 more than 6 tons per hectare for "Panumbangan soi1 l may not be recommended. 4. DISCUSSION

ATI ?lly W ex fe Perimontal work fertilizesr usinfo P g32 r studies were undei-taken. All the results obtained in these experiments might bo classified as preliminary studies. More research, especially on rice using radiophosphorus to study 'the fertilizer efficiency should be -done in the coming year.

*) This result is in agreement with the result obtained from maize experiment on acidic soil fertilized with lime and phosphate fertilizer.

- 9 12 - Although results obtained frothosl al m e experiments wer vert eno y success- ful, a bright future and a clear direction of the beneficial effect of this new technique of fertilizer studies however, has come into being. Co-ordinated research programmes should be conducted in the future in co-operation with several staffs of agricultural research institutes elsewhere in Indonesia. The main difficulties faced in the past should be overcome soon with the new capacity of radioisotope production. The possibility of getting several kinds of radio- isotopes froneighboue th m r countries will stimulat intensite eth researcf yo h in Indonesia.

5. SUMMARY

A few experimental works using radioisotopes for fertilizer studies had been carried out in Indonesia since 1966• Eadiophosphorus had been introduced to rice plants conducted at Pasar Djumat Research Centre of the NaUonal Atomic Clergy Agency by very limited well trained staff. These activities were still preliminara y investigation. Results showed that surface broadcast gave eth highest uptak phosphoruf eo ricy sb e plant earlt sa y stag growthf eo , eithen i r the experiment carrieWIDJANy b t ou dG .et^al. (13 NAZId )an R ABDULLAH (8). Other activitie thin i s s field with othe experimenre th crop e sar t with maize that had been carried out in-co-operation with the Bogor Institute of Agri- cultural Sciences ($) .investigation A n with maize seed studo st effece yth f o t seed sizes and the different methods of .phosphate fertilizer placement was also carried out. The results obtained showed that mixing a part of phosphate ferti- lizer to the seeds caused bettor growth at young plants and increased in phosphate uptake. Mixing fertilizer with seeds was recommended especially for small seeded maize. In relation to soil fertility improvement, an investigation was also carried out on acidic soil, with poor nutrients by fertilization and liming on reddish brown latoso "Panumbangant la 11 using kidney beans (Phaseolus lunatus a ) sL. indicator (3). Results from this experimental work showed that this soil gave a great response to NPK fertilization. Liming the soil with a dose of 4 - 6 tons of lime per hectare may increase the efficiency of NPK fertilization. This efficiency increas e mighth o partle t b phosphoruf eo e ydu s availabilitr yfo thdecrease eth planty b phosphoruf eo d san s fixatio soile th .y nb

ACKNOWLEDGEMTJNT The author wishes to express his profound gratitude to Prof.Dr. G.A. Siwabessy, the Director General of the Indonesian National Atomic Energy Agency for allowing the autho atteno rt meetine Prof.Dro th dt d gan Amiruddin. .A Directoe ,th f ro Pasar Djumat Research Centre, for his advice in writing this manuscript and to Dr. Rusli Hakim M.Sc., of the Central Institutes of Agricultural Research at Bogor, for reviewing the manuscript and lastly to all staff members of the Agri- culture Division of Pasar Djumat Research Centre who in a way contributed in the realization of the experiments.

- 130 - . 6 REFER 13ICES

HONGN BA ,O G Penjelidika ) (1 n tentang neratja hara mineral padi sawah, Thesis, Bogor (1956). (2) KANG BIAUW TJWAN, Pengapuran tanah mineral masam untuk pertanaman djagung suatu keharusankah? bulletin Agronorai, Pakultas Pertanian Bogo (1964. r4 ) 13. (3) KANG BIAUW TJW/N dan NAZIR ABDULLAH, Pengaruh pemupukan NPK dan pengapuran pada Latosol merah tjoklat dari Panumbangan terhadap hasil tanaman katjang merah (Phaseolus lunatus L.), Simposium Radioisotop 1-2 Agustus 1966 di Bandung (1966). . ) KAN(4 G BIAUW TJWA SUHJATNn Nda A EFFEtfDI, Tanaman djagun bortjotjon gda k tanam djagung varietas unggul, LKPM Kept. PTIP, Djakarta (1966). KAN) (5 G BIAUW TJWAN, SUGIANT SURJATNn Oda A EFFENDI, Perbedaan chasian da S tD PMP serta tjara pemupukannja terhadap pertumbuhan dan hasil pertanaman djagung (Zea May) (sedansL. g (6) MacKENZIE, A.J. and DEAN, I. A., Measurement of3 2 P in Plant Material by the Use of Briquets, Anal.Chem. 22 (1950 ) 489., KHAN) (7 , A.B., HAQ, M.S., RAHMAN HABIBULLAH, . ,L , A.K.M., HABIBUL ISLAM, A.H.M. Applicatio Isotopef no Radiatiod san Ricn ni e Cultivation, PAO/IASA-AABC Co-ordinated Programme, Nucl.Sci Appld .an . Vol , I_ U.CA ,II Dacca (1966. )1 (8) NAZIR ABDULLAH, Mempeladjari pengaruh ponempatan pupuk fosfat jang ditandai dengan P-3.2pada padi Bengawan (1967) unpublished. (9) NAZIR ABDULLAH dan KANG BIAUW TJWAN, Pengaruh penempatan pupuk terhadap pertumbuha pengambilan nda n fosfat oleh tanaman djagung, Simposium Radio-' isoto Agustu2 p1- s 196 Banduni 6d g (1966). (10) SIWABESSY, G.A NAZId .an R ABDULLAH, Radioisotope Agriculturan si l Researcn hi Indonesia. Presente llte th h n Pacifio d c Science Congress hel Tokyn i d o on 24 August (1966). (11 ) STANFORD, G. and DT5 MINT, J.D., A Method for Measuring Short Term Nutrient Absorptio Plantsy nb Phosphor. .I . Proc. Soil Sci. Soc. Amer (19573 .2 ) 355. ~~ (12) TRUOG, E., Mineral Nutrition of Plants, Univ. of Wisconsin Press (1951) 41. (13) WIDJANG, H.S., SUWADJI, "3. et_. al . , Pengaruh tjara penempatan pupuk terhadap pengambilan unsur P oleh tanaman padi, Laporan Penelitian, Pusat Penelitian Pasar Djtuna• t• (196 (unpublished8) .) (14) SUWADJI KANn da G . BIAU,E W TJWAN, Piksasi fosfat beberapa djenis tanai hd Indonesia, Simposium Radioisoto Agustu2 p1- s 196 Banduni 6'd g (1966).

- 131 - THE SIGNIFICANC VALU' 'A EE CONCEPTH P EO T IN FIELD FERTILIZER STUDIES1

D.A. Rennie2

ABSTRACT This paper consider valu' 'A ee sconceptth applicatio s it d ,an fielo nt d experiments using labelled nitroge phosphorud nan s carriers. Extensive reference is made to phosphorus experiments carried out in Saskatchewan, Canada, and the Joint FAO/IAEA's international field research programme ric n wheatsd o ean , using N-15 labelled carriers. Arguments are presented which support the conclusion that'A1 value data or calculations based thereoonlt significancno f y o e nar evaluatinn ei e gth fertility status of soils, but also in assessing, in quantitative terms, factors that interact strongly with 'plant available phosphorus or nitrogen1, such as fertilizer management practices and soil moisture.

Presente Stude th yo t d GrouIsotopef o e p d RadiatioUs Meetin san e th n go n ni Investigation Fertilizef so Wated ran e Efficiency rUs , Bangkok, Thailand, 21-25 April, 1969.

Q Head, Soils, Irrigation and Crop Production Section, Joint FAO/IAEA Division of Atomic Energy in Agriculture, Vienna, Austria.

- 132 - THE SIGNIFICANCE OP THE 'A' VALUE CONCEPT IN FIELD FERTILIZER STUDIES

D.A. Hennie The 'A 1 value concept (2,3) is based on the asaumption that when two sources ogivefa n nutrien presene tar soila n i t,plana t will absorb from eac pron hi - portion to the respective quantities available. Thus, if one source is the native soil phosphoru other'ae th d san n added source (fertilizer onls i yt )i necessar measuro yt respective eth e quantities absorbed from each, together with

the amoun addef o t d nutrient calculato ,t value-foea native rth e nutrient. This latter value, in units of the applied fertilizer nutrient is the 'A 1 value. The concept doeincludt sno methoe eth measuremenf o d thit- dictates si d by the specific objective of the experiment (4,5,6,8,9,10,11,12,13,14), a major advantage of the 'A' value is that, as a quantitative measure, it' can-be-added and subtrace provided dan measuremensa t wherei biologicalle nth y available nutrient statu f soilsso fertilizersr ,o expressee b n ,ca quantitativn i d e terms rather relativthaa s na e index. valu ' measura A Sincr s i e availablf eth eo e

soil nutrients, in units of a fertilizer standard, when the standard is changed the magnitude of thAeS ' value will change. This change in the standard can be brought about wit actuan ha l fertilizee changth n ei r materiale itselfth n i r ,o position that the fertilizer is placed with respect to the plant roots, etc. The significance of the 'A1 value concept has not gone unchallenged. Perhaps unfortunately, however, many of those who have been critical of 'A' values have tlarge-extena o t misunderstoo originae th d l concept. Russel. (llal t )le presented experimental evidence which indicated that irreversable isotopic exchang considerablee b y ema ; Terma Khasawned nan h (13) concluded that sincn ei many instances 'A' values are not constant with increasing rates of application of fertilizer P, that the "A1 value data are open to question. There is little doubt but that 'mixed placement' of a tagged phosphate fertilizer standar certain di n soils wil accompaniee lb d by.either botr ,o h significant isotopic exchange, and reversion of the fertilizer P standard to a less available form, thus resulting in 'A1 value data that is difficult to inter- usuae th prel n manneri t irreversiblf I . e exchang P-3f eo 2e occursth f i r ,o fertilizer standard transformes i portio a , r ,it o f no d int lesa o s available soile value' th for »A jn i ms wil t reaailno n constan rate f applicatioth eo s ta n is increased. However, such phenomena du not invalidate the 'A' value concept,

but rather, can be taken as yet a further application, i.e. the irregular behaviou calculatef ro ? value'A d s serveinden a isotopif s xso a c exchanger ,o fixation of the fertilizer standard, as the case may be. Phosphoru value' 'A s s using banseedr (o d ) placement ! Limited soil-fertilizer contact afforded by band placement of a phosphate fertilizer standard will minimize isotopic exchange and fertilizer P-fi-xation, thereb t onlyno y allowin usuae g1 th valu 'A l e interpretatio same -atth t e- nbu time providing a measure, in comparison to mixed placement, of the significance or degre fertilizer-f eo P fixation etc. (ll) (Tabl. el) In an experiment designed to measure the significance of decaying organic residues (wheat straw) on soil phosphorus availability both banded and mixed fertilizer-P placements were used., In the presence of decaying organic residues, the mixed placement resulted in an increased in the measured 'A' value as

- 133 - compared to the no-straw treatment; also, as the rate of fertilizer-P was increased ,shara p increase occurre calculaten i d value' 'A d sn I (Tabl . e2) contrast, whefertilizer-e nth bandes Pwa d wit seede hth lowe,a 1 value'4 r , relative to the control, and constant 'Af values with increasing rates of fertilizer-P application were recorded. Thus mixed placement suggested that an increas availabln ei e soil- occurred presencPe ha th n i ddecayinf eo g residues, while data from the band placement indicated the reverse. The latter was shown to be correct. However, it is important to note that the data obtained from the 'mixedt placement1 doe t invalidats no 1 valu'A e th econcept t demonstrate,bu d that the fertilizer standard was more subject to biological fixation than the available soil phosphorus. In 'A1 value experiments, as in most research, the investigator must adjust experimental procedures in accordance with the dictates particulae ofth r conditions encountered. Significance of Phosphorus - 'A' values Various factors affectin significance gth usefulnesd ean 1 value'A f n so si measuring phosphorus offeets(using a band placement) are documented in the following examples. Intensiv obtaine) e14 dat, (6 ad from both fiel greend an d - house experiments have shown tha generan ti l placemen taggee th f do t phosphorus standard with the seed results in an uptake pattern of soil and fertilizer phosphorus suc 1 valuh'A thae e th tremain s constan specifir tfo c soigrowind lan g conditions (Table 3). value' 'A e , Th using band placemen phosphate th f o t e fertilizer affordsa measure of the available soil phosphorus within the rooting zone (11, 14). There- fore, under field conditions, where precipitation often varies widely value' 'A , s can be expected to vary in accordance. This is illustrated in the data given in Table 4» obtained from field experiments carried out in alternate years on the same field sites (9). The uniformity of the NapCO^ extractable phosphorus affords shara valu' p 'A contras ee datath lattee o t Th . r were consistentl undew lo y r drought conditions, and high where favourable moisture conditions prevailed, while the former were constant 1 valu'A e e Th dat. a suggest thabiologicalle th t y available soil phosphorus is low under dry conditions, and, in comparison, high during wet years. This observation is supported by the percent yield values. relationshie Th p betwee 1 value'A n soid san l moisture stres furthes si r illustrate date th a n givei d Tabln ni 5 (14)e . Such data provid quantitativa e e estimate of the significance of a soil moisture stress on plant-available soil phosphorus. Similarly significance ,th othef eo r soi environmentar o l l factors affecting root distribution can bo estimated using the 'A1 value technique (9, 14). Terma Khasawned nan h (15) questione significance th d value' 'A f seo since, mann i y instances valuee ,th s increase fertilizatioratP e f th eo s a d s nwa increased date figurn Th .i a were1 e obtained from field experiment whera e nitrogen deficienc soie th l n inducedyi , indirectly shar,a p increas1 'A n ei values applicatioP rat(14)e f th eo s ,a increases nwa P_0,-/acb I 6 9 do ;t fro 2 1 m constant 'A1 values occurred only where the W deficiency was overcome. In general, wher normao 1 valuereact th 'A e no n li to sd valumanner' 'A ee ,th concept invalidatedno s i t t rathe,bu r there usuall scientifia s yi c explanation for such behaviour.

- 4 13 - The "Effective Hate of Application" of different P-fertilizera ' • Many workers (4,6,7,10,13,14) have assessed the availability of various phosphorus fertilizers using «A« value data. Wher n experimenea s laiti d down on one soil, the availability of the soil phosphorus can be considered constant, and any change in the availability of the fertilizer results in a change in the soil-P/fertiliaer-P ratio such that lower fertilizer-P uptake is reflected in a highe valu' vic'A rd ean e versa. Some ambiguities arise whor 1 value'A e s calculate usuae th ln i dmanne e rar 'compared directly since the- units change as the fertilizer standard changes. n ordeI avoio rt d this difficulty meae ,th n comparative availabilitiee th f so various fertilizers given in Table 6 are expressed as "Effective Rate of Application" (E.R.A.) in units of liE.E^O^, and as "Relative efficiency" in % units.

The P-fertility statu soilf so s The significance of the 'A 1 value concept (using band placement) as a means of assessing the phosphorus fertility sta'tus of soils is further illustrated in data reporte experimente Th Renniy db . Claytod 9) ean , s (8 nwer e carriet ou d growte th n hi fiele chambed botth dan n hi foun ro r genetic soil typese ,th Calcareous, Orthic, Illuviated and Humic .Illuviated Gleysol. These four profiles represen catenarta y sequence that dominate chernozemie sth c soil aren ai Western Canada. The 'A1 value data obtained from this six-year study not only significancf o s wa evaluatinn ei relative gth e phosphorus fertilitye leveth f lo four profile question si t alsnbu o provided dat valuf ao assessinn ei e gth effect of various growth factors that interact strongly with soil phosphorus, such as moisture, temperature and soil structure. Nitrogen 'A1 values N-1f o 5e enableus e Th direcsa t measurfate fertilizef th eo f eo rapplieN d to soils, particularly insofa thas ra t portioe th nn i use plants y a b d d san phosphate studies reviewed above, the 'A1 value concept has similar and possibly more significant applications. The determination of soil nitrogen 'A1 values has b''en carried out on 12 widely differing soils by Legg 3nd Stan^orf (5). They concluded that from the results obtained doub o n ther 1 valus t'A ewa tha e tth constitute precissa e standard for characterizing the nitrogen supplying capacity of soils. Data selected from their study is given in Table 7. No evidence was found that the mineralization rate of soil nitrogen was influenced by the addition of fertilizer nitrogen 1 value;'A s remained remarkably constant with increasing ratf eo application. The Joint FAQ/IAEA's Ricd Fertility Programme Similar data has been obtained from the Joint PAD/IAEA co-ordinated programme on rice. Result greenhousa f so e experiment conducte IAEA'e th n si d Seibersdorf laboratory (table 8) also verify that the rate of fertilizer N application has not influenced the rate of mineralization of soil N (l). An ammonium sulfate source nitrogef o uses ntheswa n di e experiment comparison si nitrat- a o nt e sourcn ei Legg and Stanford's investigations. . .

- 135 - The 'A' value data reported in Table 9 was obtained from field experiments with rice carriey co-operatorb t ou d co-ordinate e th n si d rice experimentsn I . these experiments the nitrogen carrier was applied as a surface dressing and in bana locatione d th most applicatio A f to » m sc depta significantl5 t f a nc h y lower 'A1 values were obtained from the depth placement. The type of possible mathematical manipulations using 'A' value data is illustrated in the column titled E.R.A. (Effective Rat f Application)o e . Assuming thadepto th t h placement resulte more th e n valii d d estimat f availablo e e soil-N e calculateb n , ca the t ni d (see Table 10) that the effective rate of application of the surface placement U.A.Re th N/hexperimentg I k I r . waa 9 fo s 8 , rather thaactuae nth kg/ha0 12 l . ascertainee b n basie ca th s supportinf a o sn o dr Asfa g research information (l), the difference betwee actuae th n l rat applicationf eo calculatee th d ,an d T5.R./. reflects los f fertilizeso primaril, rIT denitrificationo t e ydu . Usi^ similaga r approach effective ,th e rat applicatiof eo kg/hn ni f ao selected nitrogen carriers compared to an ammonium sulfate standard effectively illustrates tho superiority of the ammonium sources of nitrogen as compared to nitrate sources (Table 11). The Joint FAO/IAEA's Wheat Fertility Programme

The International Wheat Fertilizer Research Programme, initiated in 1968, include participatin2 s1 g countries. Initial data, obtained from Brazil affords a further illustration of the significance of the 'A' value concept to nitrogen fertility studies carrie undet ou d r field conditions. The 'A' values, given in Table 12 for the* different treatments, fluctuate widely, and in themselves, are not too meaningful. The calculated E.R.A., in unit (NH.)f so N/hg k 2a0 SO treatment)12 . e (baseth n o d , however, providesa direct, and quantitative means of evaluating 'times of application1, and relative availability of the two carriers used, NaNO, and (NH.)?SO.. Comparison of the 40-40-40 sequence for both carriers show that for the soil and environmental conditions prevailing within the plot site, nitrogen applied at the early tillering stage was used most effectively, while that applied at the boowheate y exten th an uset o y no stag.t b d s wa e The reasons for the superiority cf NaNO, vs (NH,.)pSO. will require further investigations soile yellod ;th re ,a w planosol moderatels ,wa y acid highld ,an y granular. Under such conditions, gaseous froN losammoniuo f th mso m source would not be expected.

The TS.R.A. values correlated highly with % NDFF, and a function based on yiel fertilize- d uptakerN ; (grai strawd ' an n 'r )e (seth ; e figure3) d an s2 values were 0.98?, and 0.982 respectively. The 'A1 value data was not constant for cither carrier, as the rate of applicatio seedint na gN/hg k tim increases a0 ewa 12 (Table o t 4 3 ds6 1 fro, m40 and 14)« However, where corresponding corrections were madposr efo t emergence

application nitrogef so n using E.R.A. value actuae r treatmenth sfo d l an , I t amount applietillerine th t a d g stag r treatmenefo , remarkablII t y constan1 'A t values resultethree th er ratedfo applicatiof o s n applie seedint a d g timeA ( . calculate N applie g k possiblt treatmeno 0 no t d6 d s e E.R.Awa th e I r sincI t .fo e this treatment was not sequentially labelled. However, based on the 40-40-40 sequence data, the S.R.A. was probably at least 60 kg N/ha).

- 136 - SUMMARY AND CONCLUSIONS

This paper considers the 'A' value concept, and its application to field experiments using labelled 'nitroge phosphorud nan s carriers. Extensive reference is mad phosphoruo t e s experiments Saskatchewan, carriein t dou , Canadae th d ,an Joint PAO/lAEA's international field fertility research programmes on rice and wheat, using N-15 labelled carriers. The only assumption, indigenous to the 'A* value concept, is that when two sources of a given nutrient are present in a soil, a plant will absorb from each in proportion to the respective quantities available.^ Where the fertilizer standard does not, on a relative basis, react with the soil system, '/.f values will remain constant as the rate of application is increased. However, labelled fertilizerN r o P s frequently undergo significant changesoie th l n systemsi . Such phenomena do not invalidate the 'A' value concept, but rather, as shown in

the data presented, afford a further, and significant application of. the *Af value technique. Irregular behaviour of calculated 'A f values serves as a quantitative index of the influence of many environmental and soil factors on fertilizer and soil nutrient availability.

- 137 - REFERENCES

(1) ALEKSIC, Z., BROESHAKT, H. and MIDDLEBOE, V. 1968. The effect of nitrogen fertilization on the release of soil nitrogen. Plant and Soil (in press).

) PRIED(2 1964. , valuesM ' »A . d .'E' an f Trans,»L Inth .8t . Cong. Soil Sci. IV: 29-39. (3) FRIT-ID, M. and DEAN, L.A. 1952. A concept concerning the measurement of available soil nutrients. Soil Sc. 73: 262-271. (4) HADDOCK, J.L., HAtfSENBUILLER , B.L. and STANBERRY, C.O., Studies with radio- active phosphoru Westere soiln th si f so n States (1950-53). ) LEGG(5 , J.O. STANFORDd an , 1967. ,G . Utilizatio soif fertilized o n an l y b rN oats in relation to the available IT status of soils. Soil Sci. Soc. Amer. Proc 215-219: .31 .

(6) MITCHELL, J., A review of tracer studies in Saskatchewan on the utilization of phosphates by grain crops. J. Soil Sci. 8 (1957) 73-83.

(7) MITCHELL, J., DEHM, J.E. and DION, H.G. Availability of fertilizer and soil phosphoru graio st n effece cropsth placemenf d o t ,an ratd an tapplif e o - catio phosphorun no s uptake. Sci. Agric (19522 .3 ) (8) RENNIE, D.A. and CLAYTON, J.S. 1960. The significance of local soil types to soil fertility studies. Can. J. Soil Sci. 40: 146-156.

) REUNIE(9 , D.A CLAYTONd .an , J.S. 1966 evaluation .A techniquef no s useo t d characterize the comparative productivity of soil profile types in Saskatchewan. Trans. Comm. II and IV. Int. Soc. Soil Sci., Aberdeen, 365-376. (10 ) RENNIE, D.A. and MITCHELL, J. The effect of nitrogen additions on fertilizer phosphate availability. Canad. J. agric. Sci. 34 (1954) 353-363. (11) RENNIE, D.A SPRATTd .an , E.D. I960 influence Th . fertilizef eo r placemenn o t '.A1 values. Trans Inth .7t . Congress Soil Sci Vol, .IV . Ill, 535-543. (12) RUSSELL, R.S., RICKSON, J.B., and ADAMS, S.N. 1954. Isotopic equilibria between phosphate soin d theii s an l r significanc assessmene th n i e f o t fertility by tracer methods. J. Soil Sci. 5: 85-105.

(13) SCHMEHL, W.R., OLSEN, S.R., GARDNER, R. , ROMSDAL, S.D. and KUNKEL, R. Availability of phosphate fertilizer materials in calcareous soils in Colorado, Agric. Exp. Station, Fort Collins (1955 )•

(14) SPRATT, E.D., and RENNIE, D.A. 1962. Factors affecting and the significance of 'A 1 values using band placement. "Radioisotopes in Soil-Plant Nutrition Studies", I.A.E.A., 329-342. (15) TERMAN, G.L. and KHASAWNEH. 1968. Crop uptake of fertilizer and soil phos- phoru relation si calculateo t n values' 'A d . Soil Sci. 105: 346-354.

- 138 - TABLE 1 COMPARISON OF BAUD AND MIXED PLACEMENT OF A WATER SOLUBLE FERTILIZER (NH H?PO.) ON 'A' VALUES (KG P/HA) FOR FOUR SOILS

Rat Applicatiof eo n Soil Type kg P/ha • Chemozemic Solonetzic I II I II •

A) NH4H2P04 22 mixed 30.4 76.8 74.5 113 44 mixed 34.3 86.0 75.0 126 r. 22 banded ' 17.4 51.5 29.7 76.2 44 b'anded 16.7 51.0 33.8 72.2 L.S.D. (P = .05) 4.0 7.4 6.8 5.6-

Source; Rennie and Spratt (ll)

. TABLE 2 THT5 INFLUENCE OF INCORPORATED WHEAT 'STRAW QJ. AVAILABLE SOIL PHOSPHORUS (.'.A1 VALU.ES)

Placement of Soil Amendments 'A' value NH4H2P04 kg P/ha mixed N/hg k 0 a 15 126 mixed 40,00 g straw/h0k N/hg k a0 a 540 167 banded N/hg k a0 15 72.0 banded 40,00 straw/hag 0k N/hg k a0 ;40 52.4 L.S.D. (P = .05) . 16.0

Source: Rennie and Spratt (ll)

- 139 - TABLE 3 CONSTANCY OP 'A' VALUES (KG P/HA) USING SEED PLACEMENT OP NH.HpPO. WITH INCREASING FERTILIZER P APPLICATIONS (FIELD EXPERIMENT)

Rate of Soil type application ChernozemiL C . Si - c Calc-Chernozemic - L. P/hg k a 2.6 26 19 5.2 30 24 10.5 28 23 21.0 26 23 42.0 25 22 L.S.D .&5= P ).( ns ns

Source: Spratt and Rennie (14)

TABLE4 THE 'A' VALUE AS AN INDTO OF PLANT AVAILABLE PHOSPHORUS IN SELECTED SUB-GROUP SOIL PROFILE yield NaHCO, Sub-group increase extractablfro/ , m e profile type 'A1 value (pptn) P fertilization^ P (ppm)

li/ III/ I II I II Calcareous dry2/ 12 5 56 19 8 28 wet—' 35 15 29 4 10 22 Orthic dry 12 ' 5 47 38 17 27 wet 43 25 11 25 17 30 Eluviated dry 7 3 84 55 " 8 24 wet 28 21 32 46 10 24 Glysol dry 10 4 48 62 o 24 16 wet 41 24 47 42 25 15

Sourcet Renni Claytod ean ) (9 n profiles developed on glacial till chernozcmic black II profiles develope glacian o d l till chernozeiric dark brown ^dry f storeo -<2m c 5d moisture plus precipitation storef o a weer td 3 moistur>3 e plus precipitation

3/vyiel< d increas0 10 x e check yield

- 140 - TABLE 5 INFLUENCE TH SOIP EO L MOISTURE STRES PLANN SO T GROWTH AND 'A' VALUES (GROWTH CHAMBER EXPERIMENT)

Moisture Grain Yield 1 h ' value Regime (g/Pot) (kg. P/ha) (% Water)

27 - 17 12.5 61 27 - 14 9.1 41 27 - 9 3.2 25 L.S.D. (P = .05) 0.8 7

SourcetSpratt and Rennie (14)

TABLE 6

EFFICIENCY OF VARIOUS MONO- AND DI-HYDROGEW PHOSPHATE CARRIERS USIN ' VALUE'A GINDEN A S XA S (MEAN 6 EXPERIMENT F O S S FOR THE YEARS 1961, 1962 and 1963)

Phosphate Carrier 'A' Value E.R.A.-^/ Relative (kg P/ha) kg P/ha TSfficiency as NH4H2P04 (*)

NH4H2P04 35.2 20.0 100 (NH. )_HPO. 36.7 19.2 95 KH P0 48.6 72 € 4 14.5 K HP0 51.3 13.7 68 2 4 NaH2P04 42.4 16.6 83 . .. Na2HP04 48.0 - 14.6- • ?3

Ca (HJP04)2 55.0 12.8 69 CaHP04 612.0 1.1 5

Source: Data from University of Saskatchewan experiments, using sprin gtese wheath t s cropta . 2/ E.R.A. = Effective Rate of Application, calculated Renniay sb e (11)

- 1 14 - TABLE 7 N-SUPPLYINE ' INDEVALUN •A TH A P S XO EA G CAPACIT P SOILYO S (GROWTH CHAMBER STUDY)

Soil type InitialN Aj,.( value $ Yield (ppm) (ppm)

Evesboro si 9 105 40 Redbai s y 50 . . .; 2 12 49 Miaml si i 17 207 70 Elliol c t 110 271 79 Crosby cl 231 439 93 • udata selected fro soils2 1 lisma f to ; Source; Leg Stanford gan ) (5 d

TABLE 8 '•A'" VALUE DATA (PPM) - RICE (GREENHOUSE EXPERIMENTS) Soil from Rate ..of N. application, kg N/ha 50 100 . 200 U.A.R. 123 122 116 Brazil 61 55 . 61 Romania .159 162 163 Austria 77 91 . 83

Source: Aleksic et. al. (l)

- 142 - SABL3 9 "EFFECEFFICIENCN O P PLACEMENT^ O TO )S H Y(N P O / OP UTILIZATIO FERTILIZERP NO RICY ^B E

Country 1 A ' value , T3.R. A. -surface-' Soil Surface Depth kg/ha PH

U.A.R.I 354 367 124 8.2 U.A.R. II 324 240 89 7.9 Burma 1010 360 43 4.9 Philippines 512 294 69 6.1 Hungary 226 174 72 6.7

The"(NH^y^S'O' — applies kg/h0 Vwa 12 plantint t aa a d g time, . cm i ndeptsurfacea e 5 rowst th f a ho n d ,o , an 2/ ' Calculate— d from N-15 assa finaf yo l grain samples ' E.R.A— .effectiv= e rat applicatiof eo n Source: Joint FAO/IAEA's 1965 co-ordinated rice experiments.

TABL0 E1 CALCULATIONS - EFFECTIVE RATE OF APPLICATION (E.R.A.)

PlacemenN f to . $> N in the grain A,, value derived from |kg/ha) Fertilizer-P Soil-P

Surface 27.0 73.4 032 Depth 33. 3• 66.0 724

Assumptions: surface 1th ^ valu , loso t eA, higs fertilizef ei so e hdu ; rN 2) the depth A— value is more nearly correct than an approximation surface E.R.Ae oth fth r .efo treatmens i t fert.N x A^ value : 27. x 240 « 89 kg/ha 3 7 soi lN

- 143 - TABL1 E1 CALCULATED EFFECTIVE RAT APPLICATIOF O E N/HAQ (K N P SELECTE)6 D NITROGEN CARRIERS COMPARED TO AN (NH4)2S04 STANDARD -'

Location of urea NH*N03 Experiment I Applied at'5 cm depth at planting time-' U.A.R. 120 " 116 44 25' Burma 120 99 48 15 II Applied 2 weeks before primordial initia^ion (on surface) 3 3 5 10 6 18 2 13 U.A.R. Burm9 7 a 2 "1211 ? 4 11

•i/ All carriers applied at a rate of 120 kg N/3aaj data from N-15 assay on final grain samples Source: Joint FAO/IAEA co-ordinated rica fertility experiments

TABLE 12 LABELLE FIELDN D EXPERIMENT, BRAZIL, 1968/69

N Source Treatment-^ Ndf% /f Fertilizer N «A' Value (Grain) E.R.A.-^/ Uptak N/hg ek a kg N/ha kg N/ha as (grai strawn+ ) faas) 87 e=

NaNO, 40*-40- 40 32 34.2 85 41 40 -40*-40 .39 39.6 63 55 40 -40 - 40* 13 6.6 268 13 6o*-60- 0 35 36.2 . 111 48 120*- 0 - -0 74 - 69.0 . ..42 ... 248

(NH4)2S04 40*-40 - 40 24 22.9 127 27 40 -40*-40 37 31.8 68 51 - 0 40-4 40* 2 1.7 I960 2 60*-60 - 0 29 27.4 147 35 120*- 0 - 0 58 53.3 87 120 N-1* 5 labelled nitrogen source 40-4^-4/ i bandeN 0» seedint a d topdrosseg- tillerint a d topdresseg- t a d the boot stage etc1 4 •2/32/6 = . 7 8 8x Source: Contract No. 623, A.M.L. Neptune, Piracicaba, Brazil

- 144 - TABLE 13 »A» VALUE DATA PROM 1968/69 N-15 LABELLED FIELD EXPERIMENT IN BRAZIL NaNO, use s sourcda f nitrogeo e n

Treatment-^/ % NDFF^/ '/.' Value Calculated E.R.A.-' Corrected . / N/hg k a N/hg k graia n 'Af value-' (grain) (base - 42) I 40*-40- 40 32 Si 20 51 40- 40*-40 39 63 27 - - 40 0 -4 40* 13 268 6 - II 60*-60- 0 35 111 23 SL III 120*- -0 0 74 42 120 42

Labelled NaNO, i/.40-40-4 bandeN 0= seedint a d top-dresseg- tillerint da top-dresseg- t da the boot stage. ercentage nitroge graie th nn ni derive d frofertilizere th m . ?' etc0 2 ^/32/6 = . 2 4 8x 0 6 - 1 4/811 (27+65- ; 52 )= 51.

Source* Contract No. 623, A.M.L. Neptune, Piracicaba, Brazil.

TABLE 14 «A« VALUE DATA PROM 1968/69 N-15 LABELLED FIELD EXPERIMEN BRAZIN TI L SO. USED AS SOURCE OF NITROGEN

Treatment-'' ^SHDFP^ •A' Value Calculated E.R.A.^ Corrected-'' grain kg N/ha kg N/ha 'A' value (grain) ) (bas87 e= I 40*-40-40 24 121 27 84 40-40*-40 37 68 51 40-4n-40* 2 I960 2 II 60*-6C-0 29 141 35 SI III 120*-0-0 58 81 120 81

*Labelled (NH ' S0 I/ 4 »2 4 40-40-4/ i I 0= r banded at a(eedinsr - to-od]r-esse t tillerina d g— tondreaane th t a d boot stage —'percentag—2'/ e nitroge graie th nn ni derive d frofertilizere mth . •2/24/76 i 8? = 2? etc. 4/127 - (51+2) = 84; 147 - 6u = 87. Source: Contrac 623. tNo , A.M.L. Neptune, Piracicaba, Brazil

- 145 - JIWSNCE 0." 'N7A W>f*,K*l !)KiiH€TBNn ' "AU.TA ' N O O =?(>» m v 1!^ 0? PHOSPHORUS :-'RRTTl.T7

200

UO

110

« 6 3 » tt Ib M PER ACRE

(11)

a , Ci Figure 2. Calculated 'Effective Rat Applicationf eo * (E.R.A.') Figure 3. R lationship between 'E.R.A.', and fertilizer N uptake closely approximate percene sth t nitrogee th n ni (based on grain plus straw yield functions) grain derived frofertilizee mth r (NDFF)

o> £ 90

f 80 UJ 5 70 z o * actual rate of application 0 o6 » o o effectivxs e rat applicatiof eo n :•

W 40 00 30

20

10

0 9 0 8 0 7 0 6 0 5 0 4 0 3 0 2 10 10 20 30 40 50 60 70 80 90 100 F •/OF .N FERTILIZER N UPTAKE kgN/ha PAT FERTILIZEF EO R NITROGEN APPLIE SOILO DT S J.O. Legg U.S. Department of Agriculture, Beltsville, Maryland, U.S.A.

ABSTRACT

A review of recent research involving 15N as a tracer indicates an acceleration of experimental work concerned with the fate of fertilizer nitrogen applied to soils. Factors influencing the efficient utilization of applied nitrogen, including placement, timin applicationsf go , nitrogen sourced san rates, and crop cultural conditions, have been examined. These factors are also related to nitrogen losses, which vary greatly with experimental conditions. Several studies of 15u-labelled fertilizer which has "become immobilized in the soil organic fraction indicate that the ^5n is incorporated into organic forms similar in composition to a large fraction of the indigenous soil nitrogen in a relatively short time.

- 146 - 1. INTRODUCTION

Expanded use of chemical fertilizers provides one of the means by which the gap between world food productio populatiod nan n decreasedgrowte b n hca n I . many area productioe sth distributiod nan chemicaf no l fertilizer meet no to sd the current need agriculturef so ; therefore efficience ,th y with whice hth available fertilizer is used becomes a critical factor. This is particularly case nitrogeth f trueo n ei n fertilizer, since nitroge susceptibls ni o et numerous biological and chemical transformations which may lead to rapid losses from the soil, or to conversion of mineral nitrogen into relatively unavailable organic forms. Much of the present knowledge concerning nitrogen in soils has been brought togethe monograpa n ri Bartholomey hb Clard wan k (?)• This monograps hha summarize evaluated dan numbea d variouf ro s aspect nitrogef so n researchd ,an serves as a guide in projecting future research. Allison (2, 4) has also reviewed earlier research concerned with the fate of nitrogen in soils. It will purpose th e thif b eo s report, therefore revieo ,t w onlmore yth e recent literature pertinent to the subject matter, and to discuss briefly some data recently obtained in the author's current research programme.

FERTILIZE. 2 R NITROGE SOIE TH L N NNITROGEI N CYCLE

Aliison (3) presented a rather complete diagram of the nitrogen cycle which permit overaln sa possiblle vieth f wo e reactions involved when fertilizer nitroge addes ni soilo t d . This diagra broadls i m y divided into three sections: nitrogen sources, transformations, and utilization. Part of the nitrogen enterin systee gth m from fertilizer source quickle b y sma y remove plany db t uptake, A portion of the nitrogen removed by plants may be recycled into the system through crop residues and manures, resulting in a lower net removal and a con- version of inorganic nitrogen into organic forms. The fertilizer nitrogen not remove planty db subjecs si immobilizatioo t microorganismy nb losseo t d ssan through denitrification and leaching. All of these processes involved are interrelated somt ,bu e separatio npurpose wilth mad e lr b discussionf eo efo .

PLAN. 3 T UPTAK NITROGEP EO N

The usual purpose of adding fertilizer nitrogen to soils is to obtain maximum yiel qualitd an d cropf yo s within certain economic restrictions. Maximum utili- zatio applief no d nitrogeimportann a croe s th pi y nb t consideratio attaininn ni g this purpose. Furthermore, as more fertilizer nitrogen is utilized by the crop, less remains in the soil system for possible loss or immobilization by micro- organisms. It is generally recognized that 50$ or less of applied nitrogen is usually taken up by a crop, although this figure may vary considerably. A number of recent experiments wit havN h15 e been directed toward increasin efficience gth y nitrogef o n utilizatio planty nb s through better placemen timd applicatiotan f eo n of the fertilizer (l, 11, 1?, 18, 21, 42). Much of this work has been concerned with rice production and lessea ,o t r extent, with maize.

- 147 - Rice presents some unique problems with respect to nitrogen nutrition. Sub- merged soils develop two distinct layers: a surface oxidizing layer of a few millimeters thickness deepea d ,an r surface laye chemicalla r n whici s i h y reduced state. Surface-applied ammonium nitrogen is subject to nitrification and subsequent denitrification; however, if the ammonium is placed in the subsurface layer, it is less likely to be chemically altered. Prom this standpoint alone, placemen nitrogef to ricn ni e culture assume importann sa t role. e recenTh t data obtaine y Aleksidb c _et_ al_. (l), show Tabln ni , illustrateI e the recovery of ^u-labelled (NH ) SO. by rice in greenhouse tests. It is quite evident from the data that placement at 7-cm depth resulted in increased nitrogen uptake and decreased nitrogen loss, although plant growth was not always increased by the increase in nitrogen uptake. The reduction in gaseous losses obtained by placement at shallow depth approximately accounts for the increase in nitrogen utilization. Broadbent and Mikkelsen (ll) obtained a significantly lower grain yield of rice from broadcast applications than from other types of placement. Recovery in the plants varied from 26 to 47$ of the labelled nitrogen, with highest recoveries from banded plus topdressin frod gan m banded treatment highese th t sa t (NH.) rate. pSO . FertilizesN) m (aboupp 0 t6 r nitrogen losses rangeo dt fro5 6. m 30.5$. Highest loss was from topdressed urea in split applications, and lowest losfros swa m banded Time of application is also important in placement studies. 'Patnaik and Broadbent (42) foun "thf do thae$ nitroge51 t n topdresse booe th t t staga d s ewa taken up by plants as compared with 32$ of the nitrogen topdressed at tillering. This is possibly related to the particular type of root growth that occurs at the boot stage reporo N . s givet wa nitroge f no n los thin si s case. The results given above are in general agreement with those reported earlier by Fried (21 ) and by the International Rice Research Institute (25). Another factor involved in some of the studies reported is that nitrogen from (NH.)2SO. is generally used more efficiently by rice than is nitrogen from urea, although yields may not be affected,

Cho j|t_ al^. (17 ) hav,18 e recently conducted field experiments wit, ^N h using maize as the test crop. The soil in the experiment was not low in available nitrogen, and they found no yield response; however, there were differences in uptake of the applied nitrogen. In early stages of growth, more nitrogen was taken up when the fertilizer was placed near the plant, but these differences decreased with maturity. Utilization of the applied nitrogen increased with age of the maize, and amounted to approximately 30 to 40$ at maturity. non-tracea n I r field experiment with maize ,. (37Olsoal )t e demonstraten d that utilization of nitrogen applied at 40 and 80 Ibs/acre was greater with summer sidedressing than with fall or spring application. For example, at the 40-lb/ nitrogeacre th e f utilizes rateo nwa $ ,25 d from fall application, s whereawa $ s58 utilized by plants summer sidedressed. In a separate field experiment they nitrogene th recovere graine f o th $ , n 0 Ibs/acr )applie77 4 rat(i e d f th eo t da e sidedressed, compared with a low recovery of 37$ from 160 Ibs/acre fall applied.

- 148 - Recent work on a series of isotopic studios concerned with the uptake of nitrogen "by pasture plants has been reported by Vallis et_ al. (52) and by Henzell ot_ al_. (24). In these studies inorganic and organic nitrogen sources, • respectively, were used, In both cases a legume and Ehodesgrass were grown separatel d togetheryan . Grown separately legume , th grasd ean s too p abouku t equal amounts of *5N. When grown together, the grass was a very strong compe- tito availablr rfo e nitrogen. Little nitroge transferres nwa d frolegume th m e to the associated grass. Simpson and Preney (45) worked with three pasture soils of different organic matter contents and obtained 80$ recovery 4f labelled nitrate nitroge threy nb e cutting ryegrasf so s frosoilso tw m . Ammonium nitrogen was immobilized rapidly, especially in the low-nitrogen soil, and thus plant recover s loweredwa y . Other plant uptake studies wil consideree lb n i d the following section.

NITROG5. 4 N LOSSES

Nitrogen losses from fertilizer applications to soil may be generally classifie gaseous a d s losse leachinr so g losses. Quantitative determinations of such losses are not easily made directly, since a controlled atmosphere is usually require formere lysimeteth a n d dlattei e , an th n ri typ lossf eo . Most of the data concerning gaseous losses has been determined indirectly as the difference between fertilizer nitrogen added and that recovered in the soil and plants, where leaching has been prevented. An account of the fertilizer nitrogen balanc thus ei s obtained. tracea s a rN allow f o se precisus e Th e measurement fertilizef so r nitrogen in the soil-plant system, especially in greenhouse tests. Field tests may also be used successfully to determine nitrogen balance (15, 36) by using micro-ploa t system (small areas within cylinders forced intsoil)e th on I . the latter case careful soil sampling is of the utmost importance. More recently lysimeters ,ga s have been devised which allow measurement botf so h gaseou leachind san g losses (34 43), ,39 . Volatilization of ammonia from soils will not be considered here to any great extent. Other gaseous losse generalle sar y considere resulo dt t primarily from denitrification. Such losses occur quite commonly, even in well-controlled greenhouse experiments, as evidenced by deficits in nitrogen balance sheets. Water movement in some soils may be slow enough to create small waterlogged areas in which denitrificatinn can occur readily. Frequent waterings required in greenhouse experiments accentuate this condition numbeA . othef ro r factors possibly involved in gaseous nitrogen losses have been discussed recently elsewhere (4, 10). One might expect that denitrification would be decreased by increased capacity of a soil to fix ammonium, since fixed ammonium is not readily available to microorganisms. Recently, Atanasiu et al. (6) carried out several nitrogen balance studies with ^5]j»iabelled ammonium and nitrate sources, applied to soils having different ammonium fixation capacities. After growing oats in Mitscherlich pots, appliee losseth f o sd $ wernitrogen muc30 s a e s ha e foun b o }t d however, clear-cuo thern s ewa t relationship between ammonium fixatio nitroged nan n loss. experimene on n I t nitrogen losses were higher with both nitrogen sourcea n so soil of high fixation capacity as compared with a soil of low fixation capacity. case Iammoniumf nth eo difference ,th nitrogen i e n los smals swa l (14 12$. $vs )

- 149 - betwee highe nth low-fixind -an g soils anothen I , r experiment, their data show considerably less nitrogen loss from a high-fixing than from a medium-fixing soil; however, ther littls ewa e difference between nitrogen sources, indicating that ammonium fixation was not a particularly important factor. Furthermore, the lower plant uptake of nitrogen from the medium-fixing soil approximately accounts for the difference in nitrogen loss between the high- and medium-fixing soils. Gasser et al. (22) determined nitrogon losses from applications of labelled

(NH.)pSO,. and Ca^NO, )„, with and withovt the nitrification inhibitor 2-chloro-6- -(tnrichloromethyl)-pyridin3., +o four ^-loc'.o soile th d s f o soilswer o eTw .fro m old arable werfieldso tw e d fro,an m grasslandH p a d e soi ha f On oac.lo t se h of about 5, while the othors had a pH of about 6. In the first part of the experimen treatee th t d soils were incubato weeks6 potn r i d sfo . Essentially

complete recovery of -^H was obtained upon analysis of the incubated samples. Lowest recovery (94$) was from (NH.)pSO. after 6 weeks 1 incubation; after subse- quent cropping with ryegrass, recovery $as lowest (86$) with Ca(NO,)_ applied to grassland soil. Influenc nitrificatioa th f eo n inhibito minors rwa . Result othef so r recent nitrogen balance studie e givet I s ar Tabl n ni . eII is difficult to generalize regarding nitrogen losses where soils, nitrogen source d ratessan d experimenta,an l conditions vary considerably date th a f I . are representative, however, loeses can b^ expected to exceed 20$ of the nitrogen addition about 5*"*$ of the time. Where the investigators compared nitrate and ammonium sources date ,th a indicate that losses from nitrate were neither consi- stently highe lower rno r than those from ammonium. Carte. (15d al )an t re Zamyatin . (55 al ) foun_ » 56 a ^t differenco dn e betweeo sourcetw e nth s during cropping, and Broadbent and Nakashima (13) found losses from urea to be essentially the sam thoss ea e from nitrate sources. Under submerged conditions coursef ,o , nitrate nitroge e completelb y nma y vera los n yi t short tim shows a e y MacRanb e . (33)eal t . Marti Rosd nan s (34) conducte nitrogea d n balance study, using labelled fertilizer in a gas lysimeter. They reported negligible gaseous losses of Np, NpONH,d d obtainean , ,an n averaga d e recover adde e 100f th yo df $ o 15f l froe th m soil-plant system. Overrein (39) conducted a somewhat similar type of experiment, using 15u-labelled urea, and found the highest total accumulated loss of NIL equa addee 3.5o th t l df $ o nitrogon . Other gaseous losse nitrogef so n were found onl tracn yi e amounts. Durin 12-tfeee gth k experimental perio whicn i dtotae hth l precipitation was about 3?0 mm: the -iccuiralated loss by leaching was slight at urea application rates less thakg/ha0 25 n . Leaching loss fro 1000-kg/hma a rate addee th df o nitrogen $ s equa5 wa o t l , Leaching losse f so N-leboile d nitrogen have been evaluated recently yb Takal:ash conjunction i n with lysimete field ran d studie nitrogef so n uptaky eb sugarcan Hawain ei 51), i 50 (48 ., ,Usually49 , from one-thir one-halO G de th f fo applied nitroge s re-coveren wa plan e th tn i dmate-rial , including leaf trasd han th•-; succeeding ratoon crop, Takahashi considered tha nitrogete th mos f to n remainin soie th l n aftegi r crop growt s immobilizehwa organin i d c form d thasan t little leaching occurred lysimetee th n I . r experiments (50, N 51)^ e ,th concentration of the percolates was very low; however, the amount of soil inorganic nitrogen in percolates vas relatively high during the first month or two of plant growth, and throughout the experiment in fallow lysimeters. This points towar importance th d activelf o e y growing plant reducinn si g leaching losses.

- 150 - Methods other than those involving conventional lysimeters have been used in recent years to study the downward movement of nitrogen. Wagner (53) estimated leaching by the porous cup method, designed to sample internal drainage waters within the soil profile. Water samples collected periodically during 4 years indicated that a significant amount of nitrate nitrogen had leached through the subsoi plots^treaten lo 0 Ibs/acr40 r do nitrogenwit f eo 0 h20 . Total nitratn ei profile fertilizef so d plots decreased with time d afte,an r three successive sudangras thas a contron i tw lo s lsa plotscropss wa e t th .,i f o Abou $ 35 t applied fertilize recoveres r wa sudangrass e th n i d . Kraus Batscd ean h (28) used tension-plate lysimeters 30-cplacee th mt da depth to study the movement of fall-applied nitrogen in a sandy soil at Ontario, Canada. They treated the 15-cm surface layer of soil with NH.NO, at the rate of kg/h2 collecte11 d aan d leachate weeklt sa y monthsintervals3 o t 2 ' n timeI . , the applied nitrogen moved almost completely to the 30-cra layer, primarily in the nitrate form. Apparently, nitrification of ammonium proceeded rather rapidly under suboptimum conditions. Pro"foregoine mth easils i t gi y seen that fertilizer nitrogen losses from soils may be quite large and difficult to control under experimental, as well as practical, conditions. Broadbent and Clark (10) and Parr (41) have discussed the possibilities of eliminating gaseous nitrogen losses, but at the present time, excep specian i t l cases, this doe appea t economicalle sno b o rt y feasible. The nitrogen losses shown in Table II took place primarily during short-term experiments. Broadbent and Clark (10), however, consider that losses taking place at low rates over long periods of time arc; probably of greater significance. The slower losse presumee sar resulo t d t from denitrificatio anaerobin ni nearlr co y anaerobic microareas of otherwise well-aerated soils. Denitrification losses resulting from the movement of nitrates downward into the lower part of the soil profile are probably insignificant (10) owing to the low energy supply for denitri- fiers. Downward movement of nitrates is also more likely to take place during seasons when plants are not actively growing and temperatures are low. movemene Th mineraf o t l nitrogen downward, however effectively ,ma y removt ei frorooe mth t zone belo s d i oncroote ,an t wth ei s ther s littlei e evidence that appreciable movement upward occurs least ,a humin i t d regions. Little information is available on the fate of mineral nitrogen under natural conditions, once it is leached beyond the root zone. Investigations along this line will probably be accelerated in the near future, owing to the increased use of nitrogen fertilizers and their possible accumulation in ground water.

5. IMMOBILIZATION-MINERALIZATION REACTIONS

From Table II it can be seen that the fertilizer nitrogen remaining in the soil after cropping amounts to 20$ or more of the application rate in most cases. I-Iost of the residual fertilizer nitrogen, particularly after exhaustive cropping in -i;he greenhouse, is immobilized in organic forms and becomes slowly available to subsequent crops amoune Th . inorganif to c fertilizer nitrogen tha transformes i t d into organic forms, and the rate at which it is mineralized have been subjects of a number of recent investigations.

- 151 - nitrogee Th n transformation n soilsi s tha immobilizatioe t th lea o t d f no applied inorganic nitrogen are not completely understood, but use of *5]J as a tracer has produced some very useful information in this regard. Basically, it is known that mineralization-immobilization reactions proceed simultaneously thad ,an t measures of either reaction arc essentially net differences between the two reactions. When a state of equilibrium exists, no change will be observed in the inorganic nitrogen content, although microbiological activity continues. Normally, however, either immobilization or mineralization predominates, and measurable changes occur. ratiN C/ mos f o e tTh soil sucs i s habsence th tha n i tfresf e o h additionn a f o s available carbon source soie ,th l organic matte slowls ri y decomposed during incubation under aerobic conditions, liberatin carboge e th par th s CO,,f na to d an , organic nitroge mineras na largels i l? formsC0 y e dissipateTh . d intatmoe oth - sphere, while the mineral nitrogen accumulates in the soil, usually in the nitrate form. Jansson (26, 2?) has pointed out that accumulated nitrate forms a passive pool of mineral nitroge soin ni l recyclet whicno s hi d into immobilization-mineralization reactions. If soil conditions are such that net immobilization occurs, however, nitrate wil accumulatt lno greay an to e t extent d addo,an d nitrate nitrogen will be immobilized (9). On the other hand, when -^H-labelled nitrate nitrogen is added to soils in which net mineralization is occurring, it can be recovered almost completely in the mineral form after 30 or 40 days of incubation (8, 31). One

might expect that plants could effect similar recrovs^ries however s show,a Legy nb g and Allison (30) from 10 to 36$ of the nitrogen fro5n«im1 belled NaNO, remained

soie inth l after exhaustive croppin same th e f soilgo s that wer incue e th use -n i d a bation experiment. Insofar as possible, roots were excluded from the soil analyses by removal at the end of the experiment. Only 2 or 3$ of the labelled nitrogen was accounted for by the harvested roots from the last crop. Such results emphasize the growine effecth f to gimmobilizatioe th cro n po fertilizef no r nitrogee th n i n soil. This effect can be explained on the basis that plant roots are contributing available carbon to soil microorganisms throughout the growth period, and that mineral nitroge immobilizes ni microbian di l tissue e amountTh . nitrogef so n involved are usually too large to be accounted for in roots not removed from the soil. e influenc Th rooe th t f systeo e microbian o m l activitie bees sha n recognized for many years; however, there is considerable disagreement on the magnitude of the contribution of roots to the energy supply of microorganisms during the plant growth period. Such contributions may have been underestimated. Recently, Samtsovich (44) presented data indicatin presence gth transparenf eo t gel-like substances on the root tips of a number of plants. This substance forms a protec- tive zone aroun rooe th dt caps, meristom elongatiod ,an n areasabundantls i d ,an y filled with plant cells which continuously disengage f.rorooe th mt capse Th . material is invisible if unstained, but becomes quite distinct in tho microscope if the roots are stained with methylene blue or gentian violet. Samtsevich esti- mated the volume of the gel-liko substance produced by wheat and maize, and con- cluded that even if the material contained only ifo dry matter, during the vegetative period plants exude into the soil via their roots at least as much dry matter as is produced in high yields of the crops (7 metric tons/ha for wintor wheat and 12.5 tons for maize). He suggested that the amount of excretions is even greater, especiall perenniar yfo l plants. Tost sugarsr sfo , amino acids, proteinsd ,an starch were negativsubstance th r efo e obtained from tese maizehemir th tfo t -,bu cellulos positives ewa . More wor thin ki s area should greatea lea o t d r under- standing of the plant effect on fertilizer immobilization in soils. - 152 - Immobilization of -%-labelled nitrogen accompanying the incorporation of plant residues, such, as straw, into soil has been of continued interest to a

number of investigators. Broadbent and Tyler (14) studied the effect of pH on nitrogen immobilization fro5n-labcllem1 d NH.C d KMO,1an ,soilo addetw so t dwit h or without 0.5$ straw. The ammonium sourco was used to a greater extent by microorganisms at all pH levels, but there was a marked influence of pH on the quantity immobilized. Ammonium nitrogen immobilization increased with an increase wherea, inpH reverse nitratth so trus th ewa f e o e sourco resulte Th . s appeared to be related to the physiological acidity or alkalinity of the nitrogen source. Analyse f aciso d hydrolysates indicated tha nitrogee t th mos f o t n incorporated intorganie oth c fractio presens amine nwa th on i tform . A number of other factors involved in nitrogen immobilization have been studied. Overrei Broadbend nan t (40 Overreid )an n (38) have investigatee th d influenc temperaturf o e nitroged ean n source immobilization-mineralization so n reactions involved in the decomposition of forest litter. Preferential utiliza- tion of ammonium was found regardless of soil temperature in the range of 40 to 90 F. In some soils the nitrifying microbial population was able to compete effectively for'ammonium with the hcterotrophic microflora, and considerable nitrification took place. Increases in immobilization of nitrogen in soil by additions of organic matter with high C/N ratios have been observedfor many years. Usually the C/N decomposine ratith f o gn i materia ) N $ 2 lo 5 (abou t 2 mus 5 o beloe t tb 1. t 0 2 w orde appreciablr rfo mineralizatiot ene tako t n e place somn I .e recent work with submerged rice soils, Williams _et_ al_. (54) observed net nitrogen immobilization onle tob y originae 0.54th f $weighy o ldr addef to d rice stra determines wa y db grain yield responses. This lower value was attributed to the anaerobic environ- floodee th men f o td soil which resulte n incompleti d e decompositio carboe th f -o n naceous material n thiI .s experiment, carrie without ou d t tracer nitrogeno ,n significant immobilization of supplemental nitrogen resulted from straw applications, Danneberg et al. (19) studied the transformation of N-labelled ammonium during aerobic decompositio choppef no d maize leave0 days period18 r sfo o . t p su They found that the added ammonium was immobilized in organic compounds mainly during the first 10 days. The largest amount was in a "protein" fraction, the total nitrogen of which increased up to 30 days, indicating a marked synthesis of microbial protein. This fraction decreased late microbias ra l substances decomposed. There was also a marked synchesis cf humic substances, especially in the early part of the incubation, as indicated by an increase in the acid-insoluble "humin" fraction; however, this fraction contained a relatively small amount of labelled nitrogen. This experimen absence th s carrie n soilf i twa eo t d ,ou an d was somewhat similar to a decomposition experiment with oat straw, reported by Bartholomed Kuoan w (29). They concluded that essentiall nitrogee th f o n i nl yal the plant material had been mineralizedj therefore, it may be surmised that the remaining organic nitrogen resided primarily in microbial tissue. Their conclusion face bases th t wa n thao dtracee th t r content organio th d inorganif o scan c phases tende approaco t d h equivalenc resula s ea nitrogef to n interchange. The equivalence of labelled nitrogen in soils has been studied in plant uptake and mineralization studie Broadbeny sb Nakashimd tan a (12)thein I . r experiments a quantity designated as "availability ratio" was calculated according to the equation:

- 153 - . Tc T + U Availability ration = c c Ts Us+Ts where T = tagged N in plant material (or in mineralized N from incubations), C U = untagged H in the corresponding material above, C T = tagged N in soil at beginning of vegetative or incubation period, s U « untagged N in soil at the same time. tracee th f rI nitrogesame th e soia s availabilitn lha ni planto yt r so microorganism soie th l s nitrogensa availabilite ,th y ratio wil unitye lb n O . the other hand, if it is more available than soil nitrogen, the ratio will be greater than unity. Broadbent and Nakashima (12) found that in successive cuttings of sudangrass, availability ratios ranged from 11.9 i*1 the second cutting to 1.2 in the seventh cutting of plants grown on Yolo soil. The ratios were decrease additioe th y soil e db straf th o n incubatio I .o wt n tests days2 59 lastin o ,t severap gu l ratios belo 0 werw1. e eth obtained r fo t bu , most part they were between 1 and 2 during the latter half of the experiment. Recently, Legg (unpublished) carried out a long-term greenhouse experiment in which -^U-labelled (NH,)pSO. was incorporated into the soil organic matter y successivb e cropping with oats plane Th .t materia returnes soile lwa th ,o t d excep potr tfo s which were remove f eacdo frohd experimene en th m e th t a t cropping period. Plant materia d soilan l fro mtriplicatf o «act so h e pots were analyse r tota 1d fo 5n-labelle an l d nitrogen resultse Th . , calculate termn i d s of availability ratios, declined fro initian a m l valu approximatel10.f o eo t 4 y experimente th f o d en . e Soith t la sample2 s obtaine croppin8 d dan afte5 g , 2 r periods were incubated at 35°C and leached with 0.01 IJ CaCl, (followed by -N solution) at bi-weekly intervals for 40 woeks. The availability ratio, calcu- mineralizee th late r fo d d nitroge t each.incubationa n period, gradually declined second-croe th r fo p soil s approximateluntiwa t li thereafte; y2 remainet ri d essentially constant. For the fifth- and eight-crop soils, little change was noted in availability ratios which remained somewhat above- 2 throughout the incubation period date Th .a suggest oha relativeln i t y short interchange periods inorganic nitrogen applied to soils may be converted to stable organic forms which are similar to the indigenous organic nitrogen. It could be speculated that with a soil having a stable availability ratio of 2, one-half of the indigenous soil organic nitroge essentialls ni y inert owin physicao gt bior lo - chemical inaccessibility to microorganisms. Stanford e_£ al_» (47) subjected samples of the fifth-crop soil mentioned abov repeateo et d extractions with boiling CaCl, t 0.0autoclavinf r o 1 ,, (10C) 0 g (121°C) bothr ,o studo ,t behavioue yth propertied ran immobilizef so d fertilizer nitrogen relative to soil organic nitrogen. They found the distribution of 15N among chemical fractions of the hot-water extracts, acid hydrolysate, and acid- insolublu portion to be similar to the distribution of indigenous soil nitrogen. Since appreciable equilibration between added ^-^jj Q^^ the more resistant forms soif o l organic nitrogen appeared unlikely postulates wa t ,i d thafertilizee th t r nitrogen reacte foro w compoundst d mne , simila n compositiori pre-existino nt g form soif so l nitrogen. This view seeme harmonn i d y wit observatioe hth n that

the percentage removals of total and ^-%_iabiij nitrogen by repeated extraction e e( - 154 - wore almost identical, even when recoverie hot-watey sb r extraction attained morer o $ . 55 Usin same gth e soil, Tout different frac^ionatio d extractionan n procedures, ChiChester (l6) found evidence to support the hypothesis that the labelled and unlabelled form organif so c nitroge similae nar compositionn ri initialle H . y separated the organo-mineral components of the soil into separate size fractions sievint bywe d centrifagatiogan n without using chemical dispersing agents. The resulting silt-size separate was then subjected to repeated 15-minute ultra- sonic vibration treatments, followed by centrifugation to separate the clay-size material which resulted from the physical dispersion. The separates were extracte sodiud, N extracte wit 5 th m h0. d pyrophosphat an s , werC 0 e 10 t ea fractionated into distillable, acid-hydrolyzable, ninhydrin-reactive, and residual nitrogen components. Some of the results obtained in this study, presente Figurn i d illustrat, e1 similarite eth composition i y labellee th f o n d and unlabelled fractions for the different treatments. It appears highly significant that biological, chemical physicad ,an l method same s th leae o t conclusiod n concernin fate gth immobilizef eo d fertilizer nitroge soiln ni . possiblt Althougno o into'ths g i o t t ehi e detaile th f so above researc thin hi s report appeart ,i s likely that finding thif so s nature will have considerable influence on our basic understanding of immobilization- mineralization reactions, and on the projection of new research in this area in the near future.

6. CONCLUSIONS

Tremendous progress in nitrogen research has been made in recent years throtigh the utilization of -^H as a tracer. The number and variety of experi- ments conducted have provide wealta d informatiof ho n concernin fate f gth eo fertilizer nitrogen in soils under many different conditions. In many cases this information is of direct practical importance in the efficient regulation of the nitrogen nutrition of plants. The magnitude and importance of nitrogen losses from soils have been clearl -^u,.anf o ye methodw depicteus dne e th e sar y db being devised to -3tudy this complex problem. Transformations of inorganic ferti- lizer nitrogen into organic form soin si l produce compounds which appear similar to indigenous soil organic nitrogen in a relatively short period, according to several-recent experiments. Further research on nitrogen transformations in soils shoul acceleratee db thesy db e recent advances.

- 155 - REFERENCES

) ALEKSIC(1 _e. ,A t al., Shallow depth placemen (NH^SOf o t submergen ,i d rice soils as related to gaseous losses of fertilizer nitrogen and fertilizer efficiency, Plant and Soil 2£ 2 (1968) 338^ ) ALLISON(2 , F.E. enigme ,Th soif ao l nitrogen balance sheets, Adv Agronn .i . I (1955) 213. V (3) ______• Evaluation of incoming and outgoing processes that affect soil nitrogen, Agron (1965O .J. ) 573. fate nitrogeTh f eo ' , n applie soilso t d ) , (4 Adv Agron.n i 6 .1 (1966; 219. ' . (5) ANDREEVA, E.A., SHCHEOLOVA, G.M., Utilization of nitrogen fertilizers by plants (Experiments with 15N isotope), Pochvovedenie (19.64) 47 (in Russian), (6) ATANASIU, VON N. e£ al_. N-Bilanzrechnungen mittels % im N-Mngungsverf ahr en. ) BARTHOLOMEW(7 , W.V., CLARK, F.E., eds., "Soil Nitrogen", Agro _ (1965)n10 . (8) BROAUBEtIT, P.B., Effect of fertilizer nitrogen on the release of soil nitrogen, Soil Sci. Soc. Amer. Proc. 29^ (1965) 692. ) ______(9 , Interchange between inorgani organid can c nitroge soilsn ni , Hilgardia 3J_ 6 (1966} 165. (10). _____. CLARK, F.E., Benitrification, Agron. 0£ (1965> 347. (11) ______, MIKKELSEH, E.S., Influenc placemenf eo uptakn o t taggef eo d nitrogen by rice, Agron. J. 60 (1968) 674. (12) _____ , MAKASHIMA, T., Reversion of fertilizer nitrogen in soils, Soil Sci. Soc. Amer. Proc. 31 5 (196?) 648* (13 ).__. ______. _ Plan, t uptak residuad ean ltaggex valusi f deo .nitrogen fertilizers (Sorghum sudanensis, Lycopersicon esculentunu Zea mays), .Soil .Sci. Soc: . Amer, Proc 3 (1968) 2 ,3 - 388. (14) ______, TYLER, K.B. nitrogen ,o EffecH p f no t immobilizatioo tw n ni California soils, Plan (19653 Soid 3 tan 2 l ) 314. (15) CARTER, J-»jJ al^.£ e . , Recover fertilizef yo r nitrogen under field conditions using ^N-labelled fertilizers, Soil Sci. Soc. Amer. Proc. 31^ (1967) 50. (16) CHICHESTER, F.W., Transformations of fertilizer nitrogen in soil. II. Total and •'•5N-labelled nitroge soif no l organic-mineral sedimentation fractions. (Submitted for publ.). (17) CHO al_.± ,N e fiel^ CHA, O IdMO experiment with maize withi framewore nth k of an international program, Trans. 8th Intern. Congr. Soil Sci., Bucharest, Romania IV (1964) 87.

- 156 - (18) ______al.t effece .e ,Th placemenf to utilizatioe th n o t nitrogef no n •"by maize as determined with 15ii-labelled ammonium sulphate. In: Proc of the Symposium on Isotopes in Plant Nutrition and Physiology, 5-9 Sept., 1966, Vienna, Austria (196?) 47. (19) DANNE3ERG, O.K. Transformatio, et. _al n -%-labelleno d ammonium during aerobic decompositio planf no t material. Proc Symposiumf ,o : Isotope Studies on the Nitrogen Chain, Vienna, Austria (1968) 89. (20) DINTSCHEFF, D» , Untersuchvngfcn tlber die Stickstoffverluste im Boden unter Anwendung des stabilen Isotops -^N, Trans 8th Intern. Congr. Soil Sci., Bucharest, Romani (1964V aI ) 1C05. (21) PRIED 196e Repor, 196d ,th M. 4an n 5 o t resultjoine th tf so PAO/IAE A Divisions co-operative research programm ricn eo e fertilization using isotope techniques. Intern. Rice Commission — Working Party on Rice Soils, Water and Fertilizer Practices — Lake Charles, La. (1966), (22) GASSER, J.K. jet_ al^ , Measurement of losses from fertilizer nitrogen during

incubatio acin ni d sandy soil durind san g subsequent growt ryegrassf ho , usin5N-labelleg1 d fertilizers, J. Soil Sci, 18 2 (196?) 289. stude th nitrogef yo n (23 i )N ^ GIRBUCHEVn f uptako e us e, DIHCHEV ,e I. Th , ,D, and metabolis plantsn i m , Symposium e Procth f .o : Isotope Studiee th n so Nitrogen Chain, Vienna, Austria (1968) 63. (in Russian). (24) HHfZELL, E.F. et_ aj^ .Isotopi, c studieuptake th nitrogef n eo so pastury nb e plants. Uptake of nitrogen from labelled plant material by Rhodesgrass and oiratro. Aust Agr, .J . Res(19681 9 .1 . )65 (25) INTERNATIONAL RICE RESTSAHCH INSTITUTE, Annual Report Banoss ,Lo , Laguna, Philippines (1965) (26) JANSSON, S.L., Trace? studie nitrogen si n transformation soin si l with special attention to mineralization-immobilization relationships. Kgl. Lantbruks-Eogskol. Ann (19584 ,2 ) 101- " f* (27) ______Nitroge, n transformatio soin ni l organic matter, Rpt. FAO/IAEA TechIsotopef o e . Us MeetinSoi n si e lth Organin go c Matter Studies, Braunschweig (1966) 283, (28) KRAUSE, H.H, BATSCH, W_, Movement of fall-applied nitrogen in sandy soil. Can. J. Soil Sci. 48 (1968) 363. (29) KUO, M.H., BARTHOLOMEW genesie , th W,V n organif O so ., c nitroge decomn ni - posed plan^ residue, Rept, FAO/IAEA Tech. Meeting on the. Use of laotopes in Soil Organic Matter Studies, Braunschweig (1966) 329. (30) LEGO, J.O., ALLISON, F.E. , A tracer study of nitrogen balance and residual nitrogen availability wit soils2 h1 , Soil Sci. Soc. Amer. Proc3 1 .3 (1967) 403. "~ (31) ____ ; ____ , STANFORD, G. , Utilization of soil and fertilizer N by oats in relatio available th o nt estatuN soilsf so , Soil Sci. Soc. Amer. Proc. 3JL 2 (1967) 215. . .

- 157 - (32) ______j3t_ al. , The influence of microorganisms on the degree of assimilation of nitrogen by plants from soil and fertilizer., Izvest. Timiryaz. Sel'khoz. Akad Russian) n (1966.1 (i . )22 . (33) MacRAE, I.C al_t .e . Pat nitratf eo e nitroge somn ni e tropical soils following submergence, Soil Sci, 105 (1968) 327. (34) MARTIN, A.E., ROSS, P.,0. nitrogen-balanc,A e study using labelled fertilizer lysimeters ga ina , Plan Soid 8 (1968tan 2 l ) 182. (35) MERZARI, A.H., BROLSHART utilizatioe Th , . ,H ricy nb nitrogef o e n from ammonium fertilizer affectes sa fertilizey db r placemen microbiolod tan - gical activity, Proc. of the Symposium: Isotope Studies on the Nitrogen Chain, Vienna, Austria (1968) 79. (36) NOMMIK, micro-plof Banso e ,Us t techniqu studyinr efo g gaseous losf so ammonia from added nitrogen materials under field conditions, Acta Agr. Scand. 16 (1966) 147. (37) OLSON, al_R.A £ Controllin., ,_e g losse fertilizef so r nitrogen from soils, Trans Internh t .8 . Congr. Soil Sci., Bucharest, Romani (1964V aI ) 1023. (38) OVERREIN, L.N., Immobilizatio mineralizatiod nan tracef no r nitrogen ni forest raw humus. I. Effect of temperature on the interchange of nitrogen after addition of urea-, ammonium-, and nitrate- ^N, Plant and Soil 27_ 1 (1967) 1. (39) ______Lysiraete, r studie tracef so r nitroge foresn ni t soil. :I Nitrogen losse y leachinsb volatilizatiod gan n after additio ureaf no - l5jS, Soil Sci. 106 (1968) 280. (40) ______BHOAEBENT, , P.E Immobilizatio., mineralizatiod nan tracef no r nitrogen in soils of northern California, Trans. 8th Intern. Cong. Soil Sci., Bucharest, Romani (1964I aII ) 791. (41) PARR, J.P., Biochemical consideration increasinr sfo efficience gth f yo nitrogen fertilizers. Soils and Pert. 30. 3 (1967) 207. (42) PATNAIK BROADBEUT, . ,S, - P.E,, Utilizatio tracef no r nitroge ricy nb n ei relatio timo nt applicationf o e ,(19673 Agron 2 ^ ). . J 287 . (43) ROSS, P.J., .et. al_gas-tighA -, t growth chambe r investigatinrfo g gaseous nitrogen changesoile th :n si plan t :atmospere system, Nature, Lond4 .20 (1964) 444. (44) SAMTSEVICH, S.A,, Active excretions from plant roots and their significance. Fiziol. Rast(19655 £ ,JL ) 837 Russian)n .(i . (45) SIMPSON, J.R. , FREffEY, J.R., The fate of labelled mineral nitrogen after addition to three pasture soils of different organic matter contents, Aust. J. Agr. Res. 18 4 (1967) 613. (46) SMIRNOV, P.M. et_ al, , Transformation of different forms of nitrogen ferti-

lizers in soil and their utilization by plants (according to experiments N)wit15 ,h Izvest. Timiryaz. sel'khoz. Akad Russian) n (1967.2 (i . )85 .

158- - (47) STANFORD .al... £t , . Transformation,G fertilizef so r nitroge soiln ni . I . Interpretations base chemican o d l extraction labellef so unlabelled an d d nitrogen. (Submitted for publ.). (48) TAKAHASHI, D.J. ^N-nitrogen field studies with sugarcane. Hawaiian Planters Recor 2 (1964. d52 ) 198* Pat• applief " eo ' " '' d' ' fertilize(49' ) r nitrogef o determines e na us e th y db -ON.I. Summer and fall plant and ratoon crops on the Hamakua Coast of Hawaii. (196?3 Ibi. d52 ) 23?. (50) ______, Effec amounf o t fattimine d fertilizef th an teo n go r nitrogen in lysimeter studies .with ^N, Ibid 57 4 (1967)"292. (51) ______, Fate of ammonium and nitrat.e fertilizers in lysimeter studies with -ON, (19681 Ibi 8 5 d . )1 (52) VALLIS, I. JB_£ al., Isotopic studies on the uptake of nitrogen by pasture plants. Ill uptake Th , smalf eo l addition l^N-labellef so d fertilizer by Rhodesgras Townsvilld san e lucerne\ Aust Agr. .J . (19676 Res8 1 .) 865. (53) WAGNER, G.H., Change nitratn si fieln i eN d plot profile measures sa e th y db porous cup technique, Soil Sci. 100 .6 (1965) 397. (54) WILLIAMS, W.A. et_ al^, Nitrogen immobilizatio ricy nb e straw incorporaten di lowland rice production, Plant and Soil 28 1 (1968) 49. (55) ZAMYATINA, V.B. et_ al., The use of "^N f or the study of transformations of nitrogen fertilizer soin theid si lan r utilizatio plantsy nb , Sonderdruck s "Isotopenpraxisau ' • n Russian)(1967_ "(i 3 . )62 . (56) ______studyinn i N conversioe g,th f o ete ^ us nitrogenf a.1^. no e ,Th - ous fertilizers in.soil and tks utilization" of nitrogen by the plant. Rept. FAO/IA'EA Tech. Meeting on the Use of Isotopes in Soil Organic Matter Studies, Braunschweig (1966) 307.

- 159 - Table-1. Shallow depth placement of (NH.)pSOj. in submerged rice soils as related to gaseous losse fertilizef so r nitroge fertilized nan r efficiency (Aleksic et. (l))_al .

IT recovery GaseousN Soils Treatments Plant Weight in plants losses (g) j ap N f o % jlied (150 mg/!jot).

Thailand surface 12.0 49 28 depth 10.0 65 15 Burma surface 11.5 45 35 depth 14.2 66 19 Philippines- surface 17.3 37 39 depth 15.0 50 15 Madagascar surface 6.0 35 27 depth 4.9 49 11 Ceylon surface 8.5 43 17 depth 9.5 61 7 U.A.R. surface 9.8 19 64 depth 11.2 39 42

- 0 16 - Table II. nitrogen balance experiments with 15K as a tracer.

K recovery ($) Investigators Crop sourcK e in plants in soil N loss (#)

Dintscheff [20] —— <»Uaso4 UT - 56 24 - 31 16 - 25 Andreev Shcheglovd aan ] [5 a fallow KNOa .... ti 54 - 84 16 - 46 (MB* )sSQi 55 " 72 28 - 1*5 oats KN03 71 jj'j - l£ 14 (KB4)2S04 42 - 52 19 - 3^ 23 - B9 rye _ ^ Anion-N03 58 - 67 23 » *-f .4. 1 KHOs 68 - 70 12 13 - crC HH» -cation 56 - £•> 22 !t - 24 15 - 22 (HEt) SQi 21 s 8 51 - 55 - ?5 23 - 2k p Zamyatina et al. [55] millet oats n (MH^SQt 32 - 51 22 - 45 22 - 2? I KNGj 45 " ^4 22 - 29 24 fallow - 26 (RHj )gS04 IV W * •• 59 - 80 20 - 41 (40-60 days) • ™ *• ^ 60 - 69 31 - 4o Legg et al. [32] oats KKOg 16 - 8c 9 - 11 11 - 15 Legg and Allison [30] oatd san sudangrass NaN03 57 - 85 10 - 36 0 - 18 Carte[15. al ]t re fallow 11 HaNOg • 99 - 100 0 - 1 P7- - 98 2 - 3 sudangrass HaUOg 32 - 55 - 69 0 - 4 (NHi)s S04 26 - 59 4o - 64 0 - 4

Continued Tatl . ContinuedeII .

Zamyatin . [56al t e a] corn (NtOa30* 55 - 61 19 - 23 20 - 22 " NaHQs 61 - 63 17 - 20 19 - 20 oats 4 (UIJS0 2 ) j 22 - 51 22 - p4 22 • 27 " KE03 45 • 5^- 22 - 29 24 - 26 barley (KHi)2S04 53' 30 17

Sraimov _et £l. [46] oats NaIT03 57 - 59 8 - 9 33 - ~-f: " (NKi )a SO". 58 - 6l 10 - 12 29 - 30 " • » » l? Urea 53 - 61 14 ~ £ 25 - 31 15 " JJILNO, 56 - 59 17 — J.C- 23 - 27 ' KB^lorJC^ 51 . 59 5 - 8 33 - 38 fallow NaJJQj -___ -3 - 64 3!- - 47 l! — (H^)aS04 - 68 - 74 2c - 32 j f- Mersari arid Broeshart [35] rice IC^Ci -L^ - 52 29 - 39 9 _ c- o \ — £ o- Broadben Miiucelsed an t n [11] rice (HHjJgSi^ 29 42 • i? - 15 " Urea i 26 - 33 36 +*• - 31 Broadben Makashiad an t a [13 crop3 ] - s (KHiJs^ 35 - 56 22 - 26 2? - 39 sudangrass, lsMKIICa 38 - 62 26 - 33 11 - 29 "tomatoes., and K^ N03 58 - 71 24 - 33 ~ - 1C corn KtK)3 60 - 70 23 - 32 £7 - 8 KHjOH 35 ~ 37 IB - 25 35 - 47 Urea 53 - c4 30 - 4l c" • so Girbuchev oats l£ - 25 TOTAL N 15N-LABELLED N

0 6 5 01 0 13 0 6 015 ULTRAS :.C VldR; J1OH TREATMENT, MINUTES (I) NaOH-Distiliable N Prior to Acid Hydrolysis * (I) NaOH-Disti!lab!e N Following Acid Hydrolysis of Residue from I (Jtt) NaOH-Distillabl FollowineN g Ninhydrin Reaction of Residue A from I f ) ResiduTotao (E N l eA fro mH (Y) Non-Extractable by Na Pyrophosphate ft

Fig . 1 Distributio. f sodiuno m pyrophosphate-extractable nitrogef no £ 53 IA soil part.1.cie-sizo classes in relation to intensity of xiltrasonic vibration treatment received prior r-c fractionation (Chichester [16]).

- 16- 0c N-1TRACEP A O S 5A E FERTILIZEN RI US E TH R EFFICIENCY STUD JAPAN YI N

Susumu Nishigaki Soil Fertility Division Department of Soils and Fertilizer National Institute of Agricultural Sciences Nishgahara, Kitaku, Tokyo Japa4 ,11 n

Crop plant mose sar t sensitiv nitroggo et n among many other essential nutrients. Application of nitrogen is considered at first to stimulate the plant growth. nitrogee Th n fertilizer crop e givee th s ar s o nt throng e soilth e th hd ,an fertilizer nitrogen is subjected to chemical and biological changes in the soil. So the uptake efficiency of fertilizer nitrogen is not always high enough for the efficient crop production. It becomes very importan kno o uptake t wth e efficienc dressef yo d nitrogen crope inth . The. conventional metho determininf o d g fertilizer uptake efficiency is based on the difference in uptake of nitrogen by a crop between no nitrogen and nitrogen dressed plots. However, fropointo tw m vief so leastt wa conventionae ,th l method does not seem to be very exact. Firstly, dressed nitrogen stimulates the root growth, and the roots in the nitrogen dressed plot naturally spread in bigger volume of soid tak lan morp eu e soil nitrogen frosoie th mplole th that n wheri n e nitro- above-mentionee givent th no o s S i . n ge d differenc amoune th nitrogef n to ei n treatmento tw e th n takesi wilp nu l include nitrogen from both sourcee th f so applied fertilizer and the soil itself. Secondly, the conventional method is not provided wit y devichan distinguiso et h soil nitrogen from fertilizer nitrogen. stable th f eI (non-radioactive) nitrogen isotope, N-1fora nitrof n 5o mi - fertilizern ge nitrogea uses ,i s a d n fertilize ploe testee b f on o t o n rt i d field experiment identifn ca e determind ,on y an amonne eth fertilizef to r nitro- gen :. uptaken by the crop, as the amount of N-15 isotope in a crop is measured with mass-spectrometer and by the tracer method. Thus "the uptake efficiency of dressed fertilizer nitrogen" can be accura- tely determine fiela n i dd experiment. firs e Thith ts si proble e solveb o o t mt d improve the method of fertilizer application to a crop, and the use of N-15 isotope made this possible. To obtain a good yield, nitrogen taken up by crops should contribute to the growth of proper organs in a stage of crop growth. N-15-labelled nitrogen fertilizer can be determined in any organ and in any growth stage of crops. percentage Th N-15-labellef eo d nitroge totae th ln ni nitroge orgai a n ni at growth stage will furnish information on the contribution of nitrogen ferti- lizer to the crop production. Therefore, it is sometimes called "the contribu- tion rate of nitrogen fertilizer" in an organ at growth stage of a crop. This is the second problem to be solved for the improvement of fertilizer application method. - 161 - Many methods of determining soil nitrogen fertility have developed, and the results wer goon ei de foun b correlatioo t d n with uptak soif eo l nitrogen by crops. Further, many attempts have been made to determine the rate of nitrogen fertilizer application using the data of soil nitrogen fertility] The idea, in which the late of nitrogen application should be determined considering the rate of soil nitrogen fertility is undoubtedly correct, and these attempts seem to be successful for the crop culture of moderate yield. attempe th t consideres i tBu uselese b o t dr cro sfo p culture higher yield. e probleTh supposes i m pointe exiso on t d relatioe n ,i tth tha, is tn between time th f emergenceo soif eo l nitrogetime th e d whe croe nan nth p requirement of nitrogen depending on the different growth stages- The partial efficiency of absorbed nitrogen differs at different growth stages, and in some cases absorption of much nitrogen in one growth stage can decrease the crop yield. *» Prom this poin viewf o t shoule ,on d kno onlt time wno nitrogeyf th eo n requirement by crops but also should know the time of absorption of soil nitro- gen. Then it becomes possible to determine the time and rate of nitrogen appli- catiocroa obtaio r pt nfo n higher yields. Tracer methods using N-15-labelled nitrogen fertilizer can tell not only the amount of fertilizer nitrogen absorbed t alsamoune bu oth f soito l nitrogen absorbe croe th p y planplantsde b th tf I . sample is taken and analysed for N-15 and total nitrogen of plants several times throughout the crop life of the N-15 tracer field experiments, amount of soil nitrogen utilize cropy db eacn si h stag determinedgrowte f b eo n hca . Thue sth patterutilizatioe th f no soif no l nitroge easile b cropy nb n yca s knownd ,an the rat d tim enitrogean f eo n applicatio determinee b n nca d referrine th o gt pattern of nitrogen requirement of crops through the whole life cycle. thire Thith ds si proble solvee b o improvt mo t d methoe eth nitrogef o d n fertilizer applicatio croa o pnt using N-15 isotope. Prom these above-mentioned points, (l) the uptake efficiency of dressed fertilizer nitrogen contributioe th ) ,(2 n rat fertilizef eo r nitrogen a n ni orgagrowta time t na th e h ) patter stagcrop(3 a f d eo utilizatiof , an no f no -=soil nitrogen by crop, N-15 stable isotope has been used in Japan for research to improve the method of nitrogen application on rice plants, barley, soybean, sugar beet, onion, green house tomate, mandarin orange tree persimod san n trees. The results of these rese.aro.hes done in field experiments were very fruitful and they have been already put into farmer's practices.

1. TECHNICAL PROBLEM IN N-15 PISLD EXPERIMENTS

(l) Nature of N-15 Isotope The stable isotope of N-15 is contained in the natural nitrogen at the per- centage of 0.37, and it does not have radioactivity. N-15 tracer technique does not rais y radiatioean n hazar y fiel an dusee b dn problem i dn experimenca t I . t .thn i e farmer's field, where foo produceds i d . Radioactive isotopes will decay and decrease in amount in process of time, but N-15 is stable and it does not decay. So, in principle, tracer work can be performe exprimene lons th da s ga neededs i t .

- 162 - . Isotopeasile b n yN-1ca f e o 5use double-labellen di d tracer technique with other stable isotopes alsd suc an C-13s o ha , ,radioactiv on o H-2s , d an 0-18e isotopes without disturbin determinatioe gth othef no r stabl radioactivd ean e isotopes. In many cases, double-labelled fertilizer using N-15 and P-32 is common- ly utilized in the field tracer experiment, because of the importance of both nitrogen and phosphorus in the crop production and because of the interaction of both wktrients in the plant physiology. Isotop N-1f eo 5 doe decat s no mentione s ya d aboveexperimene th o ,s t field, once useN-1r 5fo d tracer, canno usee tb d agai N-1r 5nfo tracer work, otherwise the second tracer experiment wil disturbee lb residuae s th wa y db h li N-15wh , placed in the former.field tracer experiment. The place of plot, in which N-15 givens wa , shoul accuratele db y registrated. tracee th n rI field experiment using N-15 several hundred gram kilograr so m of labelled nitrogen fertilizer will be needed, and the unit price of N-15-labelled fertilizer is not cheap, so the field N-15 tracer experiments need much greater funds than ordinary field experiments. The determination of N-15 in the nitrogen requires mass spectrometry or particular ligat spectrometry instrumente th d ,an s neede vere dar y expensive. methode Th determinatiof so alse nar o more complicated than chemical analysid san radiation counting. Productio) (2 Distributiod nan Stablf no e Nitrogen Isotope N-15 Stable nitrogen isotop mads e i concentratin y eb gnaturaf ° N-15 l nitrogen (0.376$ N-15 and 99.624 N-14). Many concentrating methods have been developed and small-scale productio • starte•- n mann i d y countrie presentt A n 1£4?si . , N-15 isotope is produced in Japan, the United States of America, United Kingdom, France, Canada, USSR and some other countries, and it is easy to purchase N-15 isotopes as a commercial product in any part of the world. N-15 isotope-labelled fertilizers in the form of ammonium sulfate, ammonium nitrate, sodium nitrate, urea, and in some other forms are available for fertilizer experiments. The labelling concentration of N-15 isotope in the available ferti- lizer nitrogen ranges, from 3$ to 99$ and it is called "abundance of N-15 isotope fertilizee inth r nitrogen". Labelled fertilizer having more abundanc tracee th uses i N-1f n eo ri d5 experiment highee ,th r precisio easils ni y obtaine resultse th n i d pric.e 'Buth et grae oN-15-labelef on o m d fertilizer goe exponentiallp su y wit increase hth f eo abundance of N-15 isotope in fertilizer nitrogen, as for example, the market price of N-15 labelled ammonium sulfate fertilizer is shown in Pig. 1. Although the N-15 labelled fertilizers are expensive, small-scale fertilizer experiments such as water culture and soil pot experiments do not cost much. In case fielth f eo d experiments ,experimentse troubl th cose causee b f th o t y y edb ma . Suppose ,fiela d fertilize conductede b applicatioo e t th s ri d ,an n rat nitrogef eo n hectare r ricr pe fo eg k cultur.0 gra0 10 1 Tha nitrogef s mo s e i ti gra Q 5 mr no N-1f o 5 labelled ammonium sulfate wil requiree lb eacr dfo h squaree meteth f ro experimentae th plo n ti l field ammoniuf I . m sulfate labelledcenr pe f t o 0 3 y 7b N-15 abundance is used, the cost for the- isotope will be around 600 dollars per square meter of the plot. But if ammonium sulfate labelled by 3 per cent N-15 abundanc useds ei cose ,th t wil onle lb y aroun dollars3 d3 . bettes Thui t si o r t

- 163 - use low N-15 abundance nitrogen as far as possible in field fertilizer experiments, frostandpoine th m f experimentao t l costs Japanesn I . e field experimentn so fertilizer efficiency, labelled fertilizers of 2$, 3$, 5$, 7^ and 10% N-15 abundanc commonle ear y used. (3) Determination and Tracer Method in the Use of N-15 Nitroge plann ni t convertee materialb o .t s dsha into nitroge befors nga e N-15 abundanc s generatio ga s determined ei - methoe IT th f o o t dn s A fro. m plant samples ther leastt a eo n the I wil'tw . firse lb t method, plant material e decomposesar d by Kjeldahl method into ammonia and' the resulting ammonia is converted into N« gas by hypobromide reagent. In the second method, nitrogen in plant sample is directly converted into N? gas by Duma method.

To determine N-15 abundanc? gasN e ,th mas n ei s spectromete molecular ro r photo-spectrometer can be used. Tracer radioisotopes r exampl,fo e t containeP-32 no naturae e th , ar n i dl element like phosphorus stablt ,bu e isotopes examplr ,fo e N-15 ,e containear n i d natural elements r exampl,fo naturan ei l nitrogen smaln ,i l abundancee th o S . tracer calculatio N-1r nfo 5 tracer metho somewhas i d t more complicated than ni radioisotope tracer method. To simplify the calculation, "the excess percent of N-15 in nitrogen" is considered, which can be obtained by subtracting^ natural abundance of N-15 in natural nitrogen, for in example C.367, from abundance of original N-15 labelled fertilizer nitrogen and in nitrogen of. plant sample, as shown below: Source of Nitrogen Abundance % access % of of N-15 N-15 Natural Nitrogen 0.36? 0 Original Nitrogen ni labelled fertilizer 5.231 4.864 Nitrogen of plant sample 0.975 ^.608 case th e s showi t i n f aboveI , isotope dilution ratio whic, wil8 obtaines e lhi b d by dividing 4.864 by 0.608, and this is the same tracer calculation as radioisotope tracer method.

Hern selec probleeca a e t on prope mw comeho r; sabundancup cenr N-1f epe o t 5 fertilizee ith n r nit.roge usede b o .t n Tabl wileI l show some ide seleco at t abundance per cent of N-15 labelled nitrogen fertilizer for field fertilizer efficiency experiment. This table was made basing on many Japanese experiences yearo8 f1 s since 195^. Tabl alsI e o shows tharequiree th t d abundanc cenr f epe o t fertilizen i N-15 r nitrogen will standare depenth n o d d deviatio N-1e th 5f no determination very close to the natural abundance of 0.36?. Namely, the higher precisio N-1f no 5 determination'will permit.the lower abundanc cenr N-1ef pe o t 5 in nitrogen fertilizer, thus the lower cost for labelling nitrogen fertilizers. Consequently kno o precisioe t wth s ha e N-1f no ,on 5 determinations before plan desige ca nth N-1d e nan on 5 abundanc fielf eo d tracer experiments.

- 164 - II. AN EXAMPLE OF N-15 TRACER FIELD 13XPERIMENTS ON NITROGM FERTILIZER EFFICIENCY It had been a common practice to harvest rice in summer and wheatin winter from paddy fiel Gifn i d u Prefectur middle th n eei par Japanf o t . National demand for vegetable production and farmer's demand to increase their income required to replac wintee eth r whea wintey tb r onio latn i n e 1950» B«i troubla t e happened rice ith ne culture after -.onion. Rice yield decrease cause th s suppose ewa d an d d to exist in excess nitrogen uptake by rice plants. To investigate this problem, a series of tracer field experiments was con- ducted. Successive N-15 tracer field experiments of onion-rice plants, wheat- rice plants and rice culture were conducted in 1957-58. The root activity distri- bution in the soil of the field was determined on onion and wheat in 1959-1960. As a result of the study, new placement of nitrogen fertilizer was established and the total amount of nitrogen applications for onion was reduced to 130 kg/ha froconventionae mth l applicatio intt methow nkg/ha0 pu o ne 19 rats e f dwa .eo Th the farmer's practice fertilizea d ,an r cos 100,00f o t 0 dollar onior sfo n culture is saved annually, and the trouble in rice culture was removed in Gifu Prefecture. The design of N-15 tracer experiment is shown in Table II. In the onion culture, all nitrogen given in Treatment A was labelled by N-15 of 0.891 excess per cent. Nitrogen top dressing of warm season only was labelled by N-15 of 2.528 exces cenr Treatmenn spe i t Treatmenn I . tB naturaD t l nitroge gives nwa n in all dressings. Treatment H did not receive nitrogen at all. In the wheat culture (Treatment F) labelled nitrogen of N-15 of 0.891 excess per cent was given dressingsl inal . After these winter culture crops were harvested, rice plants were transplanted whicn successiveli , hF . labelled TreatmenF an d , Treatmenan n B yi D d, A t, B , tA nitrogen had been given to onion, natural nitrogen fertilizer was given to rice. Treatmen whicn i , htD natural nitroge beed nha n give onionr nfo , N-15 labelled nitrogen fertilize 3.77f ro 5 exces cenr gives spe rictwa r nfo e culture. All crops obtained very good yields, i.e. over 50 tons/ha of onion, 4.3 tons of whea tons/ht5 5» grai d hullef ao nan d rice grain (abou 5 ton/ht7. graif ao n with hull) onioe Th . n cultur Treatmenn ei whicn i nitrogeo , htn H s appliednwa , yielded 32 tons/ha of onion. experimentae desige th Th f no l plot s fixeswa d accordin author'e th o gt s method, in which 1.33 m labelling small plotr. was placed inside the larger plot of 12 m . The boundary between small and large plot was made by thin galvanized iron sheet, and the plants were planted in continous rows without changing the spacing between plants, even at the point where the plant row and iron sheet cross each other. This is very important to avoid boundary effects around small labelled plot. Rate of fertilizer dressin maintaines gwa d uniformly throughout larger plod smaltan l plot in it. The N-15 abundance in the nitrogen of the plants was determined very carefully to maintai standare nth d deviatio N-1f no 5 abundanc about ea t0.001± , whee nth N-15 abundance was less than 1.000. Actually, N-15 abundance of the plant nitrogen ranged from 0.990 to 0.600 in onion and wheat, and from 1.500 to 0.307 in rice plants

- 165 - resulte Th s obtaine traceo th n ri d field experimen shows i t Tabln ni e III. Nitroge 50.f no 8 kg/h5 kg/h 3. takaiuonios takey s o ad wa a wa p nan nu y pb rice plant, from 189 kg/ha of whole nitrogen applied for onion (Treatment A). This 3.5 kg/ha uptake by rice plants exceeds 1/10 of 31.7 kg/ha (Treatment D), whic takes ricy b h wa ep n u plants fro kg/h4 8 m nitrogef ao n give ricr nfo e culture. This fact suggests that the residual of nitrogen dressed for onion will cause appreciable effects on the rice plants cultivated after onion. Nitrogen of 40.9 kg/hs. wr-* taken n?p by who?,t and 1.7 kg/ha was taken up by rice plants out of 94 kg/ha of fertilizer nitrogen given to wheat (Treatment P)» This 1.7 kg/ha taken up by rice plants is only about 1/20 of 31.7 kg/ha (Treat- men, suggestinD) t g little effec fertilizef o t succeedine whear th rfo n o t g rice culture. Table IV shows summarized re-suits of uptake efficiency of nitrogen from ammonium sulfate whic uses r threhwa dfo e different same cropth e n so soi l type of Kamosima Series (rice field soil).- The efficiency was highest at 43.5$ in wheat culture, and 37*6$ in rice culture, and lowest at 26*9$ in the onion culture, The amount of soil nitrogen -tilized :ras highest at 76.9 kg/ha in wheat culture, d 74.an 2 kg/h ricn ai e culture d lowes,an -.(.! tyj kg/h onion ai n culture. These differences of utilization of soil nitrogen waa found to be due to deep distribu- :ion of wheat roots in the soil, due to particular absorption of soil nitrogen iinder water-logged conditio rico shalloo th t e n e nculturi du w d distributioean n of onion roots.. Fertilizer uptake efficienc differenf yo t tim splif o e t applicatioe th n ni cultur oniof e o uptake s showTh n wa Tabl n nitroge f i neo . eIV n applie warn i d m season of March an'1- April showed fairly good value of 32.7$ taking up 26.7 kg/ha out of 72 kg/ha of nitrogen dressing. Hut the uptake nitrogen applied in cold season of November, December and February showed too low efficiency of 26.9$ taking up 23.6 kg/ha out of 117 kg/ha of dressed nitrogen. In spite of low root activity unde cole rth d temperature, very heavy rat nitrogef eo n (117 kg/has )wa given to the onion in the conventional method of cultivation, and residual effect thif o s par nitrogef to n dressin ricn go e culture occupies-2/ totae th lf o 3 residual effect of fertilizer nitrogen for onion on rice culture (Table III, Treatment A, B and X).

e conclusioTh n obtained h-ro we.s thr.t tb<- metho d rat an dbasif eo d subsecen - quent top dressings in cold season for onion should be studied. According to this conclusion, the root activity distribution in the soil was studied on onion whead an t usin gsame P--3th e n experimentai 2 l placepracticaw ne A . l methof o d fertiliser application onior sfo designes methoe nwa th s subjecte d dwa an d d under 11-15 tracer field experiments again» Thus the established new method of onion fertilization, in which the placemen'!; basif o c dresrin mads gi e besid onioe th e n seedlings locatet ,no d under themd ,an tho rat nitrogef eo n applicatio coln ni d dowt seasohalfcu o nt s .nwa After thin methou ne d :vas distribute y extensiodb n service, onion grower Oifn si u Prefecture- saved much oost for fertilizer and the method had no disturbing effect on the rice cultures caused by the foregoing onion culture,

- 166 - III .N-1P O WID 5E EUS

Because the nitrogen is the most important nutrient for crop, and the method of N-15 tracer easys si , N-15 tracer experiment plann so t nutrition, N-15 tracer field experiment fertilizen so r efficienc soin o ld fertilityan w conducno e yar - ted in many Federal, Regional, and Prefectural Experiment Stations and soil- fertilizer research laboratories in Colleges and Universities. A number of excellent academic resolutions in the nitrogen nutrition of the crop practicad san l improvement nitrogef so n application were achieved. But the problem left in the N-15 tracer work is that the number of instruments to determine N-15 is not sufficient, and also the mass spectrometry is a very complicated work. Consequently appearance ,th morf eo e easmethodw yne N-1f so 5 determination is hoped for.

- 16? - Pi«. 1 . 1TORLD PRICE OP AMMONIUM-SULFATE LABELLED BY N-15 ISOTOPE

$2001

10€t

S so o e CO

G

O CO

o o tc •oJ

$ 0.

(LOR) Percent of N-15 in N

- 16- ?a TABLE I. ABUNDANCE PERCENT OF N-15 IN NITROGEN FERTILIZER TO BE USED FOR FIELD FERTILIZER EFFICIENCY STUDY Accuracy of H-15 Deternination at the + 0.03 + 0.01 + 0.003 very close to the natural abundance

Tic applicatiof eo f labelleno _,,„„,,„,- n,, *4.^~„ . „• . d_ . . nitrogenf>n . Crops (Part of labelled nitrogen in total ?^iii™ »*«>««» nitrogenv applicatio e crot yearon r o > n ni ) One year crops Lab ell all nitrogen Rice plants dressingp to l (Basial )d can 10& 3* 1.5^ dressine on l el gb onlLa y (Anon dressingsgp to basi d can ) 152 & K Labell all nitrogen to see residual nitrogen absorbe nexy db t cope. y& ?.0# 5% Upland crops Conditions given above t ffluo]-No . difference shov/, _ n above for each, condition Long year crops i Kandarin Labell all nitrogen in one year 15?: & 2% orange trees Onl tine dressinf yon eo labelles gi d or among several applicatio yeara n ni . 20$ 7% 5% I (Other time application is given natural nonlabelled nitrogen) Long tarn tracer experiment over one year •#• to sun up long tern absorb tion by plant (Labell all nitrogen is labelled only in first 50% 15# 7% year) 1) Generally upland soil will give smaller amount of soil nitrogen than rice soil lower abundance % of N-15 can be used for upland crops than for rice plants. II THE DESIGN OF N-15 FIELD TRACER EXPERIMENT ON NITROGEN FERTILIZES EFFICIENC ONION Y I WHEA D NAN T CULTURE "FOLLOWE RICY DB E CULTURE Warm season Whole nitro- Whole nitrogen dressed Whole No nitro- gen for wheat Name of treatments for nitrogen nitrogenr fo n ge labelled onion labelled* for onion for rice onion labelled labelled Notation A B D H F Number of duplication 0 J 5 &' '••" 3 5 "*-—•-^^ _ V/inter Placement*—-^^^.^^ ^ crops Onion Onion Onion Onion Wheat Dressing """"""'— - — ^ kg/ha kg/hi Basic Dres. Nov. 16 K-15 0.89. 1ex Natural N Natural N No Nitrogen 47 ' N-15 ' 0.891 ex. 1st Top Dres. I/ec. 20 '46 N-15 0.89, 1ex NaturalN Natural N No Nitrogen Dree2np dTo . Feb6 .2 N-15 0.891 ex, Natural N Natural N Nc ritrogen 47 IT-15 seaso n

1/ol u 0.89. ex 1 3rd Top Dres .March 18 36 N-15 0.89. 1ax N-15 2.528 Natural K He Nitrogen o ex. I Drca4tp hTo . Apri4 l1 36 N-15 0.39, 1ex N-15 2.528 NaturalN No Nitrogen - -

llClfff l ex. seaso n Total Nitrogen AgpJLirsd 189 94 Summer Rice plant Rice plant Rice .plant Rice plant Number of crops duplication 3 3 2 "\^ 3 Basic Dres. June 23 19 Natural N Natural N N-15 28 NaturalN 3.77. 5ex 1st Top Dres. July 15 28 NaturalN Natural N N-15 28 Natural N 3.775 «*• Dres2np dTo . Aug.5 28 NaturalN NaturalN N-15 28 .NaturalN 3.77. 5ex \ 3rd Top Dres. Aug. 26 9 Natural N NaturalN N-15 9 Natural N] 3.775 ex. it&l Nitrogen Applied 93 H Note: ex. means excess percent TABLE III. FERTILIZER NITROGEN AMD SOIL NITROGEN ABSORBED BY CROPS (Shown in Kilogram per Hectar of Nitrogen) Whole Warm season Cold season Whole No nitro- Whole nitro- nitrogen dressed , dressed nitrogen gen for wheager nfo t Nam treatmenf eo t for onion nitrogen nitrogen for rice onion labelled labelled for onion for onion labelled labelled calculated B d froan mA Notation A B X D H F Nitrogen TotalN 104.4 105.9 104.4 104.0 42.4 ' '117.S take p nLabelleu dN 3 J 0 5 27.2 0 0 40.9 by plants Natural N 53.6 02.§H3 77.2 104.4 42.4 7T79 Labelled nitrogen applied* 189. 72. 117. 0 0 94. Uptake efficiency of applied nitrogen 26.9* 32.7% 23.2* - - 43.5 V/inte r cultur e Onio n o r Whea t I Nitrogen TotalN 109.1 119.5 115.0 115.0 I—» 105-9 o take p nLabelleu dN 24 1.1 2.4 31.7 by rice NaturalN 105-6 llO 112.6 74.2 - 3.13T3 p. plants I Labelled nitrogen applied 0 0 0 84.3 - 0 Total nitrogen o applietw r fo d 189. ( onio (onionn. ^72 ) 117. (onion) 84. 3( rice) - (wheat. 94 ) crops Uptake efficiency

Ric e plant s of applied nitrogen 1.9* 1.5* 1.2* 37.6* - 1.8?£ • Summe r cultur e Note: Total fertilizer nitrogen applied for onion was 189 kgAa in A,B, and D. 0 kg/ha in H. Total fertilizer nitrogen applie kg/h4 . whea9 F r s n dfo ai twa Total fertilizer nitrogen applied for rice plants was 84.3 kg/ha in A,B, and D. 94.3 kg/ha in F TABLE IV. SUMMARY OF UTILIZATION OF SOIL NITROGEN AND FERTILIZER » NITROGE ONIONY NB , WHEA RICD TAN E PLANTS

Kind of crops Onion Wheat Rice plants 4.3 tonAa 5.5 tonAa Yield 50 tonAa (bulb) (grain) (brown rice) Appliet dou Total nitrogen takep nu 104.4 kgAa " Cold Warm 117.8 kgAa season season Fertilizer nitrogen 50.8 kg/ha 23.6 kg/ha 27.2 kgAa 40.9 kgAa 31.7 kgAa

Soil nitrogen 53.6 kc-'ha 76.9 kgAa kg/h2 L a7 o -J Rate of nitrogen 189 kgAa 117 kgAa 72 kgAa 94 kgAa 84.3 kgAa (D application I Fertilizer uptake 26.9 % 23.2% 32.7 % -.3.5* 37.6 % efficiency

*» RADIATION TECHNIQUES S MEANA P IMPROVINO S E EFFICIENCGTH F WATEYO E RUS "by Y. Barrada

I. INTRODUCTION

Frequently it is a water shortage, especially at critical periods of crop growth maie , th tha nyieldw s i tcauslo f .eo Rainfall totae , th eve lf ni amoun t is sufficient, is very often so inadequately distributed among the seasons of the year, that its valae for agriculture is seriously limited. Irrigation scheme nowadaye sar s much more common, being made eithee rth major sourc wate f supplemenea o r ro naturae th o t l rainfall. Compared with dry-farmed land, the area of irrigated land is rather small, but its importance is great as its yields of food and fibres are relatively high. Increases of 30t to 50* cron ^i p production were repeatedly observed afte introductioe rth n a f no irrigation system. However, despite the growing water shortage problem, the efficiency of irrigation and the efficiency of water use are rather low, and great quantitie watef s o wasted e rar . A recent F/0 report*) states that "There is no single factor as important for saving water as proper use of water on the land". The report goes on to say that the universal use of proper water techniques would allow for an increase in the world's irrigate morer o d$ , 50 areusin f same ao gth e amoun waterf o t d ,an that the exact determination of the water requirements of plants is a basic prerequisit propeirrigatiof o o et e rus n water.

II. TERMINOLOGY

It might be appropriate to recall the definition of the following most commonly used term avoio t smisunderstandingy an d : Irrigation effioiency. amoune ratie th th Thiwatef f o to s si r ro«e storeth t n zonei d , dividey db the total amount applied. Irrigation efficiency takes into consideration the various irrigation losse deed s an includinp f percolationof n gru .

*) de MSREDIEU, J. and PILLSBURY, A.F., "Provision for more adequate supplies of irrigation water" Workine th notA .r gfo eECOSOe Grouth f Cpo Advisory Committe Applicatioe th n eo Sciencf o n d Technologean Developmento yt , FAO-1, Rome (1965) 10.

- 168 - Bv-apotranspiration (BT consumptivr )o e use. volumef o m water**f su so e Thith s 5si use durinp du g plant growt transn hi - piration and evaporation from soil in any specified time, divided by the area, i.e. aoreXin* (in**T E = r *)o heotareXcm* (cm**)T T2 = ,* acre hectare

Water use efficiency. This is the dry (crop) weight produced per unit volume of water used in evapotranspiration, i.e. dry weight/acr weighy ( dr tons/r ttono = es m (ST. ) BT volume of ^H ha, m (ET) If water is expressed in weight then water use efficiency becomes a true ratio (dimensionless).

III. WATT® USE EFFICIENCY

It should be stated first of all that maximum water use efficiency is not our goal for the following three practical reasons: Firstly, the cost of practices necessary to achieve higher yields must be related to their returns in monetary terms. For example, the yield increase from fertilizers usually follows some kind of decreasing increment function so that each successive uni fertilizef to r produces less

** Volume of water is in this context usually measured in inches or centimeters per unit surface area.

- 9 16 - This higher efficiency of course is attained at a much lower and sometimes disastrous level of production. Thus water use efficiency cannot be considered apart fromoisture th m yield ean d situation under s obtainedwhicwa t hi . Thirdly, the necessity of applying more irrigation water than is needed in orde satisfo rt leachine yth g requirement salr sfo t removal. All agricultural practices that increase the ratio of dry weight to evapo- transpiration increase wate e efficiencyrus investigateo T . effecte ,th f so certain farming practices on the efficiency of water use, we must examine their effects on the actual water use, dry weight production and finally their relative rates of change. The following practices are among the major factors that affect the efficiency of both irrigation and wateruse (a complete list, of course, would include almost all the objectives of"agronomic research): e controTh pestf lo . pland 1 san t diseases would improv watee e efficienth rus - cy by preventing or reducing crop yield losses (increasing dry weight production). . 2 Methods that reduc soie eth l moisture losseevaporatioo t e - sdu un d nan necessary transpiration (weed control, mechanical destruction of soil surface cracks, wind break increased san d plant population). effecte Th soif so . 3 l salinitvarioue th d syan fertilizer salt roon so t extra- ction of water and on infiltration and run-off cannot be laid aside in any discussion of the efficient use of water. 4. Fertilizer may increase root development within the soil so that water is greatea use o dt r exten alsd tan o from deeper soil layers. 5. Evidence indicates that water use efficiency can be greatly increased if the application of fertilizers increases yield. Often the deficiency of only a single plant-food element causes a marked increase in water requirements. As the element becomes very scarce the rate of growth as measured by the assimilation greatls i p CO y f reduceo d wit o correspondinhn g decreas transpiratione th n ei . amoune Th irrigatiof t o . 6 n water intervae applieth d an dl betwee successivo ntw e irrigations shoul determinee db relation i d differeno nt t value soif so l moisture storage capacity and the rate of evapotranspiration, so that the harmful effect of draught periods upon crop yields can be minimized. 7. As either too much or too little water causes a yield reduction, the rate of water flow throughout the irrigation time should be regulated according to the permeability of the soil,so that although water infiltrates to the rooting zone, unnecessary losses due to run-off or deep percolation are avoided, and a homo- geneous water distributio achieveds ni . In arid and semi-arid regions, the amounts of irrigation water available are so limited, tha tlimitin e wateth s ri g facto agriculturar rfo l production. Under such conditions, it is essential to make the best possible use of the water. To achieve this aim, intensive water use efficiency studies which are prerequisites developmene th r fo morf to e efficient method watef o s r usevere ar ,y much needed. Such studies would enablachievo t s followine u eth g targetst

- 170 - (a) On irrigated land, an adequate amount of irrigation water could bo applied, wit propee hth righe r th rat t t flow f a eo time d ,an . This would reduce wastage of the type mentioned above. The considerable amounts of water thus saved could be used for improving the water supply of other irrigated areas or for providing an additional area with irrigation water. necessite improvemenTh e th ) r (b yfo watef to r neesupple r th dfo r yo irrigation water coul quantitativele db y predicted thao necessar,e s tth y essential informatio plannine irrigatioth w ne r f nfo go n projects coule db provided. experimentaf I ) (c l result availablee sar assigy ma e definitna , on e recurrence value to the measured yield depression resulting from lack of soil moisture. Wheh cost of irrigation and increases in gross return are compared, onestimatn eca profie eth t that coul expectee db d fro certaima n irrigation project over a large number of years. (d) Through comparing experimental results for various crops and crop rotations, the best return for a given amount of water in monetary terms could be determined. shortn I , wate e efficiencrus y studies woul besde th leat o possiblt d e eus of the limited amounts of water, and this would in turn increase the production of foo fibred givea an d r nsfo amoun waterf to n additioI . thato t nchoic e ,th e of crop d crosan p rotation moschoice a th d t f san eprofitablo e irrigation projects becomes possible, based on sound economics. Thoug importance hth gread ean t neewater fo de efficienc rus y studies swa well know agronomisto nt lona r g sfo time reporte ,th researcn so h wor thin i k s fiel relativele ar d y scarce. Thi probabls si y becaus difficuls i t ei d costltan y to obtain valid evapotranspiration data, which are the basis for such water use studier comparisonfo d effecte san th f variouf so so s agricultural practicen so the water use and water use efficiency. Field evapotranspiration data are hard to obtain because they requir largea e numbe soif ro l moisture measurementt sa various depths and because of confusing results due to possible losses by deep percolation and run-off. In fact, many thousands of fertilizer experiments have been conducte whicn i d attempo hn s mad measurtwa o et e evapotranspirationr Fo . example more th mosn e ,i f o costlt y factorial experiment whi,cn si h irrigation regimes and fertility rates are studied in all combinations, the irrigated plots maie ar n plot practicar sfo l reason fertilitd san y treatment sub-plote sar f so the split plot design. All fertility treatments in an irrigation treatment are irrigated alikemosn i td ,casean attempo sn mads i tmeasuro t e e consumptive eus on each plot. Actually there are few field experiments that have produced information on the "fertilizer-yield, consumptive-use" complex, and most of these are from studies involving irrigatio fror no m dry-land experiment whicn si h deep percolation does not complicate the measurements of evapotranspiration. Methods availabl mea9urinr efo g soil moisture (other than neutron scattering) adequatet no e ar . These method mainle sar y limite takino t d g sample soie th l f so from various locations and depths in a field to determine the moisture content or to obtaining indirect measurements of the soil moisture by measuring the electri- cal conductivity of the soil or by using tensiometers to measure soil suction . values. \ - 171 - Soil sampling is destructive, time consuming, difficult and arduous work. A great numbe samplef ro needes si ensuro t d e thameasuremene th t represens i t - tative in addition to the necessity of determining the bulk density. resistance Th e methodt sensitivno lowee e th s ar r n ei soil moisture suction range, are affected by the salt content of the soil solution in addition to the short life expectancy of electrodes imbedded in gypsum blocks and the draft in calibration that occurs with most electrode units. "Because of the logarithmic relationship between resistanc d soiean l moisture difficuls i t ,i determino t e quantitative values of soil moisture content. The use of tensiometers is very helpful at high soil moisture contents where these instruments are sensitive. However, tensiometers cannot measure moisture condition highee th n rsi soil-moisture suction range. Like resistance units, some difficult bees yha n encountere maintaininn i d g adequate contact with soils. Likewise readinge ,th s obtaine givt no e o quantitativd e value soif so l moisture. It was with the availability of portable radiation equipment that the proble performinf o m g large number reliablf so e soil moisture measurements swa solved and the way was opened for intensive water use efficiency studies. Portable radiation equipment is also a very valuable tool for following soil moisture changes at various depths around the seasons of the year. The information gained through such studie essentias si assessinr lfo neee drainagr gth fo d wels ea s la for planning adequate drainage systems. Alspossible th o e effec variouf to s agricultural practices suc growins ha g tree servo st wins ea d breaks, associated crops, increasing plant population, hoeing-i soie nth l surface, mulchin includind gan perioga e fallof o dth n wi crop-rotation; on reducing soil moisture losses could very well be investigated with the aid of portable radiation equipment.

IV. RADIATION EQUIPMENT

e equipmenTh t consist "probea f so " containin radiatioe gth ne sourcth d ean detector as well as a portable electronic counting unit "sealer" or a "rate meter". (Fig. l). The radiation sources most widely used for neutron moisture meters are alpha emitters usually either radiu americiur o m m thoroughly mixed with berillium that functions as a target for the alpha particles. The neutron source emits a flux of fast neutron indicates sa followine th y db g equations-

4+9 1 12 /•if* + ^Be ______^ Qn + I|C + Energy

The detector is sensitive only to those neutrons that* have lost a great deal of their original energy through collisions with the surrounding atoms, became moderated or slow neutrons and were scattered back to the detector. Usually either a tube filled with borontriflouride gas or a scintillation crystal of europium-activated lithium iodide is used as a slow neutron detector. (Pig. 2). The detectio slof no w neutron followine bases th si n o d g equations:-

- 172 - •B + n ______^ Li + He + Energy

^Li + Jn ______v 2He + IH + Energy

+ Energ E n ______I yJ gH + e+ P ^ v

gamme th ar densitFo y probe radiatioe sth n sources most commonly usee dar either cesiu radiur mo m that omit gamma photons bace Th .k scattered gamma photon detectee sar Geiger-Mtllley db r tubes (Pig. .3) Surface probesoie placee th lar n s) surfaco d5 (Figd an e . 4 wit care hdu e to establish good contact through preparin locatioe gth measuremenf no e b o t flat, smootplanty frean d deptr an hf Fo eo . h probes, access tubes usuallf yo aluminiu steer o mplacee lar d intsoile th o , theappropriate nth e moisturr eo density probe is inserted to the desired depth in the access tube. The sealer or rate meter gives a count rate which varies with moisture or density variations, This count rate is then located on a calibration chart, and the moisture content or densitdirectle b n yca y read frocharte mth . This technique provides many valuable advantages, mainly the following: 1. Large volume of material is analysed in a single measurement, as the probes normally measure an almost spherical volume of soil with an average diameter of increasinm c 0 4 largea o gt r volume soiln i ,> f so witcm diamete5 ha 7 o t p ru ver moisturw ylo e contendensityw lo r to . 2. With depth probes measurements of moisture content or density can be made at y deptan h beginning approximatel soilf o m .c 5 2 p yto froe th m . 3 Measurement non-destructive sar requird ean physicao en chemicar lo l pro- cessing. 4. Long term studies of moisture content and density of the same volume of soil are possible. In soil applications, for instance, a permanent access tube can be left in the ground so that a moisture or density measurement can be made at the desired depth at any future date.

ITEUTROTHEOR. E V TH F YO N MOISTURE METER

Moisture measurements are based on physical laws governing the scattering and moderation of neutrons. When a radioactive source of fast neutrons is placed in the soil, the emitted neutrons collide with nuclei of the surrounding atoms and are scattered randoml directionsl al n yi . Each collisio neutroa y nb n causesa loss of part of its kinetic energy. The scattering and energy reduction process continues for a neutron until its kinetic energy approaches the average kinetic energ scatterine th r.tomf yo n i s g medium thit A . s lower energy levee th l neutro designates ni sloa d w neutron.

- 173 - The average energy los fasy sb t neutron mucs si h greate collisionn ri s with atomiw atomlo f cso weight tha collisionn ni s involving heavier atomsd ,an hydrogen is the only element of low atomic weight found in the soil. The moisture probe is- constructed with a special detector which is unaffected by fast neutron detectd san s only slo moderater wo d neutrons. Thereforee ,th numbe moderatef ro d noutrona dotoctc unir f timpo d o t alss i e measura oe th f o e concentratio hydrogef no nsoile atomth .n i s Since the hydrogen content of soils is largely contained in the molecules of water, the slow neutron ccui.t thu:- ^ocomes a measure of the moisture content soile th .f o

. THEORE GAMMAVI TH F .YO DTiNSITY PROBTS

The measurement of density is based on the known interaction of gamma rays orbitaane th d l electron atomsf so . Gamma rays havin energn ga y less than emitteV Me radioactiva 1 y db e source soile th , , n tha o wil places r i to l n i d interact witsurroundine th h followino tw ge atomth gn i sways : Compto) (a n effect

In this reaction the gamma photon acts like a billiard ball, collides • wit electron ha d ejectnan frot orbis i gived it menergs tan it som t si f yeo and the photon itself is deflected from its path. The photon thus proceeds in directiow ne a witd an nlesseha r energy energe Th . y remainin scatteree th n gi d photon is available for further interaction with other electrons either by compton or photoelectric effect. (b) Photoelectric effect In this interaction the gamma photon gives up all its energy in the interaction and coasee to exist. Part of the energy of the photon is consumed overcominn i bindin e electroe gth orbits th it f remaindege o n n,i th e th f ro energy appears as kinetic energy of the photo-electron. The photon has to possess energy greater than the binding energy of the electron but not so much more than the electron can take, Photoelectric

- 174 - The density probe measures the wet density of the soil. Therefore, the moisture weight should be su'btraced, if dry density data is desired.

VII. RESOLUTION OP THE NEUTRON MOISTURE METER

The sphere of influence (ellipsoid) of the neutron moisture meter is the mediume th zon f eo , which effectively contribute observeo th o st d activitf yo the detector. In practice the radius R of this sphere of influence is determined through lowering the probe (source-detector assembly) into an access tube, into homogeneoua s mediu watef mo r content takind ,an g reading variablt sa e depths. The detector count-rate is plotted as a function of the depth and the radius R is defined as the depth where the count-rate equals 95$ of the maximum count-rate. e spherTh influencf eo e varies wit soie hth l moisture content radius It . s reache minimusa waten i m abouf rc o m 5 (100$ 1 tmaximua d ) an m abouf c mo 0 t4 ver r soilsy fo ydr . The relatively big soil sample involved in every soil moisture measurement with the neutron moisture meter could be considered as an advantage or a disad- vantage, dependin objectivee th stude n go th yf s o bein g performed meant I . s that the readings we obtain represent an average value for a soil layer having a thickness equal to the diameter of the sphere of influence and varying between dependinm c moisture 0 8 th d n go an em abou c content 0 t4 . Thi resolutiow slo f no the equipment is characteristic for the method. The low resolution makes the use of the depth probe to measure the moisture content of the top soil layer rather difficult, as in such a case an appreciable amount of the neutrons escape to the air. However, tho use of a special cali- bration curv tako et e into consideratio portioa lose neutrone nf th th so f no s measuremene tth o hemisphera r o t paraffinf o e a , s plastia t ac iror co o nt reflector would enable us to start our measurements at a point as close to the . cm soi5 1 lo t surfac 0 1 s ea resolutiow Thlo e n also indicates that gaithero n takinn ns i i o g measure- ment deptt sa h intervals less than. aboucm 0 2 t

VIII. MAI NEUTRONE USETH P SO N MOISTURE METER

e deptTh h moisture probe gives directly th?) moisture conten volumr tpe d ean its performance is vory satisfactory especially if we are interested in measuring soil moisture changes on the same soil sample, as many possible sources of erro avoidee rar sucn i d h measurements. Fortunatel changee yth soin si l moisture content are the most interesting measurements for agricultural studies. maie Th n application neutroe th f so n moisture meter are: 1. Determination of the soil moisture content at a desired depth. 2. Through measuring the area limited by the curve of moisture content vs. depth (integration), the quantity of water contained in the soil down to a certain depth can be calculated. - 5 17 - 3. Determination of the "field-capacity" or water holding capacity after irrigatio heavr no y rain. amoune th watef f o tI r . containe4 fiele soie welth s th la ds n la i d capacit y knowne ar amoune ,th irrigatiof o t n water that shoul appliee d"b brino t de gth soil moisture content to the field capacity, down to a certain depth, could be calculated. . 5 Estimatio adequate th f no e irrigation interval under certain conditions especiall wiltine th f yi g poin knowns i t ? through predictin time gwhicth t e a h the moisture content of the soil would approach that corresponding to the recommended moisture level for applying irrigation water. 6. Through successive measurements rough but acceptable estimates of water percolatio d soinan l permeability "coul madee db .

7. The zone of maximum activity of root systems could be estimated at a certain time as it usually contains less moisture than the surrounding layers. 8. Changes of soil moisture distribution or fluctuation of water table level aroun yeae th dr coul followede db . This provide informatioe sth n essentiar lfo either improving or planning of drainage systems. 9. Studies aiming at investigating the effects of various cultural practices such as introducing a fallow period, using wind breaks and mulching on water conservatio cror no p water requirements.

IX. PRECAUTIONS WHILE MEASURING (a) Standard reading (in the shield) should be taken at least twice a day (at the beginning and when half the planned measurements were taken). ) Compactin(b soie gth l aroun accese dth s tube shoul avoidee db d through the use of a wooden board provided with a hole in which the access tube would fit. (c) A total of about 10,000 counts should be accumulated for each measuring poin reduco t maintaid an e statisticae th n levelw l lo erroa . t ra placemene Th accese ) th (d f sto tube shoul propee db chosed ran o ns that the readings are representative for the area of the plot (effect of little difference soin si l surface level, canopy shade, drippin raif go n water along the truntreea f ko , etc.).

- 176 - X. REMARKS ON THE USE OP SURFACE PROBES

Surface probe vere sar y valuable tools thabeine ar t g widely use teso t d t rat'her homogeneous materials where the moisture content is more or less evenly distributed. This gives such equipment great importance in speeding up moisture and density measurements during construction variouf so s types suc buildingss ha , road airfield san d runways. surfacf o However e us e e probe,th agriculturan si l studie vert no ys si widely spread because it is rather easy to take soil samples for moisture or density determinations from the top soil layer in addition to the following two main difficulties: 1. The necessity of establishing good contact between the probe and the soil surface, oblige investigatore sth preparo st surface th e becomo et e flat, smooth and free of plants. This is not always easy to do. 2. The moisture content of the top soil layers changes usually very rapidly with increasing depth. This make vert si y difficul estimato t e thicknes soie th l f so layer involve measurementa n i d facn soie volume I .th th t l f sampleo e involved in a measurement is variable and increases with the decrease of the moisture contendensitye th r to .

WELLO TW SE GAMMTH . AXI PROBE

Owing to the importance of measuring the distribution of soil moisture in the top soil layer ,vera y promising techniqu bees eha n recently develope thir fo ds purpose. Small access tubes, about 5^ cm long, are placed in the soil, so that the distance separating the fixes i mweld an dl defined, the gammna a radiation source is placed in one tube and a detector is lowered to the same depth in the other. Through using small detector and a collimated (point) radiation source the pathway of the gamma rays could be restricted to a rather thin soil layer of about 5 cm height. A portion of the emitted gamma photons is absorbed by the soil sample and the water molecules it contains, while another portion reaches the detector. The number of gamma photons that reaches the detector decreases as the moisture contensoie th l f samplo t e increases detectoe th f I s .connecteri a o t d counting unit or a rate-meter, the indicated count rate could be transferred to a measure for the moisture content of a certain well defined soil layer with the calibratioa aif o d n chart. Such equipmen bees tha n recently develope r labofo d - rator wels ya lysimetes la r investigations proved vere ,b an o yt dpromising .

- 177 - XIII. BETA GAUGING TECHNIQUE

The dynamic nature of the soil-water-plant systemhas long been recognized. However, measurement planf so t wate stile rar l absen mosn i t t experimentse On . of the reasons for this is, of course, the difficulty of making such measurements. Recent development of what is called the beta gauge gives promise of removing this block principle Th . that s esuitabli a f ,i e radioisotop places ei d unde planra t leaf, a portion of the radiation therefrom will pass through it and be detected above the leaf. The more water in the leaf the thicker it is presumably, and thus less radiation will pass through. Whil edevelopmene stilth n i l t stage, this ingenious device with improvements should permit continuing measurement of water content of a leaf without damaging or destroying it. This technique illustrated in Piglikels i . , becomo 6 yt e very helpfuneae th r n futurli determininn ei e gth plant need for irrigation thus allowing for applying water at the proper time intervals so that harmful draught effects could be avoided.

- 178 - WATER AND ION MOVEMENT IN SOILS

W.R. Gardner

Water movement in the soil profile influences many important physical and biological processes related to crop growth. For example, infiltration into the soil profile and evaporation from the soil surface are determined as much "by soil physical properties and processes as "by atmospheric factors. The availability of water for transpiration and growth is often determined by water movemen rooe th t n zcnei t . Drainage and, hence, aeratio soie th l f nprofilo e are directly dependent upo watee nth r transmitting propertie soile th .f so Water moves through the soil in response to the sum of two major forces. The first of these is the force of attraction between the soil particle surface watee anth d r molecules. This force, whic bees hha n calle matrie th d c potential, soil moisture tension, soil suction capillarr ,o y potential causes capillary rise, water movement to plant roots, and generally, movement from regions of higher to lower soil water content. The second water moving force is that of gravity. Since this force always acts downward it often results in a net down- ward movement of water in unsaturated soil profiles, though the direction of forceso tw e saturaten I th . motiof o determinem s di n su soilse th y ,db i.e, below the water table, gravity gives rise to the hydrostatic pressure which may resul waten ti r movemen directiony an n i t . There is now a large body of literature dealing with many different flow problems. Most solutions of such problems are based upon Darcy's law. This law may be generalized to state that the water flux density is proportional to the driving force, which is the gradient of the hydraulic head. The hydraulic gravitationae th f o m su e •l th heahea s i dd (elevation abov datue eth m planed )an the pressure or suction head, depending upon whether the soil is saturated or unsaturated. In vector notation this equation is written: ) (l graK - H d- Q where Q is the flux density, H is the head, and K is the hydraulic conductivity. physicaa s i K l parameter characterizin versoils e i gth yK .dependen t upon soil water content, sometimes dependent upon the concentration of ions in the soil solution and may also vary from point to point in the soil and from season to season. When combined witequatioe th h f continuityno :

?»/?-t = -div Q (2) volumetrie th wher s i e0 c wate times i r t conten. soie d th JDiuatiolan f o t ) (l n give particlsa e differential equations whose solutions.for appropriate boundary and initial conditions describe the water content and flux of water at all points and times in the system under consideration. These equations represent a very powerful mathematical tool for the understanding of soil water movement. Obtaining satisfactory solutions of the flow equation can be a very difficult task. The existence of high speed digital computers, however, now renders possible solution manf so y problems. Inhomogeneitie largd san e temperature gradients still represent formidable obstacles, but otherwise the main task now facing soil physicist hydrologistd san thas si properlf o t y definin boundare gth y conditions and other field aspectprobleme th f so , including quantitative characterization soie ofth l physical properties.

Soils Dept., Univ. of Wisconsin, Madison, Wisconsin. Published by permission of the Director of the Wisconsin Agricultural Experiment Station.

- 179 - Unfortunately cannoe ,on t ordinarily tak samplea soif eo l frofiele th m d laboratore th d analys doean e n i determininn on si t s ei ya fertilite gth y status soil e r exampleth Fo .f o muse ,on t kno onlt soie wno yth l water e contenth t tbu energy (raalric potential) with whic watee hth retaines ri soile e th Th .n i d sampling process often alters this relationship so that in order to measure the hydraulic head gradient satisfactorily i.n situ methods are necessary. Great progress has been made in the past two decades in learning how to solve the mathematical problems describing water movement in soils. However, much remains fiele donth e tn orde ob i d n ei correctlo rt y identif problenature e th yth f eo m and characterize the soil. In this regard, our knowledge of soil-water relations arir fo d region probabls si y much further advanced than thahumir tfo d regions because of the, heretofore, greater necessity for careful water management in arid zones. Increasingl future th neer higher n yei ou fo d r food production will require better managemen watef to r regime humin si d regions. This seems particularly true for tropical regions such as Southeast Asia where all of the elements essentia cror lfo p production, e.g. radiation, water, C0 nutrientd ?,an e sar potentially available year-around, but only by knowledgeable management can the potential be achieved. An obvious example of the type of problem calling for attention is the management of rice paddy soils so that they need not lie idle durin "drye gth " season. An understanding of water movement in soils is a prerequisite to an under- standing of ion movement. Water movement profoundly influences the direction and movemenimportann n a io rat e f b eo d als y tan to ma facto determininn ri g 'the rates of chemical reaction soie th l n solutiosi uptakn io plany d eb nan t roots. Ions mov t dy significanno o ean t distance throug soie hth l unles solutionsn i thee yar . Dissolved ions tend to move as the soil solution moves. The rate of ion movement, or ion flux density (quantity of ions per unit time crossing a unit cross sectio- nal area), can be described by the equation: ) (3 C Q = F where F is the ion flux density, Q is the water flux density and C is the concen- tration of ions in the soil solution. The total flux is obtained by adding up the individual products of water flux density and concentration over the cross sectional area of interest. Since the flow system in soils is so complex one ordinarily averages the waxer flux and concentration on a macroscopic rather than microscopic scale. Thus, equation (3) is frequently written in terms of the average velocitysoie th l f solutiono , ,v . This velocit watee equas th i y ro t l flux dersity divided by the volumetric water content, ©.

Dissolved ions move relative to the soil solution by the process of diffusion, describee whicb n hca d mathematically:

F = -D 0 grad C (4) flun io x e densitdiffusiono th t diffusio e w e th no y du wher s s i i ,D eF n coefficient (which is a function of the water content and of soil properties) and C is the average concentratio diffusine th f no g ion gradiene .Th takes ti n with respeco t the soil solution and not necessarily with respect to the soil matrix. Equations (3) and (4) combine with the equation of continuity to give the particle differen- tial equation (fo dimension)e ron : - 0 18 - 5*C = D £2C + > (vC) (5) *t ^X2 ^X Equation (5) derivatios ,it solutiond nan discussee sar morn i d e detail else- where. necessite Th averago t y macroscopia n eo c scale mus takee tb n into account in the application of equation (5) to transport in the soil. The actual variation in velocity of the soil solution from point to point throughout the pores results in a process similar in its effect to diffusion and analogous to eddy or turbulent diffusion. This process, called dispersion, is conveniently treated mathematically to a satisfactory degree of approximation in most soil system replaciny sb diffusioe gth n coefficien dispersioa y b tD n coefficient, here denoted by D. The frame of reference (origin of the x axis in equation (5) is assumed to move with the average velocity v of the soil solution so that (5) reduce: sto "_ (6) 4 t Many substances interact strongly with tht* soil profile surfaces, e.g. many plant nutrients, pesticit3.es, herbicides, and pollutants. The adsorption process reduces distanc movemenf eo boty tb h diffusio masd nan s transpor similaa o t r extent. Only that fraction of a substance in solution moves readily. As a rough rule of thumb, one may assume that the distance a substance will move relative to the distance it would have moved were there no adsorption is in the ratio of the fraction of the substance that is in solution. It should be noted that while adsorption reduces the distance of movement, the presence of adsorbed ions results in an increased flux density for a given boundary condition. Thus, more ionavailable sar uptakr efo e fro soia m l wit higha h adsorption capacity than from a soil with a. lower adsorption capacity, given the same concentration of ion solutionn si . If the adsorption isotherm is linear, then: A = R 0 C (7) where A is the quantity of ions adsorbed per unit volume of soil, and R is the ratio of adsorbed ions to ions in solution. The ratio of ions in solution to the total number of ions is 1/(R + l) = 1/b where b is the notation used by Olsen-3 and several other workers. If the adsorptionisotherm is non-linear, which is often the case, then R = dA/dC and the equation becomes non-linear. Exchange ions are distributed in a thin layer near the particle surfaces in a non-uniform way that requires special treatment.4

2 c.f. Gardner, W.H. 1968. Nutrient transpor plano t t roots. Trans Interh .9t . Soil Sci. Cong. Vol. I: 135-141. Adelaide; also references cited therein. Soil Sci. Soc. Amer. Proc. 1962. 26:222-22?. 4Soil Sci. Soc. Amer. Proc. 1966. 30:17-22.

- 181 - Durin uptakn gio plany eb t root additionan sa d complicatinlan g factor comes into play. This is the growth and extension of the plant roots through the soil. This growth continuously brings the root into contact with new regions of the soil and makes more ions accessible for uptake. In a one dimensional system in which ther upwars i e d movement toward plane sth t root zone maximue ,th m ratf eo uptakn io eventualls ei y determine rate roof th eo y tdb rate growtf th eo d han water movement. This rate is givon by the equation: ) (8 a ) ub * v ( C = P where u is the rate of root growth and v is the velocity of the soil solution. adsorptiono ther1 n = s ei b f I whicn ,i h case root extensio wated nan r movement are equivalent in their effect upon ion availability. For b greater than one root growth bring rooe int p region w sth soiti te one th l f sfroo m which ions then move introoe diffusionoy th tb . Both processe operatine sar g togethert i t ,bu rate roof th eo s ti diffusiot growtno d han n which limit rate uptakesf th eo . generaln I , mass transpor onle th y s procesi t whicy sb hmovee b ionn dsca through the soil any great distance, that is, more than a few millimeters. Even over short distances, mass transport will predominate over diffusion if the two processes continue long enough, because decreasing gradients in the case of diffusion inevitably lead to decreasing diffusion fluxes. Many problems remai solvee b o nt d relativ n transporio o et uptakd tan n ei soils e boundarTh . y condition e sit th uptakf rooe e o e difficult th sa ar t n ei t. to specify. Many reaction occuy sma r simultaneousl ratet ya s thapartialle ar t y determined by biological activity. But an adequate understanding and description importanf o t soil processes suc nitrats ha e leaching, volatilisatio ammoniaf no , uptaken io , etc. will only come wit adequatn ha e understandin basie th cf go principle transportn wateio f so d ran equatione Th . s presented here ear undoubtedly oversimplified. Only by careful experimentation based upon an under- standin presene th f go t concepts n the,ca y lea improvemento t d r descriptioou n si n thesf o e important systems.

- 182 - THE EFFECT OP ASPHALT BARRIERS ON THE MOISTURE AND NUTRIENTS RETENTION RICN I SUGARCANTD EAN S FIELD SANF SO D SOILS C.C. Wang, K.Y. Li, C.C. Yang, F.W. Ho and' J.T. Wang Taiwan Sugar Experiment Station, Tainan, Taiwan, China

Techniques including the use of radioisotopes have been developed to spray a thin continuous layer of asphalt berrior on the subsurface of sand soil to evaluate its capability of moisture and nutrients retention. This impervious t-o water barrier prevents the water deep penetration and increases the amount of soil moistur nutrientd an e plane s th hel tn i droo t zone. Field experiment indicatel sal d thayielde tth sprinf so g cand ean ratooned spring cane were greatly increase barriere th n do compares sa o t d that on the controls. Water consumption for spring cane on the barriers showed onl hale amoune yon fth controlse tth user greafo do N . t differencn i e water consumption among barriers on cane fields was observed. Results of first rice crop in 196? indicated that, when the water was daya ,s hr supplieone-sevent 2 1 r dfo amoune hth watef o trequires e rwa th n o d asphalt paddies as compared to that on the controls under the condition of equal rate of fertilization. The barrier plots surpassed the controls by increasin graie gth n yield 225$- fro 0 4 m« Unde conditioe rth hrs4 2 f .no irrigation in the second rice crop of 196?, one twelfth the amount of water and an increase of 40$ of grain on the barrier plots were observed over the controls which 36$ more amount of nitrogen than that of barriers was even used. Laboratory study showed that the barriers have groatly prevented the deep percolatio watef n o nitrogen d ran important no t ,phosphorur bu fo t d san potassium profile th n ,i thif eo s san ds foun soilwa dt I . tha optimue th t m depth at which to place the barrier in this sand soil is 75 era for sugarcane and 20-30 cm for rice respectively. With the purpose of efficient use of water and fertilizers on droughty sand soils this technique coulvaluabla e b d e approac improvinr hfo g food production.

- 183 - THE EFFECT OF ASPHALT BARRIERS ON THS MOISTURE AND NUTRIENTS RETENTION IN RICE AND SUGARCANE FIELDS OF SAND SOILS C.C. Wang, K.Y. Li, C.C. Yang, F.W. Ho and J.T. Wang Taiwan Sugar Cane Experiment Station Tainan, Taiwan, Republic of China

INTRODUCTION

Plants need water and nutriunts for growth. It has been found that'plant roots commonly uptake 500-150 watef o synthesizo 0g rt organif o g e1 c matter. In fact, the water magazines of a soil, cither from ground water or from irri- gation wate ry limitin actuallke e th gs yi growtfactoe th plantf o hro t d san determine soie sth l productivity. Deep sand soils usually produc yieldinw elo g of ric d cane ean Taiwan i * n becaus thuif eo watew rlo nutrition-holdind ran g capacities. Therefore suggestes i t ,i dn imperviou a tha f i t s barrier coule db artificially placed in the subsurface of sand soils their water-holding capacity and productivity should be improved. This principle has been initiated in Michigan, U.S.A. in 1958 when bentonite claplastid yan c films were place Grayina n i d g sand near Kalkaska 1961n I . , they found that using liquid form asphalt instead of bentonite and plastic film as a barrier had its advantage of costs and better joint in the second direction. Test Michigan si 196n ni showe) 6(l d that irrigated asphalt plot produced around JQffo more vegetables and at least was saving 39 mra of irrigation water per crop than that without barrier. As the increase of food production is an integral part of our economic development improvo ,t productivite th e yieldinw lo f o y g sand soibecoms lha e a. very important problem to be solved in Taiwan. This study is to investigate the efficient use of water and fertilizer by sprayin asphaln ga t barrie subsurface th n ro sann ei d soil d evaluatsan s eit effect on the water properties as well as the optimum depth in which the barrier is to be placed for rice and sugarcane.

EXPERIMENTAL

Rice and cane field experiments were established in February 196? on Fusan farm of Cheluchen Sugar Mill, Taiwan Sugar Corporation. The soil derived from sandston fins ei e santhrougl al d profile . hth Padd cm e0 y dow16 plot o nt s sizn d i tha r sugarcanea ean tfo 4r wer x 8.75x m em 4 n,>25 . Asphalt barriers were placed 20cm, 30cm, 40c60cd man m deericr fo pe plot 50cmd san , 75cd man 100c canr mfo e plots respectively. Sugarcane plots included contro disd lan - turbed control plotl Al .s were hand-excavate barriee th s hand-sprayed rwa an d d with grade 50 asphalt in a thickness of 3mm (15 tons/ha). Available rainfall and total irrigation water applied to the different plots during the growing season of rice and cane were recorded. Soil moisture contents were determined ovey ,b n drying tensiont ,a s create followss a d : 1 atmospheres0. , water pillar regulate tensios it d n wit compressorr hai ;

- 184 - 0.11-1.0 atmospheres, porous platpressura n ei e cookerj 1.0-15.0 atmospheres, ceremic pressure plate. Soil nitrogen was analysed by Kjeldahl method. The movement of phosphorus and potassium in soil profile was measured with radio- isotope technique. A simple and convenient method for measuring nutrient movement throug undisturben ha d soil prcfil boos uha e n b designey ma d an d describe followss da : One hundred ml in size of stainless steel cores wore used to take vertical undisturbed soil samples fron the pDots down to 100cm deep at an interval of 5cm. Soil cores were connected firs y tap tb thed ean n fastened with auto-bicycle inner tub foro et undisturben a m d soil column. Soil mixed with liquid forf o m radioisotopes was dried and then placed at the top of this column. Pour thousand three hundred and twenty milliliters of distilled water which is equivalent to 2200mm of total water required for one spring cane crop in this farm was used to leach down automatically through the column. At the top of the radioisotopic soil layer a constant-head water was always kept in order to make a relative uniform infiltration. The bottom of the column was supported with filter paper 0 anmes36 d h scree facilitato nt drainages eit radioactivite Th . filtratiof yo n of the column was checked periodically. Soil cores then were untired and dried radioactivitr fo y determination afte leachine rth s completedgwa .

RESULTS AND DISCUSSION

The influence of asphalt barrier on crop yieldss a. Rice: The influence of asphalt barrier on rice yield is shown in Table 2. All data indicated that asphalt barriers can be used to improve the rico production on san dfirso soilth tn I .cro 1967f po , ric ebarriee yielth n o dr plots swa highly superior to that on the controls with statistical significance at the 1$ leve secontreatmentsr e lfo th n di crot 1967f Bu o p. statisticao ,n l significant increase in rice yield was observed on the barriers as compared to that on the controls. Thi apparentls si larga o t e e amounydu waterf o 10837mto t p ,u m which was supplied to the controls 24 hours a day to keep those plots flooded durin whole gth e growing season. Under these favourable water supply conditions, it appears that there was no advantage for the asphalt barrier as far as rice yiel s concerneddwa firs e th tn I cro. 1968f barriee o p ricth e ,n th eo r plots showed abou 5 time2. t larg s controlse sa ricth s alse yielea wa n th eo t s I a d. highly significant at the 1$ level for treatments. In the second crop of 1968, the growth of rice on controls was seriously affected by drought at tho time of two weeks after transplanting due to the attack of typhoon which damaged the irrigation facilities rice controln Th .o finalls swa y kille Octoben o d r 1968 yielde th barrien d so an r plots showed much lowe compares ra previoue th o t d s three crops. It is obvious that no rice production would be obtained on sand soil when water firse suppl weeko th ttw n i ys after transplantin limiteds gi .

185- - effec* TablTh asphalf et1 o t barrier variout sa s depth cann so e yield wated san r consumptio 19*?/

Treatment 967/68 spring cano 1968/69 spring o«nc> 1967/196 *ont4 92 h [ ratooned spring cane icld, t/ha water con- yi«"l d, t/ha wator con- yield, t/ha water con- sumption, mm sumption, urn sumption, mm Control 54.3 . 2100 42.1 423 70.6 2523 Eisturb lOOcsa J.-.-?p 43.9 1950 38.9 419 •3J.9 23n9 Barrier 50cra d^p 83.3 900 49.4 394 103.2 1294 Barrier 75cm cm-?p ^04.3 900 58.8 4*-? .114.7 1 361 Barrier lOOoia .j-?rtp 97.1 1000 55.3 398 214.4 139? L.S.E. 0.01 0.13 1.25 Availa^. A &jnfa;is i 57?cam ll.7i.2nn 1743.2mm e effecT»blTh f asphalo t2 e t b^•t^i•.*7• t varioua 3 s .1-

Treatment I?o7 rl«* nrcp 1968 ric-" cr-*>p Vtta*. «r.p t cro1s p ?n<^ crop 1st crop 2n'i crop ; 1967/68 1968/30^? w.cor., W.CT.. y. i y. y. w.con. t/hn mrc t^ha mn t/hn mm t/h* mn "•*'?• t/hn Control 0.4 2539 3.4 10837 2.3 1415 — . 453 l'..5 — . * 2->.0 12! Barri'-r 20cn dcsp 4*5' 369 4.8 625 5.4 338 2.4 109 18.0 — 27.8 81 Carrier 30cts deep 4.9 359 4.6 807 5.3 314 2.0 115 19.0 — 32.0 ••:>•'• ?»rri*r 40^m deep 5.0 338 . 4.8 855 5.5 401 2.1 112 18.4 — 28.1 131 Barrier .^Osm dnep 5.6 365 4.8 840 5.4 367 1.9 10 \ 18.0 • — 34.<: 117 Barrier 40c-a ds«p 4.7 35« 4.8 868 %< 3*? 2.1 101 ^9.4 — 31.1 11?

t.S.D. 0.01 0.43, 0.53 O.S9 Available R^infallt 523nn: 240nn { 460nm * Ho d*ta available Sugarcan. b e e effecTh asphalf o t t barrie sprinn ro g cane yiel shows di n I Tabln ni . e1 spring can 1967/68f eo , treatment plots surpasse controle th d increasiny sb e gth yield over 53$ on the 50cm barrier; 92$ on the 75cm barrier and 79$ on the 100cm barrier respectively treatmente Th . controld san s were statistically signifi- cantly differen level$ 1 ratoonen t I a t. d spring can 1968/69f eo , cane yielf o d barriers also showed statistical significance at 1$ level for treatments as compare controlse th thao t dn to . Seventy fiv barrierm ec disturbed san d plots still performe highese th d lowesd an t t yieldings respectively thin ,i s crop year. In 24-month spring cane of 1967/69, 75cm barrier also had the highest yielding orer the controls. 3y comparing the total yields of spring cane plus ratooned spring cane with tha 24-montf o t h spring cane foune ,w d thalattee tth onld rha y 75$ of the total yields of the former. It seems that it is not preferable to grow 24-month spring can Tainann ei ,cans a Taiwan er yielfa s concerneds ,a dwa . reasoe Th n that l^cm barrier showed higher cane yield tha othene th tha rn to plots wil discussee lb d later significane Th . t lowe rdisturbee yielth n o d d control s comparesa control e increase th thao th t d n o o tt s f e o coul du e db coarser porosity percentage of the soil by disturbing the solum, thus the deep leaohin solublf go e nutrient rapid san d percolatio profil e watef th no f ro e were both increased. The lower cane yielding on the 50cm barrier as compared to that on the deeper shallowebarriere th . 1 apparens s: i r to effectiv e tdu e soil volum roor efo t developing. Usually 80cn ,a m dee leaspe th solu tfoune e s b dept mth wa o dt r hfo

better growt sugarcanf ho elowee porosit(3)r th profilerai e . ; 2 th f yo s A .

m we calculated, at the depth of 20-4Ccm on the 50 barriec r its air porosity only had 10-0$ by volume (4) when an appreciable quantity of water at low tension remained abov barriere s alseth wa ot I foun. d thacriticae th t l r valuai f eo porosity of the soil was 12-15$ for sugarcane. Theoretically, can e100ce yielth mn o dbarrie r highese shoulth e db t among the shallower barriers becaus deepes it f ero solu betted man r aeratione Th . reason that this was not the case could be due to the fact that the water supply was not sufficient on the ICCom barriers as shown in the water consumption column iunfavourablne TablTh . e1 e relation moisturbetweed profile an th r n ai ei e wil reasole th als e nob which wil discussee lb d later. Lettuc. c e Data show Tabln ni presene2 effece tth asphalf to t barrieyielde th f n so ro two lettuce crops. In the second crop of 1968-1969, irrigation water was not greatly saved but a marked increase in yield was obtained due to the presence of the barriers. Statistical analysis showed significance at the 1$ level for treat- ments. Lettuce on the 60cm barrier was superior to that on the shallower barriers, bugreao tn t differenc yieln ei observes dwa d amon barriee gth r treatments. influence Th asphalf eo t barrie watee th rn ro consumptio ric r sugarcaned nfo ean . As shown in Table 1 and 2, water consumption for rice and cane was greatly presence barriers e th firsdu e th o eth t f teo r ricFo . e cro 1967f po , water consumptio barriere th n no s averaged 368m compares ma thao t d2588mf to m on the controls. In the second rice crop of 1967, we irrigated the controls 24 hours a day for keeping the paddies in a flooded condition and a tremendous saving of 10,000mm of irrigation water had been found on the barrier plots. - 187 - In general, 75-85$ of irrigation water could be saved on the barrier paddies as compared to those without barrier. The discrepancy in water consumption for each rice crop was attributed to the fluctuatio watef no r supply durin growine gth g season. The dramatic effect of asphalt barrier on the water saving for rice did not e can occustilt th i en ro fielt l Bu bord a eone-hal f amounsavine th f f o tgo wate r sprinrfo barrieg© th can n eo r p^.ots wheneve available rth e rainfals lwa deficient ratoonee th n I .d spring ce^ 1968/69f co , however, ther almoss ewa t no difference in water consumption between treatments and controls because that year had its advantages in available rainfall. e influencTh asphalf eo t barrie increasine th n ro watef go r retention capacity of sand soil. soie th l s moisturi Pig1 . e tensio subsoie n th curv r 20-52cf e lo efo th f mo sand soil studied orden I . illustrato rt watee eth r retention characteristics of cane barriers, soil moisture content variout sa s depths were determined periodically by oven-dry method. Fig,2 shows the changes in soil moisture during a short period of growing season after an excessive irrigation on Nov.l6. s founIwa t d that soil wate t 25cra m controle deptth n ho d droppe e sha th o t d point startin d gonirrigato gt an nint e wiltin e th y dow th h da t o a ent g point thirty-thire ath t aftey dda r this flood irrigation. 75ce Whilth m n barrieeo r plots, they requirt ,no eved ndi e water unti 0 dayl4 s after that irrigationt I . also means thatimo sufficienf on tr e t irrigatio barriee th n no r plots wile lb available for more than 6 weeks as compared to that of 2 weeks without barrier in the dry winter season. Asplu.lt barrier had greatly increased the watesvholding deef o capa py iit san d soil. e influencTh asphalf eo t barrie nutriente th n ro s retentio sanf no d soil. n additioI watee th ro nt saving effoce ,th barrie f nutriente o t th n ro s retention was also evaluated. In paddy field, soil nitrogen is subject to leach ovt more easily in deep sand soil than in the finer soils. Soil total nitrogen of the experimental plots after 3 rice crops was analysed and is shown in Pig. 3, e distributioTh f totano l ritrogon profil e :".barriee th n th n eo r plots swa always falling in the „•• te of O..C51-0,066$ with only a very small variation. However e tota,th l nitroge profile e controlth th i ' i ne01 s decreased witie ith increas deptf eo d showehan d three times muc htopsoie morth t a el than that a t the ICCcm deep subsoil. Dat Pign ai . indicate3 d that wheasphale nth t barrier was placed in sand soil, the soluble nitrogen would be prevented from leaching profilee accumulatioe th th n i s A . soif o n l nitroge surface t occuth no n d ro e ndi of the barriers according to the res\ilt of the analysis, we would like to con- sider til at. the present ratw of fertiliser, Ns^Ckt^C = 120 kg/ha, for rice.was nrt in excess.

Pig, 4 presents the result of the movement of phosphorus and rubidium (instead of potassium) in the deep sand eoil by using radioisotopic technique, A simple method whic bees hha n described previousl uses mako ywa dt e this determination. Two thousand and two hundred mm of constant-head distilled water which equals the maximum quantity of water required for one spring cane crop was leached down through the undisturbed isotopic soil column. It was found that the distance of downward movemen :-?-3f to Rb-6d 2an 6 only showed 26cd 18cman e mth from f o ,p .thto e column .respectively. - 188 - Potassiu supposes i m leachee b o t easildt ou d y frosane th mdt i soil t Bu . was noticed that when a soil has a pH value greater than 6.5 and a high percen- tage of base saturation, potassium mobility is often very low. As'the potassium fixation capacity would not be high on the relatively aged sand soil studied, ratw th Hb-8f elo eo 6 mobilit thin i y s study migh relevane tb thio t s explanation. It seems tha presence tth barrief depte eo th 50cf ho t deeper a ro m r immobilrfo e or relatively immobile nutrients retention on this sand will not be important as far as phosphorus and potassium (in terms of rubidium) were concerned. Optimum depth and the duration of the asphalt barrier. After more thayearo ntw studyf so optimue ,th m barrie e deptth ricr f ho fo r e and sugarcane may be discussed as follows: ricer Fo : . a Since shalloa ric s i e w rooting crop measurementl ,al s indicated that yields and water consumption for rice among paddy barriers were not significantly different. Prom the economic point of view, barriers at 20-30cm depth would be preferable to the growth of rice as the barrier is considered by hand spraying. sugarcaner Fo . b : In or'der to evaluate the optimum depth of barrier for sugarcane, studies in the fiel d laboratoran d beed ha yn made simultaneously. Soil moisture contentt sa various tensions were determine d calculatean d methode th y db s mentioned abovd ean shown in Table 3 and Fig. 5.

indicates A controe Tabln Figd i dth an , .e3 5 l onlretain yca amoune th n f to water at the field, capacity through the profile. It was provided with too much air t lesbu s available moistur onlf eo y 62m depthn i m . On the 50cm barrier, available moisture increased to the amount of 168mm, 2.7'time muc s barries a e compares hth a controe o th t r o s e t deffectlit du t Bu . porosityr ai contrare th n ,o y droppe 44mo t d m which onl giv n uppee yca e th r 15cm profile layeth f ro e havin percentagr ai g e greater thaunde$ conditioe n15 th r f no maximum water-holding capacity pooe Th .r areation occurre shalloe th n i dw 15-90cm layer and is unfavourable to the root developing of sugarcane. /• Table 3. Availabfe moisture and air porosity of the sand soil studied at various depth barrierf so s

Depth Available moisture Uhsat. gravitational Dept uppef ho r layer of retained in the. moisture in the profile wit porositr hai y barriers profile (air porositv) areater tha& 1^ n 50cm deep mm index mm index 168 270 44 12 m c 5 1 75cm deep 196 316 121 34 40 100cm deep 215 346 . 208 58 65 control* 62 100 360 100 100 * Depth of the control was assumed as 100cm deep for calculation.

- 189 - 100ce Onth m barrier, both available moisturporositr ai d beed ean y ha n increased oveshallowee controe th th r d lan r barriers hige th h t contenBu . f o t suc tensiow hlo n wate 100ct ra rooe th mharo t o raiso deptto t zont d s p eu hwa younr fo g cane. Therefore, wheavailable nth e moistur lowee th rn ei laye s rha droppepoine th to t drequire irrigato t d watee eth r contenuppee th rf o t25c m layer probabl reaches yha wiltins it d growte g th poin canf d ho an te muse tb affected othee th rn O hand. costt ,i s one-third more mone placo yt barriee eth r at 100cm depth than at a depth of 75cm, with only a 9$ return of available moisture. On the 75cm barrier, a total of 196mm available moisture was conserved in the profile s 3.2'timewa t I . mucs $ morcontroe amounse a 17 th hth e d s a tan l tha 50cne th tham n barrierto . Withi 75ce nth m deep profile, upper 40cm layed rha provide percentagr d ai wite hth e greater tha$ eve15 n n unde conditione rth f so maximum water-holding capacity. In conclusion, the 75cm barrier had provided the best air and water relations with depth to allow the normal growth of sugarcane. In addition to the laboratory study, the result of the field experiment also indicated tha75ce th tm barrier plots produce highese th d t cane yieldo tw n si crop years as presented in Table 1. The duration of the barrier is still under evaluation up to the date of ' report seriouo N . s defec barrierf o t bees sha n observed Michigann I . , U.S.A. (2), they estimated the duration of asphalt barrier with 15 years. Economic evaluation of asphalt barrier. The most important thing people are interested in in this experiment must be how long this investment takes until it pays back. The cost for installing the barrier by hand was too high to be considered for oxter*-, on. An asphalt appli- cator develope Internationae th y db l bees Harvesha n. demonstrated.iCo t n March, 1969 in the States. They estimated that if tht; barrier can be installed by an applicator totae ,th l cost shoul aroune db d U.S.$ 620.00/h Unitee th n dai States. According to this study, the 75cm barrier averaged 60$ increase in yielding ove controe rth r sprinlfo g candoed considet ean sno advantage rth watef eo r saving, an additional 30 tons/ha (a very conservative estimate) of cane, or 3.6 ten sugaf so r shoul producee db year cosd pe dran t U.S.$ basi e 216.0th f so n 0(o a sugar price of U.S.$ 60.00/ton). Therefore, as the barrier can be installed by machin reasonable eth e timgettinr fo e g money bac growiny kb g sugarcane wile lb years3 .

ricer Asfo equaf ,i l amount watef so r wer controle barriee e th th use d n o dran , it seems tha productioo tn n wil obtainee lb lattere th n o d. Accordine th o gt data of the second rice crop of 1967 $ at least a 40$ increase in yielding would be maintained on the barrier over the control in spite of the tremondous saving of irrigation water. The local price for rice is U.S.ft 115/ton. Thus, as a very conservative estimate, 2.8 tons/ha (two crops) more rice will be produced every year on the barrier as compared to the control, and cost U.S.8 322.00 per year. It appears that this investment can be paid for within two years when the barrier s placei y applicatordb . .... Of course, the cost of the applicator must be taken into consideration.

- 190 - ACKNOWLEDGEMENTS

The authors wish to express their sincere appreciation to Dr. R.L. Cook and Dr. A.E. Erickson of Michigan State University, U.S.A.; Mr. L.C. Hsi of JCEE, Bepublic of China; Dr. K.C. Liu and their colleagues of Taiwan Sugar Experiment Statio their nfo r technica financiad an l l assistanc preparinn ei g this experiment.

REFERENCE

ERICKSON. 1 , A.E., HANS1N, C.M SMUCKERd .an , A.J.M Influence Th . Subsurfacf eo e Asphalt Barriers on the Water Properties and the Productivity of Sand Soils. Trans.Int.Gong.Soil Sci. £ 1 (1968). 2. ERICKSON, A.E., HAWSES, C.M., SMUCKER, A.J.M., LI, K.Y., HSI, L.C., WANG, T.S. and COOK, R.L. Subsurface Asphalt Barrier for the Improvement of Sugarcane Production and the Conservation of Water on Sand Soil. Proc. ISSCT j3 (1968). 3. SHIH, S.C., LEE, L.S., PERNO, L.S. and UWG, T. An Investigation on Root System of Sugarcane. Rept. TSES, I2s$2-49 (1954). YANG. 4 , C.C. Asphalf o Theore e Th d PracticUs t yan e Barrieth n eo Improv o rt Watere eth - Holding Capacity of Sand Soil. (Unpublished).

- 191 - Field capacity

i c r-^ '.K> ')6 -'•8 Moisture content, ^ by volume

Fig. 1 Soil moisture curv 20-5r efo dee m 2c p horizon 5k, deem c > py t a \ 35

»O

barrier, 75 en barrier,100 en n e 0 5 W P * '"^•" * disturb 100 en ^ !- control !

Dat( excessivf eo e irrigation: 11/1) 6

Soi l Moistur e :>!> - at ?5 en deep

1.5

barriern e 5 ,7 1O barrier, 100 on barrier, 50 on disturbn e 0 ,10 ,, control i :/•.*. i.V « './U i V • > Pijr. 2 Effect of asphalt barriers on the soil moisture retentio sanf no d soi sugarcann lo e field - 191 b - Fig* 3 Variation of total nitrogen contents of the asphalt paddies as a function of depth due to the presence of barriers

_0._Qf />/: 0.0rj O.Gfr 0.03 0.02 $ N

Ku 50

60

70 control barrier,60cm d«up

—.*-.._ barrier. 80 —-*—*—.barri.or,^0cm deep,(Urea)

90 —*—•—barrier130cm cloep barrier ,2Ocin deep

- 191c - d Rb-8 activiP_3a f leachean 2oj n 6i s tLe d undisturbed soil colunu ( cprn/g dry wt. ) _logo___1590

10

P-32 Rb-86 o <3

f-l T* O 30- h

50-1

Distribution curve d Rb-8 undisturben P-3a f an o sn 2 6i d soil column aftur loaoiiin^ with 2200n distillef mo d water Ft ;.5 '•>«••-*• «•-• •r rclti* i^n s>aii:>f * d and without Oorri't«r« control barrier,jOcro bar.ri*'xv/5<3n barrier, lOCciu

.a... .porosity % t»ir porosity jt .aio ?? r porosit& f y ft . '•'••> ..>'i',..?P._. 1C' 0 i^.^f%.JOJ)| 0 1 J OJ_ C O_ :-.:v«.'« • .—•!'•;. -"."V"r ., • w -.. •...• ••5«•:{«' /v.'.•.:•;;/:• « « ".*•» . .It.. ? . ..I. . 10:•'=:•:!.••!•'•:••'. a'!•••:• ;x' •-.:!,'.. . . .'••• .*<,:•{ •• ' : "' ' -vi.*•} I * * * * • • ' * ' . • -'i. . i . . .. ; • ; : 0 2 * *;. * * * ...*••.••»» r-Mi^V :;:v:-5>'-i 30 .'. jr.' ji;1'.;':';> •.*••'•"••;'.:!i/; Hv ••' • •• .'• '••'.'*x.'' " " i !'• . : *oi':"-":!ii:':"\ • .,..• - •::«-. '>^^rr-x •. • •: -•'W. •-..:•:•? • ;"v:.:^ . iihr'-.-..)'--- ' :• ••'.'-...„ : • . . ; ' w.|:.r &2%zz tezZ^^&&>••?''>*•-

r p.>rosilai y

."v-.~i r-*--''":''-• ' ' grav onui t a ill »*ator *^« _ * ' **•• **,•••• 4 »•/. '!•/-•• " -.T v."..; avilaoio nuibture 100 • . • . '. >•.;.». v •• . ..-.: « * :. •• • % o hygroscopic water

?3Oist.urc,^oy volume noi3turof%by RECOMMENDATIONS

e GrouTh p noted thaterms t it referenc f so isotopef o e e us d wer se an eth radiation in soils, fertilizer and water studies. In considering its recommen- dation Groue sth p particularl Fooe yAgriculturd th recallean d f o o tw d e Organi- zation's current priority areas, namely, high yielding varieties and increasing protein production. Further, considering the importance of ric-e as the major crop of the Region, special note was taken of the recommendations of the llth Session of the Inter- national Rice Commission Working Party on Soils, Water and Fertility Practices d theian r endorsemen e Ccmmissiorth y 11/6c t"b C it t .a meetin n Tokyogi . The Group recommends that: RICE 1. The existing results for P and K fertiliser placement and timing, attained with labelled fertilizers, should be confirmed an far ar necessary for the new high yielding varieties. In this context a limited number of studies using isotope technique studo st d comparyan rooe eth t distributio varietiew ne e th sf no are also desirable. 2. Further work is required on the time of top dressing of nitrogen fertilizer, determinatioe th asin d gan particulae N-15th » f no r plan e placth tn ei wher e eth fertilizer is utilized. (IRC Working Party Recommendation 5). 3. Further work be initiated in comparing the efficiency of different natural phosphate sources. Recognizing tha initian ta l screenin carriee n b i n t gca dou pot experiments by a modified 'A-value' technique, it is suggested that the Joint FAO/IAEA Division might assembl collectioea naturaf no l phosphate sourcesifor distributio Membeo nt r State wiso swh carro h t t auch.-^omparativyou e isotope tests on their own soil types (IPO Working Party Recommendation 4), . 4 That N-15 studie effece th made s b mid--terf f to eo m drainage (Nakabashid )an intermittent irrigation on the efficiency of N-fertilizer utilization^ For those laboratories with the necessary facilities and personnel, associated studies on N-conversion, N-fixatio lossd nan nitroged ,an n fixing nicro-organisme sar desirable. OTHER CROPS 5. The Group, although noting that rice is the moat "significant crop in the region, recommended that increased interest and effort must be devoted to other important economic crops, suc legumess ha , sugar cane seel fibrd ,oi an d e crops. Optimum fertilizer and water management practices for these crops are based on very uncertain guidelines furthes wa t I .r noted, that wit increasee hth d emphasis being devoted to better land utilization through the use of earlier maturing crops grown in sequence, that fertilizer management practices for each successive crop require attention.

192 - SOIL CHEMISTRY AMP RELATED STUDIES Groue Th p strongl. 6 y recommends that individual institutes withi regioe nth n continu expano et d research using isotope radiatiod san soil-plann ni t nutrition studies, and noted the following subject matter areas; kinetic studies of nutrient movement in soils; turnover of organic matter; the nitrogen cycle in paddy and upland soils; and micro nutrient investigations.

' . ' . ' WATER 7. The Group recognized that water has a profound influence on all physical, biologica d chemicalan l reactions influencin soil-plane gth t syste noted man d tha Agence reaa d centra tth s lan yha l rol plao t ewaten yi r efficiencd yan management studies using isotopes and radiation techniques in the region. Within this general context, and having noted the serious shortage of trained personne followine lth orden gi priorityf ro , were recommended. 8. That the water management practices and associated soil moisture budget, together with accurate measurement environmene th f so recordee tb r currendfo t and future experiments where labelled fertilizers are used. 9. The neutron moisture meter (depth probe) has proven to be a very useful tool for routine measurements of soil-moisture profiles and its extended use in irrigatio soid nan l moisture studies shoul encouragede db . 10. In order to draw attention to the potential significant applications of isotope and radiation techniques in soil water movement and efficiency studies, exchange of information and training of scientists should be encouraged in the region. ORQANIZATIOtt 11. Recalling the success of the co-ordinated approach as adopted in the Six- Year Rice Fertilization Study with Isotopically Labelled Fertilizers, the Group recommends that wherever possible this approac continuede hb fels wa t t I tha. t when a number of laboratories in different countries work on the same topic, more authoritative results are achieved. It is recognized, however, that this approac alwayt no s hsi possible when very specialized equipmen expertisd tan e is required. FUNDING 12. Recalling the continual need for funds to carry out work on the subjects which have been recommended recognizind ,an limitee gth d financial capacitf yo the IAEA research contract programme Groue ,th p request Joine sth t FAO/IAEA Division ±o continue efforts to obtain support for work in the Region concerned isotopf o e radiatiod us ewit an e hth soilsn ni , wate fertilized ran r studies.

- 193 - LIS PARTICIPANTF TO S

NAME INSTITUTION ABDULLAH, Nazir Badan Tenaga Atom Nasional Djl. Palatehan 1/26 Block K.V. Kebajura Baru Djakarta, Indonesia ANANTAKUL, Jarusari Soil Conservation Division Department of Land Development Ministr Nationaf yo l Development Thailand BAJARD, Ch. J.L. FAO, Bangkok, Thailand BARRADA. ,Y Joint FAO/IAEA Division KSrntnerring 11 A-1010 Vienna, Austria

BOONNITTEE. ,A Facult Sciencf t yo Ar d ean Kasetsart University Thailand CHOLIKUL, Wisit Technical Division, Rice Department Ministr Agriculturf yo e Thailand

CRAWPOHD. ,R Regional Development Office American Embassy Bangkok, Thailand DASANANDA, Sala Director General, Rice Department Ministr Agriculturf yo e Bangkok, Thailand DATTA, N.P. I.A.R.I. New Delhi-12, India DEWIS, J.W. FAO Bangkok, Thailand

PREDRIKSSON. ,L United Nations Curzo, 21 n Road New Delhi, India

GARDNER, W.R. Soils Department Universit Wisconsif yo n Madison, Wisconsin 53706, U.S.A.

KHAN, A.B. Atomic Energy Centre Principal Scientific Officer 4 16 x P.OBo . Ramna, Dacca-12, Pakistan LAMPOWPONG, Somboon Technical Division Rice Department Ministry of Agriculture Bangkok, Thailand - 194 - LEGO, J.O. Plant Industry Station Beltsville, Md. 20?05, U.S.A.

MISTRY, J.B. Biology Division Bhabha Atomic Research Centre Trombay, Bombay-74, India

MtTKERJEE, H.N. PAD Bangkok, Thailand

NAKOENTHAP, Art Atomic Energy Laboratory Kasetsart University Thailand NILUBOL, M.L. Anong Office of the Atomic Energy for Peace Ministr Nationaf yo l Development Bangkhen, Thailand NISHIGAKI, Akira Japan NISHIQAKI, Susumu Soil Fertility Division Department of Soils and Fertilizers National Institute of Agricultural Sciences Nishigahara, Kitaku, Tokyo, Japan PAMORNCHAN, Boonsom Soil Conservation Division Department of Land Development Ministry of National Development Thailand PATTERSON USOM, Bangkok, Thailand PUH, Y.S. FAO, Bangkok, Thailand RATISUNTHORN, Paderm Facult t Sciencf yo Ar d ean Kasetsart University Thailand RICE. ,0 642, Petchburi Road, U.S. Operations Missions AID Representative Bangkok, Thailand SANITWONOSE, Patoom Technical Division, Rice Department Ministry of Agriculture Bangkok, Thailand SHIEH, Yuh-Jang Institut Botanf eo y Academia Sinica Nankang, Taipei, Taiwan, Rep Chinf .o a SHIM, Sang Chil 46-305, Whagok-Dong, Yungdongpo-Ku Seoul, Korea SUWANAWONG, Sombhot Technical Division, Rice Department Ministry of Agriculture Bangkok, Thailand - 195 - TAOBASHI. J , FAO, Bangkok, Thailand

THENABADU, M.W. Division of Agricultural 8hemistry Central Agricultural Researcn Institute Gannoruwa, Peradeniya, Ceylon

VAIT'T VOUDT, B.D, FAO, Bangkok, Thailand VOSE, P.B. Bluehous, 94 e Lane Oxted, U.K.

WANT, Chwan-chau Taiwan Sugar Experiment Station Tainan, Taiwan, Rep. of China

YINaCHON, Yubol Soil Fertility Section Agricultural Chemistry Division Departmen Agriculturf to e Thailand

SCIENTIFIC SECRETARY Rennie, D.A* Joint FAO/IAEA Division International Atomic Energy Agency Vienna, Austria

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