lëiiiitfAK • ' SU 1313.01 The Soils and Geography of the Boliland Region of

BY A. R. STOBBS

Vegetation by Dr. T. S. Bakshi

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Published by the Government of Sierra Leone 1963 To be purchased through the Government Book Shop, Freetown, Sierra Leone, and the Crown Agents for Oversea Governments and Administra- tions, 4 Millbank, London, SWi

Printed by Eyre and Spottiswoode Limited, Her Majesty's Printers, at The Thanet Press, Margate, England CONTENTS

FOREWORD 4

PART I : GEOGRAPHICAL BACKGROUND : INTRODUCTION . . . . 5 GEOLOGY . . . . 5 TOPOGRAPHY . . . . 8 GEOMORPHOLOGY ...... 8 CLIMATE ...... 9 VEGETATION . . . . 9 HUMAN AND ECONOMIC GEOGRAPHY II THE SOIL MAP . . . . II BOLI SOIL MAPS 13

PART II : SOILS : PEDOLOGICAL CLASSIFICATION 14 SOILS OF THE UPLANDS : PENEPLAIN DRIFTS 15 RED BROWN CONCRETIONARY DRIFTS ...... 15 YELLOW BROWN CONCRETIONARY DRIFTS 16 COLLUVIAL DRIFTS. . .. 17 SEDENTARY SOILS ...... l8 SOILS OF THE BOTTOMLANDS : SOILS DEVELOPED OVER TERRACE DEPOSITS 18 SOILS OF THE LEVEES . . 21 SOILS DEVELOPED OVER SLOUGH DEPOSITS ...... 22 SOILS OVER OLD RIVER CHANNEL DEPOSITS ...... 27 SOILS DEVELOPED IN DRAINAGE GROOVES; MIXED BOTTOM SOILS, AND RECENT ALLUVIUM . . 27 NUTRIENT STATUS OF BOLILAND SOILS ...... 27 LAND CLASSIFICATION 28

PART III : VEGETATION : ANADELPHIA/RHYTACHNE ASSOCIATION ...... 31 CHASMOPODIUM/NAUCLEA ASSOCIATION ...... 31 LOPHIRA/CHASMOPODIUM ASSOCIATION ...... 32 RIVERAIN FOREST AND " SACRED BUSH " 32

PART IV : LAND USE : SIZE OF FARMS AND MANPOWER ...... • • 35 SYSTEM OF FARMING . . . . 35 CROPS 35

PART V : RECOMMENDATIONS 38 REFERENCES 40 APPENDIX : ANALYTICAL DATA 41 FOREWORD BY DR. H. GREENE Adviser on Tropical Soils, Department of Technical Co-operation

THE reconnaissance soil survey of the bolilands of Sierra content just to record the occurrence of different kinds of Leone was begun by J. C. Chisnall and after his lamented soil but are concerned to relate their field observations to death was resumed and completed by A, R. Stobbs. Both potential growth of crops. This involves an interpretation men were seconded from the Colonial Office Pool of Soil of the field observations and adds to the practical value of Surveyors. a soil map such as is presented here. The reader should Stobbs has based his soil map in part on recognised remember, however, that potential growth of crops depends sub-divisions of the land surface (geomorphological units), on changing techniques, and that practical recom- and in part on the system of soil classification that was being mendations depend on a changing economic situation. elaborated in by the late C. F. Charter, O.B.E. This The soil surveyor cannot do more than offer an assessment system has seemed well suited to the soils of West based on such information as is available to him at the time and its use in this report facilitates comparison with the of writing. His tentative conclusions need to be tested in numerous and valuable soil surveys carried out in Ghana. the field: it is a valuable feature of a soil map that it shows It should be mentioned that soil boundaries recognised by the most useful locations for field experiments. Stobbs in the field are likely to remain unchanged when The accompanying soil maps prepared and printed by Charter's system of soil classification is superseded by the Directorate of Overseas Surveys are part of the others, as is inevitable since all such systems need to be Technical Assistance provided to Sierra Leone by the revised as new information comes in, and as new ideas gain United Kingdom Government through the Department of a hearing. At the present time many soil surveyors are not Technical Co-operation. PART I

GEOGRAPHICAL BACKGROUND

Introduction the analytical programme to a selected range of Bottomland " Bolilands " is the generic term for the seasonally soils. swampy region adjacent to the Rokel and Mabole rivers Although the region has an annual rainfall of up to occurring over the Rokel River geological series. A " boli " 130 inches most of which arrives in a period of six months, is an individual swamp. it was possible to continue with a modified programme The survey of the bolilands was carried out at the in a rainy season without loss of too many days, by leaving request of the Department of Agriculture, Sierra Leone, to this period work on the upland soils much of which which was already endeavouring to develop a mechanical could be carried out from the Landrover or within easy rice cultivation scheme there. The purpose of the survey reach of shelter. was to locate, delineate, and describe suitable areas for rice At all times bicycles were a great help in keeping up in order to provide a sound basis for further progress. the speed of the survey. The scope of the survey was extended to encompass an Thanks for unfailing help with administrative, supply assessment of the whole region in which these swamp and personnel problems are due to the Agricultural Officer, areas occur, so as to allow a co-ordinated approach to its , in whose circle most of the survey area lay; also agricultural problems. to the staff of the West African Rice Research Station, Work was begun by Mr. J. C. Chisnall in April, 1957, Rokupr, whose interest and help in providing space and under Colonial Development and Welfare Scheme 3094, equipment for carrying out a number of mechanical and after a lapse consequent upon his unfortunate death analyses and pH tests locally was most useful; and to the in January, 1958, was resumed by Mr. A. R. Stobbs in Agricultural Chemist and other staff at the Departmental December, 1958, under Colonial Development and Headquarters at N'jala; and to all those others, adminis- Welfare Scheme 4019, field work being completed in trators, foresters and geologists, whose interest, advice and June, i960. local knowledge helped the survey. The survey was done at two levels. Firstly a recon- naissance survey of nearly 1,000 square miles was carried out to produce an overall assessment of soil resources. The Geology observations were mapped on R.A.F. 1951 photography The area surveyed overlies the Rokel river series which (1 : 30,000), later transferred to Aero Surveys 1958 photo- extend southwards from the frontier for about graphy (1 : 40,000) and are now presented on a scale of 140 miles, in a strip about 25 miles wide (Poliert, 1951). 1 : 50,000. Then, additional to this, detailed surveys were Two elements of this geological series have influenced the carried out of separate " bolis " with a view to defining soils with which the survey was concerned:— areas on which further research can be undertaken to 1. Sandstones and sandy shales of the series give rise relate agronomic data to the soil pattern. Some such to low, gently undulating uplands, and provide parent information can already be obtained from comparison of material for the upland soils. In the oldest soils formed the soil survey with the crop records from ploughing sites. on relict peneplain drifts covering these upland summits, In the reconnaissance survey widely spaced traverses biotic activity is slowly introducing this parent material were selected to confirm criteria which could be used to into the profiles. The same parent material is also found interpret the soil pattern from the air photographs, with present as colluvium in many of the topsoils of the subsequent additional traverses where necessary to confirm " inland " boüs. this interpretation. 2. Mudstones and shales of the series underlie most The detailed surveys were carried out along a regular of the " inland " bolis. These are now weathering in situ pattern of traverses laid down 5 chains apart and sampled into compact puddled clay subsoils, thereby exerting an at 5 chain intervals. important influence upon the water regime of these bolis. Soil pits were normally dug to a depth of 6 feet, with The rocks are rarely exposed except in the beds of the a few selected pits deepened as necessary to acquire major river courses, and more rarely on steeper hillsides pedogenetical data. Pits were sited to give a standard approximating locally to low scarp formations. As they description for each series, and demarcate the variation are inherently much poorer in minerals than the crystalline permissible in its characteristics. Other sampling and rocks on either side of the bolilands, the soils derived from identification was done by means of chisel holes (circular rocks of the Rokel river series are low in nutrient status inspection holes about 9 inches across and 36 inches deep) and have attracted less local settlement than the more and augers. fertile soils to the east and west. This inherent poverty Soil samples were analysed by Mr. C. L. Bascomb at must be considered an obstacle to development until means Rothamsted Experimental Station. Circumstances limited of overcoming it have been reliably demonstrated. MAP TO SHOW AREA OF SOIL SURVEY AND LOCATION OF DETAILED SOIL MAPS

1 BOLI 4 MADINA-TABAI BOLI

2 ROCHIN BOLI 5 ROMANKNE BOLI

3 BANTORO BOLI 6 KONTOBE BOLI

REFERENCE Inter-Territorial Boundary + • +•+• + * + Roads Railways

D.O.S. (Mile) 362 Drawn and photographed by Directorate of Overseas Surveys 1963. LANDFORM UNIT Slough Old Slough Terrace remnant Flanking slopes Upland peneplain levee surface

Résèquent stream developing as a result of base level adjustment. Termite mounds XXXXX XXX X Normal flood level Ironpan horizon

////////////////fc///^ Height difference usually Indurated layer about 40 - 80 feet

Groundwater laterites Very acid or acid gleisols and GREAT SOIL GROUP Acid gleisols and occasional Groundwater laterites Oxysols groundwater laterites add gleisols

§ |S Silty and sandy slough soils of alluvial Terrace soils Yellow brown Red brown SOILS origin overlying indurated layer usually concretionary concretionary drifts concretionary drifts •f o o"

5-8 lu ^ MAPPING UNIT NUMBER 10 10

FIGURE I Diagrammatic cross section showing the topographic relationship of soils in the inland bolis. Terrace remnants of Unit 7 may often be found within the slough areas of Unit 10. Within the upland areas of Unit 2 considerable extents of flanking slopes (Unit 3) will be encountered breaking up the peneplain surface.

LANDFORM UNIT

River I Levee'Old river Old Slough Terrace remnant Flanking slopes Upland channel levee peneplain surface Résèquent stream developing as a result of base level adjustment X X X X X X Normal flood level Ironpan horizon

. Height difference Loose sand horizon varies from some 30- 100 feet GREAT Oxysols, acid gleisols Oxysols and Very acid or add gleisols and Oxysols SOIL GROUP groundwater laterites i S I groundwater laterites =• °

I ,_ Red brown and Terrace loams Red brown SOILS Silty and sandy soils of alluvial origin yellow brown often non-concretionary concretionary drifts 2 â. concretionary drifts

i

MAPPING UNIT NUMBER 8 11 10

FIGURE 2 Diagrammatic cross section showing the topographic relationship of soils of the " riverain " bolis in the contemporary floodplains. In the northern part of the bolilands the terrace is frequently absent and the uplands terminate abruptly in a colluvial slope or a low scarp overlooking the slough. Topography stretches of the older drainage pattern successively from Practically the whole of the surveyed area is flat or very north to south, capture remaining uncompleted in the gently undulating and hes between 100-300 feet above case of the most southerly rivers, the Moa and Mano. sea level, with only a few points exceeding that, and only The 1 : 500,000 map of Sierra Leone shows how the upper the major river beds at the seaward side of the bolilands reaches of many of the rivers are directly aligned with the approaching the 100 feet level. Probably some 75 per cent lower reaches of their neighbours, or next-but-one neigh- or even more of the area lies between 130 and 260 feet. bours, to the south-east. Following this, another period of It may be sub-divided into three topographic regions :— submergence may have occurred, still indicated by the 1. The northern region extending from north of Batkanu configuration of the offshore Banana, Plantain and other to north of Babaibunda. This is the most undulating area, islands and the drowned coastline nature of the three and includes the valley and floodplain of the Mabole river. great estuaries—the Scarcies, Sierra Leone river and the To the west and south-west of Batkanu there are more Sherbro river. This would account for a Unking of the frequent moderately steep slopes which give rise to most waters of the Mabole, Rokel and Pampana rivers, either of the sedentary and non-concretionary colluvial drift soils in a common delta, or in a low-lying area similar to that encountered during the survey. of the Sudd in the southern Sudan where the waters of 2. The central region extending from Babaibunda to the Nile and Bahr-el-Ghazal mix. It was at this period, the northern edge of the Rokel floodplain a little north in a topography already flattened by the late Tertiary of Kontobe. This region is dominated by extensive peneplanation that the so-called inland bolis were formed relatively flat areas forming the interconnecting network between Mayawso and Babaibunda amidst the interlocking of inland bolis, with scattered islands of gently undulating waterways of these three rivers. The report of the geologist upland, and becoming more undulating westwards towards on Rosino Swamp quoted in the Department of Agri- Marampa (plate 5). culture's Annual Report for 1949 is interesting support for' this view. Many of the streams which are now found 3. The southern region of the Rokel (or Seli river as amongst these bolis (Kontobe creek, the Gitiwa and Belia, sometimes called) floodplain extending from Kontobe and the Tabai which crosses the Lunsar road for example) nearly down to the Pampana river, and Yonnibanna, This are palpably misfit streams carving their present courses also is a region of extensive flat areas with gently undulating through the alluvial deposits of larger former river-systems. ' interfluves. It differs from the last, however, in being a Evidence suggests that we are now again in a period of younger geomorphological area having various distinct emergence—the infilling by mangrove swamps of the terrace remnants with interconnecting slopes to the drowned coastline, the configuration of Turner's peninsula uplands and the swamps. It thus has a wider variety of and the seaward shore of Sherbro island, each displaying a soils and has attracted rather more settlement. succession of strand Unes, suggest this. This has induced a new erosion cycle—the Mabole, Rokel and Pampana all Geomorphology show a sequence of knick-point rapids where the valleys The cardinal geomorphological features are the flood- enter their upper reaches—and this renewed downward plains of the Mabole and Rokel rivers, the peneplain erosion has led to a marked contraction of the meander capped uplands, and the intricate network of inland bolis. belts and floodplains, thus once again clearly separating the three rivers, and leaving a large mass of bolis relatively The floodplains are relatively young, but the other isolated. The streams that have subsequently developed geomorphological features seem to be connected with what | in these isolated bolis are gradually incising themselves, was possibly a late Tertiary peneplanation still represented and in some cases are once more threatening to alter the by ironpan capped upland remnants at about 250 feet. It drainage patterns by capture of the major rivers. The appears to have pedological and topographical similarities headwaters of the Belia stream flowing past Yebelli ferry, to relate it to similarly dated peneplanations in Ghana for example, already have three swampy connections with (Junner 1946, Crosbie 1956, Radwanski 1956, Brammer the contemporary floodplain of the Mabole, just north of 1956b) and (De Swardt 1946, Pugh and King 1952, Baibunda. This re-incision of the drainage into a topo- Vine 1954). graphy dependent upon a different and probably lower " Boli " is a term denoting areas of flat treeless grassland base level has already been remarked on elsewhere in West annually flooded during the rainy season (see figures Africa (Brammer 1956b, De Swardt 1953) as being charac- 1 and 2). A rough classification into two groups is used:— teristic of a " zone of tension " between the Guinea (a) Riverain bolis (plates 1 and 2) savanna and Forest zones. (b) Inland bolis (plates 4 and 5) but evidence suggests that all the bolis are riverain in One of the important outcomes of the present situation origin and the classification should be:— is that the extent of actual river flooding is very limited. (a) Contemporary. The incision of the valleys, and the growth of levees has (b) Old. advanced so that the rivers flood directly about 25 per cent The drainage pattern of Sierra Leone probably originated of the present riverain boli area. The remainder of the as the scarp-slope run off from the crest of the old con- flooding is due :— tinental shield now represented by the Loma and Tinga (a) to surface and sub-surface run off from the mountains. This run off generally followed a south- surrounding uplands; south-west trend. A subsequent period of uplift or (b) direct rainfall; emergence initiated a later pattern of drainage trending (c) to spillage from tributary streams. to the west from the hill lands stretching from the Guinea These features have already been noted by agriculturalists frontier to Sumbuya and now represented by such as the (Glanville 1938). The first of these is by far the most Katikant and Kasabere hills. The erosion cycle of these important. A significant factor of the present position is streams probably led to an elaborate process of river that the riverain bolis (at least in the Batkanu area) are capture whereby the younger streams captured the upper adjacent to uplands which.appear to lie on an impermeable shale horizon so that round the inland edges of the bolis Temperature there is a spring line at the base of the uplands which Mean temperatures are nearly constant (78-84 °F); the comes to life with the early rains. The bolis themselves, cycle through the year from January shows increasing mean however, have deep subsoils of more or less loose sandy temperatures from January (Makeni figures: 78-6°F.) material of alluvial origin which act as drainage and supply to April (83 9°F.), thence decreasing to the lowest mean horizons for water. Thus the bolis do not become water- in August (77-6°F.) increasing again until November logged until the river level rises above the level of this (8o-6°F.) and decreasing until January. The mean daily sand horizon so that sub-surface drainage can no longer range shows a single cycle from a maximum of about 26 ° escape. Thereafter all the direct rainfall on to the bolis in January to a minimum of about 11 ° in August. Abso- and the run-off from the uplands is held imprisoned until lute maximum temperatures may exceed 100 °F. in the following dry season, and because there are few points February-March but seldom exceed 90 °F. in July- in the levees through which surface water standing in the September. Absolute minimum temperatures range from sloughs can escape into the river, the bolis become flooded those of the harmattan periods in December-February for several months. when the pre-dawn temperature may fall into the fifties, to April-August when the daily minimum rarely falls below 70 °F.

Climate Sunshine In common with most of Sierra Leone, the bolilands Mean sunshine per day shows a regular change from a lie within the zone traversed seasonally by the Inter minimum in the region of two hours in August to a Tropical Front associated with the equatorial low pressure maximum of a little over eight hours in January-February. belt. Consequently the climate is continuously warm to hot with well denned wet and dry seasons which control Wind the annual agricultural cycle. Wind speeds in excess of 12 m.p.h. are rare, forming The dry season extends from December to April and only 2 per cent of recorded observations over the whole contains two main weather types :— year at Makeni. The squalls from the north-east at the 1. The " Harmattan "; a period of clear skies with dry beginning and end of the rainy season are the only winds easterly winds from the and relatively high daytime likely to be damaging. In wind direction, south-west is and low night-time temperatures, combined with hazy the commonest quarter, followed by south-east, and then visibility. It occurs for periods of only a few days at a north-east in the period December-April. time in December, January and occasionally February. 2. A dry south-westerly regime, with generally high Vegetation humidity, hot and generally oppressive days, and usually This is more fully treated in the chapter prepared and warm nights. The weather is frequently characterised contributed by Dr. T. S. Bakshi, the systematic botanist (especially in the river valleys of the bolilands) by fairly and ecologist to the Department of Agriculture. A few heavy. morning fog and night-time dew. This is the basic points may be made here, however, to fit the present predominant dry season weather type. picture into the pattern of historical modifications of the Linking the dry and rainy seasons in April-June and vegetation in relation to the land-use developing on October-December are periods of thundery squalls. In the soil pattern (see figure 3). those periods of generally south-west winds, clear visibility, The region is predominantly a zone of derived Guinea and intermittent cloud, thunderstorms approach from the savanna, resulting from the destruction of forest vegetation east and north-east, preceded by a squall. They are most by human activity and fire, a process characteristic of a frequent in the late afternoon and early evening and are wide area of (Keay 1949). There are a number responsible for most of the rainfall at those times of year. of easily recognisable physiognomic vegetational units :— The.rainy season proper extends from June to October, when the weather is overcast and humid, the rain frequent, 1. Medium and tall treeless grasslands of the seasonal often heavy and prolonged and the clearances vary from swamps (plates 2 and 4). The ecological pattern changes an hour or so to a day or more. with very small variations in altitude (of the order of There are two meteorological stations in the area with 2-3 feet); and the higher drier zones show admixtures of . which the survey is concerned, Batkanu in the north and herbs, shrubs and ultimately of Lophira trees and Hyphaene Kontobe (only recently commenced) in the south, and the palms as they develop into conditions transitional to the stations at Makeni, Magburaka and Marampa lie just uplands. outside the area. The observations are published in 2. Riverain thicket. This unit contains occasional " Statistics illustrating the climate of Sierra Leone 1951 ". remnants of thicket with émergents, secondary forest, and very rare patches of old " gallery " forest (plate 12). It Rainfall may be sub-divided into:—. Only the months of May to November inclusive are (a) Dry thicket found on the levees along the major likely to have a rainfall exceeding 5 inches, and of these rivers and streams and now rarely, if ever, flooded, there is about a 25 per cent possibility of May and e.g., the bank of the Rokel near Lungi boli. November not quite reaching this amount, with November (b) Swamp thicket found on shelving slopes between rather the more likely risk. From the records it seems that the seasonal water levels, e.g., Kontobe creek. if the rains are late in commencing there is a rather better 3. Upland savanna of open grassland-with-trees. This prospect of the November fall exceeding 5 inches. April can be sub-divided into:— has a 25 per cent chance of exceeding 5 inches rainfall. (a) So-called Lophira bush, found on the thinnest The average annual rainfall for the region hes in the and most concretionary soils of peneplain remnants range 110-120 inches decreasing slowly towards the north. at 200-250 feet. This is a fire climax of tall and high TABLE i CLIMATIC STATISTICS

Period Total or of obs. Remarks Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec. average

Rainfall Mean 1926-50 0-15 025 1 05 324 8 83 15-61 17-10 1947 17-98 1896 5 93 070 106-27 Extreme max. 1926-50 1-85 2-27 3-61 697 1737 25-14 25 01 2843 29-11 21-88 11-42 261 129-13 Extreme min. 1926-50 0 0 0 0 3'71 1243 12-43 1175 1179 7-53 1-49 0 9040 Av. raindays 1936-50 + 001" rain 0-3 07 2 6 14 24 24 27 24 24 11 2 156 Av. wet days 1936-50 + 040" rain 01 0-2 07 3 8 12 12 16 13 14 5 09 85 W ATVAMTT JJnliN^UNU Temp. Mean 1933-42 To nearest 1 °F. 81 84 86 85 84 80 79 78 80 81 81 80 81-6 Av. Daily range 1933-42 To nearest 1 °F. 26 26 27 24 20 17 12 11 16 20 19 22 198 Av. Daily max. 1933-42 To nearest 1 °F. 94 97 99 97 92 89 85 83 88 91 91 91 91-5 Av. Daily min. 1933-42 To nearest 1 °F. 68 72 73 73 73 72 72 72 72 72 72 69 717 Av.

Rainfall Mean 1936-50 012 015 125 2-78 917 1482 19-16 2513 21-14 1632 685 i-ii 118-00 Av. raindays 1936-50 + 001" rain 04 09 4 7 15 22 26 28 27 26 14 2 172 Av. wet days 1936-50 + 040" rain 01 01 1-3 2 8 11 13 16 IS 14 6 07 87 \A AITFMT Temp. Mean 1942-50 To nearest 1 °F. 79 82 84 84 83 81 79 78 80 80 81 79 80-6 Av. Daily range 1942-50 To nearest 1 °F. 27 27 25 22 19 17 13 11 15 18 18 21 193 Av. Daily max. 1942-50 To nearest 1 °F. 92 95 97 95 92 89 85 83 87 89 90 90 90-3 Av. (Abs. max. 103) Daily min. 1942-50 To nearest 1 °F. 65 68 71 73 73 73 72 72 72 72 72 69 710 Av. (Abs. min. 50)

Cloud Mean amount 1944-50 In tenths 3-5 31 48 63 73 8-0 89 92 8-6 8-2 72 46 67 Av. Mean cloudy 1944-50 No. of days with 2 1 4 9 15 22 29 30 27 24 5 182 days + 7-5 tenths Rainfall Mean 1941-50 025 012 0-68 313 6-96 1078 17-57 22-55 1763 1607 691 0-87 10352 Av. raindays 1941-50 + o-oi" rain 0-7 0-5 3 8 21 23 28 25 24 13 4 164 Av. wet days 1941-50 + 0-40" rain 02 01 0-6 3 6 10 13 18 12 13 6 0-9 83 \A AB41UPA IVIAKAJVU A Temp. Mean 1941-50 To nearest 1 °F. 79 81 83 83 82 80 78 77 79 80 80 79 80 1 Av. Daily range 1941-50 To nearest 1 °F. 22 24 23 21 19 17 13 11 15 18 18 19 18-2 Av. Daily max. 1941-50 To nearest 1 °F. 90 93 95 94 92 89 85 82 86 89 89 88 892 Av. (Abs. max. 103) Daily min. 1941-50 To nearest 1 °F. 68 69 72 72 73 72 71 71 72 71 71 70 71 0 Av. (Abs. min. 56)

For a fuller tabulation of statistics see " Statistics illustrating the Climate of Sierra Leone, 1951 ". Freetown, Government Printer. grasses (particularly Chasmopodium caudatum) and early season grasses one of the most ubiquitous is Imperata Lophira lanceolata (plate 6). With the increasing cylindrica which has been noted as a typical grass of derived intensity of farming and the annual fires (often savanna zones (Michelmore 1939). It is particularly intensive late-burnings) this type of vegetation is noticeable in consociational stands in the bolis, especially rapidly spreading down the slopes from its original those of the contemporary riverain floodplains, occurring sites to reach the edge of the seasonal swamps. variously in sloughs, levees, and old river channels, often (b) Mixed Lophira bush. This occurs on con- within the same boh', in the period March-May. Little is cretionary but rather better soils, and there is a greater known of the relative grazing value of these various variety of arboreal species, which may locally be seasonally successive grass associations. sufficiently dense to cause the grass layer partially to yield to a herbaceous cover. Human and economic geography (c) Open savanna woodland. This is found on soils derived from colluvial drifts and the deeper peneplain The area of the bolilands is inhabited most extensively drifts, mainly in the northern half of the bolilands by the Temne tribe, who are intermixed towards the north where the more undulating topography gives rise to by increasing numbers of Lokkos and Limbas. No precise more soils of these types (plate 8). After cultivation population figures can be given, but because of the problems these soils carry a regrowth of dense low thicket of access and utilisation presented by these extensive in the first three or four years of fallow. Increasing seasonal swamps and relatively infertile uplands, they are farming pressure is tending to establish this latter today, and probably always have been, less inhabited than sub-unit in its own right in some of the areas around adjacent areas. the Batkanu-Mateboi-Mayanki district, especially on Coherent administration and development of the area the richer colluvial drift soils. began when the Karene district headquarters moved to Batkanu in 1904. Most of what is now Bombali, Tonkolilli, 4. Rare remnants of secondary rain forest. These are Port Lokko and Kambia districts was for a time adminis- occasionally encountered either as sacred groves or in tered from Batkanu which became an administrative, topographic sites which have afforded some measure of military, communications and trading centre of some protection from man and fire (plate 4). importance. Since then, however, it has gradually lost its A marked degradation of vegetation has taken place various functions to towns more favourably situated within recent times. Accounts of the flora in travellers' outside the bolilands, but it is still probably the largest records (e.g., Garratt 1891 and Anonymous 1899) and town in the area surveyed. correspondence in the District letter books reveals that Communications which exist today are mainly lateral much more forest vegetation was present up to the early trunk routes unavoidably crossing the bolilands. There part of this century. It is also apparent that as early are three principal through routes :— as 1906 (Governor Probyn to D. C. Karene on 23rd April, 1. That through Batkanu in the north from Port Lokko 1906) the Lophira bush (therein called grass fields) was to Makeni and . This was the old route from sufficiently prevalent to command attention with a view to Freetown into the Northern Province. economic development. Nevertheless (Governor Probyn, M.P. 13 of 5th February, 1906), the main vegetation was 2. The more modern Freetown-Makeni road which runs described as high bush, within which it was conceived that across the centre of the bolilands from Lunsar. This road agriculture might occupy hollow squares. This process of is to be improved and bituminised. degradation is continuing but is not of itself necessarily 3. The southern route from Freetown to Magburaka. a retrograde movement providing the answer to two The Government railway follows closely the line of this questions be established:— southern route on its way from Freetown to Makeni, and a proposed new mineral railway will closely parallel the 1. What ecological pattern of semi-natural vegetation Lunsar-Makeni road. will best meet the economic requirements of any proposed Three urban areas likely to influence the development scheme of agricultural development ? of the bolilands are Lunsar-Marampa, Makeni, and 2. What species the ecological pattern requires to best Magburaka lying just outside the boundary of the surveyed meet the requirement of maintenance and restoration of area. The first owes its existence to important iron ore soil structure and fertility ? deposits, round which a large population has settled, and The rapidity with which the vegetational pattern has which may increase in size, especially if in the future the altered in recent times is partly due to the type of climate. processing side of the work increases. The two latter In the uplands the heavy annual rainfall of over 100 inches have grown as administrative and communication centres, was sufficient to encourage a forest vegetation, which in with Makeni taking precedence, especially in recent years, turn probably provided sufficient shade to prevent undue by virtue of its better geographical position as a focus for drying out of the soils beneath and thus precluded severe new roads, and its possession of the railhead. Both, and dry season fires. The impact of agriculture through felling especially Makeni, are likely to increase further as urban and clearing, however, serves to make the long and severe centres, particularly when the proposed development of dry season from late November until the beginning of May iron ore deposits at Farangbaia takes place. relatively more important as a conditioning factor, because of the loss of shade and intensive fires which are con- The presence of these centres in close proximity to the sequences of the change from forest to dominantly grass bolilands may justify future agriculture development vegetation. beyond what is at present economic. A marked seasonal succession among the grass and herb species is also apparent, especially in the seasonal swamps. The soil map Short and medium grass species appear as temporary local The data for the soil map were plotted in the field on dominants until July when the growth of the major tall aerial photography with an approximate scale of 1 : 40,000. species becomes sufficiently advanced. Amongst these The work of mapping the soils was based on a geo-

11 GREAT SOIL GROUP

M* it

§3^

Bare or nearly bare exposures of ironpan Ironpan bovals.

Red-brown concretionary drifts.

1 Yellow-brown concre- III tionary drifts. ^32 S

Over concretionary or o ferruginised weathered parent material.

Scattered localised deposits. Rare. (Mainly oxys ols) Over non-concretionary parent material.

Over locally weathered Co parent material usually O on moderate to steep slopes. Over river terrace si O.P deposits :— If 11 (a) concretionary sSfS (b) non-concretionary

E'S. Over contemporary levee TO ""• deposits. Icr p S3 J&ßSffg"&; Over old levee deposits. 8"

Over contemporary and a a o w old slough deposits.

Over old river channel deposits.

A mapping complex comprising mostly groundwater laterites and gleisols of units 7 and 10 with a less well Developed in drainage defined seasonal water regime than in unit 13 grooves.

A mapping complex containing inseparably mixed elements of units 7 to 12 Mixed bottom soils.

Shallow river courses seasonally exposed Recent alluvium. morphological interpretation of these photographs under permanent and observable geomorphological features stereoscopic examination. This was checked and con- makes it possible to add future detail as the area becomes firmed in the field and the types of soils (great soil groups) better known, within the limitations, of course, of the occurring within the area determined. The detailed scale. In the present case it will be seen that in some extension of this work then comprised identifying and places on the map areas of the same colour and with describing the individual soil series found associated with the same index number are separated by boundaries. each of the geomorphological units defined for use as the This should be interpreted as indicating significant soil basis of the soil mapping units. differences at the series level or at an even more detailed Such a method is useful where large areas with poor level of classification (subseries, phase, etc.). The communications have to be examined and mapped in a limitations imposed by scale are to be found in the number limited time by a small party or a single soil surveyor. Soil of areas of compound mapping units and colour schemes. itself is not visible on air photographs in the same way as, To use the key to the maps (see Table 2) enter it say, trees are to the forestry interpreter, or the results of vertically for the index number (denoting landform site) human activity are to the land use interpreter and hence and horizontally for the colour (denoting great soil group). indirect evidence has to be sought. In an area such as Where these meet, the panel contains a hst of the closely that covered by this report, where the climate and the related soil series which may be present at that particular geological pattern are both known to be uniform through- place in the field. The number of series included in the out, the premise used is that the same landform will give table as a result of this survey may be extended by any rise to the same soil, or repeated pattern (catena) of soils future work. The key also indicates the parent material wherever encountered. Thus an initial interpretation of and original of the soils (pedogenisis). the topography to determine the geomorphological units present not only yields the provisional framework of the ultimate map, but also serves to guide the field work to Boli soil maps the best advantage. In addition to the main soil map, six individual boli As field work progresses further criteria come to hand maps were prepared on a large scale to show the soil to help interpreting the soil pattern on the photographs. patterns at series level in typical riverain and inland bolis. Chiefly such criteria are the shade and tone of particular In these maps also, emphasis was placed on the relationship soils or soil associations when photographed (care has to between sous and geomorphology, the significance of this be taken to allow for such factors as intensity and angle of at such a detailed level being the influence exerted upon light when the photography was done, and changing the flooding regime during the rainy season by minor but ground conditions such as dampness), and the relationship critical variations of height. In considering rice cultivation between existing vegetation and land use and the soils. this is of maximum importance, and to this end a contour Such criteria are useful in sub-dividing and amplifying the map of one boli has also been added. basic geomorphological units. Much of this work depends Riverain bolis : Rochin, Batkanu, Bantoro. on the quality of the photography which may vary, Inland bolis : Kontobe, Romankne, Madina-Tabai. especially when a large area is involved, and hence in the Contour map : Bantoro boli. absence of field coverage over a close network of traverses These maps should provide a basis for detailed experi- it does mean that the degree of detail shown may vary mental work, and for furthering the ecological study of the from place to place. However, basing the map on the bolilands already commenced. PART II

SOILS

With the exception of some alluvial deposits, the soils 2. Groundwater laterites within the area surveyed have all developed under similar This group contains certain peneplain drifts among the climatic conditions, from the same geological series. It upland soils, many of the marginal soils between the follows from this basic uniformity that local variations of uplands and the annually flooded lowlands, and certain topography are reflected in the soil pattern; accordingly terrace deposits. Due to their bad drainage, high acidity it has been possible to group the individual soil series on and horizons of sesquioxide concentration they present a the basis of landform sites into a number of larger units considerable agricultural problem. Oxysolic profiles grade having certain fundamental similarities, and providing a into groundwater laterites topographically under the simple and convenient classification for agricultural influence of variations in drainage. purposes. Relief and drainage are regarded as the primary deter- minants of groundwater latérite formation which achieve their maximum development in association with the very subdued topography of peneplains and river terraces. Identification is dependent chiefly on the recognition of Pedological classification acid to very acid reaction profiles, and the development of The soils have also been classified on pedological grounds massive vesicular and usually cemented pans as a result into great soil groups based upon C. F. Charter's system of alternate waterlogging and aeration. (Brammer 1956c). This has been found widely useful in West Africa, providing a ready means of extending com- 3. Very acid or acid gleisols parisons of pedological and subsequent agronomic data Here are included practically all soils annually flooded, beyond the limits of one country. covering the landform mapping units designated as sloughs, With no important exceptions, all the soils examined in old river channels and some levee deposits. Also included the course of this survey could be placed in one of four are the less well drained, sometimes flooded, soils en- great soil groups. countered on the lower river terraces. Relief and drainage are the primary determinants in the formation of gleisols and reducing conditions must occur 1. Oxysols annually. Analytical data on pages 44 and 45 show little This group contains most of the better drained upland promise of an easy separation between very acid and acid soils of reddish or brownish dominant colouring, and also gleisols : all eight profiles have a very low content of exchange- the more important river terrace deposits. These soils able bases. However, if the topsoil reaction is more than 5 -o are approximately equivalent to those once termed Reddish and the value tends to increase down the profile, it is regarded Yellow Latosols by U.S. workers (Charter 1955). They as an acid as distinct from very 'acid gleisol. Since con- are characteristically associated with high rainfall areas temporary flooding or a recent history of flooding are (+70-80 inches as denned by Charter), and are held to essential to the development of such soils, many of the have their characteristics largely determined by climate older gleisolic soils in the swamps are increasingly ac- and vegetation. The precipitation they receive connects quiring the characteristics of groundwater laterite with the with a groundwater table resulting in through leaching, last changes in erosional history in the survey area. It is and consequently the reaction profile is of primary im- with soils of this group that most of the potential swamp portance in identification. pH values in the topsoil should rice developments are associated. fall in the range 4-0-5-0, increasingly slowly down the profile. The organic matter content and C/N ratio are generally a good deal lower in the boliland oxysols than in . 4. Alluviosols Charter's modal concept, but this is probably due to their These are a group of young soils of relative immaturity having been under savanna vegetation for a long period, in profile development derived from recent alluvial deposits. though originally they were developed under rain As such, in this area their occurrence is confined to the forest vegetation—a view that agrees with the probable contemporary levees and certain older levees associated ecological history of this region. As the pH of some with old river courses of the recent past. Though not of the upland topsoils examined lies between 5-0 and 5-5 extensive they have some potential importance in diversify- it is possible that in any future more detailed classification ing the crop range and varying the working season of the of these soils some profiles will be grouped as oxysol- swamp area agriculture. ochrosol intergrades. For present purposes however it is The soil key (Table 2) arranges all the identified soil sufficient to regard all as oxysols. series in their appropriate great soil group. A—SOILS OF THE UPLANDS A typical profile is described as follows :— The upland soils of the bolilands are entirely derived Reference No. SSB 7. from the more arenaceous sediments of the Rokel river Site Middle to lower slope of dissected peneplain series. On the basis of parent material they may be topography facing the Mabole floodplain. sub-divided into :— Parent material Peneplain drift. Parent rock Sandstone and sandy shales. 1. Those developed in peneplain drift deposits. Vegetation Open high grassland with shrubs and mixed 2. Those developed in colluvial drifts. savanna tree spp. 3. A few sedentary soils derived directly from underlying Rainfall 100 + inches. weathering parent rock. Altitude 230 feet a.s.l. Locality North of Batkanu agricultural station. Those of group 1 are the most extensive and on the Source Profile pit 6 feet by 3 feet. whole the least fertile, those of 2 and 3 are more common Topsoil pH 4-4 in the northern half of the area, and although in general 0-4 inches Fine sandy light loam; weak fine crumb they have a slightly better nutrient status, they may present structure; rare small polished concretions; frequent grass roots; 10 YR 5/3 (brown). some difficulties to the agriculturalist because of a more 4-8 inches Fine sandy loam; slightly loose; weak fine fragmented geographical dispersion and the rather steeper crumb structure; frequent small concretions topography over which they are found, locally steep and subangular ferruginised rock gravel; enough to warrant consideration of anti-erosion methods occasional grass roots; 10 YR 5/3 (brown). of cultivation. 8-12 inches Fine sandy loam; slightly loose; structureless; frequent small concretions and subangular ferruginised rock gravel; rare roots; 5 YR 5/3 1. Peneplain drifts (reddish brown). This is a transitional horizon. Subsoil (1) pH 45 (Mapping unit 1 comprises only bare ironpan exposures.) 12-22 inches Fine sandy and silty heavy loam to light clay; (a) Red-brown concretionary drifts (Mapping unit 2) firm; slightly compact; structureless; fre- These are mainly soils of the upper and middle slopes; quent small concretions and subangular ferruginised travel; rare roots; 5 YR 5/4 they are all composed of fine to medium sandy material, (reddish brown). with a varying proportion of ironstone concretions, frag- 22-34 inches Fme sandy and silty heavy loam; compact; mented brash from disintegrating ironpan sheets, and structureless; abundant small concretions ferruginised rock brash, according to the particular site. and medium subangular ferruginised gravel; They are relativelv^ej^^^rainedj though susceptible to a 25 YR 5/4 (reddish brown). Subsoil (2) pH 4-3 varying degrelTóïsubsoilwSérlogging at the height of the 34-46 inches Fine sandy and silty heavy loam; compact; rainy season. At present the majority of cultivation is structureless; abundant small concretions upon such soils and the main crops grown are upland rice, and medium subangular ferruginised gravel; cassava, groundnuts, fundi (finger millet), maize and 5 YR 5/4 (reddish brown). Probably a transi- tional horizon. sorghums (plate 9). Future comprehensive development 46-55 inches Fine sandy and silty loam; compact; struc- of the bolilands would have to rely for a large proportion tureless; abundant packed ferruginised gravel; of its upland cultivation upon soils of this group, and 5 YR 4/6 (yellowish red). consequently agronomic data assessing their respective 55-72 inches Fine sandy and silty loam; compact; struc- tureless; abundant large to medium irregular potentials will be very necessary at an early stage. shaped ferruginised gravel; 5 YR 4/6 (yellowish red). V BATKANU SERIES The last two horizons are grading into the This is a red-brown concretionary drift found from the weathered substratum. upper slopes extending down to the lower middle slopes, adjoining peneplain remnants. It is generally found under Utilisation. Rotational farming with the usual upland a regrowth vegetation of open high grassland with shrubs, crops. This is probably the most suitable soil for extending and trees of Lophira, Parkia and other spp. It has a the cultivation of groundnuts in the light of other West topsoil of between 6 and 12 inches of brown fine sandy African evidence (Dougall 1948, Charter 1947, Akenhead loam, usually with a weak fine crumb structure, slightly 1951, Brammer 1956a), but its best value may lie in humic in the first 3 inches and with rare to occasional providing important long-term extents of pastureland, concretions and ferruginised gravel. This grades down- and it may be worth experimenting with improved pasture wards into a subsoil which reaches down to 5 feet or management techniques on this series. The indigenous more, and is reddish-brown to yellowish-red in colour, grass associations in general have a low carrying capacity becoming brighter with depth; comprising a compact and poor silage value (Edwards 1929, Deighton 1944). structureless mass of sandy heavy loam to clay filling Problems. Acidity; lack of nutrients; relatively shallow interstices between dominant packed ironstone concretions depth for mechanical cultivation before reaching packed and ferruginised rock brash. At some depth below 5 feet concretionary and gravelly material. from the surface this subsoil grades into reddish coloured, ironstained, weathering parent rock of variable but X WARI SERIES considerable thickness. This soil occurs on summits and upper slopes of old The reaction of the soil is very acid to acid, with pHs peneplain remnants at about 250 feet. It is very limited generally falling between 42 and 5-0, and the vertical in extent in any one occurrence, though fairly frequently arrangement showing a slight decrease in acidity in the encountered, and has little importance and less value. upper subsoil. Topsoil pHs ranged between 4-2 and 4-8. It is a relict peneplain drift comprising 12-18 inches of Nutrient status is low. brown to dark brown loam to light clay with abundant Geographically, the soil is found throughout the survey concretions and ironpan fragments, and some ferruginised area, and it is one of the most extensive series, though rock gravel, loose, with weak crumb structure, over solid more common in the northern half, where it occurs on vermicular sheet ironpan. pH values ranged from 5-5 gently undulating slopes. in the top 3 inches to 4-8 above the ironpan sheet. It supports a vegetation of open high grassland with frequent, 8-17 inches Fine sandy loam; slightly firm; structureless; stunted Lophira trees, and its best use will be as rough frequent concretions and small ferruginised gravel; rare roots; 7-5 YR 5/4 (brown). pasture. It should be avoided for cultivation. 17-38 inches Fine sandy heavy loam; slightly compact; structureless; abundant quartz grains in the f. BELIA SERIES sand; abundant concretions and ferruginised This is a contemporary drift over a sedentary subsoil. rock gravel; 5 YR 5/4 (reddish brown). It occurs on the steeper dissected topography in the Subsoil (2) pH 56 north-west of the survey area, and is of limited extent, 38-53 inches + Fine sandy heavy loam soil material in the interstices of massive, compact, concretions being found in separated small areas. and ferruginised weathered rock. This There is usually a topsoil of about 9 inches of fine horizon extends downwards for undetermined sandy loam brown in colour; humic; and a weak crumb depths. structure with rare to frequent small concretions, and abundant roots in the upper 3 inches. This grades down Land use. Relatively favoured for cultivation at present, into a horizon up to 2 feet thick which is yellowish-brown especially for upland rice and cassava. It is utilisable for or pale brown fine sandy heavy loam with abundant rotations putting emphasis upon the creation of improved packed concretions and some ferruginised rock brash; pasture, and can be cultivated for maize, cassava, ground- and this in turn into 2 or 3 feet of parent material composed nuts, fundi, and indeed most local crops. of yellowish-red weathering ironstained rock brash. At Problems. Seasonally impeded subsoil drainage; lack the top of this parent material zone there is a narrow horizon of nutrients; concretionary nature of subsoil a "drawback of unweathered pebbles and pieces of quartz, and the zone to mechanical implements. seems to become increasingly clayey and mottled with depth, until at about 5 feet hard purplish rock as yet little (b) Yellozo-brown concretionary drifts (Mapping unit 3) weathered may be encountered. This group contains the soils of mapping unit 3, and The soil may be susceptible to erosion if frequently with the exception of the rare small ironpan bovals of cultivated or heavily grazed because of the moderately unit 1 it is the most intractable group of upland soils. steep slopes on which it occurs. It does however seem to The profiles are dominated by the generally massive be more fertile than most, is often farmed and quickly development of groundwater latérite at a relatively shallow gives rise to a luxuriant thicket growth when abandoned. depth, they are seasonally waterlogged as the result of The topsoil pH is a little over 5 -o and this figure decreases impeded subsurface drainage and they are generally very steadily down the profile. It would seem therefore that acid. As they probably cover 50 per cent of the uplands it is worth utilising, perhaps for perennial crops giving in the south and centre, and a good 25 per cent in the north adequate ground cover. they are worth attention in any coherent development. ]\ MALINKA SERIES This is a medium extensive series found on upper slopes "/. MAYANKI SERIES mainly among the gentle undulations of the southern A yellow-brown concretionary peneplain drift usually topographical region. There is some doubt as to whether encountered upon the lower slopes of the central topo- it should be classed as a colluvial or peneplain drift, but graphical region and to lesser extents of the northern and though the topsoil appears to be largely colluvial in origin southern regions, but occasionally found on the wetter the soil seems to have developed originally in peneplain peneplain summits. It is one of the more extensive series. drift material. It appears commonest in association with Commonly there is a topsoil of about 9-12 inches of the extensive terraces of the Rokel river and is usually brown concretionary fine sandy loam grading down into found under open high grassland with mixed trees. 2 or 3 feet of fine sandy and silty heavy loam to clay, in Typically it has a topsoil of about 9 inches of grey brown which a mass of packed concretions is bedded. The to brown sandy heavy loam with rare concretions, loose overall colour varies from brown to yellowish-brown. and structureless; passing into 2-3 feet of brown sandy This passes downwards into a reddish-yellow sandy loam, loam which becomes more compact with depth and shows usually with soft reddish mottles and frequent to abundant an increasing abundance of concretions and ferruginised concretions, and usually at least 2-3 feet thick. Below rock gravel. At a depth of about 3-4 feet this passes this the profile passes into ironstained, and sometimes abruptly into a compact horizon of massive, tightly packed indurated, weathering sandy bedrock. concretionary gravel and ferruginised weathered rock with Drainage is moderate and seasonally impeded, and the soil in the interstices. profile acid, the acidity increasing slightly with depth. A typical profile is :— Topsoils examined had pHs between 4-5 and 5-2. Reference No. SSB 75. A typical profile is described as follows :— Site Upper slope of gentle undulation. Parent material Peneplain drift. Reference No. SSB 23. Parent rock Sandy shales. Site Lower slope of gently undulating dissected Vegetation Open high grassland (old cassava farm). peneplain topography. Rainfall 100 + inches. Parent material Peneplain drift. Altitude 220 feet a.s.l. Parent rock Sandstone and sandy shales. Locality Near Mamalia. Vegetation Open high grassland and mixed trees. Source Profile pit 6 feet by 3 feet. Rainfall 100 + inches. Topsoil pH 52 Altitude ? 0-2 inches Fine sandy heavy loam; slightly loose; Locality North of Babaibunda. structureless; frequent roots; 10 YR 5/2 Source Profile pit 6 feet by 3 feet. (grey-brown). Topsoil pH 49 2-8 inches Fine sandy heavy loam; slightly firm; 0-3 inches Fine sandy light loam; loose; very weak fine structureless; occasional roots; 10 YR 5/3 crumb structure; slightly humic; frequent (brown). concretions; frequent roots; 10 YR 4/3 (dark Subsoil (1) pH 50 brown). 16 3-8 inches Fine sandy light loam; loose; very weak fine 2-6 inches Fine sandy and silty light loam; loose; very crumb structure; very slightly humic ; abun- weak fine crumb structure; very slightly dant concretions; occasional roots; 10 YR 5/3 humic; 'occasional roots; 10 YR 5/2 (grey (brown). brown). 8-19 inches Sandy light clay to clay; compact; structure- 6-11 inches (Transitional horizon.) Fine sandy and silty less; abundant packed concretions; rare roots; loam; slightly firm; structureless; rare roots; 7-5 YR 5/4 (brown). 10 YR 6/3 (pale brown). Subsoil (1) pH 48 Subsoil (1) pH 5.0 19-29 inches Sandy heavy loam to light clay; compact; 11-20 inches Fine sandy and silty clay; compact; structure- structureless; abundant packed concretions; less; packed ironstone concretions; 10YR6/3 75 YR 5/6 (strong brown). (pale brown). Subsoil (2) pH 46 20-36 inches Fine sandy and silty light clay to clay; com- 29-41 inches Sandy heavy loam; firm; structureless; pact; structureless; abundant concretions; abundant packed concretions; 5 YR 6/6 10 YR 7/3 (very pale brown). (reddish yellow). 36-50 inches Silty and sandy heavy loam to light clay; 41-53 inches Sandy loam; slightly loose; structureless; compact; structureless; frequent concretions; abundant irregular concretions; 5 YR 7/6 10 YR 7/4 (very pale brown). (reddish yellow). Subsoil (2) pH 48 Weathered substratum pH 45 50-66 inches Silty and fine sandy loam in a compact mass of 53-71 inches Sandy loam of decomposing indurated reddish stained cemented concretions and weathered bedrock; 25 Y 6/6 (olive yellow). seepage pan forming groundwater laterite. Land use. Not greatly favoured at present. Occasional Land use. Occasionally used at present (on the evidence crops mainly of cassava, and on the wetter areas, of dry of one season) for cassava and leguminous crops. Emphasis season sweet potatoes. Should be amenable to improve- is probably best placed on rotational farming designed to ment by drainage with possible low value for corn, cassava produce improved pastures; possibly worth attention as and pastures in a rotation. second class groundnut land and for oil palms. This soil, Problems. Acidity; lack of nutrients; drainage. A in common with other yellow-brown concretionary drifts, potential danger lies in speeding up induration of the may often be capable of improvement by open drains to seepage pan in the zone of the fluctuating water table due reduce the seasonal subsoil waterlogging which is a major to easier aeration following on more intensive cultivation. factor in reducing crop productivity. With improved drainage response to fertilisers would be better. MAKOIMA SERIES Problems. Lack of nutrients; accelerated wear on A very poor lower slope soil fortunately of restricted and mechanical implements from ironstone content; to a lesser local occurrence chiefly in the northern topographical extent drainage and acidity. region where it is found at the edges of disserted peneplain uplands. It is of little agricultural value, and of small , MATUTU SERIES importance because of its restricted extent, but where This is a more mature associate of Mayanki series in encountered should be avoided owing to its liability to which biotic activity and colluvium have produced a sheet erosion in heavy rainstorms, if the topsoil is loosened more distinctive topsoil. It is often found in close by cultivation when dry. proximity to Mayanki series, and is most common in the It comprises about 12 inches of brown to grey-brown centre of the survey area, occurring on middle to lower fine sandy loam changing to yellowish-brown fine sandy slopes amongst gently undulating uplands fronting on light clay, structureless and free of concretions with little " inland " bolis. It is a yellow-brown loam to clay over humus, over solid vermicular structured seepage pan. It groundwater latérite. seems to occur on moderate sloping sites adjacent to where Commonly it has 9-12 inches of brownish-grey to pale an impermeable shale horizon near the foot of the uplands brown loose fine sandy light loam over 2-3 feet of pale gives rise to a spring line facing riverain bolis. A particular brown to yellow compact loam or clay, containing abundant site is to be found to the north-east of the agricultural and often packed concretionary material, forming a zone compound at Batkanu (SSB 11). of groundwater laterite locally cemented into a solid layer of orange and black coloured seepage pan. 2. Colluvial drifts (Mapping units 4 and 5) Drainage is very much impeded, and the soil is water- This group comprises soils of mapping units 4 and 5, logged in the rainy season. It is very acid, with a slight chiefly the former. In general, though more attractive decrease in acidity in the upper subsoil. soils from the viewpoint of tilth and freedom from gravel A typical profile is described thus :— and concretionary material than the soils of units 1-3, they may have a slight susceptibility to slopewash erosion Reference No. SSB 19. because they occur on somewhat steeper topography. By Site Lower slope of gently undulating dissected peneplain upland, adjacent to swampy drainage the appropriate methods of cultivation, however, they groove. should be used safely for arable and perennial crops and Parent material Peneplain drift with overlay of colluvial drift. yields will be higher than on soils of units 1-3. The Parent rock Sandstones and shales. application of fertilisers and increase of humic content Vegetation Mixed open high and medium grassland with shrubs and occasional trees. should further increase yield from these soils to a profitable Rainfall 100 + inches. degree. Altitude ? Locality North of Babaibunda. MANKAHUN SERIES Source Profile pit 6 feet by 3 feet. This is a colluvial drift found on middle slopes of Topsoil pH 49 disserted peneplain topography only in the Batkanu 0-2 inches Fine sandy and silty light loam; loose, weak fine crumb structure; slightly humic; frequent district. It gives rise to a rich, dense, regrowth vegetation roots; 10 YR 4/1 (dark grey). of close tall grassland with abundant shrubs and small trees, but in proximity to villages as at Batkanu, it rarely gave 51 for the topsoil, 46 for the subsoil and 48 for the has time to recover beyond that stage (plate 8). weathering parent rock. It usually has 3-4 feet of concretion free brown or A wide range of annual and perennial crops could be yellowish-brown loam over a pan horizon. There is a grown on this soil, and it is possible that it attains greater topsoil of 6-12 inches of grey-brown to brown sandy extents over the Rokel River geological series to the north light loam; firm, with a weak crumb structure and abundant of the survey area. roots, which gradually changes downwards to become more compact, brighter in colour, more clayey in texture (up to heavy loam), and at depth may include small frag- B—SOILS OF THE BOTTOMLANDS ments of quartz. This changes abruptly at 3 feet or more From the point of view of the main purpose of the into a packed concretionary horizon, reddish-yellow in survey, the bottomland soils are of paramount importance. colour with fragments of ferruginised sandstone, and which They are distributed in three main locations: the flood- often becomes cemented into a pan layer with depth. plains of the Mabole and Rokel rivers, and amongst the The soil is very acid with a topsoil pH of about 4-8, uplands between these two broad shallow valleys. the acidity increasing in the subsoil, but decreasing to The soils of the two floodplains are developed in material about 4-6 in the concretionary horizons. chiefly alluvial in origin, subsequent development being Though limited in extent it is a useful soil and much mainly the result of colluvial infilling of the sloughs and L used locally. It could well be utilised in the vicinity of old river channels with material derived from the adjacent 7 villages for garden crops and higher class pastures to uplands. The only truly alluvial profiles encountered have \ improve the local food supplies. It does not appear to been the soils of the levees. Closely related soil series J have sufficient extent to make it the asset it could have have been grouped together for mapping purposes into been for cash crop farming. topographical units which from the point of view of the agriculturalist have the added advantage of defining MASURI SERIES significantly different water regimes (see .figure 2). A minor series developed in colluvial drift material and The soils of the inland bolis being older, show a much found -occupying the flanks of upland drainage grooves more mature range of profiles, many of them associated on the north side of the Rokel river. It is derived from with the development of ' groundwater laterite. In those sandy shales and found under a vegetation of open high inland bolis where deep inspection pits could be dug, the grassland and scattered trees. soils were found to lie upon fine grained shales and siltstones I It normally has about a foot of dark grey to grey silty which were weathering in situ (see figure 1). ' and fine sandy light loam, a weak crumb structure and The clays derived from these rocks were white and very abundant roots, with pH about 46; grading into 2 or 3 feet plastic and apparently when readily accessible are much of grey-brown, compact, structureless sandy loam with prized locally for the making of a kind of whitewash with pH about 4-4; in turn passing into several feet of sandy which to paint houses. heavy loam to clay, light grey in colour, with increasingly Practically all the lowland soils found were acid to very frequent concretions, and hardening red and yellow acid in reaction, acidity being particularly marked in those mottles, which at perhaps 5 to 6 feet from the surface soils subjected to regular annual flooding. may form an incipient groundwater laterite. Such soils can be utilised for sweet potatoes and cassava Soils developed over terrace deposits (Mapping unit 7) in association with rice in the adjacent drainage grooves. Although occurring throughout the survey area, the most important terrace deposits from the point of view of 3. Sedentary soils (Mapping unit 6) the agriculturalist are likely to be those associated with the These soils are unfortunately of limited extent and only northern and southern floodplains of the Rokel river, as one series has been defined as having a worthwhile they have important extents of the more valuable oxysolic mappable extent. Where found they can be considered soils. They are worth investigating further with a view agriculturally to be very similar to the soils of units 4 and 5. to developing for commercial crops in association with the more usual rotations. DIABAMA SERIES A further group of terrace deposits which may prove of This is a sedentary soil of restricted and local occurrence some value are those associated with the Mabole floodplain, encountered in the north and north-west of the survey particularly those on either side of the river to the east area. It is found on summits and upper slopes from which and north-east of Babaibunda. These terraces, however, erosion has removed the old peneplain surface, and is do not include as great a proportion of the more desirable therefore a younger soil with probably a higher nutrient series as the Rokel floodplains. status than most. Although not a shallow soil, the profile Terraces associated with the tributary valleys and the is largely composed of incompletely weathered bedrock. abandoned floodplains between the Mabole and Rokel It is favoured for cultivation and when abandoned gives rivers are in the main of lesser potential owing partly to rise to dense low thicket regrowth mentioned in the their fragmentation, and partly to comprising chiefly section on vegetation. groundwater laterites and gleisols. Their value will lie in Typically it has about a foot of loose to firm, weak adding to the available rice acreage where water conditions crumb structured, dark brown to grey-brown, humic sandy are suitable (gleisols) and diversifying local food crops loam which grades into 2-3 feet of rather compact sandy (groundwater laterites), and possibly in providing some heavy loam to light clay, yellowish-red in colour which dry season pasture in association with other seasonal contains abundant rock and ironstone fragments, before swamp areas. reaching light red coloured weathering sandstone which It can thus be seen that these terrace soils, developed may have rusty red mottling and appears to give rise to a originally in alluvial parent material, now present a diversity heavy loam or light clay texture. A typical pH profile of characteristics ranging through the three great sou 18 groups oxysols, groundwater latentes and acid gleisols. gravel, it should be amenable to mechanical farming and This subsequent differential development is largely due to responsive to fertilisers. differences in drainage related to minor topographical It promises well for further development, and in variations. The influence of parent material is to be found particular should be considered for tobacco growing if this in the sandier nature of the more recent terraces associated is to be further encouraged within the bolilands. Oil with the two major floodplains. The nvysn]^, wVii^b as palms are likely to do better here than on most boliland reddish or brown silty and sandy loams are associated soils. with these deposits, grade laterally into groundwater Problems. Obtaining year-round access to many of the latérites in the marginäTzones round the edge of most occurrences of this soil; acidity and low nutrient status. terraces, and into acid gleisols in the heavily waterlogged or flooded depressions which occasionally occur within the (\ MARA SERIES (analyses on page 42) jerrace areas. Among the older terraces, the near pene- This is a very similar soil to Mabang series, but it occurs pïanation ot the topography with which they are associated, on what is possibly a younger terrace, immediately facing and the finer material in which they were developed, have the present sloughs of the major rivers. precluded the development of oxysols on an important It usually has a brown, crumb structured, topsoil about scale. 6-12 inches deep containing humus, but very acid in reaction, and is a loam or light loam in texture. This (a) Oxysols (Mapping unit 7) grades down through 2 or 3 feet of increasingly yellowish- The following three series include the most desirable brown heavy loam or clay rather less acid in reaction, soils of the river terraces, sub-divided into unit 7a (con- before reaching at a depth of 4 or 5 feet a concretionary cretionary profiles) and 7b (non-concretionary profiles). horizon reddish in colour, very acid in reaction and lighter From the practical viewpoint of cartographic representation in texture than the preceding horizon. it has not always been possible to separate the soils of the There are still frequent patches of forest associated with terraces in sufficient detail to decide whether a given this terrace—that on the western side of Mara village, terrace is predominantly 7a. or 7b. Hence on the map for example—but this is giving way to cultivation and many such sites are simply indexed 7. thicket regrowth. A typical profile is :— i MABANG SERIES (analyses on page 42) Reference No. SSB 87. This is one of the group of deep concretion-free loams Site Terrace associated with the Rokel floodplain. associated with the terraces of the Rokel and Mabole Parent material Alluvium. Vegetation Recently abandoned cultivation—shrub re- floodplains. It is found on the higher parts of what may growth. be the oldest terrace overlooking the contemporary flood- Rainfall 100 + inches. plain, under conditions of good drainage, and a vegetation Altitude 200-210 feet a.s.l. of forest remnant and close thicket regrowth. Locality Near Mara village. Source Profile pit 6 feet by 3 feet. It usually has a topsoil of about 6 inches of fine sandy Topsoil pH 42 light loam grey-brown or dark brown in colour with a 0-6 inches Fine sandy light loam; weak crumb structure ; moderately good crumb structure passing down into a loose; small and medium roots; slightly to deep subsoil showing a gradual transition in colour and moderately humic; 75 YR 5/2 (dark brown). 6-12 inches Sandy heavy loam; very weak crumb struc- texture from loam to clay and from brown to reddish ture; slightly loose; slightly humic; frequent yellow. It has an acid topsoil and very acid subsoil. roots; 75 YR 5/4 (brown). Subsoil (1) pH 46 A typical profile has the following description:— 12-29 inches Fine sandy and silty light clay; slightly firm; Reference No. S SB 84. structureless; occasional large roots; 10 YR 5/4 Site Extensive terrace remnants in the Rokel (yellowish brown). floodplain. 29-50 inches Fine sandy and silty light clay; firm; Parent material Alluvium. structureless; frequent small quartz frag- Vegetation Close thicket regrowth. ments and grains ; rare large roots ; 10 YR 6/4 Rainfall 100 + inches. (light yellowish brown). Altitude 210—220 feet a.s.l. Subsoil (2) pH 44 Locality Kumrabai-Mabang road. 50-71 inches Fine sandy and silty heavy loam; firm; Source Profile pit 6 feet by 3 feet. compact; structureless; containing numerous 4-o inch Leaf litter layer. small round ironstone concretions; rare large Topspil pH 5 2 roots; 75 YR 7/6 (reddish yellow). 0-5 inches Sandy light loam; fine crumb structure; frequent roots; humic; 10 YR 4/2 (dark grey brown). Land use. This soil is much sought after, and wherever Subsoil (1) pH 4-5 met in the Rokel floodplain (e.g., around Mara, Mabang, 5-25 inches Fine sandy and silty heavy loam; weak fine and Magbas) it was, by local standards, intensively farmed crumb structure; occasional roots; occasional penetration of topsoil down old root channels; with groundnuts, whilst care is also taken to preserve oil slightly humic, slightly firm; 10 YR 5/4 palms (plate 11). Mechanical equipment can be used to (yellowish brown). good effect in this soil whilst, having a good tilth, it should Subsoil (2) pH 44 show a profitable response to fertilisers. This suggests it 25-72 inches + Fine sandy and silty light clay; firm; slightly should be marked out for developing cash crops of which compact; very weak crumb structure; large roots still present; 75 YR 7/8 (reddish tobacco and oil palms are probably the best prospects. yellow). Near Mara an old cocoa and coffee plantation founded when the Agricultural Department office was at Magburaka Land use. Increasingly sought by local farmers who has persisted under shade with little or no attention. use it for a wide range of crops including upland rice. Possibly these crops would also have a limited development With its deep loamy profile free from concretions and on these soils. Problems. Access, acidity, nutrients and fragmentation associated with, the foregoing terrace soils, particularly of occurrence. Maroki and Mabang series. Kontobe series which also occurs in association with these soils is more fully described ^ MAROKi SERIES (analyses on page 42) This is the third of the important river terrace soil series under slough soils. (Mapping unit 10.) offering scope for development in the major floodplains. It is similar to the others in acidity and in having a deep ^jL MAKOLI SERIES concretion-free profile developed from sandy alluvial This is an old terrace soil associated with ancient river parent material, but it is lighter in texture and paler in courses now long abandoned and difficult to trace because colour. they are usually infilled. It is a groundwater laterite which with the regional lowering of river base levels in the recent Typically, it has a topsoil of grey-brown loamy sand geological past is slowly developing oxysolic characteristics. grading down gradually into a brown loamy sand subsoil which at 4 or 5 feet from the surface becomes increasingly Typically it has a foot of grey or brownish fine sandy yellow in colour and may have a pattern of separated light loam topsoil grading down into 3 or 4 feet of brown reddish mottles. to yellow heavy loam or light clay containing increasing numbers of ironstone concretions, which in turn passes With its looser, sandier quality it has readier drainage into a horizon of often cemented groundwater laterite in the upper 5 or 6 feet of the profile and it tends to dry boulders and pebbles of very variable depth. Beneath this out with the onset of the dry season. Consequently the at a depth usually more than 5 feet from the surface, the vegetational ecology is rather different from that of the groundwater laterite zone changes form to a grey, white Mabang and Mara soils; the thicket regrowth is more and blue clay matrix in which are embedded gravel and open and contains more savanna species, and is more cauliflower heads of ironstone amongst a reticulate pattern readily converted into grassland with the encroachment of of bright mottling. cultivation and fire. The usual pattern of vegetation is a mixture of medium A typical profile is as follows :— and high grassland with small scattered trees dominated Reference No. SSB 72. by Lophira sp. Site Terrace. Parent material Alluvium. A typical profile is described as follows :— Vegetation Open high grassland and scattered thicket. Reference No. SSB 31. Rainfall 100 + inches. Site Old terrace. Altitude 220 feet a.s.l. Parent material Old alluvium, more recently colluvium added Locality Kontobe road east of Maroki village. to the upper profile. Source Profile pit 6 feet by 3 feet. Vegetation Open medium and high grassland with Lophira Topsoil pH 42 bush. 0-10 inches Loamy medium sand; loose; structureless, Rainfall 100 + inches. slightly humic; frequent roots; 25 Y 5/2 Altitude . 220 feet a.s.l. (grey brown). Locality Babaibunda road some miles south of Babai- Subsoil (1) pH 50 bunda. 10-20 inches Loamy medium sand; loose; structureless; Source Profile pit 6 feet and 3 feet. occasional roots; 10 YR 6/2 (light brown). Topsoil pH 45 20-38 inches Loamy medium to coarse sand; slightly loose; 0-2 inches Fine sandy light loam; weak crumb structure; structureless; rare roots; 10 YR 6/3 (pale slightly loose; abundant roots; 10 YR 6/2 brown). (light brownish-grey). Subsoil (2) pH 46 2-10 inches Fine sandy light loam; slightly firm and 38-55 inches Loamy medium to coarse sand; slightly firm; slightly compact; structureless; occasional to structureless; 10 YR 8/6 (yellow). rare roots; 10 YR 6/3 (pale brown). 55-72 inches Loamy medium to coarse sand ; slightly loose; Subsoil (1) pH 46 structureless; rare reddish mottles; 10YR7/6 10-23 inches Sandy heavy loam containing much coarse (yellow). quartzose sand; slightly firm; slightly com- pact; structureless; rare roots; some small Land use. At present where this terrace is encountered red and yellow speckling visible; 10 YR 6/4 extensively (as along the Kontobe road from Masore past (light yellowish-brown). 23-31 inches Sandy heavy loam to light clay; firm; com- Maroki), it has oil palms in fairly dense stands on cultivated pact; structureless; frequent irregular areas though no trees remain. A wide range of crops ferruginised gravel and ironstone concretions; including upland rice is grown on the terrace, and it may 10 YR 6/3 (pale brown). well prove useful for further extension of tobacco acreage. Subsoil (2) pH 52 31-40 inches Sandy heavy loam to light clay; compact; Problems. Access is no problem as this terrace mostly structureless; forms matrix in which are hes a mile or more from the river in a zone adjacent to the embedded abundant large and small irregular upland soils. ironstone gravel, ferruginised rock brash and Acidity, lack of nutrients, and possibly weak root hold broken old groundwater laterite. Abundant smooth rounded quartz and rock gravel may be problems. observed as from alluvial deposits; 10 YR 7/6 (yellow). (b) Groundwater laterites and gleisols (Mapping unit 7) 40-50 inches Very similar to above with more laterite gravel and a reticulate pattern of hardening reddish The next two examples of terrace soils described are mottles appearing. typical of the wide range of profiles, varying slightly in Parent material pH 45 detail and appearance at many points, but maintaining an 50-66 inches Compact grey and white plastic silty clay in the interstices of a reticulate pattern of massive overall similarity that outweighs their differences. They hardening reddish, yellow and brown mottling are the groundwater laterites and gleisols, widely dis- containing rare ironstone concretions. Abun- tributed in relatively small units throughout the old dant small quartz grains were mixed with the abandoned floodplains, and in the tributary valleys. They silty clay matrix. 66-75 inches Very similar with the clay becoming bluish in also occur about the edges of, and in local depressions hue and the mottling brighter.

20 Land use. Little utilised at present. These terraces of light brownish-grey (10 YR 6/2) silty and fine sandy could be developed as pasture and for crops such as yams, light loam of weak crumb structure, with frequent roots, cassava and sweet potato. grading into a foot or so of firm, structureless, pale brown Problems. Drainage, nutrients, irregular occurrence. silty heavy loam to clay, which abruptly overlies massive groundwater lateritic ironstone. The pH lies between i MAMALIA SERIES 4-4 and 4-8, the nutrient status is very low. Usually it This is a very acid gleisol with strong groundwater supports a vegetation of open high grassland and poor lateritic affinities; it is typical of the various terrace profiles Lophira bush and when utilised gives moderate crops of developed in areas of annual heavy waterlogging or flooding cassava and sweet potatoes. It has no development and particularly of those profiles associated with the locally potential. elevated remnants of old river terraces within the main mass of " inland " bolis between the Mabole and Rokel K MATAMBA SERIES rivers. This soil also is of limited extent, and occurs on either Usually there is a foot of silty light loam, grey to grey- side of the Mabole floodplain in such small patches as to brown in colour, over 3 to 4 feet of silty and fine sandy be of very limited value agriculturally. heavy loam containing an increasing profusion of con- It can probably best be utilised as pasture and for local cretions, down to a zone of usually hard and impenetable subsistence crops. The topsoil usually comprises about vesicular groundwater laterite. The reaction becomes 9 inches of grey-brown to brown fine sandy light loam, more acid down the profile from a topsoil pH of between with very weak crumb structure, loose, slightly humic 4-8 and 5-2. and with abundant roots, grading into 1-2 feet of pale The vegetation is usually open high grassland. brown to yellowish-brown or yellow rather silty heavy loam or light clay, compact and structureless. This in A typical profile is :— turn grades into several feet of yellow to reddish compact Reference No. SSB 62. structureless silty loam, becoming increasingly mottled and Site Old terrace remnant within a boli. concretionary with depth, forming incipient groundwater Parent material Old alluvium. Vegetation Open high grassland. laterite. The usual vegetation is a mixture of medium Rainfall 100 + inches. and high grasses with some shrubs and rare trees. There Altitude 190 feet a.s.l. is little cultivation apart from a few small gardens of Locality Kontobe boli. cassava, sweet potato and banana. The pH is rather Source Profile pit 6 feet by 3 feet. Topsoil variable, the topsoils varying from 4-4 to 5-7, but the 0-4 inches Silty and fine sandy light loam; very weak profile shows a steady increase in acidity with depth. crumb structure; slightly loose; abundant roots; 10 YR 6/2 (light brownish-grey). Soils of the levees (Mapping units 8 and 9) 4-13 inches Silty and fine sandy loam; compact; hard (when dry); structureless; occasional roots; These comprise soils of mapping unit 8 (contemporary 10 YR 7/2 (light grey with frequent yellow active levees) and mapping unit 9 (old levees associated stains round pore spaces). with old river channels). Such soils are confined to the Subsoil (1) pH 47 present day floodplains of the Mabole and Rokel and to a 13-24 inches Silty and fine sandy heavy loam; compact; hard (when dry); structureless; rare roots; lesser extent the principal tributary valleys. In the old rare small ironstone concretions and frequent floodplains this separation is largely obscured by diverse small hardening reddish mottles with yellow factors of pedogenesis and erosion. staining round pore spaces; 10 YR 8/3 (very Such soils, developed in recently deposited alluvium, pale brown). 24-42 inches Silty heavy loam; compact; hard (when dry); show a wide range of characteristics, and it is not possible structureless; frequent small concretions and to define series with any precision. This is especially true hardening reddish mottles with faint yellow of the immature layered profiles of the contemporary staining round the pore spaces; 10 YR 8/4 levees, although the old levees naturally show a greater (very pale brown). Subsoil (2) pH 4-6 measure of maturity as they are no longer acquiring fresh 42 inches + (Depth unknown) hard impenetrable vesicular alluvial deposits. Most of the contemporary levees now ironpan with soil material in the interstices. appear to be above the annual flood level, a change which, judging from their lack of profile development, is due to a Land use. Locally used in the vicinity of habitations for recent change in base level of the rivers. cassava, beans, sweet potatoes (plate 10). The main use The profiles examined have been grouped together will continue to he in local diversification of a farming under a number of series names, each having a basic system based upon swamp rice. measure of similarity and each will be described briefly. Problems. Wet season access, scattered occurrence, Some of the levees have considerable extent, and the nutrient status and acidity pose a series of difficulties which soils as a whole should form an important factor in future make the future value of these soils doubtful in relation agricultural development. They lend themselves readily to the effort required to utilise them. to tilling and a wide range of subsistence and cash crops The next two series are typical of the groundwater can be grown upon them with success especially in the laterites developed on old terrace remnants associated with presence of fertilisers. They can add to the acreage of the inland bolis and along the main tributary valleys rotational pasture, provide fodder crops, and perhaps be leading off the Mabole river. utilised for cash crops such as tobacco and oil palms.

A MALOP SERIES Soils developed over contemporary levee deposits This soil is found particularly in the valleys of the w (Mapping unit 8) Malop and Belia streams. It has nowhere any great extent y\ SELi SERIES (analyses on page 43) and is thus relatively unimportant to the agricultural This series is found on the levees bordering the Rokel picture as a whole. It comprises a topsoil of about 6 inches river. It comprises a foot of silty heavy loam dark grey

21 in colour, pH about 48, with a weak crumb structure, TABAI SERIES over a variegated subsoil in which the characteristics This series differs from the foregoing soils in being a depend upon the successive layers of alluvium. In general groundwater laterite, having reached a greater degree of it becomes more clayey with depth, but may include local maturity. It is found along such tributary streams as the sand lenses. The colour of the clayey matrix varies from Tabai (e.g., on the west bank south of the Lunsar road pinkish white to white with a scattered and sometimes bridge) and Beha, and supports a vegetation of open high reticulate pattern of red and ochre mottles. It is under and medium grassland and shrubs. medium grassland with shrubs, no longer flooded, but not much utilised, probably because of its difficult accessibility, Topsoil pH 58 save in the neighbourhood of riverside villages where a This usually consists of about a foot of silty and fine sandy loam to heavy loam; usually with a weak crumb structure; variety of crops grow well. The pH of the subsoil usually loose; slightly humic; brownish-grey to pale brown with shows an increase in acidity down to 4 or 5 feet, then a faint rusty staining round the pore spaces. decrease. Subsoil (1) pH about 54 This is usually up to 2 feet of silty light clay, light ^ MAGBUNGA SERIES (analyses on page 43) yellowish-brown, compact and structureless, with rusty staining round pore spaces, dispersed small reddish and This is the equivalent series in the Mabole valley. It yellow mottles, and rare nodular ironstone gravel towards possesses a well denned topsoil 6 to 9 inches deep, of silty the bottom. and fine sandy light loam, grey to yellowish-brown in Subsoil (2) pH about 48 colour, with a weak crumb structure, pH about 5 -4. Below This derives gradually from subsoil (1) and extends to this, the subsoil is generally firm, compact and structureless, great depth. It usually has a silty light clay to clay texture on the whole silty but with occasional fine sand horizons, and an increasingly abundant reticulated pattern of hardening a loam to heavy loam in texture, but rarely clayey, and red and yellow mottles forming incipient groundwater laterite superimposed upon a pale brown to white back- yellowish-brown to yellow in colour. Mottling is rare, ground. When exposed this zone rapidly hardens. and moisture retention appears to be quite good. The pH shows a gradual increase in acidity with depth to about 4-8-5-0 at around 6 feet. In this series and in Seli series, Soils developed over slough deposits (Mapping unit 10) nutrient status in the topsoil is probably higher than in These soils form the great bulk of those available for most bolilands soils. They are, however, wanting in expanded rice production. They are contiguous with the organic matter and nitrogen, but could be readily improved areas subject to annual inundation and fall into two main by management. It is difficult to approach areas of this topographical groups relevant to potential development:— soil in the wet season. (a) those associated with contemporary sloughs adjacent to the present courses of the Mabole and Rokel rivers; Soils developed over old levee deposits (Mapping unit 9) (b) those associated with the old sloughs of the The next two series—Mateboi and Bom—represent the " inland " bolis. old levees in the present floodplains, adjoining cut-offs and The soils nearly all fall into the great soil group of very old meanders of the comparatively recent past. Tabai acid gleisols but there are marked and important differences series represents old levees associated with the old flood- between the two groups. The soils of the contemporary plains; the soils being definable only along the courses sloughs have deep profiles, free of incipient ironpan or of the principal tributary streams which for the most part concretions, developed in sandy or silty alluvia and usually follow ancient river courses and are hence enclosed in underlaid at some more or less great depth (usually over large levee banks. 6 feet) by a rather loose sand horizon which exercises a critical control over the flooding regime (see figure 2). As MATEBOI SERIES already stated in the section on geomorphology, direct This series has a topsoil about 12 inches thick of grey- flooding from the rivers on to these areas accounts for only brown to yellowish-brown silty and fine sandy light loam, a small proportion of the flood water. However, when weak crumb structure, loose, and slightly humic, with the river level has risen to the level of this porous sand pH about 5-0 grading down into 2 or 3 feet of yellow horizon it becomes waterlogged and the normal vertical heavy loam to clay, very silty, firm, compact and structure- drainage can no longer take place, hence the run-off from less. Below this the texture usually becomes lighter, the surrounding uplands plus direct precipitation on to the profile is rather puddled in appearance and a faint pattern sloughs is trapped until the level of the river subsides of reddish mottles and brown staining appears. The pH again. This accounts for the abrupt arrival and departure remains fairly constant at about 4-8. The usual vegetation of the floods and for the fact that the contemporary is open high grassland, with rare shrubs and trees. (riverain) sloughs dry off sooner than the old (inland) sloughs. The subsous, however, are usually sufficiently BOM SERIES clayey to retain a measure of moisture well into, if not The topsoil comprises about 9 inches of silty and fine right through, the dry season. It is also possible, however, sandy light loam, loose and crumby, grey to grey-brown in that much of this moisture is bound hygroscopically to the colour, with pH 4-5. Below this there is usually 12-18 fine clay fraction and is consequently not available to inches of silty heavy loam, pale brown, compact and . structureless, with pH about 4-6. This grades into a The slough soils of the " inland " bolis appear to have considerable depth of yellow silty loam to light loam. been developed in finer material and in consequence of This zone is compact and structureless and the average their place in a senescent and near-peneplanated landscape pH is about 4-7. Faint dispersed mottling may appear frequently have massive groundwater laterite horizons in with depth. Occasional layers of pale brown silty and fine their profiles (see figure 1). This development has been sandy heavy loam are found. accentuated by their occurrence over very fine shales,

22 siltstones and mudstones which are weathering in situ to 0-4 inches Silty light loam; weak crumb structure; give considerable depths of very fine, plastic, impervious loose; abundant matted roots; slightly humic; 10 YR 4/1 (dark grey). clays below the groundwater laterite. Consequently, the 4-10 inches Silty heavy loam; weak crumb structure; water which collects in these shallow depressions from slightly firm; frequent roots; slightly humic; run-off from the adjacent uplands rapidly waterlogs the some speckles and patches of whitish colouring profile and can then only escape through the small tributary observed; 10 YR 5/1 (grey). Subsoil (1) pH 49 streams which now drain these old floodplains. This 10-34 inches Silty clay; puddled, firm, compact, structure- accounts for the fact that these soils remain flooded longer, less; 10 YR 8/3 (very pale brown); with and usually flood earlier than the soils in the contemporary much small reddish and yellowish speckling (riverain) sloughs. The majority of the profiles are now and small mottling. 34-71 inches Silty clay; a reticulate pattern of red mottling at a stage of pedogenesis where their groundwater lateritic on a background of firm compact structureless characteristics are becoming of nearly equal significance 10 YR 8/1 (white) silty clay. with their characteristics as very acid gleisols. Subsoil (2) pH 48 From the point of view of irrigation and drainage this 71-114 inches A pattern of hardening coarse yellow and brown mottling with 10 YR 8/2 (white) silty clay in division of the potential rice soils into two major groups the interstices. Sand content slowly increasing is of paramount importance. The soils of the contemporary with depth. sloughs are undoubtedly much more readily cultivable, have a better tilth, and often a better nutrient status than Land utilisation. At present these soils are used re- those of the " inland " bolis, but present a difficult problem latively little for rice farms. Similar areas (e.g., Mayeliba for irrigation due to the variability of flooding. During boh south of Mara) have been used by the Agricultural the flood season changes of depth are more sudden and Department in the course of mechanical rice farming marked than in the " inland " boh's, due to proximity development. They provide a reasonably good ploughing to the primary means of water evacuation via the major medium and should be responsive to fertilisers. They river channels. Control of flooding level in these areas may be worth investigating for intermediate and dry would presumably lie in barrage control of the river flow. season crops, particularly sown pastures and small dry- The inland bohs would be an easier irrigation problem season gardens dependent upon small pumps drawing if a source of water could be maintained, but they present from the adjacent rivers. Pasture in turn should help more problems of development through the presence of improve soil structure and humus content. the lateritic horizons, which would be a physical obstacle to Problems. Acidity and nutrient status. mechanical equipment both agricultural and engineering. These " inland " boli soils show another feature of pedo- V MABOLE SERIES (analyses on page 44) genetic importance in the upper foot or so of their profiles This is one of a number of series associated with con- where increasing quantities of colluvium can be found temporary sloughs along the Mabole river. It has a high giving a sandy admixture to the texture, this material being silt and clay content, increasing down the profile and pH derived from the surrounding uplands. ranges between 4-0 and 5-0. The soil is commonly associated with slight depressions and grooves in ' the (a) Soils of the contemporary sloughs sloughs where new drainage is slowly being initiated. It is (Included in mapping unit 10) thus likely to be a rather leached profile. This group will be dealt with first. It comprises a Commonly it has up to a foot of loose fine dark grey- number of important and extensive series, mostly occurring brown topsoil over 1-2 feet of grey to white heavy loam. in relatively accessible areas, which should lend themselves Below this lies a variable but considerable depth of white readily to improved methods of cultivation. or pale brown clay. A typical description is :— \ ROKEL SERIES (analyses on page 44) Reference No. SSB 13. This is a generally clayey very acid gleisol which, with Site Drainage groove in slough. numerous minor variations in colour, texture, and Parent material Alluvium. Vegetation Open medium grass with sedges. appearance as between one boh and the next, is probably Rainfall 100 + inches. the most extensive series found in the contemporary Altitude 120 feet a.s.l. sloughs adjacent to the Rokel river. Locality Rochin boli, Batkanu. It commonly has about 1 foot of grey to dark grey silty Source Profile pit 6 feet by 3 feet. Topsoil pH 5 o loam, over 2 or 3 feet of compact, structureless, pale brown 0-2 inches Silty and fine sandy light loam; very weak clay, which passes down into a very deep mottled zone. crumb structure; loose and rather powdery The texture often becomes lighter and sandier with when dry; frequent roots; slightly humic; increasing depth, usually over 8 feet from the surface. 2 5 Y 4/2 (dark grey-brown). 2-8 inches Silty and fine sandy loam; very weak crumb The topsoil pH is about 5-0 and the acidity increases structure; loose; occasional roots; very gradually with depth. slightly humic; 10 YR 5/1 (grey). The following may be taken as a typical profile :— Subsoil (1) pH 48 8-15 inches Silty heavy loam; firm; structureless; 10 YR Reference No. SSB 85. 7/1 (light grey). Site Contemporary slough. 15-23 inches Silty heavy loam; firm; structureless; 10 YR Parent material Alluvium. 8/1 (white). Vegetation Close medium grassland. 23-32 inches Silty light clay; firm; compact; structureless; Rainfall 100 + inches. 10 YR 8/2 (white). Altitude 160 feet a.s.l. Subsoil (2) pH 5 o Locality Opposite Rochin-Malal village across the 32-45 inches Silty light clay; firm; compact; structureless; river Rokel. 10 YR 8/3 (very pale brown). Source Profile pit 6 feet by 3 feet. 45-57 inches Silty clay; firm; compact; structureless; Topsoil pH 50 10 YR 8/3 (very pale brown). 23 57—7° inches Silty clay; firm; compact; structureless; Nutrient status. Very poor indeed, wanting in every io YR 7/2 (light grey). respect. Percentage base saturation in the topsoil, for Nutrient status. Very low. Total exchangeable bases example, is less than 1 per cent. Capable of a much for the three zones above are respectively 0-7, 04 and 05, higher status with proper management. of which half is calcium. Land use. At present used spasmodically by the local Land use. At présent rarely used. Can be utilised as population for rice, apparently largely as a result of the part of the rice areas, and should be capable of increased mechanical rice cultivation scheme having successfully yields with modern management including fertilisers. used this soil. It is also used for dry season grazing Problems. Acidity and nutrient status. especially in the Mateboi area, and in this respect has a similar potential to that of the Rokel series in the Rokel X^ MALANSA SERIES (analyses on page 44) floodplain. This is the principal series of the contemporary sloughs Problems. Acidity, nutrient status, and control of along the Mabole river. As is usual with profiles developed flooding with regard to length of time, depth of water, in alluvial parent material, numerous variations occur and timing. but the essential basic characteristics remain constant over wide extents. (b) Soils of the old sloughs (inland bolis) There is usually 6-12 inches of grey to grey-brown, or (Part of mapping unit 10) occasionally dark grey to black, light loam topsoil. This These are generally much more mature soils showing in grades fairly sharply into a subsoil which may be up to some cases a degree of senility. Because of their extent 10 feet deep and in which changes are very gradual. The they are important to any project for developing swamp colour varies from pale brown at the top to yellow at rice acreage. depth and yellow-red mottles and brown rusty staining round the pore spaces are common particularly in the Y^ KONTOBE SERIES (analyses on page 45) middle subsoil. At some depth of from 6 to 10 feet the This soil is typical of those older bolis associated with profile becomes increasingly sandy and may occasionally the Rokel floodplain and found in the main to the south reach loose unconsolidated yellow sand. The pH is usually of the river, but also, as for example, Kontobe boli, to the about 5-0-5-2 in the topsoil, 4-5-5-0 in the upper half of north of the river. It is a common and widely found the subsoil then rising again to about 5-0 or 5-2. series in these sites, and the same profile also occurs on Vegetation is usually a close cover of medium grasses. certain flooded or waterlogged low terraces associated with A typical profile is :— this floodplain level, as, for example, that to the west of Reference No. SSB 36. Kumrabai Mamila road junction. Site Slough. Typically it has a topsoil 12-18 inches thick which ends Parent material Alluvium. fairly abruptly. It is a grey to grey-brown silty light Vegetation Close medium grassland. Rainfall 100 + inches. loam, with a weak crumb structure. Below this there Altitude 120 feet a.s.l. are 2-3 feet of light grey to pale brown loam to clay dis- Locality Bantoro boli, Mateboi. playing an increasing profusion of mottling, and this in Source Profile pit 6 feet by 3 feet. turn grades down into a groundwater laterite zone which Topsoil pH 5 2 0-2 inches Silty and fine sandy loam; weak crumb varies from a massive abundant reticulate pattern of structure; loose; abundant matted roots; hardening mottles and concretions to massive vesicular 10 YR 5/1 (dark grey). red yellow and black groundwater laterite. 2-6 inches Silty and fine sandy loam to heavy loam; very The pH lies mainly in the range 4-2-5-0 with the topsoil weak crumb structure; loose; frequent roots; 10 YR 5/1 (dark grey). about 4-2-4-6, but different profile patterns have been Subsoil (1) pH 50 observed. The commonest shows a steadily increasing 6-14 inches Silty heavy loam; firm; compact; structure- pH value, and this is usual to the south of the Rokel river. less; 10 YR 8/3 (very pale brown) with Other patterns from north of the river show a steady slight occasional very small yellow-red mottles. decrease in pH value; an increase followed by a decrease; 14-21 inches Silty light clay; firm; compact; structure- less; 10 YR 8/3 (very pale brown) with and a decrease followed by an increase. These three occasional yellow-red mottles and slight rusty reaction profiles all occur in close proximity in the series staining round pore spaces. within Kontobe boli itself, but the soil is universally found Subsoil (2) pH 5 o to be very acid. Ultimately it may be found desirable to 21-35 inches Silty light clay; firm; compact; structure- less; 10 YR 8/6 (yellow); frequent small distinguish these variations as phases within the series yellow-red mottles and rusty staining round and to relate them to other features by a more detailed pore spaces. programme of examinations than was possible with this 35-51 inches Silty light clay; firm; compact; structure- survey, especially as the series has such extent as to be less; but slightly friable; 5 Y 8/3 (pale yellow); frequent hardening yellow-red mot- bound to play an important part in any programme extend- tles, and some yellowish and brown staining is ing rice cultivation in the bolilands. observable. A typical description is as follows :— 51-70 inches Silty and sandy heavy loam; firm; compact; structureless; friable; 5 Y 8/3 (pale yellow) Reference No. SSB 83. with yellow mottling and some hardening Site Slough associated with old seasonally water- yellow-red mottles. logged terrace. Substratum Parent material Old alluvium and some colluvium. 70-80 inches Sandy loam; slightly loose; structureless; Vegetation Close medium grassland containing scattered 2-5 Y 8/4 (pale yellow), with yellow and clumps of open high grassland. yellow-red mottling. Rainfall 100 + inches. 80-94 inches Coarse, apparently granitic, sand, pale yellow, Altitude 200 feet a.s.l. and only slightly consolidated and compacted. Locality Near old Agricultural Department ploughing 94-108 inches Loose, yellow-brown quartzose sand. site north-east of Kumrabai Manila. 24 Source Profile pit 6 feet by 3 feet. 33-57 inches Silty light clay; compact; structureless; Topsoil pH 42 10 YR 8/3 (very pale brown) with yellow and 0-5 inches Silty light loam; weak crumb structure; red soft and hard mottles. This horizon slightly loose; abundant roots; slightly humic; contains some small pockets of silty, white 10 YR 5/1 (grey). clay. 5-18 inches Silty loam; firm; structureless; occasional 57-72 inches + Silty light clay with pockets of white clay; roots; very slightly humic; 10 YR 5/2 (grey- compact; structureless; reticulate pattern of brown) with rare yellowish staining. yellow and red hardening mottles; 10 YR 8/3 Subsoil (1) pH 43 (very pale brown). The quantity of white 18-32 inches Silty light clay; firm; slightly compact; clay in this horizon increases as the substratum structureless; rare roots; 10 YR 7/2 (light is approached. grey) with occasional yellow staining. 32-50 inches Silty clay; firm; compact; structureless; 10 YR 8/3 (very pale brown) with frequent Land use. Used locally for rice and dry season sweet small reddish and red-yellow mottles. potato patches. Is suitable for inclusion in acreage for Subsoil (2) pH 44 rice development and dry season pasture. 50-71 inches Silty clay; compact; plastic and structureless ; Problems. Acidity, nutrient status, and water control. 10 YR 8/1 (white) in the interstices of a dominant pattern of red and yellow hardening mottles forming incipient groundwater laterite and becoming more ferruginised and massive MASSIMO SERIES (analyses on page 45) with depth. This is a soil very similar to Kontobe series and found widely distributed through the inland bolis. It differs Land use. Only locally used for rice. It is capable of from Kontobe series in that the groundwater laterite zone further development in this direction, and also in the is more fully developed and usually near the surface, provision of dry season pastures and crops with the aid without the deep sequence of transitional horizons between of water supply. the topsoil and the groundwater laterite. This probably Problems. Acidity, nutrient status, control of water indicates its greater age and maturity and it is confined supply. to the older bolis now encountered for the most part further away from the present major floodplains. There is usually 12-18 inches of grey to dark grey silty tf> BABAiBUNDA SERIES (analyses on page 45) light loam to loam with a pH of about 4-8-5-6. This is This is another important and widespread series of the succeeded by about a foot of grey to white compact heavy inland bolis, this time of that group lying between the loam rather more acid, before entering about 2-3 feet Mabole river and the Kontobe-Makeni road. from the surface the zone of groundwater laterite in which It is a typical very acid gleisol developing strong ground- acidity again increases. water laterite characteristics and usually has a topsoil A typical profile is described below:— 6-9 inches deep of grey to light brownish-grey silty loam, passing into 2-3 feet of pale brown to yellow mottled silty Reference No. SSB 77. Site Old slough. heavy loam to light clay. Below this is a zone of developing Parent material Old alluvium and colluvium. groundwater laterite comprising a massive reticulate Vegetation Close medium grassland. pattern of hardening mottles tapering upwards into Rainfall IOO + inches. columns and occasionally downwards into a zone of Altitude 200 feet a.s.l. Locality Massimo. lateritic boulders and mottling. Below this level, when it Source Profile pit 6 feet by 3 feet. can be penetrated, lies the zone of weathered substratum Topsoil pH 51 comprising white, yellow and pale brown puddled plastic 0-3 inches Silty and fine sandy light loam; very weak clay derived from the underlying argillaceous sediments. crumb structure; slightly loose; abundant matted roots; slightly humic; 10 YR 4/1 This zone appears to lie at the level of a permanent water (dark grey). table and is usually 10 feet at least from the surface. 3-13 inches Silty loam; slightly firm; slightly compact; The topsoil usually has a pH of about 4-7-5-0, the structureless; occasional roots; 10 YR 6/1 acidity increasing slightly in the upper subsoil. (grey). Subsoil (1) pH 4-8 The following is a typical profile:— 13-23 inches Silty heavy loam to light clay; firm; compact; structureless; rare roots; 10 YR 7/1 (light Reference No. SSB 74. grey). Site Slough of old floodplain. Subsoil (2) pH 47 Parent material Old alluvium and contemporary colluvium. 23-35 inches Silty light clay; firm; compact; structureless; Vegetation Close medium grassland. 10 YR 7/1 (light grey) with yellow and pale Rainfall 100 + inches. red smears and mottles, some hardening and Altitude 210 feet a.s.l. tending to cement into masses. Locality Kafali boli. 35-77 inches Massive incipient groundwater laterite com- Source Profile pit 6 feet by 3 feet. prising intricate columns and networks of Topsoil pH 50 red-brown and yellow hardened mottling with 0-8 inches Silty and fine sandy light loam; weak crumb boulders and gravel of ironpan. In the structure; slightly firm; abundant roots; interstices of this mass there is grey and white slightly humic; 10 YR 6/2 (light brownish- plastic silty clay. grey). Subsoil (1) pH 48 8-24 inches Silty heavy loam; firm; slightly compact; Land use. Used locally for rice, and is also the soil over structureless; rare roots; 10 YR 8/6 (yellow) which many of the co-operative departmental ploughing with occasional small hardening red mottles. sites about Massimo are situated (i960). Its future 24-33 inches Silty light clay; hard when dry; compact; development potential will be very much the same as for structureless; 10 YR 8/4 (very pale brown) with frequent large red mottles and smears. Kontobe and Babaibunda series. Subsoil (2) pH 49 Problems. Acidity, nutrient status, water control. K ROMANKNE SERIES (analyses on page 45) Vegetation Close high grassland. This soil is chiefly found in the boüs about the Lunsar Rainfall 100 + inches. Altitude 220 feet a.s.l. road, and is typical of much of this area. It has close Locality 200 yards south-west of Babaibunda. affinities with Massimo series and the two can probably Source Profile pit 6 feet by 3 feet. be regarded together for agricultural purposes. Topsoil pH 44 It has about 12 inches of grey silty and fine sandy loam 0-2 inches Silty and fine sandy light loam; weak crumb structure; loose, abundant roots; slightly topsoil with an acid reaction, with a transitional upper humic; 10 YR 5/1 (grey). subsoil of about 2 feet of mottled grey to pale brown silty 2-6 inches Silty and fine sandy loam; weak crumb heavy clay, very acid, above the zone of groundwater structure; slightly loose; frequent roots; laterite which in this series seems to have developed in slightly humic; 10 YR 5/1 (grey). Subsoil (1) pH 41 parent material containing a higher sand content than 6-23 inches Silty loam; compact; structureless; occasional most of the other series developed in these old floodplain roots; 10 YR 6/1 (grey). sloughs. This groundwater laterite zone is variable in 23-36 inches Silty heavy loam to light clay; compact; reaction and may be more or less acid than the zone above. structureless; rare roots; 10 YR 6/3 (pale brown) with frequent small red and yellow The following is typical of the series :— mottles, and much rusty staining round pore Reference No. SSB 42. spaces. Site Old slough. Subsoil (2) pH 44 Parent material Old alluvium with contemporary colluvium. 36 inches-unknown depth. Hardened impenetrable massive red, Vegetation Close short and medium grassland. brown and black groundwater laterite with a Rainfall 100 + inches. little soil material in the interstices. Altitude 170 feet a.s.l. Locality Romankne boli, Lunsar road. Land use. Used locally (depending on land availability) Source Profile pit 6 feet by 3 feet. for a wide variety of crops if necessary. Sweet potatoes, Topsoil pH 5 7 beans, cassava, groundnuts, bananas have been observed 0-2 inches Silty and fine sandy light loam; weak crumb structure; loose; abundant roots; slightly on these sites but results appear indifferent. May be humic; 10 YR 5/1 (grey). utilisable with management for tobacco crops, as planting 2-11 inches Silty and fine sandy loam; slightly firm; on such sites could be undertaken a little earner than on structureless; frequent roots; slightly humic; topographically lower sites. 10 YR 5/1 (grey). Subsoil (1) pH 53 Problems. Nutrient status, acidity, localised occurrence. 11-23 inches Silty and fine sandy heavy loam; firm; The next two soils are much alike—acid gleisols with slightly compact; structureless; occasional roots; 2-5 Y 7/2 (light grey). strong groundwater lateritic affinities found round the 23-40 inches Silty and fine sandy light clay; firm; compact; " inland " boli margins. By virtue of their site they are structureless; rare roots; 25 Y 8/0 (white) less subject to inundation and are rarely more than water- with a columnar pattern of sandy yellow and logged. They have also acquired topsoils largely derived pale brown hardening mottles. Subsoil (2) pH 49 from colluvial drift parent material. Thus with a fairly 40-54 inches Similar to the horizon above, but with the deep cultivable layer above the lateritic subsoils they can mottled pattern dominating the profile. form a useful part in the local agricultural pattern. Un- 54—72 inches A reticulate hardening mass of reddish and fortunately though widespread they are of limited individual yellowish groundwater laterite containing nodular concretions and ironstone gravel. In extent, chiefly confined to indentations into the sur- the interstices there is firm, compact, silty sounding upland flanks, and similar sites favourable to the clay; 10 YR 8/2 (white). gathering of colluvial material. When encountered, however, they should as far as possible be incorporated Land use. Locally used for rice and dry season sweet into the arable pattern for food and cash crops—for potato patches plus a Uttle dry season grazing. To judge example, tobacco and groundnuts—as they are easily tilled from experience at Kontobe it seems that in all these and should prove readily responsive to fertilisers. capacities its scope can be developed and the very poor nutrient status improved. V- MAKONTE SERIES Problems. Acidity, nutrient status, water control. This is probably the more extensive and important soil of the two. It usually comprises some 9-18 inches of ^ MASEBRA SERIES grey to brown, weakly crumb structured, loose, slightly This is a common but not extensive series of the inland humic silty and fine sandy light loam over about 2 to 3 feet boüs about the Lunsar road and the tributary valleys of of grey-brown to yellow-brown, compact, structureless, the Mabole river. It occurs on locally elevated areas of heavy loam or light clay with a pattern of yellow and these old sloughs, and on small degraded remnants of river reddish mottles, and rusty staining round pore spaces terrace associated with and lying within them, as well as appearing towards the bottom of this horizon. Below this on such remnants round the marginal edges of the old the mottling becomes dominant and often hardens into boüs where the profile extends into the transitional zone vesicular ironpan with depth, the soil matrix being grey at the foot of the adjacent uplands. It is not so regularly to brown silty loam or clay. The pH is fairly constant or completely flooded as the true slough soils, but because down the profile and hes between 46 and 5-0. Termite of the manner of its small spasmodic occurrences it has activity is often marked in this soil with low dome-shaped been mapped with them. termitaria, and the soil is often used for a variety of crops. Its characteristics are closer to the typical groundwater laterite than the acid gleisol, and it is classified accordingly. Y. MADINA SERIES A typical example is :— This series has a topsoil of from 6 to 18 inches deep composed of grey-brown silty and fine sandy light loam, Reference No. SSB 52. with a weak crumb structure; rather loose and slightly Site Elevated locality in old boli slough. humic. This grades into about 2 feet of compact structure- Parent material Old alluvium. 26 less silty and fine sandy loam, pale brown to brownish-grey Land use. Nil, but they could be used locally for rice in colour, usually displaying rusty staining round the pore (varieties suitable to deep flooding) and dry season spaces. Below this there is an abrupt division marking off pasturage in the presence of water control. the largely colluvial upper profile. The lower profile Problems. Acidity, low nutrient status; deep rapid comprises a packed mass of large and small nodular flooding. ironstone gravel in the process of cementing into massive ironstone and the interstices of this mass are occupied Soils developed in drainage grooves; mixed bottom soils, with grey or brownish-grey silty clay. The pH of the and recent alluvium (Mapping units 12, 13 and 14) topsoü is about 4-8-5.0, the acidity increases in the lower part of the upper profile and decreases in the zone of These are units enforced largely by practical con- groundwater laterite. The usual vegetation is a mixture siderations of representation on the map. The soils of of medium and high grasses with some shrubs and trees. unit 12 all occur elsewhere among units 7-11, and are The series is capable of the same utilisation as Makonte principally groundwater latérites and gleisols. By im- series. plication the term drainage groove indicates valleys or sinuous depressions without a well defined water course, and hence with ill defined drainage characteristics such Soils over old river channel deposits (Mapping unit 11) areas warrant separate consideration by the agriculturalist. These soils occur as long narrow strips in the bolis below Unit 13 has had to be evolved to suit areas containing the level of the adjacent land. They are principally found elements of units 7-12 which cannot be satisfactorily in the present day floodplain. The old river channels separated at this scale. associated with inland bolis, though sometimes discernable The recent alluvium of unit 14 is found between the on air photographs, are more rarely mapped because they seasonal water levels in very gently shelving river courses. are now topographically obscured and pedologically similar Kontobe creek is a good example of this, it being an old to adjacent slough soils. river channel now nearly infilled and with dense swamp Though originally developed in alluvial parent material thicket growing in the zone of mud between the seasonal such soils now show close affinities with the acid gleisols water levels. It has also been used in rare instances to and as they approach maturity tend to develop the indicate sandbanks in the main river bed which have characteristics of groundwater laterites. almost attained dry land status and support a perennial ROCHIN SERIES vegetation. This soil is characteristic of the profiles in the old river channels associated with the major floodplains. Inevitably NUTRIENT STATUS OF BOLILAND SOILS such soils show, especially in the subsoils, a wide range of characteristics appertaining to colour and texture, but there A limited analytical programme was undertaken to gain is a basic degree of uniformity, and the multitudinous some knowledge of the status of bottomland soils available variations respectively cover such small areas that a detailed for extending the mechanical rice cultivation scheme. examination and classification was not attempted. All fall The results are presented in the Appendix, Table 8. This into the great soil group of very acid gleisols, and are work was undertaken by Mr. C. L. Bascomb at Rothamsted subject to deeper flooding than other soils by virtue of Experimental Station, Harpenden, England. their topographical site. All the soils are acid, their content of exchangeable cations is very low and they are almost completely A fairly typical profile is the following one :— unsaturated. Since 1957 workers at the agricultural experi- Reference No. SSB 48. mental station at Kontobe have been studying the cultivation Site Old river channel. of rice on these soils but, at the time of the survey, few Parent material Alluvium. Vegetation Close medium grassland. conclusions could be drawn apart from the striking response Rainfall 100 + inches. to superphosphate. Some figures in the 1958 annual report Altitude 120 feet a.s.l. of the Department of Agriculture indicate a surprising Locality Bantoro boli. increase in nitrogen content of the topsoil at the onset Source Profile pit 6 feet by 3 feet. Topsoil pH 49 of the rainy season. Jeffery (1961) has published important 0-2 inches Silty and fine sandy light loam; weak crumb observations on the low redox potential of Kontobe soil structure; loose; abundant roots; slightly when waterlogged. humic; 10 YR 4/1 (dark grey). 2-9 inches Silty and fine sandy light loam; weak crumb structure; slightly firm; frequent roots; Soil reaction (see Appendix , Table 7) slightly humic; 10 YR 4/2 (dark grey-brown). 9-21 inches Silty and fine sandy loam; very weak crumb Soil reaction determinations were made locally during structure; firm; slightly compact; occasional the survey on profile pit samples. All the pH's fell in the roots; 10 YR 4/2 (dark grey-brown). range 4-0-5-8, and principally in the range 4-2-5-4. Subsoil (1) pH 48 The waterlogged bottom soils show an increase in acidity, After an abrupt division from the topsoil the profile continues :— at the start of the wet season, probably averaging about 21-32 inches Silty heavy loam; compact; hard; structure- less; 10 YR 6/6 (brownish-yellow). one unit, a seasonal variation comparable with what 32-41 inches Silty light clay; compact; hard; structure- Russell (1950) has described for European cultivated soils. less; 10 YR 6/4 (light yellowish-brown) with Between the soils of different great soil groups and different occasional small brownish-yellow mottles. landform sites there is little distinction in acidity: 41-56 inches Silty light clay; very compact; hard; struc- tureless; 2-5 Y 8/4 (pale yellow) with frequent small brownish mottles and stains. Mechanical analysis Subsoil (2) pH 46 The gleisols from the contemporary sloughs in the 56-75 inches Silty heavy loam; very compact; structure- less; 2-5 Y 8/4 (pale yellow) with frequent Mabole and Rokel floodplain show a very high silt plus small brownish mottles and stains. clay content, which may exceed 90 per cent below the top foot or so, more commonly in the soils associated with the and drainage characteristics than any other soils of com- Mabole river. The levee alluviosols have a similarly high parable extent within the survey area and as a result silt plus clay content, usually higher for those profiles should lend themselves most readily to development. along the Rokel river than those along the Mabole. This Their structure and consistency are such that they should suggests that these soils should have a high water retaining readily respond to fertilisers, and the vegetation growing capacity under irrigation. By contrast the gleisols as- upon them—mainly thick low forb regrowth—can be sociated with the inland bolis have lower horizons occupied cleared easily for mechanical cultivation. Permanent with variable, sometimes dominant, masses of groundwater cropping, however, can only be contemplated with caution laterite, with silt and clay filling the interstices to form an and in association with a capitalised agricultural system impervious zone which will also give a high water retention using fertilisers regularly. capacity. Class la. This class is tentatively proposed to contain Among the terrace oxysols Mara and Mabang series the gleisols found in the sloughs adjoining the Mabole have an appreciable clay content which increases in the and Rokel rivers (unit 10). They comprise Rokel, Mabole subsoil. and Malansa series and also Rochin series of unit n. Intensive development would require highly specialised Organic matter management and for this reason they can only be regarded The organic matter content of the topsoils is generally as Class I soils in relation to availability of capital for such low to very low with the exception of the gleisols and management. These soils offer the best prospects for alluviosols associated with the contemporary floodplains, development of water control by reason of their con- in which it may attain 9-15 per cent. In the terrace figuration and extent. They lie immediately adjacent to oxysols and the best upland oxysols organic matter content the main rivers, they are subject to seasonal flooding, are reflects farming pressure. Where such soils have been easily cultivated mechanically in fairly large homogeneous under a fairly dense forb regrowth the percentage of units, and usually drain through a single low point at one organic matter may rise sharply (see figures for SSB 84, end of each slough. Appendix, Table 8), but otherwise it is low. Nitrogen In the vicinity of Batkanu and Mara these soils have content being largely a function of organic matter it is also already been used for some years for mechanical rice generally very inadequate in boliland soils. cultivation and an acquired body of agronomic knowledge exists (Piggott and Nichols 1958, Glanville 1938). Exchangeable bases The sketch maps of individual bolis show typical Total exchangeable bases in all soils analysed are examples of these sloughs or bolis as they are more com- extremely low. Unpublished work by the departmental monly described. It can be seen that the soil pattern is agricultural chemists who in the past have examined other somewhat complicated by the existence of levee and old profiles represented in this area, confirms that this is river channel soils, but in any comprehensive scheme for probably true of all the soil series defined. Percentage drainage, irrigation and flood control the bolis would base saturation is in general very low and in so far as this necessarily be treated as a whole though the cropping reflects the availability of the nutrients present, the soils programme could be adjusted to suit the soil require- in the contemporary floodplains beside the Rokel and ments as will be suggested later. Mabole rivers are mostly slightly superior to those of the Class II. This group contains a large area of diverse inland bolis. In this respect the terrace oxysols are soils sub-divided as follows:— markedly the best of the profiles analysed in terms of both total exchangeable bases and availability. Nevertheless it 1. The better upland oxysols. These comprise is worth noting that these oxysols, which have been under Batkanu, Mankahun, Masuri and Diabama series of derived savanna for a long time, are inferior to the oxysols units 2, 4 and 6 plus the small areas of unit 5 and have of the high rainfall forest areas of Ghana (Ahn 1961), a limited extent, but an important place in the develop- who quotes the averages of exchangeable calcium and ment of upland arable farming. They are superior to potash, for example, as being 2-2 and 0-32 respectively. the remaining oxysols in having a higher proportion Here again the figures for SSB 84 are worth examining. In of soil material to gravel, concretions and ironpan and this profile which was taken from thick forb regrowth the thus being easier to till. Otherwise they have no topsoil figures compare with those for Ghana. This greater nutrient reserves. strongly emphasises the importance which bush fallowing 2. Alluviosols of the contemporary and old levees is likely to play, at any rate initially, in any programme of (units 8 and 9). In many respects these soils could agricultural development. be placed in Class I, but the inconvenient form in which they occur—usually long narrow strips— detracts from their value, and their higher topo- LAND CLASSIFICATION graphical position does not permit placing them in A brief classification is offered here as a basis for planning the same class for rice cultivation as the soils in the broad outline of future development. It is solely Class la. The groundwater latentes and very rare intended to make an internal comparison of the soils gleisols profiles of unit 9 may also be included here. examined during the survey. In view of the very low base 3. The groundwater latentes and gleisols of unit 10 status, and the poverty of the parent materials, very few other than those specified in Class la. This group of these soils would compare favourably in an international comprises the main mass of soils in the old sloughs classification or even in a national Sierra Leonean classi- forming the inland bolis. They have a major part to fication scheme. play in any development for rice growing but the Class I. In this group the oxysols of mapping unit 7 presence of groundwater laterite in varying degrees are placed as being potentially the most versatile soils of induration and massiveness places them in an available. They are more favourable in topographic site inferior class to the soils of Class la. They are mostly 28 too far from possible reservoirs to permit economic 1. The oxysols of unit 2 except Batkanu series. development for irrigation; and the presence of heavy These soils are all red-brown concretionary drifts silty clays in association with the groundwater laterite derived from ancient peneplain material. In con- in most soils suggests that drainage facilities may sequence the profiles are dominated by concretionary have to be included if irrigated dry season crops are material and ironpan, often leaving only an inch or contemplated on a large scale. The gleisols and two of cultivable soil. groundwater latentes mapped as units 12 and 13 can 2. The groundwater latentes of unit 3. These soils be included collectively with these soils. have the same disadvantages as the previous group 4. This group comprises the gleisols of unit 7. plus the additional one of inferior drainage qualities, They have many similarities to the last group, and which further limits their utility. indeed Kontobe series is present in both. However, 3. The groundwater laterites of unit 7. These are they are grouped separately by virtue of their slightly the poorest soils found developed in the river terrace different liability to flooding and waterlogging. deposits, but may be utilisable for very limited purposes such as inter-seasonal vegetable crops and Class III. This class contains three sub-units and local grazing areas in association with adjacent rice comprises the least valuable, but some of the most extensive cultivation in the sloughs and cash crop development soils in the survey area:— on the better terrace soils.

29 PART III

VEGETATION BY T. S. BAKSHI Systematic Botanist and Zoologist

Unlike several other West African countries (see Ainslie area, and a distinctive combination of unions is considered 1926, Jones and Keay 1946, Keay 1953, Mangenot 1958, a separate association. A designation such as Lophira/ and several others) studies of the vegetation of Sierra Chasmopodium association signifies a dominant union of Leone have so far been restricted mostly to the Lophira combined with a subordinate union of Chasmo- of flowering plants. Consequently, we have reasonably podium. The collective area which one association occupies good information about floristics, but hardly any on the is called a habitat type, and the area occupied by a closely other botanical problems. Ecological studies, in particular, related group of associations is called a zone. have been conspicuous by their absence. A climatic climax is the type of vegetation characteristic The first preliminary survey of the vegetation of Sierra of undulating topography and loamy, moderately drained Leone was published by Martin (1938). It was based on soils (Tansley, 1935). Those climaxes which differ from taxonomie collections, not on the ecological findings, and the climatic climax due to some stable, specific and was followed by a brief account of the vegetation by ecologically important soil condition are called edaphic Waldock et al (1951) whose description was similar to that climaxes, and vegetation which is peculiar because it has of Martin (1938). The third study is by Rattray (i960) attained equilibrium with a particular frequency and who has very briefly enumerated some of the species intensity of burning is called a fire climax (Daubenmire, comprising the grasslands of this country, and his account 1952). is based on information supplied by this Department. The survey was carried out during February 1960-June Thus for practical purposes ecological research based on 1961. Most of the areas of bolilands mentioned in the fundamental and widely accepted principles has not been section on the soil survey report were visited once a month carried out in Sierra Leone. during the dry season and every other month in the wet. Inland swamp farming has been the concern of this Since the reconnaissance was not carried out over several Department for many years. Some of its problems have growing seasons, statistical methods could not be applied. been discussed by Newland (1944). The soil survey of As far as possible most of the ecologically significant these seasonal swamps was undertaken in 1958, and the species growing in the area were listed, and were pressed vegetation survey in early i960. Since the present work for later positive identification at the Njala Herbarium. is based on the reconnaissance undertaken during one Doubtful cases were referred to the Kew Herbarium. growing season only, it is only a preliminary description of Those still under study are preceded by a question mark the existing communities, which will have to be in this report. All plant names are after Alston (1959) and supplemented in future with statistical and experimental Hutchinson and Dalziel (1931-35 and 1954-58). work. The coverage, i.e., ground covered by a given species, The assistance of the following at various stages of the was estimated for nearly all species. This was obtained present study is gratefully acknowledged: Mr. James P. first by examining all bons and adjacent uplands as Law, Mr. George Ross, Mr. R. S. Liney and Mr. J. L. thoroughly as possible. Small areas in each vegetation Boboh. type were then studied for coverage. As a check, estimates In the interests of clarity the various ecologie terms of the bare ground were also made. The two for each used here are briefly defined. Most of the terms follow species should total 100 per cent. Coverage classes were Daubenmire (1952). estimated on the following scale of Braun-Blanquet (1932) A community is considered serai if interrupted age- as modified by Daubenmire (1959):— gradients in species populations show that the sociologie status of at least some of the species is temporary, but Per cent Coverage climax if it appears to be self-regenerating and there is no Class Range Mid point concrete evidence that it is followed by a different com- 1 0-5 2-5 munity. The term association is applied only to climax 2 5-25 15-0 communities. The union is considered the smallest 3 25-50 37-5 structural unit in the organisation of vegetation, each 4 50-75 62-5 union consisting of a population of one or more species 5 75-95 85-0 that are closely similar in ecology. 6 95-100 97-5 The association is the basic unit of vegetation. It It should be noted that most communities are composed includes all unions that are superimposed on the same of superimposed layers of plants so that the ground is

30 covered more than once in many places. Any attempt Although the Anadelphia I Rhytachne habitat type extends to make the total coverage of any taxa, plus any bare over most of the seasonally flooded bolis, its constituent ground, add up to ioo per cent is, therefore, unrealistic species are not necessarily the same at each site. Local (Daubenmire, 1959). changes in the soil bring in some species which may be The preliminary surveys indicated that there are three either new introductions or replacements. Thus at the fire climaxes in the boülands. This was confirmed by Madina-Tabai boli there are few dicotyledons of the later detailed study which also indicated that the three are typical AnadelphiajRhytachne association, and the new closely interrelated and can, therefore, be included in introductions include Ctenium newtonii, Fuirema umbellata, the Lophira lanceolata zone (figure 3). The three fire Xyris anceps, Polygala rarifolia, all belonging to the climaxes and the forests fringing the rivers are described coverage class 1. Of these Ctenium is the most conspicuous under the following heads :— due to its characteristic curved spikes noticeable even from a distance of about 20 yards. It occupies niches similar to 1. Anadelphia/Rhytachne association. those of Anadelphia. All bolis along the Lunsar road 2. Chasmopodium/Nauclea association. show this slight change in the pattern of the association. 3. Lophira/Chasmopodium association, and The seasonally flooded areas of all bolis around Batkanu 4. Riverain forest and " sacred bush ". are occupied by stands of Anadelphia/'Rhytachne association. Here again, there are fewer dicotyledons than at Kontobe. 1. AnadelphiajRhytachne association The most conspicuous addition is Setaria Pmegaphylla, The area seasonally flooded during the rainy season is a 5-7 feet tall grass, forming dense stands near smaller occupied by this association. It consists predominantly creeks and gradually thinning towards the uplands. Other of short and medium grasses, not more than 5 feet high, additions include Andropogon psendapricus, Saccolepis and sedges with some scattered forbs. Typical stands of africana and Eragrostis Psquamata of the coverage class 2, AnadelphiajRhytachne association (see Table 3 for its and Cassia mimosoides and Rhynchospora schroederi of the species composition) are found along "the Kontobe creek coverage class 1. On the old river beds where waterlogged (plate 4). The dominant union of Anadelphia leptocoma conditions prevail up to about February, Phyllanthus reaches its maximal seasonal development during muellerianus, a spiny shrub, is quite conspicuous. October-November when it gives the boli a reddish-brown appearance. It appears that A. leptocoma cannot tolerate prolonged waterlogging since it is absent from depressions 2. Chasmopodium jNauclea association holding water after October. On the other hand Rhytachne All the unflooded treeless areas of the bolilands belong rottboeliodes, the major component of the subordinate to the ChasmopodiumjNauclea habitat type (plate 2). The union, can stand prolonged waterlogging, and is a constant typical stands of the association (Table 4) are again at member of the association almost throughout the year. Kontobe. These are in the form of narrow strips of Even when Anadelphia is at the peak of its flowering Chasmopodium caudatum (and associated species) lying activity, Rhytachne can be seen in the form of low, greenish between the Anadelphia jRhytachne association and the patches breaking the continuity of the reddish-brown so-called " Lophira bush ". Most members of the Anadelphia. These patches demarcate those depressions association cannot stand prolonged flooding, consequently which hold water longer than the adjacent areas (plate 3). they never occur on the same area as the Anadelphia j When fire has swept through the bolis, Rhytachne quickly Rhytachne association. At Kontobe and other bolis, rejuvenates; Anadelphia, however, does not begin its there are occasional patches of the tall Chasmopodium vegetative activity until the beginning of rains in May. caudatum growing in the midst of the reddish-brown Therefore the reddish-brown hue of the boli during the AnadelphiajRhytachne association (plate 4). However, rains is changed to a pleasant green in the dry season. these are always on soil a few feet higher than that of the

FF LC

Normal flood level

FF Fringing Forest CN Chasmopodium/Nauclea association AR Anadelphia/Rhytachne association LC __: Lophira/Chasmopodium association FIGURE 3 Diagrammatic cross section showing the topographic relationship of vegetation in the " inland " bolis. The relative height of trees in FF and LC varies from site to site. With slight changes, the vegetation is repeated in the " riverain " bolis. Compare with figure 1 for the corresponding landform and soil classes. 31 AnadelphiajRhytachne habitat type, and are, therefore, not seedlings or saplings of Lophira. This becomes significant continuously flooded throughout the rains. in view of the fact that the Belia-Mayanki area is subject Chasmopodium caudatum is the most abundant tall to more intensive and regular burning than the Mayanki- (10 feet) grass of the Lophira zone since it is present in Mateboi area. It may be inferred, therefore, that this area two of its three associations. It is the dominant species of is a " derived savanna " where the forest species are held the Chasmopodium INauclea association and the second back by fires thus giving rise to a Lophira]Chasmopodium dominant in the Lophira I Chasmopodium. Along with other fire climax. When the forest species receive some degree members of the Chasmopodium I Nauclea association it of protection from fire, they tend to close the canopy, occurs over extensive areas from Yonibana to Magburaka and the members of the subordinate unions of the Lophira] and in the Makeni-Marampa-Batkanu region. Chasmopodium association gradually cease to regenerate In the vegetative stages several tall grasses appear similar under the closing conditions (Table 6). to Chasmopodium caudatum. However, shortly after the The Lophira I Chasmopodium stands in the Kontobi-Malal rains, one can easily distinguish it from Andropogon area give a somewhat different picture. Here, the forest gabonensis and Pennisetum purpureum, and the recognition tree species are fewer (" Kontobe " in Tables 5 and 6), of the three grasses reveals a definite pattern of distribution and they can be classified into the following groups:— for each. Andropogon which rarely, if ever, exceeds 20 per cent coverage in a typical Chasmopodium j Nauclea 1. Forest fringing upon rivers in savanna (Parinari stand, more or less completely replaces Chasmopodium congensis, Erythrophleum guineensis, Samenea dinklagei, under continued disturbance. This is evident along most and Cathormion altissimum). " bush roads " and paths, and around habitations and 2. Regrowth forest on old farmland (Phyllanthus farms. Except for their individual responses to disturbance, discoides). Andropogon and Chasmopodium appear to have similar 3. Regrowth forest (Albizia adianthifolia). ecology. On the other hand, Pennisetum purpureum differs 4. Open parts of forest (Sterculia tragacantha). from both Andropogon and Chasmopodium in its greater 5. Forest (Parinari excelsd). tolerance of prolonged waterlogging as well as some 6. Forest and savanna (Morinda geminaia). amount of flooding. Such conditions prevail in some 7. Savanna (Pterocarpus erinaceus and Lophira parts of the Bantoro boh where, therefore, Pennisetum lanceolata). replaces Chasmopodium in certain areas. It is at once evident, therefore, that here most of the Lophira lanceolata, the dominant member of the Lophira I so-called forest species are those which can be expected Chasmopodium association, does occur here but it never to grow normally in a savanna; hence this area may not reaches a height of more than a couple of feet. Lophira, be a " derived savanna ". therefore, appears to be sensitive to flooding as well as The subordinate Chasmopodium union is dominated by waterlogging. Chasmopodium caudatum whose behaviour with respect to Nauclea latifolia, the dominant member of the sub- disturbance is the same as in the Chasmopodium I Nauclea ordinate Nauclea union, is conspicuous in the tall grasses association, i.e., under continued disturbance it is replaced even from a distance. It is always shrubby in habit, never by Andropogon gabonensis. Some of the ecologically more attaining its normal tree form in the Chasmopodium j Nauclea important species of the ground cover include the association. There is a woody rootstock which survives following:— fires and from which long thin branches are given off. Amorphophallus aphyllus. These usually rest against the Chasmopodium stems and Amorphophallus elliotii. almost attain their height. Amphiblemma mildbraedii. At the Madina-Tabai and several other bolis, the flat Dioscorea hirtiflora (trailer in earlier stages). ground has a number of termitaria protruding above the Dissotis sp. level of maximum seasonal flooding. In all such cases Elinurus pseudapricus. the unflooded tops of the termitaria are occupied by the Eragrostis plurigluma. Chasmopodium j Nauclea association. Nephrolepis undulata. Smilax kraussiana (trailer in earlier stages). 3. Lophira j Chasmopodium association Of these the two species of Amorphophallus appears to be In the bolilands this is the most conspicuous association very interesting ecologically. They occur only in those of the uplands (plate 6). It extends from the upper stands that are subject to regular fires, and where the topographic margins of the Chasmopodium /'Nauclea as- ground cover includes few dicotyledons. sociation to the crest of the uplands, and attains its maximal development under the continuous effect of fire. The apparent pure stands of Lophira lanceolata along roadsides 4. Riverain forest and " sacred bush " between the Beha creek and Mayanki on the Makeni- Almost all creeks and rivers of the bolilands are fringed Batkanu road are excellent examples of this ("Belia" in by forests. These riverain forests have a characteristic Tables 5 and 6). A closer examination of these, however, species composition (" Riverain in Tables 5 and 6). Most reveals the presence in the undergrowth of the seedlings of them have been affected by fires and human disturbance, and saplings of trees which normally occur in moist forests. and all of them can be considered as secondary forests. Between Mayanki and Mateboi the moist forest tree species Further detailed studies are necessary to decide their are more numerous (" Mayanki " and " Mateboi " in present status. One factor, however, appears to be Tables 5 and 6) and attain larger proportions, tending to significant; they would disappear if the creeks or rivers form a close canopy with Lophira (plate 8). Under these were to dry permanently. This is evident along the old circumstances, the grasses and herbs of the ground cover river channels near Batkanu. Depth of water table is, tend to decrease, and there are none, or hardly any, therefore, of critical importance. TABLE 3 TABLE S SPECIES OF ANALDELPHIA/RHYTACHNE FOREST TREE SPECIES IN WOODED AREAS ASSOCIATION

Coverage 1 ain •0 No. 1 1 No. Species Class Habit •2 Q s> b 1 û3 i Anadelphia leptocoma 6 Grass 1 2 Phytachne rottboelioides 5 Grass i Parinari congensis X X 3 Panicum congoense 4 Grass 2 X 2 Cathormion altissimum 4 Anadelphia arrecta Grass Sterculia tragacantha X 2 3 5 Cyperus pustulatus Sedge 4 X 6 2 Erythrophleum guineense Mesanthemum radicans Forb 5 Albizia ferruginea X X Neurotheca loeselicides 2 Forb 7 6 Terminalia ivorensis X X 8 Saccolepis auriculata 2 Grass 7 Albizia zygia X X 9 1 Alectra sp. Forb 8 Anthonotha macrophylla X IO Aspila latifolia Forb 9 Bombax buonopozense X X ii Borreria ruelliae Forb IO Harungana madagascariensis X X 12 Buchnera leptostachya Forb ii Samanea dinklagci X X 13 Crotolaria hyssopifolia Forb 12 Phyllanthus discoides X X X 14 Cyanotis sp. Forb 13 X X X 1 Albizia adianthifolia 15 Desmodium linearifohum Forb X X 16 1 14 Parkia bicolor Eragrostis chalarothyrsos Grass Calpocalyx brevibracteatus X 1 15 17 Eriosema glomeratu Forb I6 X 18 1 Cnestis ferruginea Fimbristylis dichotoma Sedge X 1 17 Vitex grandifolia 19 Fimbristylis diphylla Sedge I8 X X X 20 1 Morinda geminata Jussiaea linofolia Forb X X X 21 1 19 Chlorophora regia Indigofera leptoclada Forb 20 X X X X 22 Parinari excelsa Paspalum scrobiculatum var. 21 Holarrhena africana X X 1 commersonii Grass 22 X 1 Caloncoba echinata 23 Polygala rarifolia Forb Craterispermum laurinum X 24 1 23 Scleria mitella Sedge X 1 24 Dichrostachys glomerata 25 Rhynchospora ?triflora Sedge X 26 1 25 Diospyros elliottii Sopubia parviflora Forb 26 Pterocarpus santalinoides X 27 Vigna venulosa 1 Forb 27 Anisophyllea laurina X X 28 Dialium guineense X X 29 Hymenocardia lyrata X X 30 Mareya micrantha X X 31 Napoleona heudelitii X X 32 Bersama abyssinica X 33 Diospyros sp. X 34 Ficus mucosa X 35 Funtumia elastica X 36 Hippocratea iotricha X 37 Pycnanthus angolensis X 38 Tetracera potatoria X 39 Trichilia heudelotii X TABLE 4 40 Voacanga obtusa X 41 Xylopia aetheopica X 42 Xylopia quintasii X Coverage No. Species Class Habit TABLE 6 1 Chasmopodium caudatum 6 Grass SAVANNA TREE SPECIES IN WOODED AREAS 2 Andropogon gabonensis 2 Grass 3 Nauclea latifolia 2 Shrub 4 Thaumatococcus daniellii 2 Forb 1 5 Abrus precatorius Forb No. 6 Amorphophallus aphyllus 1 Forb 1 Sacred 7 Amorphophallus elliottii Forb Belia Kontobe Mayanki Mateboi Riverain 8 Amphiblemma mildbraedii 1 Forb 9 Commelina gambiae Forb 1 Parinari congensis X X 10 Fimbristylis ferruginea Sedge 11 2 Dichrostachys glomerata X X Ground orchid (unidentified) Forb X X 12 Kyllinga sp. Sedge 3 Vitex cuneata Nauclea latifolia X X X 13 Lophira lanceolata Tree 4 I4 Loudetia arundinacea Grass 5 Pterocarpus erinaceus X X X 6 X 15 Ocimum viride Forb Allophylus africanus 16 Paspalum scrobiculatum var. 7 Lophira lanceolata X X X X 8 Phyllanthus discoides X X X commersonii Grass X X 17 Pennisetum purpureum Grass 9 Harungana madagascariensis 18 Pennisetum subangustum Grass 10 Parkia biglobosa X X 11 X X 19 Pilostigma thonningii Phychospora sp. Sedge X X X 20 Rhytachne rottboelioides Grass 12 Morinda geminata 21 Sauvagesia erecta Forb 13 Bersama abyssinica X 22 Smilax kraussiana Forb 14 Cassia sieberiana X 23 Striga macrantha 1 Forb 15 Dialium guineense X 24 Uraria picta 1 Forb 25 Urginea indica 1 Forb It is to be noted that because of their wider ecologie amplitude a few species are common to Tables 5 and 6. 33 The so-called " sacred bushes " are often met with Nye and Greenland, i960). It is difficult to say precisely along the creeks and rivers and near habitations (plate 4). when this agricultural custom started. Probably it has These are low, sometimes high, forest patches locally been the rule ever since man and fire have been together associated with the supernatural, and have become places in Sierra Leone. However, in the light of the available of worship for those living in the vicinity. According to literature (Anonymous, 1910), it can be said with certainty Harris (1954) " one large tree is usually the object of that the vegetation of the seasonally flooded areas of the veneration, yet because of its proximity all the surrounding boliland has not changed much during the last fifty years. bush is regarded as sacred ". Such a tree in the " sacred This study seems to indicate that the present Anadelphiaj bush " near Kontobe is Chlorophora regia. The sur- Rhytachne and ChasmopodiumjNauclea associations may rounding vegetation is rarely destroyed, but these " sacred not be occupying the habitat types of some forests as some bushes " cannot be considered as remnants of primary authors would like to believe. forest since people who do not regard it as sacred, are On the other hand, most, if not all, of the Lophiraf known to interfere with these, sometimes to a considerable Chasmopodium habitat type appears to be what Keay (1959) degree. Species of the Kontobe " sacred bush " are given has described as a " derived savanna " where under the under " sacred " in Tables 5 and 6. controlling influence of fire, fire-resistant species have An interesting species in the ground cover in these more or less replaced the fire-tender species. As has forests is Guaduella oblonga, a grass, which is usually found already been pointed out earlier, when the burning is in the near-primary forests of south-eastern Sierra Leone. stopped, even for a few years, the fire-tender forest tree species which could not grow beyond the seedling or Notwithstanding the numerous soil series in the boliland sapling stages, quickly attain tree-like proportions tending region, there are only four distinct natural plant com- to shade out the fire climax species. It is to be noted, munities. This is primarily because the communities in however, that the entire LophirajChasmopodium association question can endure a wide range of habitats, i.e., they is not necessarily a " derived savanna ". In this respect, have a wide ecologie amplitude. No one association of the Elaeis guineensis, the oil palm, is of special significance. present report can, therefore, be taken as an indicator of As pointed out by Keay (1959) Elaeis will readily regenerate the soil series. There are no doubt slight variations in the in secondary forest but hardly at all in " savanna ". Elaeis species composition from stand to stand on a given habitat guineensis in " savanna " is therefore a good indication of type. These, however, can hardly be seriously considered former forest conditions. This is precisely the case in to have an indicator value. An association occupies the Mayanki-Mateboi area and on the moister habitats different soil series simply because the ecologie sums of of Kontobe region (plate 11). Therefore, it may well be the different sets of conditions are essentially equivalent that the absence of this species from certain stands of with respect to the nature of the climax. Lophiraj Chasmopodium association is an indicator of their Most of the boliland is burnt over annually. This firing being " true savanna ". Given fire protection, Elaeis of the countryside is bound up with cultivation. (For the guineensis will grow in most derived, but not true, effects of annual burning on soil the reader is referred to " savannas ".

34 PART IV

LAND USE*

In general the land use system is closely similar through- investigation of the relationship of yield to length of fallow out the area surveyed. It is founded upon the growing of would be of great value in planning development. For rice, cassava, guinea corn, millet, and groundnuts, chiefly most crops the local farmers did not seem to be aware of in upland environments, on a system of cyclic shifting any decrease in yield with the reduction of fallows to ten cultivation depending upon bush fallow. Livestock play years or less. Their ideas on this subject, however, were a surprisingly minor part in the economy except in the vague and varied greatly. Mateboi district, where there is a concentration of cattle. The agricultural cycle begins with the " brushing " There is little tribal distinction in activity save that the and burning of land to be brought into cultivation. The Fulas are characteristically found as the stockmen where African farmers locally recognise two vegetational types cattle herds exist. Economically it is still subsistence in the upland, both secondary regrowth:— agriculture designed to support the family unit with little thought of sale beyond disposing any local surplus in the (a) Lophira bush. nearest village market. However, the first signs of change (b) All other regrowth. have now appeared with the encouragement of swamp rice Apart from this the only environmental distinction cultivation by the Department of Agriculture, and the recognised in the land use pattern is in using the annually arrival of a tobacco company. flooded bottomlands for the appropriate crops. The Lophira bush is cut and cleared in February-March Size of farms and manpower and burned in March, a small proportion of the trees being left for shade, whilst the majority are reduced to stumps In general size seems to vary between 2-10 acres, some of which are killed in burning (plate 7). Other types depending on the size of the family, with 4-6 acres the of bush are cleared in the period January-March and commonest size. The basic labour force for these farms burnt in March. In the Lophira bush upland rice is the is the family itself, supported seasonally by communal first crop planted on newly cleared land, but in contrast to gangs for clearing and preparing farms. Generally these other types of land the rice is quite commonly planted gangs comprise 40-60 men, but for influential local per- alone and the time of planting may be three or four weeks sonalities may amount to 100. The normal procedure is later to permit adequate moisture to collect. This in to work in turn upon the farms of all group members itself is an indication of the poverty of the relict peneplain requiring such assistance, but it is becoming increasingly soils of units 2 and 3. common for additional paid labour to be employed by the more prosperous farmers to prepare their land in good Rotational practices are still elementary. On all types time for planting. Although under traditional methods of land rice is the commonest initial crop, frequently food is the only charge upon the farmer for whom the work intercropped with cassava, guinea corn or millet, and less is done, the system has the disadvantage in that for some commonly with vegetable crops such as tomato and okro. it is done too early necessitating repetition, and for others The rice will be followed by cassava, groundnuts, or too late for planting at the best time. As yet payment guinea corn in various annual sequences, but the land is amounts to a very few shillings per labourer in addition to rarely used for more than four seasons before reverting to his food, and the time devoted to any one farm by the bush. The maintenance of fertility, other than by bush communal labour force is only three to four days. fallowing and burning cleared vegetation, is rare. Some manuring is carried out on the vegetable gardens adjacent to the huts, and rice stubble is usually dug in on the System of farming wetland farms prior to planting a dry season sweet potato It seems probable that formerly twenty years was the crop, but this is the limit of fertility maintenance practised minimum period for which the land was allowed to lie outside the Department of Agriculture's mechanical rice fallow. Nowadays most land seems to have a fallow of cultivation scheme. eight to ten years, but in the Mateboi area upland rice was observed being planted on land fallow only four years, Crops due to increasing population pressure. A thorough The following is a brief account of the principal crops observed in the survey area :— * The field data upon which this chapter is based was largely collected by Mr. W. O. Tayler, Agricultural Instructor of the 1. Rice (Oryza sativa) Department of Agriculture, and also by students of the Geography Several varieties of both upland and swamp rice are Department of the University College of Sierra Leone during a week's field excursion in April, 1959. Their assistance is grown. These have been commented upon in various gratefully acknowledged. Departmental bulletins of the Agricultural Department 35 (Roddan 1937, Squire 1943, Annual Reports of Depart- harvested after the rice crop. ment of Agriculture and W.A.R.R.S., Rokupr). Cassava is widely tolerant of soil and climatic conditions Planting is controlled by the onset of adequate' rainfall (plates 9 and 10). It is normally planted in ridges or but in general it is in April in most parts, and mid-May heaps, more rarely on the flat when planted as a separate in Lophira bush areas, with late planting until the end of unmixed crop. The ground is well prepared by hoeing, July. and cuttings about 6 inches long are planted in pairs on Upland rice is usually sown broadcast and then hoed in, the heaps, or spaced about 3 feet by 3 feet apart on the being weeded twice, after the rice has taken hold and ridges or level ground. Disposal of surplus crops is on before flowering. The early crop is usually the main the principle of " come, pick, and pay ", and such a crop crop and an average yield is probably about five bushels* may even be sold well in advance of the harvest time, this per acre with ten bushels as a very good yield by local usually applying to the single crop plots, the mixed crop standards. Early maturing varieties are ready for plots being used for subsistence. harvesting after four to five months, others after about six months. Some of the steeper slopes employed for rice 3. Guinea corn (Sorghum marganitiferum) cultivation are liable to soil wash after clearing, and are This is an important cereal crop often grown mixed occasionally unsuitable for the second season's cropping. with upland rice. In this area a white seeded broad leaved, To an increasing extent the rice crop is now being long stemmed variety is commonest and the crop is grown sold to traders from Makeni, Lunsar, Magburaka and to a greater extent about Yonnibanna in the south-west even Freetown. than elsewhere within the survey area. It is harvested This is not entirely satisfactory, as the farmers often some time after the rice and commonly kept along with a keep insufficient grain for their own needs and later on high proportion of the cassava against the " hungry " have to buy it back at the higher prices prevailing in the season preceding the next harvest. " hungry season ". 4. Maize (Zea mays) Wet-land rice is an increasingly important proportion The amount of maize grown in this area is just about of the rice ctop; especially since the initiation of the Department of Agriculture scheme on the seasonal swamps equal to local demand. Though grown over a wide variety of the '; bolis ". In addition to the contemporary and old of soils it appears to do best on the red sandy loams of sloughs used by that scheme swamp rice has long been good depth in units 2, 4 and 6. It is grown in gardens customarily grown in the seasonally waterlogged or flooded around huts as well as in a mixed or single crop on the drainage grooves and valley bottoms among the uplands. upland farms, and Yonnibanna is again the main centre of Nowhere, however, is even the most elementary water production. If dried well and stored carefully it keeps for control attempted, and yields are at the mercy of un- long periods and is used roasted, boiled, in a porridge, predictable flood levels. To generalise, the rice grown cooked with a sauce, or made into a local alcoholic drink. in the sloughs of the riverain bolis is often sown broadcast, 5. Bullrush millet (Pennisetum leonis) that in the inland bolis and the upland valleys is generally sown by transplanting from local nurseries (plate 12). In This cereal does not figure so largely in the cropping good years the swamp rice may yield up to ten to fifteen programme of this area, being more favoured in the drier bushels per acre harvested in December and January. north-east. It is usually planted simultaneously with the Under the mechanical cultivation scheme the grass is rice and there appear to be early and late maturing varieties burnt off in December-January, ploughing takes place in taking respectively three and six months to mature. Birds January to April or May and harrowing continues until are one of the principal pests of the crop which is used as June when the seed is sown. If a thorough weeding is a porridge, flour, or boiled like rice. well timed to precede the arrival of the flood weeds do not 6. Fundi (Digitaria exilis) (also known as Finger millet) present a great problem subsequently in the riverain This is a common cereal closely related to indigenous sloughs. In the inland bolis the method of growing sweet grasses and growing about i-| feet high. It is usually sown potatoes on heaps in the dry season is an aid to controlling after rice, or even as a substitute for it in unfavourable the weed problem (Glanville, 1938). These heaps are seasons, in a wide variety of sites. It is sown by broad- puddled out in July-August when the rice seedlings are casting and the seed hoed in to germinate in about four transplanted. Sowing broadcast on newly ploughed days and ripen in three to four months from planting in virgin land in these swamps seems to present a greater April to June. It grows too closely to be much bothered weed problem. The farmers taking part in the mechanical by weeds after it is established, but birds cause heavy cultivation scheme are encouraged to use superphosphate damage. at the rate of two cwt. per acre. The straw from the crop is commonly used to stuff Despite the development of this scheme there is still a mattresses and the grain may be used as a porridge or strong traditional preference for growing rice on the cooked in a variety of ways as a course by itself or as an uplands (possibly because of the practice of mixed cropping) accompaniment to meat, fish and vegetables. and the people still regard that as their main source of" this staple diet. 7. Yams (Dioscorea spp.) This crop is not encountered as commonly as might be 2. Cassava (Manihot utilissima) expected given the soil and climatic conditions, and its This is probably the second most extensive food crop production could well be increased, especially on ground- grown in this area, the bulk of it being of sweet cassava water latentes and poorer soils of the peneplain drift type varieties planted in association with upland rice, and in lieu of some of the rice and cereals grown there with poor results. * " Bushel " in Sierra Leone is taken as being equivalent to The local farms discriminate between several varieties about 84 lbs. of clean rice and 60 lbs. of paddy rice (Dent, 1956). of yam, namely :— (1) White yam (D. notunda). (2) Oil palm {Elaeis guineensis). (2) Yellow yam (D. cayenensis). (3) Cola (Cola nitida). (3) Bush yam (D. praehensilis). (4) Coconut palm (Cocos nucifera). (4) Chinese yam (D. esculenta). (5) Cocoa (Theobroma cacao). (5) Water yam (D. alata). Coffee and oil palms are being supplied to farmers by Yams are principally grown hereabouts as a garden the council under a development project, crop, and except in the case of the Chinese yam the tubers but very little of the area surveyed is even remotely suitable for planting are cut into two, three or four pieces and for developing coffee. Oil palms would probably grow on dried for several hours before being placed in the mounds the oxysols and alluviosols of units 4 to 8, but the return previously prepared for the crop. The Chinese yam, on the crop may not justify any large investment here as introduced by missionaries, is planted as a whole tuber. compared with growing it in the more customary regions The bush yam is collected in the wild state and not usually on soils derived from granites and Bullom sands. A few cultivated. small orchards of coffee exist, for example, one at Mara sited on terrace sands, and oil palms are encountered 8. Coco yam (Colocasia esculenta) growing at random, chiefly on terrace soils (plate 11) and This is another crop, grown at present as a garden in the transitional zones between the swamps and upland crop, which could well be expanded in this area, possibly valleys, and the adjacent uplands. Cola trees are dotted as a unit in rotations on the better oxysolic red earth sandy about the villages as are coconut palms, but neither is loams of units 2, 4, 6 and 7. Several varieties are en- numerous, the coconuts being most commonly found east countered differing in minor respects. of the Mabole river. To some extent Colocasia esculenta is being replaced by Xanthosoma sagittifolium, more commonly found in the 13. Fruit colony peninsula. A great variety of fruit is grown, almost all haphazardly The Coco yam is propagated either by planting tubers in and around the villages. Mangoes and oranges are the whole or cutting them in half. commonest, and the larger villages sometimes have small citrus plantations. These are followed in popularity by 9. Sweet potato (Ipomoea batatas') bananas, plantains, pineapples, and pawpaw. This is becoming an increasingly important crop The following is a list of fruits encountered:— associated with the expansion of swamp rice production. (1) Orange (Citrus sinensis). It is grown on mounds in which are buried the grass and (2) Sour orange (Citrus aurantium). weeds collected during clearing the site. Too much (3) Lime (Citrus aurantifolia). humus appears to encourage leafy growth at the expense (4) Grapefruit (Citrus paradisi). of tubers, but grown as a dry season crop on the swamp (5) Lemon (Citrus limona). rice sites the production of humus is wholly beneficial to the rice, whilst the prior clearing of weeds aids control (6) Tangerine (Citrus nobilis). of that problem. It is grown to a lesser extent on the (7) Pineapple (Ananas comosus). uplands, usually after groundnuts. Red and white varieties (8) Banana (Musa sapientum). exist, and an American variety has been introduced by (9) Guava (Psidium guajava L.). missionaries east of the Mabole river where it is becoming (10) Avocado pear (Persea americana). increasingly popular. (11) Mango (Mangifera indica). (12) Plantain (Musa paradisiaca). 10. Groundnuts (Arachis hypogea) (13) Pawpaw (Carica papaya). Groundnuts are not as extensive a crop as might be (14) Water melon (Citrullus vulgaris). expected in an area having a large proportion of red-brown 14. Vegetables concretionary soils similar to those used elsewhere in West Africa (Stobbs 1959, i960, and in preparation). A wide variety of vegetables is grown in small gardens Probably the heavy rainfall and very acid topsoil are largely round the village huts and in occasional small plots on the responsible for this, together with the inherently infertile farms, usually adjacent to the farm hut which the farmer nature of the soil. In the Rokel valley soils of unit 7 are erects as a shelter for the working season. This aspect favoured for this crop and high yields are obtained there. could well do with more emphasis solely to improve local Elsewhere groundnuts are a minor crop in the agricultural diet, requiring nothing more for its extension than the system. effort to cultivate the plots and the habit of making compost to manure them satisfactorily. 11. Legumes The following are the chief vegetables :— Other legumes grown in small quantities in the survey Egg plant (Solanum melongena). area, either as garden crops or as an element of mixed Tomato (Lycopersicum esculentum). upland crops are pigeon peas (Cajanus cajan) and Kabala Cucumber (Cucumis sativus). beans (Voandzeia subterranea?). Benniseed {Sesamum Ogusi (Cucumis spp.). indicum) is used for flavouring sauces and is a popular Sorrel (Hibiscus sabdariffa). small garden crop. Okra (Hibiscus esculentus). Pumpkin (Cucurbita pepo). 12. Plantation crops Native spinach (Amaranthus hybridus var cruentus). These nowhere rank as important in the economy of " Indian " spinach (Basella alba). the survey area. The following are spasmodically en- Crain crain (Corchorus olitorius). countered:— Chillies (Capsicum frutescens). (1) Coffee (Coffea robusta and C. stenophylla). Shallot (Allium ascalonicum).

37 PART V

RECOMMENDATIONS

It is intended to give here only an outline of possible areas, coupled with controlled early burning along the future development. In the preceding chapters occasional lines suggested by Scott (1952), and also Deighton in his reference has been made to potential use of various areas, most valuable Departmental paper (1944), there is a but to place the picture in perspective it is desirable to definite place for increasing the cattle population in start with a broad division of the whole area on association with local areas of protected and possibly the basis of development potential. This gives a improved pasture to complement land use developments threefold classification :— on other areas to be discussed below. Livestock develop- (a) The broad mass of the uplands comprising ment should be confined to cattle with sheep and goats oxysolic red-brown, and yellow-brown earths and discouraged for the present. some groundwater latentes developed mainly from On upland areas where the cultivable depth to the peneplain drift. concretionary or ferruginous horizons is greater than average—say 9 inches or more—yams, groundnuts, and (è) The colluvial drifts of the upland flanks together fodder crops of sorghum, millet, and corn, can be grown with the gleisols and groundwater laterites of the in rotation with pasture, and, with the corralling of stock, upland valleys and drainage grooves; certain transi- crop yields should improve. Better soils of this group tional soils round the floodplain and boli margins; when adjacent to villages could advantageously be devoted and the higher terrace remnants, to citrus and mango plantations. (c) The contemporary floodplains and inland bolis. The recommendations take no cognisance of higher policy considerations governing the relative economic Colluvial slopes, upland valleys, river terraces, etc. merits of siting proposed developments in the bolilands as against rival areas elsewhere. These areas contain the main zone for general arable development. They comprise the Class II soils of units 2, 4, 5 and 6, the Class I oxysols of unit 7; and units 12 and 13. The present range of arable crops cultivated The Uplands on these areas could be extended in association with a The future development of these lands is likely to be management system using cattle to provide manure and in land rotation cultivation and extensive rather than periodic leguminous crops and green manure crops for intensive livestock ranching (given disease and tsetse fly ploughing in, in order to maintain the land's productivity control), of a type proposed for the similar soils of Northern in the face of the present day shortened fallows. Never- Ghana (Brammer 1954, 1956a). Cattle already have some theless, bush fallowing must remain the principal means of prominence in the Mateboi area, and to a lesser extent regeneration. between Babaibunda and Kontobe. The predominant The Class I soils of unit 7 are in a group by themselves soils are Class III soils of units 2 and 3 and support a high here. They are open to the most intensive development grass-low tree vegetation which is delicately balanced available in the area, and are chiefly to be found in the ecologically and easily susceptible to degradation through Rokel valley, as, for example, about Mara and Maroki. overgrazing. Such soils are collectively too infertile These soils should be used wherever possible for cash and gravelly to encourage prospects of any important crops, and being amenable to fertilisers, and mechanical arable development. cultivation, could support oil palms and tobacco, but in Before a satisfactory livestock industry could be view of the poverty of the soils prospects for coffee or cocoa developed much research will be needed to determine the are not favourable. carrying capacity of the various grass associations; the Soils of units 4, 5 and 6 could be used for protected and advisability of controlled early burning, or of burning only improved pasture of a semi-permanent nature. These soils every two or three years; the effects of mowing versus characteristically provide a lusher regrowth than other burning for encouraging regrowth; the possible merits of soils, and regeneration by pasture instead of bush would allowing grazing to cause the replacement of the present be an advantage in establishing a rotation and at the same tall grass association (which are less palatable when mature), time providing higher quality grazing for breeding herds bv closer short or medium grass associations. In the and fattening beef stock. Nevertheless, since experience economic circumstances of i960 it is certainly not worth- has shown that on heavily cultivated land risks are involved while contemplating any large scale fencing for pasture in trying to foreshorten the natural botanical succession protection, or the widespread introduction of new grass (Macgregor 1940) developments of this kind must be species. However, on a basis of rotational grazing of large approached with caution. Taking the uplands as a whole therefore, and starting whose moisture requirements are much more limited. No from a basis of land rotation cultivation and rough grazing data exist for infiltration rates or permeability of these there is room for steady improvement in productivity profiles, and whilst problems of this nature are not through improved methods gradually introduced to suit anticipated in view of the history of seasonal flooding, the various pedological and environmental conditions it seems possible that the maintenance of flood conditions described. for rice for long after the damming effect of the river has ceased may prove beyond the capacity of small, cheap, supply arrangements. Nevertheless moisture supplies should be adequate for dry season pasture, food and The floodplains and inland bolis cash crops of dry land types. The levees in such bolis are These areas comprise Class la, Class II and Class III normally above flood level throughout the year and on soils of units 7-11. It is from this group, and particularly them rotations of upland rice with other food crops can be Class la that any notably increased productivity in this sited in association with the adjacent swamp rice. area must come. Here the main prospects for swamp rice Inland bolis present a more difficult problem. Few he development exist, together with possibilities for dry near adequate supplies of water which can be relied upon season pastures, and on the alluviosols of units 8 and 9, for an early start to the growing season. Furthermore, arable farming. Swamp rice must be the principal crop, most of the soils contain at shallow depths actual or not only because of environmental suitability but also incipient groundwater laterite, liable to further hardening because it produces higher food yields per acre than other on exposure. With this in mind the siting and levelling of cereals. The whole picture has also to be regarded in the contour bays would have to ensure the preservation of at light of prospects for water control which should help least 12 inches, and preferably 18 inches, of cultivable soil the farmer in two ways :— above the groundwater laterite subsoil. The subsoils of (a) controlling depth of flooding; these profiles are almost all highly impermeable so the creation of contour bays would make it possible to retain (6) controlling length of flooding and therefore flood water for considerably longer than the present free length of growing season. flooding arrangements. The use of the highest bays on From this point of view water control would only modify each boh as supply units or the creation of small earth the effects of the existing climatic regime, and not radically dams in adjacent tributary valleys and drainage grooves alter the soil climate. Probably such water control can would make possible the cultivation of limited areas of best be effected by contour bunding and levelling, and the dry season pasture and subsistence crops on these bolis. sites most suited to early developments are the floodplains The value of levelling and bunding even without irrigation adjacent to the Rokel and Mabole rivers. The sketch was suggested some years ago for this area, by analogy maps of Rochin, Batkanu and Bantoro bolis indicate typical with the methods in the Malabar area of western India soil patterns encountered in the succession of bolis strung (Glanville 1938). out along the present river courses, and the form line map The early supply of water to both riverain and inland gives a good idea of the usual topography found in such bolis is likely to enhance weed problems in the rice crop. bolis containing as they do levees, sloughs, and old river This can be met possibly by discarding the method of channels. sowing broadcast so that the crop can be more easily Characteristically these bolis have a high point somewhere harrowed, and by the development of dry season farming on the levee at the upstream end of the boli, and a low such as the growing of sweet potatoes which is in itself a point where an old river channel debouches into the river means of weed control. at the downstream end of the boli. This can be seen on As with the inland bolis, many of the upland valleys the form Une map of Bantoro boh' where in the lower would repay lateral contour bunding to improve the yield right hand corner the levee attains 13 feet above the survey of the rice crop by controlling the water supply. Small datum while in the upper left hand corner old river channels earth dams can be constructed in the upper reaches of coalesce about lines E and D to pass through dense riverain these valleys to assist this, and to make possible limited forest back into the river. areas of dry season pasture to assist maintaining livestock, The water control arrangements should take cognisance and dry season vegetable gardens to improve local food of the probable need to prevent the backing up of river supply. Dr. F. J. Martin first demonstrated locally the water at the height of the flood season into the boh via advantages of simple valley water control in 1931 (Glanville the old river channels, and to prevent undue run off on to 1938). the boli from the surrounding uplands in years of heavy In none of these areas suggested for water control is rainfall. Subsequently to the development of such water salinity likely to be a problem owing to the highly acid control, consideration can be given to water supply. This and generally leached nature of the profiles. at present seems economically feasible only in terms of a The complex but interconnecting pattern of riverain small pumping unit for each boh, lifting water from the and inland bolis offers a tempting subject when thinking river to the high point on the levee and thence by gravity of irrigation. Between the groups of bolis associated with along open earth supply channels sited either along the the Rokel and Mabole rivers, and the Belia, Gitiwa and crest of the contemporary levee, or along the upland flanks Tabai streams there are many interconnecting seasonally to the contour bays, any excess being drained off into the swampy channels as can be seen from the soil map by old river channels. The guarantee of water supply between tracing bottomland soil patterns. However, the probable reliable dates at the beginning and end of" the season capital cost of providing a comprehensive scheme of water could create the potential for a two-crop season. Rather supply throughout this pattern from barrages or dams than attempt two rice crops, however, it may be preferable to the east, even if technically feasible, is unjustifiable to make the second crop either a food crop, as in Portuguese having regard to the poor quality of most of the com- Guinea (Dougall 1948), or a cash crop such as tobacco mandable soils. 39 REFERENCES RADWANSKI, S. A. (1956). Soils associated with the late Tertiary peneplain, and its erosion in the Upper Tano drainage basin AHN, P. M. (1961). Soils of the Lower Tano Basin, South of the Gold Coast. Kumasi, Gold Coast Department of Western Ghana. Kumasi, Scientific Services Division, Soil Soil and Land Use Survey. (Conference paper presented and Land Use Branch. Memoir No. 2. to 6th International Congress of Soil Science, Paris, 1956.) AKENHEAD, M'. (C. 1951). Preliminary report on the groundnut RODDAN, G. M. (1937). Swamp rice varieties. Sierra Leone soil survey (Pilot scheme). Accra, Department of Agri- Department of Agriculture Notes (No. 5). culture. (MS.) RUSSELL, E. W. (1950). Soil conditions and plant growth. Annual reports of the Sierra Leone Department of Agriculture. 8th edition. London, Longmans Green. Annual reports of the West African Rice Research Station, SCOTT, J. D. (1952). Management of Range pastures in Africa. Rokupr, Sierra Leone, since 1953. Proceedings of 6th International Grassland Congress. ANONYMOUS (1899). The Sierra Leone Protectorate Expedition. 1952. 1,477-483- London, Journal of the Royal United Services Institute. SQUIRE, F. A. (1943). Preliminary report on upland rice varieties. 43i P- 534* Sierra Leone Department of Agriculture Notes No. 10. BRAMMER, H. (1954). Agricultural potentialities of the northern Statistics illustrating the climate of Sierra Leone, 1951. Meteoro- savannah regions of the Gold Coast. Kümasi, Gold Coast logical Department, Freetown, 1952. Department of Soil and Land Use Survey. Departmental STOBBS, A. R. (1959). Report on the semi-detailed soil survey of Paper No. 7. Wenchi Agricultural Station. Kumasi, Ghana Division of BRAMMER, H. (1956a). Principles of agricultural development in Soil and Land Use Survey. Technical Report No. 33. savannah regions comprising red loams on uplands and glei STOBBS, A. R. (i960). Report on the semi-detailed soil survey or vlei soils in the depressions. Kumasi, Gold Coast Depart- of Pong Tamale Veterinary Station. Kumasi, Ghana ment of Soil and Land Use Survey. Departmental Paper Division of Soil and Land Use Survey. Technical Report No. 11. No. 38. BRAMMER, H. (1956b). Visit to Haute Volta. Kumasi, Gold STOBBS, A. R. In preparation. The soils, vegetation and land Coast Department of Soil and Land Use Survey. Technical use of the Nasia basin. Kumasi, Scientific Services Division, Report No. 9. Soil and Land Use Survey Branch. BRAMMER, H. (1956c). C. F. Charter's interim scheme for the VINE, H., et al. (1954). Progress of soil surveys in south-western classification of tropical soils. Kumasi, Gold Coast Depart- Nigeria. Proceedings of 2nd Inter-African Soils Conference, ment of Soil and Land Use Survey. Occasional Paper No. 2. Leopoldville, 1954, Vol. I. Brussels, Ministère des Colonies, CHARTER, C. F. (1947). Soils of the Voltain basin with special pp. 211-236. reference to groundnut production. Tafo, W.A.C.R.I., WALDOCK. E. A., et al. (1951). Soil conservation and iand Divisionof Soil Science and Chemistry. (MS.) utilisation in Sierra Leone. Freetown, Government Printer. CHARTER, C. F. (1955). The nutrient status of Gold Coast forest soils with special reference to the manuring of cocoa. Kumasi, Gold Coast Department of Soil and Land Use VEGETATION Survey. Conference Paper No. 8. AlNSLiE, J. R. (1926). The physiography of southern Nigeria CROSBIE, A. J. (1956). Peneplain remnants in the Kumasi region. and its effect on the forest flora of the country. The Kumasi, Gold Coast Department of Soil and Land Use Clarendon Press, Oxford. Survey. Conference Paper No. 15. ALSTON, A. H. G. (1959). The ferns and fern-allies of West DEIGHTON, F. C. (1944). Pasture and fodder plants in Sierra Tropical Africa. The Crown Agents, London. Leone. Sierra Leone Department of Agriculture Notes ANONYMOUS (1910). Military report on the Colony and Pro- No. 6. tectorate of Sierra Leone. Vol. 11 : Routes. Harrison and DENT, J. M. (1956). Sierra Leone measures. Sierra Leone Sons, London. Department of Agriculture Notes No. 24. BRAUN-BLANQUET, J. (1932). Plant Sociology. McGraw-Hill, DE SWARDT, A. M. J. (1946). The Ife-Ilesha goldfield and the London. (Translated by G. D. Fuller and H. S. Conard.) recent erosional history of the Kaduna valley near Kaduna DAUBENMIRE, R. (1952). Forest vegetation of northern Idaho township. Nigerian Geological Survey. Departmental and adjacent Washington, and its bearing on concepts of Annual Report, 1946, pp. 39-45. vegetation classification. Ecol. Monog. 22, pp. 301-330. DE SWARDT, A. M. J. (1953). The geology of the country around DAUBENMIRE, R. (1959). A canopy-coverage method of vege- Ilesha. Lagos, Government Printer, Geological Survey of tational analysis. North-west Science 33, pp. 43-64. Nigeria, Bulletin No. 23. HARRIS, W. T. (1954). Ceremonies and stories connected with DOUGALL, H. W. (1948). Report on a visit to the Gambia and trees, rivers and hills in the Protectorate of Sierra Leone. Portuguese Guinea. Sierra Leone Department of Agriculture Sierra Leone studies. N.S. I (2), pp. 91-97. Notes. HUTCHINSON, J. and DALZIEL, J. M. (1931-35). Flora of West EDWARDS, D. C. (1929). The palatability of possible pasture Tropical Africa. Vol. II. The Crown Agents, London. grasses in Sierra Leone. Tropical Agriculture 6, 141-143. HUTCHINSON, J. and DALZIEL, J. M. (1954-58). Flora of West GARRETT, G. H. (1892). Sierra Leone and the Interior to the Tropical Africa. Vol. I. (Revised by R. W. J. Keay.) Upper Waters of the . Proc. R.G.S., Vol. XIV, The Crown Agents, London. No. VII, pp. 433-455- JONES, A. P. D. and KEAY, R. W. J. (1946). Descriptive terms GLANVILLE, R. R. (1938). Rice production on swamps. Sierra for the vegetation of the drier parts of Nigeria. Farm and Leone Department of Agriculture Notes No. 7. Forests 7, pp. 34-40. JEFFERY, J. W. O. (1961). Defining the state of reduction of a KEAY, R. W. J. (1953). An outline of Nigerian vegetation. Second edition. Government Printer, Lagos. paddy soil. J. Soil Sä. 12, 172-179. KEAY, R. W. J. (1959). Derived savanna—derived from what? JUNNER, N. R. (1946). Progress in geological and mineral investi- Bulletin de VI.F.A.N. Ser. A. 21 (2), pp. 427-438. gations in the Gold Coast. London, Imperial Institute. MANGENOT, G. (1958). Les recherches sur la végétation dans les Gold Coast Geological Survey. Bulletin No. 16. régions tropicales humides de l'Afrique occidentale. Study KEAY, R. W. J. (1949). An outline of Nigerian vegetation. of Tropical Vegetation: Proceedings of the Kandy Sym- Lagos, Government Printer. posium, pp. 115-126. MACGREGOR, W. D. (1940). First impressions of forestry in MARTIN, F. J. (1938). A preliminary survey of the vegetation Sierra Leone. The Nigerian Forester 1, pp. 20-1. of Sierra Leone. Government Printer, Freetown, pp. 1-6. MiCHELMORE, A. P. G. (i939). Observations on tropical African NEWLAND, C. H. (1944). Problems associated with development grasslands. Journal of Ecology, Vol. XXVII, No. 2, in Sierra Leone. Farm and Forest 5, pp. 21-24. pp. 282-312. NYE, P. H. and GREENLAND, D. J. (i960). The soil under PiGGOTT, C. J. and NICHOLS, E. H. (1958). Factors affecting the shifting cultivation. Technical Communication No. 51. yield of rice on the bolis of Sierra Leone. Sierra Leone Commonwealth Bureau of Soils, Harpenden. Department of Agriculture unpublished note. RATTRAY, J. M. (i960). The grass cover of Africa. F.A.O. POLLETT, J. D. (1951). The geology and mineral resources of Agricultural Studies, No. 49, pp. 1-168. Sierra Leone. Colonial Geological and Mineral Resources 2, TANSLEY, A. G. (1935). The use and abuse of vegetational pp. 3-28. concepts and terms. Ecology 16, pp. 284-307. PUGH, J. C. and KING, L. C. (1952). An outline of the geo- WALDOCK, E. A., CAPSTICK, E. S. and BROWNING, A. J. (1951). morphology of Nigeria. South African Geographical Journal, Soil conservation and land use in Sierra Leone. Government Vol. XXXIV. Printer, Freetown. 40 APPENDIX

ANALYTICAL DATA

TABLE 7 TABLE 7—continued pH TABLE BASED UPON FIELD COLOMETRIC DETERMINA TIONS

Profile Series Name Subsoil 3. Acid and Very Acid Gleisols No. (2) (a) Inland bolis (old sloughs) 1. Oxysols 53 Babaibunda 46 4-6 4-7 (a) Uplands 58 33 4-7 4 2 45 42 74 33 50 50 48 5 Batkanu 4-7 4-6 56 Kontobe 46 4-7 4-6 4-4 45 43 7 60 33 5 2 4-6 4'2 4-7 48 46 15 33 42 42 76 43 V O i6 48 51 56 •i f 81 33 45 45 35 52 49 48 4-8 83 33 4-2 43 44 12 Mankahun 42 46 70 5-6 5'2 50 Wari 5-5 Massimo 14 4-8 73 33 48 46 44 Diabama 51 46 4-8 i8 77 33 5-1 4-8 4-7 28 Belia 51 4-8 46 80 Masuri 46 33 4-6 4-3 4-6 69 44 48 42 Romankne 5-7 53 49 Malinka 52 49 4-8 75 43 33 48 45 4-7 (b) Terraces 54 Makonte 44 48 46 72 Maroki 42 50 46 65 33 50 50 50 84 Mabang 52 4'5 44 57 Madina 4-8 46 4-7 «7 Mara 4-2 4-6 4 4 (b) Riverain 60/15 (contemporary sloughs) Rokel 50 48 2. Groundwater Latérites 85 49 88 33 SO 45 4'2 (a) Uplands 4 Mabole 4-4 41 42 n Makroma 4-2 40 50 47 Malansa 53 47 44 17 Matutu 48 51 48 (c) Terraces 23 Mayanki 4-9 48 45 59 Alamalia 46 43 45 (b) Terraces 62 50 4-7 4-7 34 Masebra 50 4-6 4-6 61 Kontobe 52 46 48 47 82 45 46 4-8 41 49 4'8 52 44 Old river channels 44 41 4-2 w 24 2 Rochin 47 4 4 40 25 Matamba 44 4-2 46 4-8 48 33 49 48 46 30 51 5-2 4. Alluviosols 31 Malop 44 4-8 45 45 Makoli 45 49 46 6 Magbunga 5 4 47 51 Madina 50 4-4 49 33 5 4 5-2 51 10 20 (c) Sloughs Bom 45 46 4-7 3-8 39 Mateboi 50 48 48 Masebra | 48 | 45 86 Seli 48 44 48 (d) Levees 4-8 50 I Tabai | 5-8 | 5-4

41 TABLE 8

Profile No. SSB84 Profile No. SSB87

Series Name Mabang Series Name Mara

Great Soil Group Oxysol Great Soil Group Oxysol

Site Terrace Site Terrace

Sample Top- Subsoil Subsoil Sub- Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum soil (0 (2) stratum Depth 0-25' 25-72' Depth 0-12" 12-50" Moisture 100-105 °C. 237 1 67 Moisture 100-105 °C. 228 i-6o 200/1-2 mm. 200/1-2 mm. 20/1-200/t 20/1-200/1 2/1-50/1 Amer, silt 10 8 2/1-50/1 Amer, silt 10 5 2/1-20/1 % silt 6 4 2/1-20/1 % Silt 6 4 < 2/x % clay 18 27 < 2/1 % clay 24 38 Loss on ignition 8-0 57 Loss on ignition 6-8 6-4 Organic carbon % C. 366 0-79 Organic carbon % C. 11 0-47 Nitrogen % N. 0-192 0059 Nitrogen % N. 0-12 005 C/N ratio 191 134 C/N ratio 92 94 pH in water (1 : 2-5) 55 4-5 pH in water (1 : 2-5) 4-8 46 pH in M/ioo CaCl2 5-0 42 pH in M/ioo CaCl2 44 4 4 Exchangeable Exchangeable m.e./ioo gms. Ca 232 0« in.e./100 gms. Ca 0-47 0-34 „ Mg 114 0-39 Mg 0-62 0-84 K 028 0-12 » K- 0-19 027 Na 013 OO7 Na 012 O-II Total exch. bases 39 0-9 Total exch. bases 1-4 16 Base exch. capacity 79 75 Base exch. capacity II-8 84 % Saturation 12 49 12 % Saturation 19 Note: All percentages are calculated to oven dry basis. Note: All percentages are calculated to oven dry basis.

Profile No. SSB 72 Series Name Maroki Great Soil Group Oxysol Site Terrace

Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum Depth 0-10" 10-20"

Moisture 100-105 °C. 0-47 0-50 200/1-2 mm. 20/1-200/1 2/1-50/1 Amer, silt 1 3 2/1-20/1 % Silt — 1 <2/i % clay 5 6 Loss on ignition 2-1 2-1 Organic carbon % C. O48 0-29 Nitrogen % N. O-O36 OO25 C/N ratio I33 II-6 pH in water (1 : 2-5) 5-0 5-o pH in M/ioo CaCl2 45 46 Exchangeable m.e./ioo gms. Ca 025 006 Mg O-II 0-19 0-05 009 Na 0-03 004 Total exch. bases o-4 04 Base exch. capacity 47 51 % Saturation 9 8

Note: All percentages are calculated to oven dry basis.

42 TABLE 8—continued

Profile No. SSB 6 Profile No. SSB 49 Series Name Magbunga Series Name Magbunga Great Soil Group Alluviosol Great Soil Group Alluviosol Site Contemporary levee Site Contemporary levee Sample Top- Subsoil Subsoil Sub- Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum soil (1) (2) stratum Depth 0-7" 7-28" 28-70" Depth 0-6" 6-20" 20-72" Moisture 100-105 °C. 396 305 1-77 Moisture 100-105 °C. 453 2 69 1-33 200/1-2 mm. 13 2 4 200/1-2 mm. 9 1 50/1-200 /i 10 9 24 50/1-200/1 23 31 39 2/4-50/1 Amer, silt 46 47 33 2 /1-50/x Amer, silt 41 39 24 2/1-20/t % Silt 32 32 21 2/1-20/1 % silt 25 25 15 <2/i % clay 27 39 38 <2/i % clay 18 20 34 Loss on ignition 171 12-7 75 Loss on ignition 17-6 10-6 69 Organic carbon % C. 404 I-8I 0-37 Organic carbon % C. 5-47 2-08 030 Nitrogen % N. 0-226 0-117 0037 Nitrogen % N. 0-352 0160 0068 C/N ratio 179 155 100 C/N ratio 155 130 4 4 pH in water (1 : 2-5) 5-4 47 51 pH in water (1 12-5) 5 4 52 51 pH in M/ioo CaCl2 4-6 4-4 4-6 pH in M/ioo CaCl2 4-7 4-6 43 Exchangeable Exchangeable m.e./ioo gms. Ca 1-67 027 035 m.e./ioo gms. Ca 084 009 008 Mg 0-72 007 o-io Mg 016

Note: All percentages are calculated to oven dry basis. Note: All percentages are calculated to oven dry basis.

Profile No. SSB 86 Series Name Seli Great Soil Group Alluviosol Site Contemporary levee Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum Depth O-Il" 11-37"

Moisture 100-105 °C. 733 3-47 200/1-2 mm. 20/1-200/1 2/1-50/1 Amer, silt 37 26 2/1-20/1 % Silt 34 22 <2/i % clay 51 66 Loss on ignition 253 12-9 Organic carbon % C. 728 1-33 Nitrogen % N. 0565 0097 C/N ratio 12-9 130 pH in water (1 : 2-5) 51 48 pH in M/ioo CaCl2 47 44 Exchangeable m.e./ioo gms. Ca 032 Mg 037 K 015 Na 007 Total exch. bases o-9 Base exch. capacity 87 % Saturation 10

Note: All percentages are calculated to oven dry basis.

43 TABLE 8—continued

Profile No. SSB 85 Profile No. SSB 13 Series Name Rokel Series Name Mabole Great Soil Group Very Acid or Acid Gleisol Great Soil Group Very Acid or Acid Gleisol Site Riverain slough Site Riverain slough Sample Top- Subsoil Subsoil Sub- Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum soil (1) (2) stratum Depth 0-10" 10-34* Depth 0-8' 8-32" 32-70" Moisture 100-105 °C. 11-50 4-30 Moisture 100-105°C. 645 2-67 3 39 200/4-2 mm. 200/4-2 mm. 23 1

Note: All percentages are calculated to oven dry basis. Note: All percentages are calculated to oven dry basis.

Profile No. SSB 36 Profile No. SSB 40 Series Name Malansa Series Name Malansa Great Soil Group Very Acid or Acid Gleisol Great Soil Group Very Acid or Acid Gleisol Site Riverain slough Site Riverain Slough Sample Top- Subsoil Subsoil Sub- Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum soil (1) (2) stratum Depth 0-6" 6-21" 21-70" 70-108" Depth 0-14" 14-41" 41-76"

Moisture 100-105 °C. 475 271 305 017 Moisture 100-105°C. 491 3 45 276 200/4-2 mm. 7 2 4 94 200/4-2 mm. 15 3 6 50/4-200/4 2 1 1 50/4-200/4 7 2 4 2/1-50/4 Amer, silt 46 32 19 2/4-50/4 Amer, silt 46 20 21 2/4-20/i. % Silt 38 26 19 2/4-20/4 % Silt 39 17 20 <2/4 % clay 31 59 68 2 <2/4 % clay 23 74 68 Loss on ignition 237 130 136 1-5 Loss on ignition 192 147 12-6 Organic carbon % C. 5-38 085 029 O-OII Organic carbon % C. 531 069 0-22 Nitrogen % N. 0397 0107 0026 0-005 Nitrogen % N. 0-321 0074 0 022 C/N ratio 134 79 II-3 2-1 C/N ratio i6-5 93 100 pH in water (1 : 2-5) 5'2 5-o 5-0 5-2 pH in water (1 : 2-5) 5 4 51 53 pH in M/ioo CaCl2 4-6 43 43 46 pH in M/ioo CaCl2 475 44 4 45 Exchangeable Exchangeable m.e./ioo gms. Ca 009 012 014 0-08 m.e./ioo gms. Ca 0-14 0-06 027 Mg 006 0-06 007

Note: All percentages are calculated to oven dry basis. Note: All percentages are calculated to oven dry basis.

44 TABLE 8—continued

Profile No. SSB83 Profile No. SSB53 Series Name Kontobe Series Name Babaibunda Great Soil Group Very Acid or Acid Gleisol Great Soil Group Very Acid or Acid Gleisol Site Old slough Site Old slough Sample Top- Subsoil Subsoil Sub- Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum soil (1) (2) stratum Depth 0-18" 18-50" Depth 0-18" 18-41" Moisture 100-105 °C. 1-44 119 Moisture 100-105 °C. 136 1 89 200/X-2 mm. 20O/i-2 mm. 20/i-2O0/i 2O/i-2O0fi 2/i-5O/x Amer. silt. 32 28 2ft-5O/i Amer, silt 34 38 2jU.-2O/i % Silt 20 20 2fl-20/l % silt 22 29 <2ft % clay 15 28 <2ji % clay 23 17 Loss on ignition 47 46 Loss on ignition 41 6-2 Organic carbon % C. 1-45 062 Organic carbon % C. 2-5 0-66 Nitrogen % N. 0077 0038 Nitrogen % N. 015 0053 C/N ratio 188 16-3 C/N ratio 16-7 12-4 pH in water (1 : 2-5) 47 47 pH in water (1 : 2-5) 49 45 pH in M/ioo CaCl2 44 43 pH in M/ioo CaCl2 4-2 41 Exchangeable Exchangeable m.e./ioo gms. Ca 023 008 m.e./ioo gms. Ca 005 o-io » Mg 0-53 0-29 Mg 0-12 0-41 K 019 0-12 K 009 0-12 Na 0-09 006 Na 0-06 o-o8 Total exch. bases 10 0-6 Total exch. bases o-3 0-7 Base exch. capacity 96 6-6 Base exch. capacity 72 12-7 % Saturation 10 9 % Saturation 4 6 Note: All percentages are calculated to oven dry basis. Note: All percentages are calculated to oven dry basis.

Profile No. SSB77 Profile No. SSB 42 Series Name Massimo Series Name Romankne Great Soil Group Very Acid or Acid Gleisol Great Soil Group Very Acid or Acid Gleisol Site Old slough Site Old slough Sample Top- Subsoil Subsoil Sub- Sample Top- Subsoil Subsoil Sub- soil (1) (2) stratum soil (1) (2) stratum Depth 0-13" 13-35" Depth O-II" 11-40" 40-72" Moisture 100-105°C. 071 077 Moisture 100-105 °C. 0-77 0-46 052 200^-2 mm. 200/L4-2 mm. 19 30 34 2O/x-2O0ft 5O/i-2OO/i 36 27 22 2/i-5Ofi Amer, silt 46 25 2/i-5O/x Amer, silt 29 26 23 2/i-20fi % silt 27 17 2/i-20/i. % silt 22 18 15 < 2fi % clay 6 16 <2n % clay 10 11 16 Loss on ignition 35 24 Loss on ignition 4-0 2-1 2-2 Organic carbon % C. 092 0-43 Organic carbon % C. 138 O-40 o-ii Nitrogen % N. 0095 0041 Nitrogen % N. 0-098 OO34 0-015 C/N ratio 97 10-5 C/N ratio 141 II-6 7-2 pH in water (1 : 25) 47 4-6 pH in water (1 : 25) 57 53 49 pH in M/ioo CaCl2 41 42 pH in M/ioo CaCl2 48 45 43 Exchangeable Exchangeable m.e./ioo gms. Ca 009 023 m.e./ioo gms. Ca 045 0-14 015 Mg 008 0-08 Mg 084 0-69 023 003 0-05 K 0-09 004 0-04 Na 0-02 003 Na 003 002 0-03 Total exch. bases 0-2 04 Total exch. bases 1-4 09 o-5 Base exch. capacity 7 9 52 Base exch. capacity 51 2-6 31 % Saturation 3 8 % Saturation 27 35 16

Note: All percentages are calculated to oven dry basis. Note: All percentages are calculated to oven dry basis.

45

PLATE I Batkanu Boli. Anadelphia Rhytachne association on very acid gleisols with Rhytachne in those areas waterlogged longest. This is a view across a riverain boli towards the résèquent stream entrenching itself along the foot of the upland in the background. PLATE 2 Rochin boli near the Batkanu-Mateboi ferry. This shows the old river channel (Rochin series soils) leading to the present river (hidden behind the fringing forest in the background). Beyond the old river channel is the old levee (Mateboi series soils) supporting Chasmopodium j Nauclea vegetation. PLATE 3 Anadelphia iRhytachne association in an old river channel (Rochin series soils) of a riverain boli with an old levee behind. R. rottboeïiodes occupies a pocket waterlogged longer than the adjacent areas. ISfir

PLATE 4 Anadelphia. Rhytachne association on very acid gleisols at Kontobe Boli. Tall grasses belonging to the Chasmopodium/Nauclea association on a termite mound (top left), and " sacred bush " (old forest remnant) is seen top right on an island of concretionary upland soils adjacent to the river. Rkyrachne rottboeliodes is the lighter grass in the foreground. PLATE 5 Typical landscape of an "inland" boli along the Makeni-Lunsar road. The swamp is under AnadelphiaiRhytachne association on very acid gleisols; the uplands in the background are covered with Lophira'.Chasmopodium vegetation on infertile concretionary drift soils; the foreground gives a close-up of Chasmopodium caudatum. PLATE 6 Upland area 11 miles south of Batkanu with LophirajChasmopodium vegetation growing on relict peneplain drift soils. PLATE 7 Lopkira IChasmopodium association on groundwater laterites and yellow brown concretionary drifts near Babaibunda. Foreground burned and cleared for new cultivation with upland rice. PLATE 8 Vegetation which has not been subject to recent fire on colluvial loams near Mayanki. '*. .*

PLATE 9 Upland cassava farm near Batkanu on red brown concretionary drift soils of Unit 2. PLATE IO Cassava (Manihot uiilissima) growing on groundwater lateritic terrace soils near Tabai bridge, among " inland " bolis. Note the high grass on termitaria in the background. PLATE II Typical stand of oil palms (Elaeis guineensis) on terrace oxysols of Unit 7 near Maroki, PLATE 12 Local rice " nursery with seedlings growing at the side and in the middle of the road, Riverain and secondary forest in the background. 31 lf 1 a na 3. o SOIL SKETCH MAPS OF BOLIS IN SIERRA LE RIVERAIN BOLIS

SAMPLE STRIPS 1 & 2 Scale : 1 Inch ~ 5 Chains STRIP 1 STRIP 2 ROMANKNE BOLI ROCHIN BOLI BANTORO BOLI MADINA-TABAI BOLI BANTORO BOL! (FORM-LINES) Locality :- On south side of Lunsar road about 1 mile Locality :- On north side of Lunsar road about 1 mile Base- east of Tabai Bridge. east of Tabai Bridge. line 10 15 20 25 Chains Chains 50 45 40 35 30 25 20 15 10 0 H G F D C B A G Chains 30 -1

0 — S t ream

T - 5- Ta Mag. N 5 - SS 25 - 10- - 10 Re -RR 15 - 15

Q - - QQ 20 H 20 - - 20 - PP Q. 25- - 25 - OO 15- o- Mu 30 - - 30

N •- - NN 35 - -35

M - -MM 10 40- •- 40 L - - - LL

45 - - 45 Re K- - KK 5 H 50 - - 50

- JJ 55- - 55 Te o f T 60 - 0 5 10 15 Chains ferry - 60 A B C D CO n U 5) 65 - 65

G

70- - 70 LEGEND F - Matutu Series _ _ _ _ _._ Mu 75- - 75 Matutu Series, shallow phase Mus E — Fabai Series _ __ ._ Fa Masebra Series _ _ _ _ _ Mr D - Romankne Series .... Re 85- 85 Romankne Series, depression phase _ Red

c_ Makonte Series _ -..... _ Me 90 Makonte Series, shallow sub-series Mes LJn-named Series in minor drainage groove Dg 95 - Soil developed over degraded termite mound -Te 95 • = Pit Sites - AA 100 - - 100

105 Chains 50 45 40 20 25 Chains •105

110-

Base 115 Scale :1 Inch =20 Chains line •115 Chains 55 50 45 40 35 30 25 20 15 10 5 0 5 10 Chains 120 - -120

Form-lines at interval of 1ft. 125- -125 j C iiiiiiBiil^ G H G E D C

c - -C

-D Scale : 1 Inch = 1 0 Chains

E _E LEGEND

UPLAND CONCRETIONARY SOILS _F OLD LEVEE SOILS OLD RIVER CHANNEL SOILS Batkanu Series-_ _.. .. Mateboi Series Roch in Series.. _ - _ Mk::: Makoima Series _.. __ Mateboi Series, brownish-yellow Rochin Series, Bantoro variant _ G - G sub-soil variant. Upland Transitional Soil . Rochin Series, sandy phase.. ._ Mateboi Series, degraded phase... SLOUGH SOILS Mateboi-Rochin Transitional Soil [TTÏTT Mateboi Series, brown loam top-soil Ml Malansa Series variant CONTEMPORARY LEVEE SOILS Transitional Soils __ Mateboi Series, variable phase.... Maqbunga Series. _ Bom Series ._. Pi LJLJJL Magbunga Series overlying Rochin Series Chains 55 50 45 40 35 30 25 20 15 10 5 0 5 10 Chains DRAINAGE GROOVE SOILS Magbunga-Bom Transitional Soil LEGEND Bas Mabole Series..- BATKANU BOL! lin' Malansa-Mabole Transitional Soil Profile Pit Site ALLUVIUM .- - -- - Ko< Kontobe Series ._ -- Kontobe Series, terrace variant... Recent alluvium __. Kol. :Mmi Kontobe Series, leached drainage groove phase Mamalia Series. -. liUUJI. Red brown concretionary soils __ rrr Bb Babaibunda Series... - - .err Madina Series Yellow brown concretionary soils. T~TT' ||Me Babaibunda Series, leached phase -. Bbl Makonte Series

Limit of Survey D Profile Pit Farm Track Secondary Road

D.O.S. (Misc.) 310 _ j COPYRIGHT RESERVED Drawn by Directorate of Overseas Surveys 196-3 from material supplied by A.R, Stobbs, Printed for D.O.S. by S.P.C..R.E. ÖOO/3/63/362/SPC