Vol. XVI. No. 392. 



THE AGRICULTURAL NEWS 



U:^ 



LATERITE FORMATION IN SOILS. 



The phenomenon of laterite ibrniation has re- 

 ceived attention in British Guiana, and the following 

 article, reproduced frotn the Agricultural Bulletin 

 of the Federated Malay States, will therefore serve 

 to call further attention to the matter. Below will 

 also be found an extract from .Schimper's Plant 

 Geography' dealing with the same subject: — 



Laterite is the name given to a superficial rock form- 

 ation characteristic of tropical countries. Although it has 

 a very wide distribution, and is formed from very variable 

 rock formations, it exhibits a remarkable uniformity in its 

 characteristics. In composition it consists almost entirely 

 of insoluble metallic oxides, and is characterized by an 

 absence of combined silica. 



It is the product to which all rocks in tropical countries 

 in which the rainfall continjously exceeds the evaporation, 

 tend to be ultima'ely converted. In this country most of 

 the soils, except the recent alluvial coastal clays and certain 

 satidstone formations, are lateritie in character to a greater 

 or less degree, although for various reasons the ultimate pure 

 laterite consisting of nothing but bydrated metallic oxides is 

 practically never reached. 



All rocks consist mainly of free silica (quartz), silica 

 combined with oxides of iron, aluminium, magnesium, calcium, 

 potash and soda, and sometimes calcium carbonates. A sand- 

 stone or quartzite may consist of practically nothing but 

 pure silica, and a liraestoce of little but calcium carbonate. 

 Such rocks cannot of course form laterite The majority of 

 rocks, however, do contain silica combined with varying 

 proportions of metallic oxides. In temperate countries, 

 •when such rocks decompose, the oxides are removed in 

 solution, silica combined with aluminium oxide and water 

 remains. This is bydrated silicate of alumina or clay. In 

 countries of high temperature this does not however, occur: 

 the oxides of soda, potash and calcium are removed as before, 

 but the intense solvent action also results in the removal of 

 the combined silica, leaving behind the insoluble oxides of 

 aluminium and iron, which in combination with water form 

 the product which we know as laterite Neither pure clay 

 nor pure laterite can be a fertile soil. 



The importance of lateritie formation from an economic 

 point of view, is that it results in the removal from the surface 

 soil of those substances which are useful to the plant. This 

 ■washing out which occurs in t];e F.M.S. lateritie hill soils is 

 the reason for the poverty in chemical composition of these soils 

 compared wi;h tho.se of temperate co'.intries. Two factors 

 are operative in retarding their entire exhaustion. Firstly 

 the formation of secondary compoundes rich in silica less 

 easily decompo.sed than the original rock, and secondly, 

 a factor which is very potent in this country, the absorption 

 of the soluble substances by the humus formed from the 

 dense tropical vegetation. The retention of the humus of 

 the soil is therefore most important in maintaining the fer- 

 tility of the soil. Yet when bukit land is opened up for 

 cultivation, the humus is the first thing to disappear, being 

 quickly decf)niposed and washed out from the bare unpro- 

 tected soil. Where no cover crop is grown, and no measures are 

 taken to prevent wash, not only is much of the surface soil 



•removed in toto, but the process of laterizition and therefore 

 ultimate infertility vastly accelerated. It is not until the 



■crop covers the ground that this process is retarded. To 

 this cause may be attributed the well-known poverty of 

 previously cultivated sjils on which rubber is planted, and 



•an explanation is otfered of the good results which can be 



obtained by the application of organic manures to these soils. 

 The question of the formation of lateritie soil in .Tava. 

 and Sumatra was recently fully dealt with in a 'Report oa 

 Certain Aspects of the Tea Industry of .Java and Sumatra', 

 by G p. Hope, Scientilie OtHcer to the Indian Tea 

 Association. 



The following information concerning the cecology 

 of lateritie soils is taken from Schimper's 'Plant 

 Geography': — 



Physically, laterite is i;haractenzed by very low capacity 

 for retaining water; in p:irticular, old washed-out lateritie, 

 rich in coarse fragments, is very permeable Being a soil 

 poor in nutriment and arying rapidly, especially after its- 

 finely grained constituents have been washed out, laterite 

 affords a vtry unfaiouraMe substratum for the existence of 

 plants. It is not yet known how far the large proportion of 

 iron also affects the characteristic peculiarities of the. 

 vegetation. 



Laterite, especially in its stony porous forms, induces 

 in the forest a physiognomy which is characteristic both as 

 regards its cecological features and its systematic composition, 

 and which has been described by Brandis and Kurz in respect, 

 to Burma. 



A tree characteristic of the laterite localities in that 

 country is the eng, Diplerocarpus tuherculatus, which 

 dominates the forest through its social habit, and distinguishes 

 itself essentially from the other accompanying trees by the 

 fact that it exhibits a normal growth in height, whereas the 

 other trees are reduced to gnarled, more or less dwarfed, 

 forms. Such forests are termed 'eng-forest' by Brandis and 

 Kurz. 



DRUGS AND SPICES ON THE LONDON 

 MARKET. 



The general character of the drug and .spice markets 

 during the month of February has shown no improvement 

 since the date of our last report. The increasing shortage of 

 imports, together with the depletion of office staffs and 

 warehouse labour, and the German submarine menace, have 

 done much to lessen the amount of products brought forward, 

 and consequently the extent of business transactions. The 

 general result has been the increase in prices, as will be 

 seen from the following details. Amongst those articles 

 which have commanded higher prices are ginger, arrowroot 

 and sarsaparilla, while West Indian mace and lime oil have 

 been lower. The following are some of the details. 



NUTMEGS AND M.\C'E. 



At the spice auction on the 1st of the month as many 

 as 393 packages of West Indian nut)uegs were otfered and 

 381 sold at steady rate:- icr small and medium sizes. There 

 was no demand for tlie larger sizes. At the same auction mace 

 was also in good supply. 78 packages of West Indian being 

 sold at the following ratjs: Is. IQd. to 2s for good pale, 

 Is. 5rf. to Is. M. for ordinary to fair, l.s- Zd. to l.s. bd. 

 for red, and 9(i. to Is. Id. for broken. 



Quite at the beginning of the month it was reported that 

 quantities of kola nuts had been exported to the Continent^ 

 (Jood bright West Indi.m nuts, whole and halves, realized '"td. 

 per lb. at the first spice auction. As many as 54 pack- 

 ages were otfered and 34 disposed of. At the same salst- 

 3 bags of Cassia Fistula pods were offered and dispo3C<ft 

 of at 40s. per cwt. for common wormy Dominica. 



