Rbpres^entative Transvaal Soils. 



175 



in one year after cowpeas tlian in two years in botli of which maize 

 was jj'rown. The dih^erence on plot No. 8 in the total yield of maize for 

 two years and the yield of maize in the second year only after cow- 

 peas is very small, and this difference in the last plot (No. 9) is due to 

 the effect of the nitrate of soda which supplied the necessary nitrogen 

 in the first yc^ar. The increase in the yield of maize after coAvpeas 

 on field B would probably have been still greater had the crop of cow- 

 ])eas been ploughed under instead of reaped in the first year. 



The geiy:'ral conclusions drawn from these experiments are: — 



(1) That on very poor soils of this nature, in other words on 

 the quartzite soils, the best fertilizer is one containing 

 phosphates. 



(2) That since the soil also requires lime, in order to promote 



nitrification, basic slag would be the best form in which to 

 supply the necessary phosphates. 



(o) That it pays better to enrich the soil with nitrogen by 

 growing a leguminous crop than by applying* expensive 

 nitrogenous fertilizers. The leguminous crop also improves 

 the soil by supplying organic matter. 



(4) That if a phosphatic fertilizer is used, a greater yield of 

 maize may be obtained after a crop like cowpeas than would 

 l)e got in two years during which maize is grown con- 

 tinually. 



A manurial experiment on wheat was carried out on soil No. 1818, 

 the analysis of which is given elsewhere, with the following 

 results (2): — 



Plot. 



Manuri.al Treatment per Acre. 



Yield of Grain in 

 lb, per Acre. 



150 



700 



750 



770 



.520 



730 



620 

 260 



The soil on which this exi)eriment was carried out contains the 

 same percentage of nitrogen as soil No. 760 on which Mr. Watt 

 carried out maize experiments, it is richer in available phosphoric 

 oxide and contains much more available potash. The results of the 

 experiment again point io the need of phosphatic and nitrogenous 

 manures. Curiously enough the plot manui-ed with superphosphate 

 and nitrate of soda gave a greater yield than the one manured with 

 the same quantity of these two fertilizers, plus 100 lb. of sulphate of 

 potash. On this soil it certainly would mean a waste of money to 

 apply a potassic fertilizer. This soil would have given better results 



