726 



Journal of the Department of Agriculture. 



Second series : Maize alone. 



Sample No. 1977 is representative of the soil of tlie experimental 

 plots. The plots marked x were, unfortunately, spoilt during the 

 season 1911-12. 



The beneficial effect of phosphatic manures, and particularly of 

 the insoluble phosphates basic slag and ground Weenen phosphate, 

 is evident. The application of superphosphate to soils of this type 

 must result in a partial combination of the soluble phosphoric oxide 

 with the finely divided ferric oxide, whereby the activity of the 

 phosphate may be decreased. That this view is correct is substan- 

 tiated by the results obtained on Plots Nos. 2 and 4 in both years and 

 Plots Nos. 10 and 12 in the first season. The efficacy of the insoluble 

 phosphates applied in the first season on the second crop is most 

 marked. A sliglit increase, due to the nitrate of soda on Plot No. 14, 

 is indicated, while the addition of sulphate of potash resulted in a 

 decreased yield. The bone-meal plots deserve some remark, since 

 the consignment used was partially rotted and quickly available, 

 to which fact the big yield in the first season and comparatively low 

 yield in the second were due. 



From a consideration of the chenrical ;ind i)hysical comjiosition 

 of the Ivoedoespoort loam and the results of the above-quoted manurial 

 experiments the following conclusions may be drawn : — 



1. That the application of phosphates is essential in order to 



raise good crops. 



2. That nitrogenous and potassic manures are of little use. 



3. That insoluble phosphates will give the best results, if not 



immediately, at any rate in the long run. 



4. That in order to maintain tilth and to maintain the native 



supply of nitrogen in the soil, the incorporation of organic 

 matter is desirable. 



5. That if superphosphate be used, lime should also be applied. 



* This phosphate is no longer obtainable ; the results are given in order to show the 

 efiEect of a very insoluble phosphatic manure. 



