SOILS AND MANURES 



369 



expensive of commercial fertilizers, the farmer should make CHAP, 

 sure that it will prove beneficial before going to the expense VI "' 

 of purchasing. 



A three-year series of trials at the Government Experiment 

 Farm, Potchefstroom, showed that the average yield of grain 

 was only 30 lbs. per acre more (worth is. 3d.) with the use of 

 nitrate of soda than without. As the cost of this manure 

 was £1 os. id. per acre, the net loss from its application was 

 1 8s. iod. per acre. The amount used was 200 lbs. the first 



Fig. 126. — Effect of growing maize without manures (on plot adjacent 

 to that shown in Fig. 127). 



year and IOO lbs. each year in the two succeeding years {Holm, 

 1). Similar results have been obtained with maize at Cedara, 

 Natal (Sawer, 1), and with other cereals at Potchefstroom. 



336. Superpliosphate and Nitrate of Soda. — On poor sandy 

 soils at Koedoespoort, near Pretoria, Prof. Watt obtained an 

 increase of 500 per cent on his maize crop, the first season, on 

 the plot on which nitrate of soda (200 lbs. per acre) and super- 

 phosphate (400 lbs. per acre) were used, as compared with that 

 on which superphosphate was used alone. The second crop 



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