FERTILIZERS FOR WHEAT 125 



Uncertainty of Rules. Cultural rules are very uncertain, since, 

 in general, the crop is more affected by the kind of general manage- 

 ment the land has had during the past ten or fifteen years than the 

 particular kind of treatment given just preceding planting. The 

 general effect of cropping systems on yield is developed in Chapter V, 

 and should be here reviewed. 



Fertilizers for Wheat. In the older farming sections farmers 

 begin applying commercial fertilizer to wheat before other cereal 

 crops, as corn or oats. This is apparently because (1) wheat, being 

 more sensitive to soil conditions, responds somewhat more quickly; 

 (2) grass and clover are commonly sown with wheat and the fertilizer 

 is often for the benefit of the new seeding also. The principles of 

 fertilizing for wheat have already been fully developed (p. 36) and 

 will not be further considered here. 



Since fertilizers are to be used to supply needed mineral elements, 

 it will be well to note the minerals most in demand by the wheat 

 plant. Following is the average analysis, as reported by I^aws and 

 Gilbert, of the ash of wheat grain and straw : 



Mineral Constituents of Wheat 



Grain Straw 



Ferric oxide 0.645 0.69 



Lime 3.175 5.075 



Magnesia 10.48 1.525 



Potash 33.345 15.355 



Soda 0.18 0.265 



Phosphoric anhydride (P 2 O B ) 50.065 3.10 



Sulf uric anhydride (SO 3 ) 1.42 3.84 



Chlorine 0.05 2.13 



Silica 0.655 68.505 



Total 100.015 100.485 



Phosphoric acid and potash are by far the most important. In 

 the grain phosphoric acid leads, while in the straw there is five times 

 as much potash. The large silica content is not important, as the 

 crop will do quite as well without it and the presence of silica in the 

 straw may be considered more as a by-product. The other minerals 

 in the list, except lime, are ordinarily present in abundance. Nitro- 

 gen is also added in fertilizers, but for wheat where a good rotation 

 including clover is practised or manure is occasionally applied, only 

 a little nitrogen is needed in the fertilizer. 



On the wheat soils of tha middle States phosphate is required 



