CULTURE OF WHEAT 73 



tity of fertilizer used. It is perfectly obvious that the amount 

 of fertilizer to be applied, whether zero pounds, one hundred 

 pounds, or a thousand pounds, is an economic and therefore a 

 local question. Experiments have shown clearly that some in- 

 crease in yield will result when fertilizers are applied in proper 

 ways, at proper times, in proper proportions, and in proper con- 

 dition, to clay soils such as produce much of the winter wheat 

 east of the Mississippi River. WTiether the application of a 

 certain quantity of fertilizer will increase the yield sufficient to 

 pay for the cost of application depends upon many factors, some 

 of which are purely local and some can only be determined 

 by trial. 



A great many careful trials have been made by experiment 

 stations on their own ground and upon the farms of the citizens 

 of their own respective States. In some cases, the yields have 

 paid good returns for money invested ; perhaps in more cases, 

 the value of the increased yield of wheat has not been equal to 

 the cost of the fertilizers used. The longer the land has been 

 under cxiltivation the more general has the application of fertili- 

 zers to wheat become, so tiiat in all of the States east of Illinois 

 large quantities are annually applied for this crop. 



ii8. Indirect Fertilization. — Two methods of adding plant 

 food to the soil for wheat are practiced, viz., (i) the direct 

 method and (2) the indirect method. 



In the indirect method the plant food may be increased in 

 two ways : (i) by growmg wheat in a rotation with other crops 

 which will, by the vegetation which they leave in the soil, or by 

 the culture which the soil receives in growing the crop, increase 

 the available plant food, or in other ways physical and biological, 

 increase the wheat producing capacity of the soil ; or (2) by 

 adding fertilizers in the production of other crops in the rota- 

 tion, the residual effect of which is beneficial to the wheat crop. 

 The best results are obtained in the indirect method when both 

 features are combined in the system of rotation. 



