212 SOILS AND FERTILIZERS 



crops as wheat and corn, in the western prairie states, 

 they have tfot as yet been used. If there is a good 

 stock of natural fertility, the soil is well tilled, farm 

 manures are used, and crops systematically rotated, the 

 use of commercial fertilizers can be avoided. With 

 poor cultivation and a soil that has been impover- 

 ished by injudicious cultivation their use is more 

 necessary. Commercial fertilizers sometimes fail to 

 give beneficial results, because of either an excessively 

 acid or alkaline condition of the soil. 



289. Amount of Fertilizer to Use per Acre. When 

 commercial fertilizers are used, it should be the aim 

 in general farming to apply just enough to produce 

 normal yields. Heavy applications at long intervals 

 are not as productive of good results as light applica- 

 tions more frequently. From 400 to 600 pounds per 

 acre is as much as should be used at one time unless 

 previous trials have shown that heavier applications 

 are necessary. The way in which the fertilizer is to 

 be applied, as broadcast or otherwise, must be deter- 

 mined by the crop to be grown. The fertilizer should 

 not come in direct contact with seeds, neither should 

 it be plowed under or worked into the soil to such a 

 depth that it may be lost by leaching before it can be 

 appropriated by the crop. 



290. Excessive Applications of Fertilizers Injuri- 

 ous. An overabundance of plant food has an inju- 

 rious effect upon crop growth. Plants take their food 

 from the soil in dilute solutions, and when the solu- 

 tion is concentrated abnormal growth results. Pota- 



