FIELD TESTS WITH FERTILIZERS 217 



to a wheat crop grown on a clay soil, or an application 

 of nitrate of soda on land seeded to clover, or of land 

 plaster to flax grown on a limestone soil, would be a 

 useless waste of money. 



277. Proper Use of Fertilizers. — In order to make 

 the best use of commercial fertilizers, both the soil and 

 the crop must be carefully considered. All crops do 

 not possess the same power of obtaining food from the 

 soil ; turnips, for example, have very restricted powers 

 of phosphate assimilation, hence they require special 

 manuring with phosphates. Wheat requires help in 

 obtaining its nitrogen. A wheat crop will starve for 

 the want of nitrogen, while an adjoining corn crop will 

 scarcely feel its need. Wheat has strong power of 

 assimilating potash compounds, while clover has less. 

 Hence in the proper use of fertilizers the power of the 

 plant to obtain its food must be considered. An 

 application of potash to clover, nitrogen to wheat, and 

 phosphoric acid to turnips, would be a judicious use of 

 these fertilizers, while if a mixture of the three ele- 

 ments were applied to each crop alike, the clover 

 would not be particularly benefited by the nitrogen 

 or the wheat by the potash. Before commercial fertili- 

 zers are used, careful field trials should be made with 

 different crops. 



FIELD TESTS WITH FERTILIZERS 



278. Experimental Plots. — A piece of land well 



