COMMERCIAL FERTILISERS 393 



chemical analysis of a soil. Both are useful hints, 

 and may point out striking needs or deficiencies, 

 but other factors are much more important. An 

 experiment at the New York State Experiment 

 Station, for example, showed that a fertiliser con- 

 taining nearly the proportions of plant food used 

 by the potato plant was much less useful than one 

 containing very different proportions, based on 

 the experience of observing growers. An abun- 

 dance of phosphoric acid in the soil contributes 

 more to the profitable growth of the cotton crop 

 than either of the other plant foods ; yet an analy- 

 sis of the cotton plant shows that it contains less 

 phosphoric acid than either nitrogen or potash. 

 The needs of the soil and the needs of the crop 

 cannot be studied separately and independently 

 with any degree of satisfaction ; they are coordinate 

 and complementary. 



Crops do differ, however, in their demands upon 

 the soil. A knowledge of the special needs should 

 be helpful to the man who does not have the 

 results of a home fertiliser test to guide him. A few 

 general suggestions follow: 



The small grains wheat, rye, oats, and barley, 

 are especially benefited by an abundance of nitro- 

 gen and of phosphoric acid. The latter is espe- 

 cially needed in the development of grains. 



Indian corn, a very exhaustive crop, is more apt 

 to need applications of the mineral plant foods 

 especially phosphoric acid, than of nitrogen. 



Forage crops, including the grasses and grains 

 grown for forage, but not clovers, are most apt to 

 need nitrogen. 



The clovers, including all legumes, need potash 

 and phosphoric acid, but not nitrogen; they also 

 draw heavily on lime. 



