FIELD TESTS WITH FERTILIZERS 223 



growth is obtained, and a better yield is the result. 

 Heavy applications of nitrate of soda produce a rank 

 growth of straw, with a low yield of grain. The ex- 

 cessive amount of nitrogen causes the mineral matter 

 to be utilized for straw production and leaves only a 

 small amount for grain production. When applica- 

 tions of commercial fertilizers are too heavy, plants 

 take up unnecessary amounts of food and fail to make 

 good use of it. In fact crops may be overfed the 

 same as animals. Hence in the use of fertilizers ex- 

 cessive applications are to be avoided. 



288. Fertilizing Special Crops. — There are crops 

 which need special help in obtaining some one ele- 

 ment, and in the use of fertilizers it should be the rule 

 to help those crops which have the greatest difficulty 

 in obtaining food. When the soil does not show a 

 marked deficiency in any one element, light dressings 

 of special purpose manures may be made to the follow- 

 ing crops : 



Wheat. — Nitrogen first ; phosphoric acid to a less 

 extent. 



Barley, oats, and rye require manuring like wheat, 

 but to a less extent. Each crop has a different power 

 of obtaining nitrogen. Wheat requires the most help 

 and barlev and rve the least. 



Corn. — Phosphoric acid first ; then nitrogen and 

 potash. 



