CHAPTER XVI 



THE USE OF FERTILIZERS 



We have seen that a very considerable economy in the 

 purchase of fertilizers may be effected through a knowledge 

 of their composition. There is still further opportunity 

 for both economy and profit through a study of their use. 



261. Fertilizers for different crops. — It has already been 

 pointed out that there is a difference in the ability of plants of 

 different kinds to extract nutriment from the soil. Some 

 crops are able to draw abundant nourishment from soils 

 from which others derive but little. This may be due, in 

 part, to (1) a deficiency in the soil of the particular sub- 

 stance most greatly needed b,y the crops, or (2) the inherent 

 ability of one crop to make available plant-food materials, 

 while another crop may possess that quality in much less 

 degree. There are therefore two ultimate considerations 

 in the selection of fertilizers : (1) the nature of the soil ; 

 (2) the kind of crop. The second of these will be discussed 

 first. 



262. Small grains. — Most of the small grains, like wheat, 

 rye, oats and barley, need the principal part of their nitrogen 

 early in the season, before the soil has warmed sufficiently 

 to induce the germs that produce nitrates to lay up an abun- 

 dant supply. Consequently the application of nitrate of \ 

 soda, when growth begins in the spring, is very beneficial 

 to these crops. Wheat in particular needs such an appli- 

 cation. Since it is a " delicate feeder " it grows best after 

 fallow, or a cultivated crop, and when it follows oats, as is 



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