COMMERCIAL FERTILIZERS 



67 



form. Those which grow slowly and take a long time to mature can 

 utilize the more difficultly available forms of plant food. These facts 

 explain why plants differ in their requirements. 



Fertilizers for Cereals and Grasses. The cereals and grasses (Indian 

 corn excepted) are similar in habits of growth and are distinguished by 

 having extensive, fibrous root systems. They require comparatively 

 long periods of growth, and this enables them to extract mineral food 

 from comparatively insoluble sources. As a rule, however, these crops 

 make the major portion of their vegetative growth during the cool part 

 of the growing season. During this period nitrification is comparatively 

 slow; consequently, such crops need readily available nitrogen and respond 

 to fertilizers containing some nitrogen. This demands the application 



EFFECT -OF COMMERCIAL FERTILIZER ON WHEAT ON A POOR SOIL. 

 A complete fertilizer on the left, no fertilizer in center. 



of nitrogen in a readily available form, preferably just at the beginning 

 of vegetative growth in the spring. 



Legumes Require No Nitrogen. The clovers, peas, beans, vetches 

 and in fact nearly all the crops that belong to the family of legumes have 

 the power under proper soil conditions to utilize free nitrogen from the 

 air; consequently, such crops require no nitrogen in the fertilizer. They 

 use relatively more potash than most other forage crops; consequently, 

 the mineral fertilizers with a rather high proportion of potash are generally 

 most beneficial. Corn is a rather gross feeder, and since it makes the 

 major portion of its vegetative growth in the warmer portion of the grow- 

 ing season when nitrification is especially active, it seldom pays to apply 

 much nitrogen to it. Furthermore, corn is able to make use of relatively 

 insoluble phosphorus and potash. 



