210 



SOILS AND FERTILIZERS 



desired. During the first few years after setting out, there 

 should be a liberal supply of nitrogen. An acre of apple 

 trees in bearing removes as much plant-food material from 

 the soil in one season as does an acre of wheat. Green- 

 manures may be used to advantage in orchards, as by plant- 

 ing these crops in midsummer, moisture is removed from 

 the soil and the wood of the trees is thereby hardened and 

 thus prepared to withstand the low temperatures of winter. 

 The green-manures also hold snow on the ground, if allowed 

 to stand over winter, and may then be plowed under in the 

 spring. 



268. Fertilizer mixtures for different crops. — On ac- 

 count of the large number of factors that enter into the pro- 

 cesses of crop production, it is obviously impossible to pre- 

 scribe accurately the proportion and quantity of fertilizer 

 carriers that should be applied. Some rough approximation 

 can, however, be arrived at on the basis of the peculiarities 

 of the various classes of crops that have just been enumerated. 

 It must be remembered that different soil conditions may 

 materially change the proportions of the fertilizer ingredi- 

 ents that should be applied. The following proportions of 

 nitrogen, phosphoric acid and potash for different classes 

 of crops have been proposed and have been found a fairly 

 useful guide in the home mixing of fertilizers. 



Table 43. — Fertilizer Formulas for Different Crops 



