COMMERCIAL FERTILIZERS 59 



spring than in the fall. Leaching and washing, which are 

 very likely to take place on fall-plowed land, are prevented 

 by a cover crop which is not plowed under till spring. 



68. Commercial Fertilizers. While a leguminous green- 

 manure crop such as those suggested in the previous para- 

 graph will supply nitrogen it is usually necessary throughout 

 the East and South to supply some phosphorus and potash 

 to meet the demands of the corn crop. Quite frequently, a 

 complete fertilizer which contains all three of the elements 

 just mentioned is used. The fertilizer is quite commonly 

 distributed along the row in two applications, the first when 

 the corn is about 2 feet high and the second just before it 

 tassels, though sometimes it is all applied either broadcast 

 before or in the row at the time of planting. The fertilizing 

 materials generally used are cottonseed meal, muriate of 

 potash, and acid phosphate. The quantity which is applied 

 and the proportions of the three constituents vary greatly 

 with the soil on which the crop is grown . The usual quan- 

 tity of the mixture ranges from 300 to 500 pounds, about two 

 thirds of which is put on at the first application. A good 

 corn fertihzer should contain about 8 per cent of phosphoric 

 acid, 5 to 6 per cent of nitrogen, and 5 to 9 per cent of potash. 

 It is not usually profitable to use commercial fertilizers in 

 the corn belt where there is plenty of vegetable matter in 

 the soil, though on some soils which are decidedly deficient 

 in some one element, marked benefit is obtained from it. 



PREPARATION OF THE SOIL 



69. Preparation of Fall-Plowed Sod Land. The abihty of 

 corn to use plant food in a crude form makes it possible to 

 plant it on newty broken sod land. It frequently follows 

 clover or some other hay crop, or is planted on a field that 

 has been in pasture. Such crops leave the land some- 



lAt the present time (1918) the prices of certain fertilizers are so high that 

 thei." use is practically prohibitive. The general use of green manures and the 

 more careful and economic use of barnyard manure is imperative. 



