156 INFLUENCE OF MANURE ON THE SOIL 



increases the bacterial count of the soil. The greatest number of 

 organisms developed from the soil receiving 10 inches of irrigation 

 water. 



The ammonifying power of the cropped soils was slightly lower 

 than similarly treated fallow soils. The application of 5 and 15 

 tons of manure on each acre increases the ammonifying power of the 

 soil. The application of irrigation water up to 30 inches increases 

 the ammonifying power of the soil. The greatest increase resulted 

 in those soils receiving 15 tons of manure to the acre. The applica- 

 tion of 40 inches of irrigation water to corn land, especially to that 

 receiving 15 tons of manure an acre, depresses the ammonifying 

 power of the soil. 



The nitrifying power of fallow soil was higher than similarly 

 treated cropped soils. The application of manure to a cropped soil 

 greatly increases the rate of nitrification. The application of irriga- 

 tion water up to 30 inches, especially to a soil receiving 15 tons of 

 manure, greatly increases its nitrifying power. 



Green manures are rapidly taking the place of bare fallows in all 

 of the better systems of agriculture where the rainfall will permit of 

 the practice. The practice of green-manuring consists, essentially, 

 of the turning under of green crops for the benefit of succeeding 

 crops. In addition to the various legumes, which are preferred on 

 account of their ability to take nitrogen direct from the air, crops 

 like rye, wheat, oats, buckwheat, mustard, rape and even turnips 

 have been used more or less extensively as green manures. 



The plowing under of green manure produces either a beneficial 

 or injurious effect, depending upon the nature of the soil to which it 

 is applied, the kind of manure added, and the season of the year 

 when applied. Some of the beneficial influences noted are: 



1. They carry to the soil large quantities of organic matter which 

 on decaying yield humus, and this in turn changes materially the 

 physical and chemical composition of the soil. Schultz started in 

 1855 on an extremely poor, coarse-grained, sandy soil, and gradually 

 improved it by the use of lime, phosphoric acid, and potash in con- 

 nection with such green-manuring crops as lupines, serradella, and 

 field-peas, until he could produce three hundred to four hundred 

 bushels of potatoes to the acre. Neale noted a marked gain in the 

 yield of corn when crimson clover was used as a green manure. He 

 believed the nitrogen thus applied to be much more economical than 

 when nitrate of soda is used. For sandy soils the results of Delwiche 

 would indicate cowpeas, hairy vetch, soy beans, and crimson clover 

 to be best, and Pfeiffer's results indicate that it is the open, sandy 

 soils which give the best results with green manures. The actual 

 effect produced, however, varies with the time of application. 

 Bassler recommends that where lupines, serradella, crimson clover, 

 and hairy vetch are used for green manure on sandy soils they should 



