EXPERIMENT STATION BULLETINS. 



345 



They usually rot ofif or are broken off at or near the surface of the 

 ground, yet decay takes place at greater depths but to a much less ex- 

 tent depending upon the nature of the soil, that is, whether heavy or 

 light as well as the water content. This is shown in Fig. 1, after Fippin. 

 Decay takes place more rapidly in soils that are devoted to row or tilled 

 crops than it does in those devoted to others. These processes proceed 

 rapidly in fallow land or land not occupied by crops that is stirred fre- 

 quently. 



vV.^^^ 



^Ltrtoce of soil 



/ ■■ ; \ 



"7r^7:j3:j^:^jTrrrrr?r- 



: ///7 SO// sofurored ^ith n^afcr 

 most of if ear 



2. /n c/aij so//, t/i/c// c/ra//^ecf 



3. /f7 //ghf sonc/cy SO//, 



kyef/ (^ro'ryea 



3." 



Figure 1. — The rate of decay of manure and crop residues is controlled by soil texture, moisture 



content and the depth of covering. 



Decay should not be too rapid. If these processes take place too 

 rapidly great losses of nitrogen may take place. This is true because 

 nitrates are readily soluble in or are dissolved by water and thus if 

 not utilized by growing plants they may be washed out of the soil and 

 pass away in the drainage water. We have found for example that 

 they move about quite readily with the soil moisture. Dr. T. L. Lyon 

 of the New York Agricultural College at Cornell University found that 

 heavy land unoccupied by a crop lost 444.8 pounds of nitrogen per acre 

 by leaching, whereas the losses from the same soil when cropped were 

 25. G pounds per acre per year. 



We may say therefore that the presence of vegetable matter in the 

 soil is essential to successful crop production because it is from this 

 that plants obtain much of their nitrogen supply. Moreover tliere are 

 other decidedly beneficial effects such as the improvement of soil tilth, 



