ORGANIC MATTER AND NITROGEN 219 



plants, as timothy or blue grass, whose roots may come in contact 

 with the decomposing tubercles. In case of the noninfected cow- 

 peas, only 7 per cent of the nitrogen was found in the roots at that 

 stage of growth. 



Pot-culture experiments by the Dominion of Canada Experiment 

 Station, with plants planted May 20 and harvested August 4, 

 showed that very poorly infected horse beans contained 19 per 

 cent of their nitrogen and 18 per cent of their organic matter in the 

 roots, while better infected plants made a larger yield and contained 

 25 per cent of their nitrogen and also 25 per cent of their organic 

 matter in the roots; whereas well-infected mammoth red clover 

 contained 40 per cent of its nitrogen and 35 per cent of its organic 

 matter in the roots. 



In a field experiment with mammoth clover, seeded with barley 

 in the spring and harvested May 25 the following year, the Cana- 

 dian Station found, per acre, 123.8 pounds of nitrogen in the tops 

 and 48.5 pounds in the roots, to a depth of four feet, corresponding 

 to 72 per cent in the tops and 28 per cent in the roots. 



As an average of four determinations with red clover, the Con- 

 necticut Station found 28 per cent of its nitrogen, 35 per cent of 

 its phosphorus, and 21 per cent of its potassium in the roots and 

 stubble. 



As an average of two determinations by the Illinois Station, the 

 red-clover roots found in the surface soil (o to 7 inches) contained 

 25 per cent of the total nitrogen of the plants, while only one per 

 cent of the total was contained in the roots in the subsurface stra- 

 tum (7 to 20 inches). In the case of nearly mature cowpeas, 12 

 per cent of the total nitrogen was found in the surface roots (o to 

 7 inches) , and i per cent in the subsurface (7 to 20 inches) ; and 

 the corresponding figures for nearly mature soy beans were 8 per 

 cent and i per cent. 



In Table 34 are recorded the data from an Illinois investigation 

 of sweet clover, in which determinations were made of the total 

 dry matter and nitrogen; (i) in the tops as they would ordinarily be 

 cut with a mower, (2) in the surface residues, consisting of stubble 

 and fallen leaves and old stems, (3) in the large roots in the plowed 

 soil to a depth of seven inches, (4) in the smaller roots in the 

 plowed soil, and (5) in the roots of the subsurface stratum from 7 



