972 Value of Different Crops as Green Manures, [mar., 



yielded 20' 1 bushels; indeed, all the manured plots in this 

 field gave very poor results. 



The following determinations of the percentages of nitrogen 

 in the grain and straw would indicate that the superiority in 

 the yield of the plots on which the vetches and crimson clover 

 had been grown was due to the greater amount of nitrogen 

 there available in the soil, but the general superiority of these 

 plots over the wheat elsewhere must be set down to the better 

 condition of the soil brought about by the accumulation of 

 organic matter. 



Table II. — Quality of Wheat Grown after Green Manuring. 



Previous Green Crop, 



Weight 



per 

 bushel. 



Lb. 



Nitrogen 

 in grain. 

 Per cent. 



Nitrogen 

 in straw. 

 Per cent. 



Ratio of 

 Grain to 

 Straw = 100. 



Ratio of 

 Offal to 

 Dressed 

 Grain = 100. 



I907. 



After mustard 



64*3 



2*065 



0*276 



59'9 



5'o 



I907. 



„ rape 



647 



2'088 



0*267 



56-5 



5'4 



I907. 



crimson clover 



64-5 



2*217 



0'320 



58-0 



14*0 



1907. 



vetches 



64-0 



2- 3 86 



0*441 



61 -3 



8-2 



I9IO. 

 I9IO. 

 I9IO. 

 1910. 



After mustard 



„ rape .., ... 



crimson clover 

 , , vetches 



63-5 

 6 3 -8 

 627 

 62'4 



I -849 

 1-852 



1-888 

 1-953 



0-3162 

 0-3054 

 0-3756 

 0-3595 



74-8 

 74-6 

 66-4 

 58-4 



2*7 

 2-8 

 4 '4 

 5 '9 



The grain and particularly the straw of the wheat grown 

 after vetches and crimson clover are much richer in nitrogen 

 than the corresponding grain and straw following the non- 

 leguminous crops, pointing to a greater amount of nitrogen 

 in the soil available for the former crops. 



Speaking generally, the results are what might have been 

 expected from the known power of the leguminous crops to 

 gather nitrogen from the atmosphere, but until the experi- 

 ments have been repeated for a somewhat longer period of 

 time it will be impossible to determine with any accuracy 

 whether there has been any accumulation of nitrogen in the 

 soil of the plots growing mustard and rape, though these 

 crops are themselves incapable of fixing any nitrogen. One 

 might expect that the soil bacteria, particularly the Azoto- 

 bacter, would increase the nitrogen compounds of the soil 

 when supplied with the carbonaceous matter which the green 

 plant has drawn from the atmosphere. The Azotobacter 



