190 



Journal of Agricultural Research 



Vol. XIII, No. 5 



Considering the fresh and air-dried green-manure mixtures as two 

 groups, we find, if we include in these groups only those materials repre- 

 sented in both series, these differences: 



Excess of organic matter over soil 



Per cent 



Pounds in 2 ,coo,ooo 



Loss by soil fermentation : 



Poimds in 2,000,000 



Per cent 



Apolied 

 fresh. 



0.679 



73, 580 



22, 083 

 61. 91 



Applied 

 air-dry. 



O- 734 

 74, 680 



20, 976 

 58.63 



That is, at the end of nine months there was lost by fermentation 

 about 1,100 pounds more of the organic matter applied in a fresh green 

 state than in an air-dried green state. This amounts to but 3.3 per cent 

 of the total application of organic matter. The delayed fermentation 

 of the air-dried material, the rather marked effect of which fermentation 

 difference with respect to both limestone requirement and nitrate devel- 

 opment has received earlier comment, resulted finally in much less dif- 

 ference in total decomposition than might have been forecast from the 

 soil acidity and nitrification differences. 



Several years ago in studying the grass roadways bounding the several 

 tiers of the General Fertilizer Series of plots, it was found that these 

 roadways differed much in their lime requirement, and that in each 

 instance the lime requirement bore a fixed ratio to the amount of the free 

 humic acid — that is, that portion of the humus that was soluble directly 

 in weak alkali without the previous removal of lime, etc., by acid washing. 

 The constant ratio observed in that grass-land soil was 11.27 of the free 

 humic acid to i of lime. 



To determine whether these green-mianuring soils would exhibit a like 

 condition with tlie grass lands mentioned above and also more generally 

 to ascertain whether the humus of the several green-manuring soils, as 

 they existed nine months after the application of the manures, was 

 possessed of peculiarity in the proportion of alkali-soluble humus — some- 

 times called "active humus" — this group of constituents was determined 

 by a modification of the McBride method in which the filtration of the 

 alkaline liquid was performed by the aid of Chamberland-Pasteur filters, 

 which effectually remove suspended matters and yield a clear filtrate. 

 The weakly alkaline solution was made to act upon the soil in two con- 

 ditions: 



A. — Ten gm. freed from basic materials by washing with i per cent 

 of hvdrochloric acid and then with water w^as shaken for 15 hours in a 

 Wagner shaking apparatus with 1,000 c. c. of 4 per cent ammonia water, 

 the suspended matter allowed to settle, the overlying liquor then filtered 

 in the manner just stated, and an aliquot of the filtrate evaporated in a 

 weighed platinum dish and dried at 103° C. for four hours. The material 



