192 



Journal of Agricultural Research 



Vol. XIII, No. 3 



The comparison of the results obtained by the two methods of de- 

 termining the alkali-soluble humus in this acid soil, and in its fermented 

 mixtures with various organic manurial substances, shows strikingly 

 that more organic material was obtained by the direct solvent action 

 of ammonia (method B) than by washing with weak hydrochloric acid 

 and water for the purpose of breaking up the humate combinations 

 with basic substances and then treating with the dilute ammonia water 

 (method A). The mineral matters associated with the dissolved humus 

 are more abundant with the former treatment than with the latter; 

 but even in the two individual cases where the reverse is true, the direct 

 action of the ammonia removed more organic material. 



From these facts we may conclude that in this acid soil, both un- 

 treated and as modified by fermentations of organic manures applied, 

 very little of the "active humus" is combined with bases; that washing 

 with weak acid and water removes a considerable amount of the or- 

 ganic matter and usually some basic materials. 



It is further clear that the data obtained by these analytical methods 

 are not such as to make it possible to establish a relation between the 

 limestone requirements of the respective soils and a particular fraction 

 of their active humus. 



The facts set forth in Table XVI do not show any noteworthy differ- 

 ence between the soil percentages of active humus in the mixtures ob- 

 tained from fresh as compared with the air-dried manures. 



We may present, however, a comparison from the data of Tables XV 

 and XVI to show the respective proportions in which the total humus 

 in the several groups of manurial mixtures, in excess of that accounted 

 for by the untreated soil, is composed of active humus as determined 

 by the usual method A. The proportion shown by the soil itself is 

 added for further comparison (Table XVII). 



Tabls XVII. 



-Percentage of active kumtis in the organic matter of ike manurial 

 mixtures 



Material. 



Utitreated soil 



Excesses contributed by — 

 Legume green manures: 



Fresh 



Air-dry 



Nonlegume green manures 



Fresh 



Air-dry 



Stable manure 



Poultry manure 



Total 



organic 



matter 



(pounds in 



2,000,00c). 



97. 560 



13, 556 

 14, 660 



13. 59S 



14, 680 



13) 700 



9, 800 



Active 



humus 



(pounds in 



2,000,000). 



24, 600 



4,000 

 3>400 



4, 800 



4, 200 



2, 000 



800 



Percentage 

 of active 



humus in 

 organic 

 matter. 



!5-i9 



29.36 



20. 46 



35- 31 



28.61 



14. 60 



8. 16 



