196 Journal of Agricultural Research voi. xm, no. 3 



products at the time when the experiment ended. Under these condi- 

 tions the red clover did not develop at any time a neutral soil; and at the 

 end of the experiment all the mixtures, except that with red clover, had 

 a greater limestone requirement than the soils alone exhibited. 



V. — EFFECTS OF THE ORGANIC MANURES UPON THE AMOUNT AND CONDITION OF THE 

 HUMUS SUPPLY OP THE SOIL 



(18) The organic matter of the soil is the net result of manured and 

 crop-root additions and the fermentative decomposition subtraction. 

 With open soil, good moisture supply, summer temperature, and vigorous 

 bacterial life, the additions may be matched by a greater subtraction, 

 with no permanent gain in humus as the result. In the case of this silty 

 loam, with such lime deficiency as is usually accompanied by a lowered 

 activity of the fermentative soil organisms, a less rapid destruction of the 

 organic matter should be expected. 



(19) In every case the soils mixed with the various organic manures 

 showed, nine months afterward, larger quantities of organic matter than 

 the untreated soil. 



(20) The amounts of these excesses vary much with the individual case, 

 but on the average the amounts for legumes and nonlegumes, green 

 manures and stable manures are well within the limits of analytical error. 

 Soybeans, rape, alfalfa, and poultry manures left the smallest residues; 

 red clover, rye, timothy, and redtop the greatest. The figures for the 

 red clover residue, like those for its limestone requirement, are so peculiar 

 that, although the results have been confirmed by repeated analyses, 

 repetition of the experiment seems needful to establish their full correct- 

 ness. 



(21) The absence of a determination of total organic matter in the soil 

 at the beginning of the experiment makes impossible the calculation of 

 the total quantity lost by the soil and its mixtures during the experiment. 

 By comparing the amounts in the mixtures in excess of that in the un- 

 manured soil, at the end of the experiment, with the organic matter 

 added in the manures, the amounts and proportions of the destruction of 

 the added organic supplies can be approximated. This comparison indi- 

 cates that, in the cases of the poultry manure and of the average green 

 manures applied in a fresh condition, three-fifths of the added organic 

 matter was destroyed by the soil ferments during nine months, while of 

 the organic substance of the stable manure, partly rotted when applied, 

 little more than two-fifths was destroyed. The largest proportion of 

 destruction was 72.8 per cent in the case of rape; the lowest — omitting 

 the peculiar red clover results from consideration — was 50.8 per cent in 

 the case of rye 



(22) These residual organic decomposition products, each considered 

 as a whole, have no specific effect upon lime requirement, for while all 

 the mixtures held at the close of the experiment more organic matter 



