1918.1 SOILS FERTILIZERS. 623 



The average loss of carbon from tlie clover left on the surface was 48.38 per 

 cent, and from that incorporated in the soil 34.26 per cent. A previous experi- 

 ment showed losses of G6.05 and 28.45 per cent, respectively. No loss of 

 nitrogen was indicated where the clover was incorporated with the soil, and 

 although some nitrogen leached out of the clover applied to the surface of the 

 soil, it was nearly all retained in the soil beneath. 



Comparing the results of these experiments with those of previous experi- 

 ments with manure, it is concluded that, eliminating " the comparatively small 

 amount of fertilizing elements lost in metabolic processes when feeding clover 

 to farm animals, and considering the carbonaceous matter only, there is little 

 to be gained by plowing the crop under, as compared with feeding it and apply- 

 ing the manure. . . . 



" While it is advisable to grow cover crops to be plowed under in the spring, 

 in order to conserve the nitrates formed in the autumn and early spring, it is 

 doubtful whether it pays to grow a crop during the summer months for green 

 manuring, except when it could be used to good advantage for feeding purposes 

 and the organic matter returned to the soil in the form of manure." 



Decomposition of green and stable manures in soil, R. S. Potteb and R. S. 

 Snyder (U. S. Dcpt. Agr., Jour. Agr. Research, 11 (1911), No. 13, pp. 677-698, 

 figs. 9). — This paper is the third of a series of reports of investigations on 

 this subject made at the Iowa Experiment Station (E. S. R., 38, p. 118). 



The conclusions reached from experiments with stable and green manures 

 applied in dry and ground condition are that " lime in the form of a carbonate 

 under the conditions of this experiment appreciably enhances the rate of decom- 

 position of both original soil organic matter and the organic matter of stable 

 manure and the green manures, oats and clover, when added to soil. Two 

 of the more important results of this are the increased availability of plant food 

 and the more rapid depletion of the soil organic matter. This latter effect 

 would be partially and perhaps entirely offset by the fact that with lime larger 

 crops could be grown which would give more organic matter to return to the 

 soil. The green manures, oats and clover, under the conditions of this experi- 

 ment are decomposed much more completely than stable manure. Clover is 

 decomposed somewhat more rapidly . than oats. Stable manure increases the 

 rate of decomposition of gi-een manure when used in connection with the latter. 

 Both stable and green manures act as conservers of lime." 



In experiments in which the green manures and stable manure were applied 

 in the fresh condition, the decomposition of the original organic matter in the 

 soil was increased and that of the added manure decreased by liming. The 

 net result, however, was an increased decomposition due to liming. 



" The carbon of stable manures is evolved as carbon dioxid from soil under 

 unlimed conditions to the extent of approximately 55 per cent. The cjtrbon of 

 oats under like conditions is evolved to the extent of 79 per cent and that of 

 clover 95 per cent. Under unlimed conditions the amount of stable-manure 

 carbon evolved is only slightly less than under limed conditions, while only 

 about 57 per cent of the carbon of oats and 53 per cent of the carbon of clover 

 is given off under limed conditions. All the manures tended to conserve the 

 lime. Under unlimed conditions stable manure did not increase the rate of 

 decomposition of the green manure as measured by the evolution of the carbon 

 dioxid. With lime there was a slight increase in the amount of carbon given 

 from the green manure when used with the stable manure over that given by 

 the green manure when the latter was used alone. It should be recalled that 

 in the former experiment stable manure enhanced the rate of decomposition of 

 the green manure only to a slight extent. There is not a very great difference 



