1096 AGRICUI^TURAIv BOTANY, CHEMISTRY AND PHYSIOI.OGY OF PI^ANTS 



852 - Amount of Humic Substances in Decomposing Leaves (i,aboratory of Scientific 



Agriculture of the University of Petrograd). — TrusovA. C, in Cf.thcKOc Xo3fiiicm60 

 i( Jliufoiiodcmeo (Agriculture and Sylviculture), Vol. CCIy. year I<XXVI, pp. 339-3G1. 

 Petrograd, March 191 6. 



Contintung his researches into the huniilication of the elements which 

 constitute the vegetable organism (i), the writer now communicates the 

 restilts of his experiments into the quantity of humus soluble in water and 

 dilute ammonia, produced in the leaves of maple and birch in decomposi- 

 tion ; the influence of the conditions under which decomposition takes place ; 

 a comparison between the two methods of determination of humic substances, 

 namely the colorimetric method and the permanganate of potash method ; 

 and the composition of the humic substances extracted from the decompos- 

 ing leaves ; finally he also gives the conclusions drawn on the basis of these 

 experiments. 



In these investigations, maple and birch leaves were employed. The 

 maples leaves were chosen on account of their richness in tannic substances, 

 which, as is proved by the writer's early work, should play an active part in 

 the formation of humus. 



The leaves were taken in September, that is, when already 5^ellow ; 

 a number of them were taken from the tree, so as to have a product not 

 far advanced in decomposition, and the rest were gathered from the ground 

 a order to secure the bacterial flora, which, under normal conditions, plays 

 a part in the decomposition of maple leaves. For some days, the leaves ga- 

 thered were dried at a temperature of 15-17"^ C,, 5 grms by weight were then 

 put into each capsule, and 15 cc. of water added every day for a period of 

 40 days, in order to keep the conditions of decomposition constantly favour- 

 able ; after this first period, during the following 60 days, only 10 cc. of 

 .water were added, with a view to avoiding excessive moisture, as about one- 

 third of the leaves were already decomposed ; on the expiry of 100 days 

 only 5 cc. were added. In spite of the addition of this large quantity of 

 water, it may be assumed, in view of the constant temperature of 37° C. 

 that the decomposition of the leaves takes place under the conditions in 

 which it would occur in the case of incomplete water saturation of the 

 leaves, the saturation really only having been complete for a comparatively 

 short time in these experiments. In addition to distilled water, the 

 leaves were, in order to allow of inoculation by their respective micro- 

 organisms, wetted occasionally with some drops of water in which leaves 

 decomposed on the ground had been steeped, the said leaves having been 

 taken from the same tree as those tised for the experiment. 



The decomposition of these latter was carried out in an incubator at 

 a constant temperature of j(>-37" C. , which was selected in order to hasten the 

 process in question. 



The determination of the humic substances was made after 4,8, T2, 16, 

 25,40,66 and 100 days from the start of the experiment. Each time 4 dishes 

 were taken, two for ascertaining the quantity' of dry matter and, after- 



(i) .See P>. 1913, Nos. 347, 888 and 1123 ; J^- January 1916, No. 11. {Ed.) 



