1917] SOILS FERTILIZERS. 217 



The increase of nitrogen in fermenting manures, W. E. Tottingham {Jour. 

 Biol. Chem., 24. (1916), No. 3, pp. 221-225; abs. in Chem. Abs., 10 (1916), No. 14, 

 p. 1901). — Experiments conducted at the Wisconsin Experiment Station are re- 

 ported on the increase in nitrogen content of a mixture of fresh cow and horse 

 manure mixed in the ratio of 2:1, with and without fine and coarse chopped 

 wheat straw at rates of 0.5 and 6.25 kg. per 6.25 kg. of manure. 



After four weeks it was found that there was an appreciable gain of nitro- 

 gen in the straw-littered manures. Further tests of the manures for nitrogen 

 fixation in mannite solution showed that " the manures contain nitrogen-fixing 

 organisms of considerable activity. As their activity was greatest in the fer- 

 mentation experiments in those manures which were mixed with straw, the 

 latter material appears to be an important source of energy for the organisms." 



The action of barnyard manure and commercial fertilizers, P. Wagner 

 (Arb. Deut. Landtv. GcscU., No. 279 (1915), pp. 544). — This is a report of re- 

 sults of a series of cooperative experiments extending from 4 to 14 years. They 

 included 20 series of rotations varying in length from 3 to 14 years. The series 

 were divided into two groups, one with commercial fertilizers alone and the 

 other with the addition of manure. The soils varied from sand to clay loam. 

 The crops grown included potatoes, beets, winter rye, winter wheat, barley, oats, 

 and clover. The general plan and methods of conducting the experiments were 

 substantially the same as in previous experiments reported by the author. Ex- 

 perimental data are given in detail and carefully summarized and analyzed. 



Among the conclusions reached are that $100 expended for fertilizers pro- 

 duced an average increase worth $210 in the series of experiments with commer- 

 cial fertilizers alone and $190 in the series in which manure and fertilizers were 

 combined. 



It was found to be necessary to apply phosphoric acid in the form of Thomas 

 slag in great excess, namely, six to seven times as much as the increased yields 

 contained in order to meet the crop requirements for this constituent. Only 18 

 per cent of the citric acid-soluble phosphoric acid in the slag applied was recov- 

 ered in the crops in the course of three rotations on a soil very deficient in phos- 

 phoric acid. The assimilation of the phosphoric acid increased from year to 

 year with continued applications of slag, reaching its normal level in about 

 seven years. The phosphoric acid of manure was much more quickly utilized by 

 plants than that of Thomas slag, the ratio being 100 : 181 in the first rotation 

 and 100 : 172 in the second. 



Of the potash applied in form of potash salts 34 per cent was utilized in the fii-st 

 rotation and 51 per cent in the course of the two rotations. The author concludes 

 from these and previous experiments that not more than 60 per cent of the potash 

 applied is likely to be utilized under any circumstances in practice. The potash 

 in manure appeared to be somewhat more quickly utilized by plants than that 

 of Stassfurt salts. For example, 34 per cent of the potash of the Stassfurt 

 salts as compared with 40 per cent of the potash of manure was utilized in the 

 first rotation. On the other hand, the corresponding figures for the second rota- 

 tion were 51 and 52 per cent. 



About 60 per cent of the nitrate nitrogen applied was utilized by the crops, 

 but only 25 per cent of the manure nitrogen was utilized in the first rotation. 



The avei'age figures for the utilization of the fertilizing constituents of manure 

 and commercial fertilizers by crops may be summarized in brief as follows : 



