722 EXPERIMENT STATION RECORD, 



and organic matter it was much greater than this, wliile witli soils witli abun- 

 dant aeration it was about tlie same as in sand cultures. 



The influence of organic substances on nitrification and denitrification in 

 cultivated soil, C. Baethel (Meddel. Centralanst. Forsoksv. Jordbruksomrddet, 

 No. 83 (1913), pp. 36, fig. 1; K. Landtbr. Akad. Handl. och Tidskr., 52 (1918), 

 No. 8, pp. 599-632, fig. 1; abs. in Zentbl. Agr. Chem., 43 {1914), No. 6, pp. 372, 

 373). — The author's experiments showed, in conformity with those of Wino- 

 gradski and Omelianski (E. S. R., 11, p. 711), that in the presence of easily solu- 

 ble organic matter nitrification does not take place until the organic matter is 

 completely mineralized. For example, a small amount of dextrose not only 

 hindered nitrification to a marked extent but strongly promoted denitrification, 

 and nitrification did not occur until the dextrose was completely mineralized. 

 A very small amount (0.1 per cent) of dextrose, however, produced the opposite 

 effect, due probably to stimulating action. 



The danger from the harmful effect of organic matter upon nitrification is not 

 considered as great as the investigations of Winogradski and Omelianski would 

 indicate, because soluble organic substances seldom occur in soils in large 

 amounts. The conditions, however, are different in the manure heap, and this 

 accounts for the feebleness or failure of nitrification there. 



The course of nitrification in fallow soil, B. Velbel {Khutor{anin, 1912, 

 Nos. 10, pp. 12-18; 20, 22, 23, 24, pp. 26-28; abs. in Zhiir. Opytn. Agron. {Russ. 

 Jour. Expt. Landw.), 13 (1912), No. 5, pp. 717, 718).— The experiments here 

 reported indicated that the chief factor controlling nitrification in fallow soil was 

 the humus and humus nitrogen content of the soil. Nitrification increased di- 

 rectly with the humus. The largest amount of nitrates observed in these experi- 

 ments (2,137 lbs. per acre to a depth of 14 in.) was found at the beginning of 

 August in a heavy clay chernozem containing from 8 to 10 per cent of humus 

 in the surface soil. Nitrification was found to be greater in early fallow than 

 in late. It was also increased by the cultivation of leguminous plants. 



The first result of the application of manure was to produce a certain amount 

 of denitrification, but later in the summer the nitrification was more rapid in 

 manured soil than in unmanured soil, and the favorable effect of the manure 

 was still noticeable after four years. 



Green manuring experiment, 1912-13, C. M. Hutchinson and S. Milligan 

 (Agr. Research Inst. Pusa Bui. 40 (1914), PP- 31, pi. 1, fig. i).— Field and labora- 

 tory experiments to determine the best stage of growth and methods of turning 

 under green manures, with a special study of the relation of various conditions 

 of soil, rainfall, supplementary fertilization, bacterial activity, etc., to the char- 

 acter of decomposition which takes place, are reported. The experiments were 

 confined to one plant, namely, Crotalaria juncea. 



The results indicated that water was probably the controlling factor in the 

 decomposition and nitrification of green manure in soil. It was found that three- 

 eighths saturation of the soil was the optimum moisture content for nitrification 

 of the green manure under the conditions prevailing in these experiments. The 

 best results were obtained by turning under the plant while it was still green 

 and succulent. With plants 4 weeks old 67 per cent of the nitrogen was nitri- 

 fied, while with plants 10 weeks old only 34.5 per cent of the nitrogen was 

 nitrified. The optimum depth of burying the green manure varied with the age 

 of the plant and probably with the character of the soil and its subsequent 

 treatment, but in general the more mature the plant the less the depth to which 

 it should be plowed under in order to insure nitrification. The optimum mois- 

 ture content, 16 per cent, for carbon dioxid formation was the same as that for 

 nitrification of the green manure. The addition of superphosphate promoted the 

 decomposition of the green manure. 



