SOILS FERTILIZEES. 19 



available nitrogen and thus decreased crop yields. Liming of an upland moor 

 soil which had been fertilized with sodium nitrate caused a biological or 

 biochemical decomposition of the nitrate, a part of the nitrogen of which was 

 made unavailable to plants purely by denitriflcation and part by biological 

 reduction of the nitrate to nitrite and by chemical decomposition of the nitrite, 

 accompanied by nitrogen losses and transformation into insoluble organic forms. 



It is generally concluded that the injurious action of the larger additions of 

 lime to upland moor soils resulting in decreased crop yields can be attributed 

 mainly to a gradual increase in the number and activity of soil bacteria with 

 increasing decomposition of the soil. 



Experiments on the action of certain humus preparations, particularly the 

 so-called humus silicate, on plant growth, E. Haselhoff {Landw. Jahrb., 1ft 

 {1914), No. 3, pp. 345-369). — The work of others bearing on the subject is 

 briefly reviewed and pot culture and field experiments to determine the fertiliz- 

 ing value of the so-called humus silicate fertilizer, alone and mixed with 

 different other fertilizers, are reported. The humus silicate is a specially pre- 

 pared fertilizer, consisting of moor soil, treated with caustic soda or potash, 

 and alkaline silicates. 



It was found in pot experiments that additions of humus silicate slightly 

 increased the yield of barley on sand soil and of buckwheat on a loam soil, and 

 increased the silica content in the straw of barley from sand soil. The humus 

 silicate had no effect on beans on sandy loam soil and only a slight favorable 

 effect on wheat. Additions of humus silicate to wheat increased the nitrogen 

 content of both grain and straw, but had no effect on oats. Evaporation was 

 less in uncropped soil treated with humus silicate than in untreated soil, and 

 the water utilization by wheat was greater in treated than in untreated soil, 

 while the opposite was true for oats. Pot experiments with oats on a loamy 

 sand soil, with barley on loam and sand soils, and field experiments with beets, 

 in all of which mixtures of humus silicate and other fertilizers were used, 

 showed that the humus preparations had no special effect on the composition 

 of the crops, especially with reference to nitrogen. 



Further experiments on the formation of carbon dioxid from humus prepara- 

 tions in a medium heavy clay soil showed that the humus preparations con- 

 tributed but little to carbon dioxid formation in soil and that the treatment 

 of the organic matter of the preparation by alkalis had, in a large measure, 

 prevented carbon dioxid formation. 



From these experiments it is concluded that humus preparations are effective 

 as fertilizers only to the extent to which they contain plant food and that the 

 humus content is of no special value. 



Sulfofication in soils, P. E. Brown and E. H. Kellogg {loiva Sta. Research 

 Bui. 18 {1914), pp. 49-111; Centbl. Bakt. [etc.l, 2. AM., 43 {1915), No. 19-24, 

 pp. 552-601). — This bulletin reports investigations on bacterial action in soils 

 in its relation to sulphur oxidation in the soil and on methods of measuring 

 such bacterial action and determining the sulphate content of soils. 



Preliminary tests showed that the sulphates in soils are not completely ex- 

 tracted by dilute hydrochloric acid because of the interference of organic sub- 

 stances and iron compounds but may be extracted by shaking for from 6 to 8 

 hours with water. Grinding the soil was found to be unnecessary for this 

 purpose, although the finer the soil the more readily were the sulphates dis- 

 solved. Calcium sulphate was the most difficult of the sulphates to dissolve, but 

 it was dissolved quite readily upon shaking with water for the time specified. 

 The sulphur photometer proved to be well adapted to the determination of 

 sulphates in soils. 



