1920] SOILS FERTILIZERS. 213 



lS7-l.'i9). — Studies on the comparative rate of deconipositlon of preen and of 

 cured red clover tops in soil, conducted at the University of Illinois, are reported. 

 Curing retarded the rate of decomposition as measured hy ammonification, 

 nitrification, and loss of carbon in both laboratory and greenhouse experiments. 

 The green clover produced nitrate very rapidly, with a niaxinuun transformation 

 in the laboratory experiment at 43 days of 3r).S per cent, while with the cured 

 clover at the same period only 15.7 per cent of the nitrogen had been transformed. 

 In the greenhouse experiment the green clover was well in the lead in nitrate 

 production during the first two months. Greei\ and cured red clover underwent 

 the same kind of decomposition under aerobic conditions. With the oxygen sup- 

 ply limitetl, the types of decomposition of green and cured red clover were vastly 

 different. Tliere was no measurable loss or gain of nitrogen during the experi- 

 ment. The loss of carbon and the change in the carbon-nitrogen ratios agreed 

 with the other determinations in showing a difference in rate of decomposition 

 between the green and the cured clover, but did not indicate a difference in kind. 

 Tlie change which dehydration (curing) brought about in the rate of the 

 Initial decomposition appeared to be of a physical nature only. An explanatory 

 hypothesis is advanced that dehydration resulted in a hardening and shrivel- 

 ing of the tissues, which interferes with the reentrance of water and conse- 

 quently delays the decomposition because the bacteria must await the soften- 

 ing of the tissues before they are able to start their work, while with the green 

 no such delay occurs, as the cells are already hydrated. Planting oats three 

 days after treating the soil with green and cured clover resulted in serious 

 Injury which delayed growth. It was greater with the green clover. 



Determination of the degree of decomposition of moor and peat samples, 

 G. Kki'pki.eu {Mitt. Ter. Ford. MoorkuU. Dvut. Reiche, 38 {1920), No. 1, pp. 

 iS).—X method for the determination of the degree of decomposition of peat 

 and moor soils is described, which is characterized as the percentage of total 

 reducti(»n process. 



Tests of this method with different peat and moor soils, including two samples 

 of brown coal, are reported, which show that sphagnum peats of recent origin, 

 particularly the varieties which are used for peat litter, have a very low 

 degree of d(>composition which hardly exceeds 25 per cent, or, in other words, 

 iiliproximately 75 per cent of the original plant substance still exists in the 

 peat. Samples of sphagnum peat of more ancient origin were much more 

 strongly decomi)osed, the degree of decomposition varying between 70.9 and 

 Ts.s per cent. Lowland moor soil samples also showed a rather high degree of 

 'leconiposition which increased with the depth. Brown coal showed an almost 

 lix) per cent degree of decomposition. Studies of a profile of a large moor were 

 made for purposes of comparison, which gave approximately the same results. 



It is concluded that while the method used needs considerable further testa 

 with different kinds of peat, it has considerable usefulness and will give results 

 which can answer numerous questions. 



The humin acids, S. t)nf:N {KoUoidchcm. Bcihefte, 11 {1919), No. 3-9, pp. 

 ';'>-2(;0, fif/.s. 21). — The author in this work attempts to summarize the chem- 

 istry and physical chemistry of the natural human acids, especially as they are 

 ihought to exist in soils. The first part deals purely with the chemistry and 

 lihysics of humin acids, and the second part takes up these acids with reference 

 to the formation of humus in soils. 



It is maintained that humin acids are an essential constituent of the materials 

 of soils characterized as hunuis, and in this respect play an important part as 

 a result of their acid nature and their individual physical characteristics. It 

 is slated that they are relatively easy to isolate in a lair blate of purity. At- 



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