812 EXPERTATF.I<rT STATTO^"■ EEOOP.D. [Vol. 41 



Biological studies of bliatta soils containing al)Out 69 per cent of stones and 

 gravel show that this soil is quite efficient in the production of carbon dioxid 

 and also in ammoniflcation. The rate of nitrogen fixation is, however, about 

 half of what takes place In black cotton soil. "Nitrification, though not as 

 good as the black cotton soil, can still safely be classed as average. ... It 

 was found that the gi'owth of plants in bhatta soil was very much inferior to 

 those from black cotton soil ; and that the former had a very poor development 

 of root nodules. This effect was not, however, so much noticed in the case of 

 groundnut crop. Subsequent pot culture experiments on sann hemp alone have 

 conclusively shown that inoculation of the bhatta soil with black cotton soil 

 shows much improvement in the growth of the plants, and that inoculation 

 combined with a dressing of til cake ... at sowing time gives most promising 

 results." 



Cultures of bacteria on sterilized soil, C. Babthel {Meddel. K. Vetensk. 

 Akad. Nobelinst., 5 (1919), No. 20, pp. IS, pi. 1). — Studies are reported on the 

 growth of pure cultures of different organisms introduced into garden soil 

 rich in organic matter and containing some sand which was previously 

 sterilized in the autoclave. The organisms tested were Azotohacter chroo- 

 coccum., Bacteritim, radicicola, Strejitococciis lactls, Bactentmi easel, and Ba- 

 cillus mycoldes. 



It was found that in most cases these organisms, when introduced in pure 

 culture into the sterilized soil, grew and developed much more easily and better 

 than in crude unsterilized soil. These results are considered to be of some sig- 

 nificance from the soil fertility standpoint. 



Nitrification in Egyptian soils, J. A. Prescott (Jour. Apr. Sci. [England'], 9 

 (1919), No. 3, pp. 216-236). — Two years' study on the biological conditions of 

 the soil of an Egj-ptian farm, with special reference to nitrification, ai'e re- 

 ported. The soil was typical of the Nile alluvium. 



It was found that in all cases the moisture content of the soil limited biologi- 

 cal processes more than any other factor. " There was observed throughout 

 the season in a cotton field a relatively large amount of nitrate, more than 

 sufficient for the immediate needs of the cotton plant. The lack of response on 

 the part of the Egyptian cotton crop to nitrogenous fertilizers may be ac- 

 counted, for in part, if not entirely, by the fact that nitrification in the soil is 

 well ahead of the needs of the crop." There was no accumulation of nitrate 

 in soil under wheat and maize. 



It is thought that the period of winter fallow, during which the soil de- 

 pends for its water only on the rainfall, may be a period of steady nitrification 

 when the amount of rainfall is sufficiently high. The summer fallow soils 

 immediately after removal of the winter crops were found to be biologically 

 dormant. They were characterized by very low moisture content and by fairly 

 high temperatures. 



I'ot experiments with wheat and maize showed that the root activities of a 

 growing crop have some limiting effect on the production of nitrate in the soil 

 In both cases the fallow pots accumulated appreciably more nitrate than the 

 cropped pots. 



The relationship between contraction and the percentage of colloidal clay 

 (West Indian Bui.. 11 (1918), No. 2, pp. 113-118, fig. /).— Studies on the amounts 

 of internal pore space existing in blocks of 16 different soils which have been 

 allowed to contract to the full extent and from which any residual water has 

 been removed by subsequent drying to a constant weight at ]10° C. are 

 reported. 



Comparison of these amounts with the observed value for linear shrinkage 

 showed that a linear relationship appears to exist between the two values. 



