SOILS — FERTILIZERS. 821 



"The relatlou of meteorological conditions to the rate of loss of soil water is 

 important, but somewhat obscure. Temperature is probably the most important 

 factor; then sunshine; and then relative humidity. 



"The larj;er the percentage of water in the first foot, the more rapidly is 

 water drawn from the soil. This is probably due in part to the larger develop- 

 ment of plant roots near the surface. 



" Early maturing crops cause the highest rate of loss of soil moisture. Dif- 

 ferent crops leave different percentages of water in the soil at the time of har- 

 vesting. 



" The rate of loss of soil water varies with the age of the crop. Less water 

 is used during the early and late periods than during the middle one. 



" When water is abstracted from a soil, the loss is felt by every foot to the 

 depth reached by the augers. 



"When a i)ractical irrigator declared irrigation to be necessary, the soil was 

 found to contain from year to year about 1.*? per cent of water." 



The biochemical relation of phosphoric acid in the soil, Mxjlleb {Mitt. 

 Dent. Landw. Gescll, 21 (1912), No. 33, pp. .',70, .',12. .'/7,i).— This is a review of 

 the work of vStoldasa {Yl S. R., 25, p. 624) on this subject. 



Soil conditions and plant growth, E. J. Russell {'New York. Bombay, and 

 Calcutta, 1912, pp. VIII+KiH, /ifj.s. 0). — This treatise by the former soil chemist 

 and present director of the Rothamsted Experimental Station, is one of the 

 series of monographs on biochemistry edited by R. H. A. Plimmer and F. G. 

 Hopkins. Its finrpose is to give a concise and orderly account of the present 

 knowledge of the soil as a medium for plant life. It is a comprehensive critical 

 survey of the literature of this subject, and while presenting the gist of the 

 more important and fundamental contributions to the knowledge of the subject, 

 points out what has really been demonstrated and in what directions further 

 investigation is necessary. The book is therefore of special value to the 

 investigator. 



The first chapter is historical .-md introductory, others deal with the require- 

 ments of plants, the constitution of tha soil, the carbon and nitrogen cycles in 

 the soil, the biological conditions in the s^oil, the soil in relation to plant growth, 

 and soil analysis and its interi)retalion. An appendix gives methods of soil 

 analysis and a select bibliography of the subject. 



Some observations on the effect of soil aeration on plant growth, C. 

 HuNTEK {Proc. Univ. Durham Phil. Soc, .', (1911-12). No. .',, pp. 183-1 Sli, pis. 

 2). — Observations on the growth of sunflowers, peas, wheat, and cress in soils 

 of five different textures with and without artificial aei'ation are reported. 

 Observations were also made on the varying moisture and bacterial contents 

 and on the resistance of the soils to the movement of air. 



The results indicated an optimum amount of circulation of air in tlic soils 

 for different kinds of plants. "The circulation of the air in the soil affects 

 the development of the root system and through that the development of the 

 subaerial portions of a plant. The production of artificial air currents in the 

 soil appears to be beneficial to plant growth. This point is at present under- 

 going further investigation." 



The relation of different systems of crop rotation to humus and asso- 

 ciated plant food, G. W. Walker (Minnesota Sta. Bui. 128, pp. 165-186).— The 

 author reviews investigations by others on the physical and chemical proper- 

 ties of, and methods of determining, humus and in continuation of previous 

 work by Hays (E. S. R., 20, p. 4.3.5), reports a study from 1S95 to 1905 of the 

 changes produced in humus and of the proportion of the total nitrogen, phos- 

 phoric acid, and potash associated with the humus in soil of plats under known 

 cropping and fertilizer systems. The term humus is used by the author to 



