Maech 20, 1914] 



SCIENCE 



423 



Dr. Otto Klemm, docent at Leipzig, has 

 been appointed professor of psychology in 

 Alberta University, Edmonton, Canada. 



Dr. Karl Hesoheler has been appointed 

 professor of zoology and anatomy at Zurich, to 

 succeed Professor A. Lang, who retires from 

 active service. 



Professor Axbert Bushnell Hart has been 

 selected by the German government as Har- 

 vard exchange professor at the University of 

 Berlin for the academic year 1914^15. 



DISCUSSION AND COEBESPONDENCE 



the relative importance of sulphates and 



phosphates in soils 



It has been demonstrated by a number of 

 investigators^ that the total sulphur content 

 of soils is generally low, the amount usually 

 not exceeding 1,000 pounds in an acre surface 

 foot. Further, it has been shown that an equal 

 mass of soil will contain quite as much and 

 very often a greater quantity of phosphorus. 

 Another fact of equal importance and which 

 has been abundantly demonstrated is that the 

 demands for sulphur by farm crops is not 

 appreciably less than for phosphorus. 



No one familiar with this subject would 

 question the necessity of maintaining the sup- 

 ply of phosphorus in a soil, but only lately has 

 attention been focused on the sulphur prob- 

 lem, placing that element in the same category 

 with phosphorus as an element of low supply 

 and an economic factor in crop production and 

 permanent fertility. 



On the basis of " total " analysis it appears 

 certain that the amount of sulphur in our 

 common soils is not larger than the phosphorus 

 supply, and, further, that the amount brought 

 to the surface annually in the rainfall will not 

 compensate for the loss the land sustains by 

 drainage. 



Yet when we admit these facts we have only 

 opened the problem of the necessity of sulphur 



1 Bogdanoff, Abstract Expt. Station Eec, 11, 

 723 ; Dymond, Hughes and Dupe, Jr. Agr. Sci., 

 1905, 1-107; Hart and Peterson, Eesearch Bull. No. 

 14, Wis. Exp. Station; Shedd, Bull. No. 174, Ky. 

 Agr. Expt. Station. 



fertilization. It is becoming rather common. 

 practise to attach a great deal of importance 

 to the total quantity of any given essential 

 plant food element in the soil, believing that 

 this alone will measure or determine the per- 

 manent crop-yielding power of a given soil. 

 For a measure of permanent crop production 

 and for the knowledge upon which to build the 

 soil to a certain plane of efficiency these deter- 

 minations undoubtedly have value, but in the 

 problem of continued fertilization too often 

 we lose sight of the influence of the added 

 material on the biological soil processes and 

 the physiological balance of nutrients essential 

 for the optimum growth of plants. 



While it is admitted that the soil supply of 

 sulphur is as low as the phosphorus supply, 

 yet the question must be raised and answered — 

 will sulphates influence crop production to the 

 same extent as added phosphates? 



It is apparent that part of the soil sulphur 

 is in organic forms and part as sulphates, but 

 that the organic forms are constantly being 

 oxidized to sulphates. The additional fact 

 that drainage waters are richer in sulphates 

 than in phosphates must lead to the conclusion 

 that the solubility of the sulphates in the soil 

 water is much greater than the solubility of 

 the phosphates. This being true, it is apparent 

 that a lesser total quantity of sulphates in a 

 soil would be as efficient in maintaining a suffi- 

 cient sulphate concentration in the feeding 

 zone of the plant as a much greater total quan- 

 tity of phosphates. 



In addition to the question of solubilities 

 the important factor of the relative effects of 

 sulphates and phosphates on the biochemical 

 soil processes must be raised. Such important 

 biochemical processes as ammonification, 

 nitrification, nitrogen fixation, and the rate of 

 decomposition of organic matter with its ac- 

 companying liberation of carbon dioxide can 

 not be too greatly emphasized in deciding on 

 the relative fertility of soils. 



It has been demonstrated beyond question 

 in certain phases of fermentology that cellular 

 and enzymatic activities are markedly in- 

 creased by the presence of soluble phosphates. 

 Harden and Young have shown that the ac- 



