SOILS FERTILIZERS. 621 



From these data it follows in general that the black fallow was inferior to 

 the April fallow in moisture, which is corroborated by the average yields of 

 winter wheat during 5 years. This result, which stands in direct contrast with 

 the generally accepted view of the significance of the blade fallow, is ascribed 

 by the author to the conditions of the three-course rotation. 



Investig'ations on the behavior of fallows, W. Kruger and B. Heinze (Landic. 

 Jnhrb., 36 (1907), Xo. 3, pp. 383-^23, pi. 1).—In a study of the form and amount 

 of nitrogen compounds in fallow and unfallowed soil and of changes in the 

 l<ind and number of micro-organisms in the soils, especially those which fix 

 nitrogen, it was found that there was a considerable increase of water-soluble 

 nitrogen compounds, especially nitrates, in the fallow soil. There was also an 

 increase in total nitrogen in the fallow. The organisms increased decidedly 

 after the first cultivation and then gradually decreased. The organisms which 

 grow on gelatin were more numerous in the fallow than in the unfalUnved soil. 



Certain organic constituents of soils in relation to soil fertility, O. 

 ScHREiNER, H. S. Reed, and J. J. Skinner (U. 8. Dcpt. Agr., Bur. Soils Bui. -'/7, 

 l>l). 52, pis. 6). — It is stated in this bulletin that the unproductiveness of 

 soils is frequently due not to deficiency in nutrient mineral substances but 

 may be explained by the presence of substances actually deleterious to plant 

 growth derived from plant excretions or from the breaking down of organic 

 matter in the soil. Various facts which substantiate this belief are presented 

 and simple operations by which such toxic properties can be overcome are 

 described, as has already been done in previous bulletins of the Bureau (E. S. 

 R., 17, p. 340; 19, pp. 13, 117). 



Assuming that " the toxic properties of soils have been demonstrated and the 

 existence of toxic bodies is a reality with which it is necessary to deal in 

 future soil studied on the fertility and infertility of our agricultural lands," 

 and in view of the difficulty of isolating the toxic organic bodies from the soil 

 by purely analytical methods, the authors undertook a series of exiieriments 

 in which seedling wheat plants were grown in solutions to which varying 

 amounts of pure compounds of known composition, properties, and derivation 

 from plants were added. These compounds included a series of substances 

 formed by the breaking down of proteid bodies and derived from lecithins 

 and other nitrogenous bodies, as well as certain nonnltrogenous bodies which 

 it was believed might occur in soils. 



The compounds experimented with were as follows : Derived from proteids — 

 aspartic acid, asparagine, glycocoll, alanine, leucine, and tyrosine ; derived from 

 lecithins — choline, ueurine, and betaine; other nitrogenous bodies — alloxan, 

 guanine, xanthine, guanidine, skatol, pyridine, picoline, piperidine, quinolin, 

 ricin, and mucin ; nonnltrogenous bodies — pyrocatechiu, arbutin, phloroglucin, 

 vanillin, vanillic acid, quinic acid, quinone, cinnamic acid, sodium cinuamate, 

 cumarin, daphnetin, esculin, piperonal, (heliotropine). borneol, camphor, and 

 turi)entine. The literature of previous investigations relating to the derivation, 

 occurrence, and pi'operties of these bodies is noted. 



In studying the effect of the various compounds on the growth of the wheat 

 plants "two, and sometimes three, criteria of growth were employed, viz, tran- 

 spiration, green weight, and tiu'gidity. No one of these criteria can be regarded 

 as absolute, but they usually agreed in indicating the order of results, which 

 was the i)oint sought for in these experiments." 



The results show in general a marked toxi<* effect in case of a large proportion 

 of the compounds used, but the limit of toxicity varied widely and the toxic 

 effect was often replaced by a stinnilating action in the lower concentrations. 



A study of means of removing or overcoming toxic conditions indicated " that 

 there are numerous ways in which such unfavorable conditions may be over- 



