1919] Soils FERTILIZERS. 319 



may account for some of the soil acidity, and may help to dissolve the Insoluble 

 phosphates nud other minerals necessary for the growth of the green plants. 



A number of organisms parasitic to green plain- have been isolated from soils, 

 upon which these plants have often never been grown before." 



A list of t;-j titles comprising the literature cited is appended. 



Nitrate reduction in cultivated soils, AxiCE OlSLSNEB {Oentbl. Bakt. [etc.], 

 ..'. \i>t.. js' [1918), No. 10-15, pp. 210-221).— The author describes Investigations 

 with different t.\p''s of soil containing from 18 to go per cenl of moisture 

 and to which solutions of nitrates had hern added, decided nitrate reduction 

 resulting without the addition of any energy-producing material. The effects 

 Were mosl pronounced with the higher moisture contents, and the conclusion 

 was reached that the exclusion of air from the soil led to the utilization of 

 the oxygen of the nitrates by the soli organisms. The end product <>f this 

 reduction is said to be elemental nitrogen, while the necessary energy material 

 was thought to be derived from carbonaceous matter in the soil. It is con- 

 cluded further that danger of denitritication in the field is always present if 

 soil aeration is seriously interfered with, even in the absence id' cellulose, 

 straw, or other similar materials usually regarded as sources of energy for 

 denitrifying processes. 



Researches on certain " soil sicknesses " in the Netherlands, X. T.. S6] vt- 

 6EN, A. Knktkmann. and K. T. Wieringa (Verslag. Landboutok. Onderzoek, 

 Rijkslandbouwproefstat. [Netherlands'], No. 21 (1917), pp. / 11-165, figs. 6; ai>s. 

 i>i Internat, hist. Agr. [Rome], Internat. Rev. Sci. <ni<i Pract. Agr., !> (1918), 

 No. 6, pp. 659-462). — The so-called "soil sicknesses" appearing in Holland, 

 Germany, and Denmark are briefly noted, and studies made by the authors 

 of soil acidity and its Influence on vegetation are described. It is stated that 

 the direct and Immediate cause of these soil sicknesses has not yet been 

 ascertained, but that a close relationship was observed between their appear- 

 ance and the free humic acid content of the soil, enabling the soil to be ren- 

 dered healthy by means of suitable treatment. 



[Report of soil fertility work in Kansas, 19171 (Kansas 8ta. Rpt. V.ill. 

 pp. 16, /?', 21. 22. ,."/>. — Corn grown continuously since 1910 produced 23 bu. 

 per acre in 1916 as compared with 4'_ , .'_'."i bu. for that grown in rotation with 

 cowpeas and wheat. Wheat grown in rotation also yielded better than wheat 

 grown continuously. 



Applications of barnyard manure on corn in a rotation of corn, cowpeas, 

 and wheat had a marked effect on the succeeding wheat crops, although the 

 wheat yields were almost identical on plats receiving one-half the manure 

 on corn and one-half on wheat. Marked Increases in yields were also ob- 

 tained from the use of manure on alfalfa grown continuously and in rotation 

 with corn and wheat. 



Commercial fertilizers on corn grown in rotation failed to Increase yields 

 sufficiently to pay for the fertilizers, hut decided increases in yields followed 

 their use on corn grown continuously since 1911. Phosphorus is said to ln> 

 the principal factor in increasing yields. Fertilizers on wheat grown con- 

 tinuously increased yields, potassium giving only slight Increases, while appli- 

 cations of phosphorus alone or in combination resulted in a test weight of 2 

 lbs. or more per bushel above the other piaN. Pronounced effects were ob- 

 tained from the use of fertilizers on alfalfa grown continuously but no marked 

 Influence was noted where it was grown in rotation. 



observations on the effect upon the nitrogen content of the soil of prolonged 

 alfalfa production indicated that in the semiarid portion of the State the 

 alfalfa soils had as great n percentage of nitrogen as the soils in native sod 

 and that the difference between the nitrogen content of the latter and of the 



