1918] SOILS FERTILIZERS. 419 



Evaporation from the uncropped lysimeter averaged 0.677 acre-inch per one- 

 week period in 1915 and 0.583 acre-incli in 1916, as compared with an evapora- 

 tion of 1.811 and 1.403 in. from a free water surface for the same periods. 

 The evaporation and transpiration from the lysimeter with soy beans averaged 

 0.986 acre-incli per week in 1915 and with soy beans and vetcli 1.307 in. in 

 1916. The evaporation and transpiration of the two alfalfa lysimeters aver- 

 aged 1.323 acre-inches per week in 1915 and were comparatively constant. In 

 1916 there was considerable variation, depending upon the amount of water 

 applied, amounting to 1.509 acre-inches per week with 1.5 acre-inch irriga- 

 tions, 1.672 acre-inches with 2 acre-inch irrigations, and 2.57 acre-inches with 

 3 acre-inch irrigations. The variations are thought to be due to the fact that 

 the crop received rather less moisture than was required for maximum growth 

 with the 1.5 and 2 acre-inch applications, but an amount greater than the 

 actual needs of the crop with the 3 acre-inch applications. 



Experiments in methods for determining' the reaction of soils, H. R. Chris- 

 TENSEN {Soil ScL, 4 (1917), No. 2, pp. 115-178, figs. 4).— The results of experi- 

 ments reported in this article indicate the necessity of distinguishing sharply 

 between the absolute acidity of the soil and its ability to free acids. 



" The majority of methods suggested for making a quantitative determination 

 of the acidity of the soil give no information as to the content of truly acid- 

 reacting substances in the soil, but only of its ability to absorb bases, which is 

 partly determined by the presence of acid-reacting substances and partly by the 

 presence of nonbase saturate colloids, or other nonaoid-reacting but base-absorb- 

 ing substances. ... In determining the ability of the .soil to absorb bases, a 

 method based on Baumann and Gully's principles, in which acetates are em- 

 ployed, should be preferred." 



It is thought probable that free acids exist in sphagnum peat, and the results 

 of the investigations are taken to indicate that the ability of this type of soil to 

 absorb bases is partly dependent on the presence of acid-reacting substances. 

 It is fui'ther thought that the ability of a soil to color a neutral litmus solution 

 red is an indication of the presence of free acids. 



" A determination of the base-absorption power of the soil is not sufficient for 

 determining its lime requirement, for it has been found that many soils which 

 were considered to require lime (such as those not causing Azotobacter vegeta- 

 tion under the Azotobacter test) possess less power to free acids in a calcium 

 acetate solution than those which do not require lime (such as those causing 

 Azotobacter vegetation under the Azotobacter test). . . . The qualitative de- 

 termination of the lime requirement, according to the combined litmus and 

 Azotobacter tests, can to a certain extent give information as to the degree of 

 the lime requirement of the soil. . . . 



" It is probable that the question of the lime requirement of the soil is pre- 

 dominantly a question of the presence or absence of certain easily decomposed 

 acid-saturating calcium (or magnesium) compounds." 



The nitrogen-fixing' bacteria in water and the soil beneath the water, 

 H. Fischer (Centhl., Bakt. [etc.1, 2. Aht., 46 {1916), No. 11-16, pp. S04-32S; 

 abs. in Chem. Zcntbl., 1916, II, pp. 764, 765; Cliem.. Abs., 11 {1917), No. 15, p. 

 2251; abs. in Internat. Inst. Afft: [Kotne], Internat. Rev. Sci. and Pi-act. Agr., 

 8 (1917), No. 1, pp. 26, 27). — Experiments are reported in which it was found 

 that soil before the construction of a farm pond contained large numbers of 

 Azotobacter while two years after the pond was built very few Azotobacter 

 were found and in 1915 thqj^ were almost completely gone. Attempts to grow 

 the organism in symbiosis with water plants were unsuccessful. It is con- 

 cluded that Azotobacter plays no important role in such ponds. 



