191S.] SOILS — FERTILIZERS. 815 



removed. The average annual development of nitrates for tlie period of 1914 

 to 1916, inclusive, amounted to 81.6, 413.3, 481, and 556.3 lbs. per acre, respec- 

 tively. In 1916 and 1917 the quantity of nitrogen contained in the weeds on 

 the weed plats was determined, calculated as nitrates, and when added to the 

 nitrates present in the soil of the weed plats amounted to 474.3 lbs. of nitrate 

 per acre in 1916 and 35S.8 lbs. in 1917, as compared with nitrate contents of 

 531.5 lbs. in soil cultivated 3 in. deep and 445.7 lbs. in soils with a bare surface 

 in 1916, and 372 and 361.2 lbs., respectively, in 1917. Further observations of 

 nitrate formation in the soils of plats left to weeds and those plowed early 

 (July) and cultivated led to the conclusion that the small amounts of nitrate 

 found in the soil of the weed plats were due to the fact that the nitrates had 

 been reduced by weed growth. Available data seemed to indicate that the 

 depth of cultivation did not greatly affect nitric nitrogen accumulation in the 

 soil of plats prepared in different ways for wheat. 



Data similar to that compiled by Gates and Cox (E. S. R., 28, p. 233), rela- 

 tive to the effect of tillage on corn, have been obtained in experiments con- 

 ducted at this station from 1914 to 1916, inclusive, aud show that the unculti- 

 vated plats where the weeds were removed produced practically as high yields 

 as the cultivated plats. 



In summarizing, the authors state that " if moisture is lost from the soil prin- 

 cipally through weed growth, and if nitrogen and other elements of plant food 

 become available rapidly in unstirred soil, it is a matter of economy to handle 

 the soil so that weeds may be controlled with the minimum of labor. It should 

 not be understood that tillage is unessential. It will be necessary ... to 

 maintain the proper structural conditions of the soil, to dispose of crop residue 

 on the surface of the soil, to incorporate manures and organic matter In the 

 soil, and to place the soil in suitable condition for seed. Further than this, 

 with the possible exception of heavy types of soil, it is doubtful if tillage is 

 essential where the soil is in a receptive condition to absorb rainfall and 

 where there is no weed growth." 



A list of 19 titles is appended, comprising the literature cited. 



Alkali soils: Some biochemical factors in their reclamation, J. H. Babnes 

 and Baekat Au {Ac/7: Jour. India, 12 {1917), No. 3, pp. S6S-389, pis. 5; abs. in 

 Cliem. Abs., 11 {1917), No. 22, p. S082).—This is a full account of investiga- 

 tions, previously noted (E. S. R., 35, p. 516) from a briefer report, wliich 

 indicate that the activity of the oxidizing, nitrifying, and nitrogen-fixing bac- 

 teria of the soil may be utilized as a simple and effective means of measuring 

 the progress of the reclamation of alkali soils. The methods of making the 

 tests are fully described, and laboratory and field tests in which they were 

 successfully used to measure the progress of reclamation by washing and 

 drainage are reported. The proposed procedure is based upon the conclusion 

 that the salts present in alkali soils do not exert any toxic effect on the plant, 

 hai-mful effects being observed only when the osmotic pressure of the saline 

 solution exceeds that of the cell sap. The author maintains that this condition 

 can be determined as well aud more quickly and easily with soil bacteria than 

 with the higher plants. 



It was found that nitrifying organisms are comparatively resistant to the 

 ordinary alkali salts and can withstand a solution of higher osmotic pressure 

 than the higher plants. That is, increased nitrification begins in a soil before 

 it is sufficiently freed of soluble salts to admit of the growth of ordinary crops. 

 The ammonifying organisms were found to be still more resistant than the 

 nitrifying organisms. Apparently all of the organisms affecting the nitrogen 

 supply of the soil are present in alkali soils, but are dormant as long as the 



