1919] BOILS — 7KBTQJZKBS. 621 



nitrates present As a rule, more nitrates were found in soil kept one-half 

 saturated with water than In soil kept one-fourth saturated. The soils that 



had been kept fully saturated with water for the 10 months contained no 

 nitrates ami formed no nitrates when Incubated with ammonium sulphate; 

 '1 lie relation of nitrates present in the uneropped soils before incubation to the 

 nitrates present after incubation shows that the nitrate contents of these arid 

 soils tend to reach an equilibrium, above which no increase is obtained without 

 additional treatment. 



"The bacteria] flora of each soil was different from that of every other soil. 

 No bacteria developed into colonies visible to the eye as long as plates were 

 Incubated in an atmosphere of flowing carbon-dioxld gas. Calcium-carbonate 

 additions increased the bacterial contents of the soils. This Increase was 

 largely in the aerobic organisms. Small increases in bacterial content resulted 

 from the use of fertilizer. 



"The degree of saturation at which the soil was kept changed the propor- 

 tions between the aerobic, anaerobic, and carbon-dioxid-surviving bacteria. 

 Cultures from samples that had been kept one-fourth saturated with water 

 contained the largest proportions of organisms forming mold-like colonies. 

 Under optimum moisture conditions both without and with lime and fertilizer 

 treatments the nitrates after incubation varied directly with the aerobic 

 counts. 



• " In general, the greater aerobic bacterial content and the nitrifying power 

 of the soil the larger the crop yields." 



The results of the investigations indicate in general the value of a system 

 of soil improvement which includes the addition of lime, phosphate, and organic 

 matter, and suggests the importance of both chemical and biological examina- 

 tions of the soil in soil fertility investigations. 



A list of 26 references to literature on the subject Is given. 



Manure supplies under present conditions [in Rhodesia], E. V. Flack 

 [Rhodesia Agr. -lour., 15 (1918), No. 6, pp. 516-528). — Analyses and other data 

 are given regarding the supplies of kraal manure, cave guanos, rock rabbit 

 manure, wood ashes, corncob ashes, tobacco waste, mineral phosphates, bone 

 manures, and limestones available in Rhodesia. 



The effect of unbalanced fertilizers, especially unbalanced potash fertili- 

 zers, W. Si hnkidkwind (Illus. Landw. Ztg., 57 (1917). pp. 4'J.i, 494; Zcnthl. 

 Agr. Ohem., 47 (1918), No. 4-5, pp. 109-111; so* in Ohem. Abs., 13 (1919), No. 

 2, p. 157). — In plat experiments on soil which had not received any phosphoric 

 acid for 14 years, it was observed that the best results were obtained with a 

 combination of potash, nitrogen, and phosphoric acid, and that potash and nitro- 

 gen increased the yields more than potash alone. On soil that had received 

 no nitrogen for 14 years the yields were considerably greater with potash, 

 phosphoric acid, and nitrogen than with potash and phosphoric acid only, 

 although the potash and phosphoric acid combination produced noteworthy in- 

 creases of yield. 



The conclusion was reached that potash salts increase the availability of soil 

 nitrogen and phosphoric acid to only a limited extent, of no practical signifi- 

 cance. The effect of unbalanced potash fertilizers is, therefore, solely that of 

 the potash. No great significance can be attached to the effect of lime fertiliza- 

 tion on the formation of nitrates in the soil because most cultivated soils eon- 

 tain all the lime required. 



The crops used in the experiments were sugar beets, potatoes, wheat, and 

 barley. 



11633S°— No. 7—19 3 



