218 SOIL SCIENCE [BoT. Absts., Vol. VIII, 



SOIL SCIENCE 



J. J. Skinner, Editor 

 F. M. ScHERTZ, Assistant Editor 



(See also In this issue Entries 772, 773, 774, 775, 805, 806, 810, 811, 813, 814, 935, 1087, 



1177, 1453, 1582) 



INFLUENCE OF BIOLOGICAL AGENTS 



1509. CowiE, G. A. The mechanism of the decomposition of cyanamide in the soil. Jour. 

 Agric. Sci. 10: 163-176. Fig. 1-5. 1920. — The decomposition of cyanamide in the soil has 

 been attributed by certain workers to the action of bacteria. The author finds that his 

 results coincide with those of Ulpiani, who holds that cyanamide breaks down to urea by a 

 purely chemical change. Sterile soils were capable of transforming cyanamide to urea but 

 little or no ammonia was produced under such conditions. Urea is broken down to ammonia 

 by a change which appears to be due to the action of soil organisms. Clay soils are more 

 efficient in the breaking down of cyanamide to urea than are sandy soils. A sample of Thanet 

 sand taken from borings through London clay was found capable of breaking down cyana- 

 mide even after ignition. This sand was found to have the power of softening water as have 

 zeolites. Following this clue it was found that the effect of adding a definite zeolite, preh- 

 nite, to ordinary inert quartz sand was to produce a mixture capable of converting cyanamide 

 to urea. Urea was found to accumulate in sterile soils when cyanamide was added. — V. H. 

 Young. 



1510. Crump, Lettice M. Numbers of protozoa in certain Rothamstead soils. Jour. 

 AgTic. Sci. 10: 182-198. SO fig. 1920. — Methods are described for counting the protozoa of 

 soil, which are adaptations of the methods commonly used for estimating soil bacteria. Two 

 soils are dealt with in detail — a well manured arable soil and a soil which had had compara- 

 tively small applications of manure. Flagellates, amoebae, and thecamoebae are usually 

 present in these soils in large numbers, and in the trophic condition are practically confined 

 to the top 6 inches of soil. There is a definite inverse relation between the number of bac- 

 teria and amoebae. Variations in the water content and temperature of soils as well as the 

 rainfall have no influence on soil amoebae. Soils rich in organic matter are richer in protozoa 

 and especially in amoebae and thecamoebae. A bibliography of 23 citations is included. — 

 V. H. Young. 



1511. Cutler, D. W. A method for estimating the number of active protozoa in the soil. 

 Jour. Agric. Sci. 10: 135-143. 1920. — A method is described by which it is possible to esti- 

 mate the numbers of active protozoa in a soil. The total number of protozoa is first found 

 by a dilution method and a fresh portion of the soil is then treated with 2 per cent HCl (sp. 

 gr. 1.15) overnight. By this means all active forms are killed. A second count by the dilu- 

 tion method gives the number of cystic protozoa in the soil. — V. H. Young. 



1512. Davis, John J. Miscellaneous soil insecticide tests. Soil Sci. 10: 61-75. PI. 

 1-2. 1920. — In field experiments on the control of the commoner white grubs 1 gallon of 8-10 

 per cent kerosene emulsion per 6-8 square feet of soil washed in with water, slightly browned 

 the tips of the grass. Sodium cyanide at the rate of 165 lbs. in 12,000 gallons of water per acre 

 appreciably injured cultivated crops like corn but produced no permanent injury to grass. 

 Sodium cyanide treatment was more effective in controlling white grubs than kerosene emul- 

 sion or coal tar products. — W . J . Bobbins. 



1513. KoMP, William H. Wood. The use of carbon bisulfide against the white grub. 

 Soil Sci. 10: 15-28. 1920. — The maximum dosage of carbon bisulfide for ordinary lawn and 

 golf-green grasses lies nearer 5 ounces than 1 ounce per square foot. The minimum dosage 

 for the white grub is 1 ounce, and injections should be made about 6 inches apart and below 

 the grubs. The soil should be medium moist to wet. — W. J. Bobbins. 



