808 EXPEBIMENT STATION BECORD. 



fall covers three periods in the year: (a) Mid-December to mid-April, great 

 rainfall intensity in the north becoming less marked in higher latitudes, maxi- 

 mum effect in February; (b) Mid- April to mid-August, winter rains especially 

 in the southwest, maximum in June; (c) Mid- August to mid-December, rela- 

 tive dryness throughout the continent, maximum dryness in November, (4) 

 The heavy summer rains accompanying falling temperatures and the northward 

 swing of the sum. (5) The absence of rain accompanies rising temperatures 

 when the land air is relatively much warmer than the sea air. (6) The heavy 

 winter rains are most intense during the coldest months. (7) The rainfall 

 regime of Australia is essentially similar to that of Africa and is associated 

 with the similarity of air movements south of the equator." 



SOILS— FERTILIZERS. 



The biochemical decomposition of nitrogenous substances in soils, W. P. 

 Keixey (Hatcaii Sta. Bui. 39 {1915), pp. 25, fig. 1). — Ammonification experi- 

 ments in silica sand and fresh heavy clay soil from a citrus orchard to deter- 

 mine under different conditions the percentage, of ammonia derived from the 

 bacterial decomposition of casein, dried blood, soy-bean cake meal, cotton-seed 

 meal, and linseed meal are reported, together with a study of the effects of 

 bacterial action on different groups of nitrogen compounds. 



It was found that ammonification of casein in both silica sand and soil was 

 much more rapid during the first two days than that of dried blood, soy-bean 

 cake meal, cotton-seed meal, or linseed meal, while soy-bean cake meal was 

 second in the order of decomposition. A much higher percentage of the total 

 nitrogen in casein was ammonified in soil than of the other materials. When 

 equal amounts of nitrogen were added, casein was still more rapidly ammoni- 

 fied than the other materials and cotton-seed meal and soy-bean cake meal were 

 more completely ammonified than dried blood or linseed meal. Later the yield 

 of ammonia from dried blood exceeded that from cotton-seed meal. Under 

 anaerobic cenditions all of the materials were ammonified very slowly during 

 the first two days, after which the casein was converted into ammonia ap- 

 proximately to the same extent as under aerobic conditions, but the other ma- 

 terials were decomposed much less vigorously. 



With equal amounts of both nitrogenous and nonnitrogenous matter present 

 the final yields of ammonia from the different materials, with the exception of 

 dried blood, agreed closely, but the initial decomposition of casein was still 

 greater than that of the other substances. By adding 1.586 gm. of starch 

 to 1.072 gm. of casein ammonification was reduced practically 50 per cent 

 throughout nine days, and effects on the ammonification of dried blood were 

 still more marked. With varying amounts of casein the yields of ammonia in 

 four days increased as the amounts of casein present increased. Extending 

 the incubation period beyond four days did not materially increase the yield 

 of ammonia, and the decomposition of the second and third gram added after 

 1 gm. had been acted upon four and eight days, respectively, was slightly more 

 vigorous than that of the first gram. 



Casein when mixed with silica sand or in solution was completely hydrolyzed 

 by the action of bacteria in seven days. In solution the rate of hydrolysis 

 exceeded that of ammonification, but the latter was not so active during the 

 first five days as when mixed with soil. 



The determination of the different groups of nitrogen compounds before and 

 after bacterial action in casein, dried blood, soy-bean cake meal, cotton-seed 

 meal, linseed meal, coconut meal, globulin from cotton-seed meal, and zein 

 from maize showed that, with the exception of linseed meal and zein, the basic 



