1026 EXPERIMENT STATION EECOED. 



believed that the straw promotes deiiitrlflcation l).v furnishing food for the 

 denitrifying organisms in the form of pentosans. Calcium nitrate was more 

 effective in combination with straw, manure, and like substances than sodium 

 nitrate, being apparently more resistant to denitrification. 



The yields were invariably lower when fresh manure was applied just before 

 seeding than when applied some time before this operation. In order to 

 obtain the best results, therefore, the manure should either be w^ell rotted 

 before it is applied or it should be applied some time before the seeding. 



The objections noted in the case of straw were not found to hold in the case 

 of green manures similarly used, and this is ascribed to the fact that the 

 organic matter of the green manures is moi-e rapidly converted into humus than 

 that of the straw. 



Comparative tests of different kinds of manure showed that the least denitri- 

 fication and largest yields occurred in the case of sheep manure, the order 

 of efficiency of other manures tested being cow manure, horse manure, cattle 

 manure with litter, and horse manure with litter. In general, denitrification 

 was moi'e active with manure of horses than with that of cattle or sheep, the 

 addition of litter in all cases increasing the rate of denitrification. The low 

 rate of denitrification in case of maniu'e from sheep is ascribed to the fact that 

 with these animals the carbohydrate materials which serve as food for the 

 denitrifying organisms are more thoroughly digested than in case of cattle or 

 horses. 



The results do not warrant the conclusion that stable manure is of question- 

 able value, provided care is taken to use manure in a proper state of decomposi- 

 tion or to apply it a sufficient length of time before seeding or before application 

 of nitrates. 



Belation of soil bacteria to nitrogenous decomposition, C. Hoffmann 

 (Wisconsin Sta. lipt. 1906, pi). 120-1.3 ■/, //(/. 1). — The rate of decomposition as 

 measured by the formation of ammonia and nitrates in the nitrogenous matter 

 of blood meal, bone meal, bran, and peat was studied in culture experiments 

 with gelatin extracts, according to Kemy. of 4 distinct types of soils, namely, 

 black marsh soil sandy in character, a heavy sticky clay, a light sandy loam, 

 and a pure sand. The facts apparently established by the investigations are 

 summarized as follows : 



" The numbers and the character of the bacterial flora in soils are largely 

 influenced, first, by the nature of the fertilizers applied, and second, by the 

 character of the soils themselves. 



" The number of bacteria in sand is the smallest, amounting to only about 

 one-fifth of that found in the black marsh soil, which contained the greatest 

 number of any of the four soils. 



" The total number of bacteria which may develop in soils richly fertilized 

 is enormous, aggregating hundreds of millions per gram. 



" The degree of nitrogenous decomposition is, in a general way, directly 

 dependent upon the total number of bacteria present. 



" The progress of such decomposition is marked by numerous fluctuations 

 which coincide, in a general way, with an increase or decrease in the number 

 ■ of bacteria. 



" Extensive ammonification invariably occurs before nitrification becomes 

 active. Large amounts of ammonia may be formed in soil, without interfering 

 with the subsequent developiuent of the nitrate-forming organisms. In soils 

 highly fei'tilized, as in the foregoing experiment, appreciable amounts of am- 

 monia are invariably present. 



"As regards the degree of deconii)Osition. the soils tested rank in the follow- 

 ing order : black marsh, clay, sandy loam, and sand. 



