SOILS FERTILIZERS. 621 



the soil, and reports observations wbicli show that freshly fallen leaves and 

 other plant remains are better sources of plant food than the older humus, 

 which is almost incapable of further oxidation and is therefore practically 

 inert. 



It is stated that humic acids are present in the freshly fallen leaves and 

 are leached out into the soil by rains. The amount of such compounds found 

 in the leaves varied with the kind of trees, being much larger in beech leaves 

 than in oak and ash leaves. Clay loams appear to be able to fix and neutral- 

 ize humus acids in the soil, forming the so-called mild humus, which increases 

 the productiveness, and to change the acids into carbon dioxid, which has a 

 high solvent power for the mineral plant foods. Conditions which favor aera- 

 tion and oxidation promote the productiveness of humus soils. 



On the occurrence of Azotobacter in peat soil, H. von Fpjilitzen (Srenska 

 Mosskulturfor. Tidskr., 25 {1911), No. 1, pp. 53-57). — Azotobacter was found to 

 occur to only a very limited extent in the peat soils, of the Torestorp and Fla- 

 hult substations, even in the best soils that had been under cultivation for 

 nearly 25 years. No connection could be traced between its presence and the 

 lime content of the soil. 



The part played b/ raicro-organisms other than bacteria in determining 

 soil fertility, E. J. Russell and H. B. Hutchinson (Chem. News, 102 {1010), 

 No. 2656, pp. 202, 203; ahs. in Chem. Ahs., 5 {1911), No. 6, p. ii^S).— This arti- 

 cle briefly reviews the indirect evidence tending to show that protozoa injuri- 

 ously affect the bacteria which produce ammonia in the soil. It is stated that 

 " direct evidence has not yet been satisfactorily obtained." 



Methods of improving sandy soils, S. Bogdanov {EJioztaistvo, 1909, Nos. 

 37, 41, Ji2; ahs. in Zhur. Opytn. Agron. {Russ. Jour. Expt. Landw.), 11 {1910), 

 No. 3, p. 415). — Two means of improving sandy soils, viz, use of manure and 

 green manuring with lupines, are discussed in detail. 



The management of pineapple soils, W. P. Kelley {Hodvaii Sta. Press Bui. 

 29, pp. 10). — This bulletin calls attention to the fact that the continued culti- 

 vation of pineapples on the same land has brought about unfavorable physical 

 conditions which have greatly reduced the yield. The injury has been caused 

 largely by cultivating the soils when wet. Methods of overcoming the unfavor- 

 able conditions by better tillage, the use of manure, and rotation are described. 



The results of soil investigations as affecting the use of fertilizers, F. B. 

 Carpenter {Amer. Pert., 34 {1911), No. 1, pp. 15-20). — This is an address de- 

 livered before the fertilizer division of the American Chemical Society at Min- 

 neapolis, December, 1910, and discusses particularly the bearing of recent soil 

 investigations upon Liebig's theory relating to fertilizers as a source of plant 

 food. 



Fertilizing for profit, E. E, Miller {Raleigh, N. C, 1910, pp. i06).— This 

 book attempts to* explain briefly and plainly the fundamental facts underlying 

 the use of fertilizers and to show the ordinary farmer how he can apply fer- 

 tilizers so as to make better crops and build up the soil. It applies particularly 

 to conditions in the South, where it is stated that the use of fertilizers is in- 

 creasing faster than the average crop production per acre. " In other words, 

 Southern farmers spend $50,000,000 a year for plant foods and then fail to 

 improve their soils. This is true, not because commercial fertilizers are not 

 good to use, but because they are used extravagantly and unwisely." This book 

 was therefore written with the hope that it might point a way to a more 

 judicious and profitable use of fertilizers. 



The titles of the different chapters are: What fertilizers are and why used, 

 what commercial fertilizers are, what nitrogen does and where we get it, about 

 phosphoric acid, potash in commercial fertilizers, why fertilizers pay best on 



