424 EXPERIMENT STATION EECOED. 



creased tlie assimilable phosphoric acid. As a solvent for determining the 

 available phosphoric acid the author uses vpeak nitric acid (5 cc, of nitric 

 acid of 1.4 sp. gr. to 5 liters of distilled water). Satisfactory agreement was 

 obtained between the results secured by this method and those of pot and field 

 experiments. 



The effect of earthworms on soil productiveness, E. J. Russell (Jour. Agr. 

 SgL, 3 {1910), No. 3, pp. 246-257, figs. 2). — Pot experiments are reported In 

 which various crops wei-e grown on soil to which earthworms were added and 

 on soil from which they were excluded. 



The results indicate that " earthworms do not appear to have any marked 

 direct effect on the production of plant food. Organic matter seems to decom- 

 pose with formation of nitrates equally quickly whether they are present or 

 not. They are rich in nitrogen, containing about 1.5 to 2 per cent, and they 

 decompose rapidly and completely ; thus they furnish a certain amount of 

 plant food to the soil when they die. Their chief work is to act as cultivators, 

 loosening and mulching the soil, facilitating aeration and drainage by their 

 burrows." 



The influence of stubble burning' on the fertility of the soil, A. J. Ewakt 

 iJoHi: Dcpt. Agr. Victoria, S {1910), No. 10. pp. 6.'i6. 6'/7').— It is stated that 

 stubble burning not only decreases the amount of humus returned to the soil, 

 but also accelerates the exhaustion of that already present in it. This de- 

 crease in the carbohydrate material diminishes the food supply of the Azoto- 

 bacter, causing a decrease in their numbers and thus diminishing the nitrogen 

 supply added to the soil from the air. 



Changes in soils through forestation of cultivated lands, Fricke (ZtscJrr. 

 Forst u. Jagdw., //:3 (1910). No. 5, pp. 2.5.9-26'/) -—This article reports the re- 

 sults of studies on the influence of forestation of cultivated lands, investiga- 

 tions having been made to determine the effect of forestation on composition, 

 hygroscopicity, percentage of carbon dioxid, humus, and nitrogen of the soil. 



There was no gain in the humus content of the forest surface soil over that 

 of the cultivated soil, and no appreciable difference in texture. The vegetative 

 layer or forest debris increased in humus content with the age of the forest 

 The forest debris is a source of nitrogen for the present generation of trees, 

 but it is of no value to the succeeding generation of trees unless it be incor- 

 porated into the soil by means of cultivation. 



Fatigue of the soil, H. Rousset (Nature [Paris]. 38 (1910), No. 1911, pp. 

 86-90, figs. 5; Engrais, 2.5 (1910). No. 18, pp. Ji96-J,99).—A review is given of 

 recent investigations bearing upon this subject, particularly those of the Bu- 

 reau of Soils of this Department. 



The story of the soil, C. G. Hopkins (Boston. 1911, pp. 350, pis. 8).— In 

 this book an attempt is made to present certain scientific facts relating to the 

 soil and its improvement in the form of popular fiction. The author states 

 that the story rests upon a "basis of absolute science and real life." It dis- 

 cusses current theories of soil fertility and sets forth in popular way the 

 author's well known views regarding the permanent improvement of poor or 

 exhausted lands, such as those of the Atlantic seaboard and of southern Illi- 

 nois, which are more fully presented in technical form in the author's treatise 

 on Soil Fertility and Permanent Agriculture (E. S. R., 23, p. 17). 



Fertilizer experiments, W. Schneidewind et al. (Landw. Jahrb., 39 (1910), 

 ErgdnzHiigsh. 3, pp. 20-109; ahs. in Chcnv. ZentM., 1910, II. No. 6, p. IiO-)).— 

 Accounts are here given of plat tests of nitrogenous, phosphatie, and potash 

 fertilizers with and without the addition of stable manure, the action and value 

 of stable manure, the utilization of the plant food of commercial fertilizers and 

 stable manure, soil robbery and increase of plant food, the amounts of lime and 



