1917] SOILS — FERTILIZERS. 423 



acid removed from the soil by these organic solvents in the four soil extractions 

 did not equal the total amount added to the soil with the solvents. However, 

 the amount of iron dissolved from the soil by the organic solvents exceeded the 

 amount dissolved by distilled water from 1 to 5.5 times. The amount of 

 phosphoric acid dissolved from the soil exceeded the amount dissolved by water 

 from 1.7 to 5.4 times. These various organic solvents, whether derived from a 

 leguminous or a nonleguminous crop, had about equal solvent action on the 

 soil minerals. 



" Organic solvents obtained from cow manure treated in a manner similar 

 to the freshly decomposing green manures did not dissolve as much calcium 

 from the soil as the solvents derived from the latter substance. They exerted 

 about the same solvent action, however, on the other elements under investiga- 

 tion. The solvent action of these organic extracts on the soil minerals appeared 

 to be due both to the inorganic salts present in the organic solvents and to the 

 organic compounds. Green manures liept moist until thoroughly decomposed 

 gave organic solvents which removed calcium from the soil in amounts several 

 times that added with the organic solvents. These solvents also removed mag- 

 nesium, phosphoric acid, and iron considerably in excess of the amount dis- 

 solved by water alone The organic solvents showed no alkaline reaction with 

 phenolphthalein nor acid reaction with methyl orange. Three per cent of 

 green manures and stable manure mixed with soil and allowed to undergo 

 partial decomposition increased the solubility of calcium and phosphoric acid 

 in the soils from 30 to 100 per cent. 



"Artificial humus solutions free from calcium, magnesium, iron, and phos- 

 phoric acid were prepared by hydrolyzing green manures and sugar with strong 

 acid, washing them free from acid, and extracting with ammonia. These or- 

 ganic solvents, when freed from ammonia, increased the solubility of calcium 

 in the soil, compared with its solubility in water, by amounts varying from a 

 few parts to 240 parts per million of soil. They also increased the solubility 

 of magnesium, phosphoric acid, and iron, but to a less extent. 



" In brief, the solubility of calcium, magnesium, iron, and phosphoric acid in 

 citrus soils of the Riverside [Cal.] district is measurably increased by the ad- 

 dition of green manure, stable manure, or their extracts. This increase in 

 solubility is due in part to the action of the inorganic salts contained in the 

 organic substances or their extracts and in part to the solvent action of the 

 soluble organic compounds formed during organic decomposition. The fact 

 that a deficiency in soluble iron is known to induce certain types of chlorosis 

 suggests that the beneficial effects following .the addition of organic matter to 

 citrus soils may have been in part due to its solvent action on iron and other 

 soil compounds." 



Conversion of soluble phosphoric acid into insoluble phosphoric acid in 

 the soil under the influence of physical, chemical, and biological factors, 

 S. Skalkij {lush. Russ. Selsk. Khoz. Gaz., 17 (1915), Nos. 33, pp. 6, 7; 34, 

 pp. 6, 7; 36, pp. 7, 8; 37, pp. 9-11; 38, pp. 6-8; abs. in Internat. Inst. Agr. 

 [Rome^, Internat. Rev. Sci. and Pract. Agr., 7 {1916), No. 8, pp. 1084-1086; 

 Jour. Soc. Chem. Indus., 36 {1917), No. 2, p. 94; Chem. Abs., 11 {1917), No. 9, 

 p. 1237). — Field and laboratory experiments conducted at the Ploty Agricul- 

 tural Experiment Station on the fixation of water-soluble phosphoric acid in 

 April fallow soil, uncultivated land, kitchen garden soil, and forest soil are 

 reported. 



The soils were studied in two depths, to 17.7 cm. (about 6.97 in.) and 17.7 to 

 35.5 cm. (about 13.98 in.). In the first series of experiments potassium nitrate 

 at the rate of 3.605 gm. per kilogram was applied in addition to acid phosphate 

 12883°— 17— No. 5 ^3 



