248 SOIL SCIENCE [Bot. Absts., Vol. IV, 



substantiated by the results obtained. From the results obtained on soils receiving green ma- 

 nures the general tendency is toward the creation of an alkaline condition in the soil, rather 

 than an acid one. In a well-planned rotation, taking into consideration the loss of bases in 

 the drainage water and the restoration of these bases by means of moderate applications of 

 lime, at regular intervals, little, if any, harm should result from the turning under of green 

 crops as a means of replenishing the store of organic matter in the soil. — //. //. Hill. 



1653. Hoagland, D. R. Relation of the concentration and reaction of the nutrient medium 

 to the growth and absorption of the plant. Jour. Agric. Res. 18: 73-117. Fig. 1~4. 1919. — See 

 Bot. Absts. 4, Entry 1421. 



1654. Hoagland, D. R., and A. W. Christie. The effect of several types of irrigation 

 water on the P H value and freezing point depression of various types of soils. Univ. California 

 Publ. Agric. Sci. 4: 141-157. 1919. — The effects of artificially prepared "alkali" waters upon 

 some physico-chemical properties of seven distinct types of soils was determined. Methods 

 of investigation included electrometric determinations of the OH ion concentration, freezing 

 point determination of total concentration of the soil solution, and chemical analysis of water 

 extracts of the soils. The analyses were calculated in terms of the characteristic groups as 

 proposed by the United States Geological Survey. Their reaction values are obtained from 



V 



the expression — C, where V = valence of the ion, W = the atomic weight, and C = con- 

 centration in parts per million. The characteristic groups represent the percentage properties 

 of the water and are independent of concentration. Different waters may thus be classified 

 readily irrespective of total concentration. — The soil must be considered as a chemical system 

 in which the effect of any added water will be modified by the chemical and physical reac- 

 tions in the soil. Consequently it is not sufficient to calculate the amount of sodium salts 

 added to an acre of soil by a given number of inches of irrigation water. — It is not possible to 

 compute the extent to which a given quantity of salt will increase the depression of the freez- 

 ing point in a soil of optimum moisture content unless account is taken of the free and unfree 

 water. — Waters with a high percentage of primary alkalinity applied in moderate quantities 

 to soils produced greatly increased OH ion concentrations, especially in light sandy soils. — 

 Waters with high concentrations of alkali salts soon produced excessive concentration of the 

 soil solution. — Any appreciable increases in OH ion concentration of the soil (especially when 

 exceeding Ph 8.5) appear to be injurious to seedlings. — The determination of the OH ion 

 concentration and freezing point depression of soils may be more practical and useful as a 

 basis of interpretation than the procedures hitherto used in analyzing alkali soils. — H. S. 

 Reed% 



1655. MacIntire, Walter Hoge. The carbonation of burnt lime in soils. Soil Sci. 7: 

 325^53. PI. 1-4, fig- 1-11. 1919. — Extensive studies in vitro and in soil show that calcium 

 oxide and calcium hydroxide in 2-4-ton applications will revert to the carbonate if left on the 

 soil surface for several days prior to inworking. This reversion will occur more rapidly during 

 humid atmospheric conditions. Less rapid carbonation occurs when the oxide or hydrate is 

 mixed with the soil. Neither the oxide nor hydrate can be considered chemically destructive 

 of soil organic matter when used in the amounts and in the manner considered as practical 

 applications. If the oxide or hydrate is incorporated within the upper zone of the soil, prior 

 to a more thorough dissemination throughout the soil the concentration thus affected will 

 bring about in the treated zone a temporary or partial sterilization. — William J. Robbins. 



1656. Noyes, H. A. Soil acidity — the resultant of chemical phenomena. Jour. Indust. 

 Eng. Chem. 11 : 1040-1049. 1919. — The reaction of a soil at any time is dependent both on the 

 nature and the proportions in which its constituents are present witli water. Changing the 

 water content, removing substances from solution, and the addition of other substances change 

 the reaction in accord with the working of the law of mass action. The solubilities of sub- 

 stances, the possibilities of combination, and the rate at which reactions take place in soil 



