752 EXPERIMENT STATION RECORD. 



Summer fallow and the conservation of moisture in the soil, A. L. Knisely 

 (Oregon Sta. Rpt. 190S, pp. of), 40). — This work is in progress in a section of the 

 State where the rainfall is about 10 in. A table is given showing the percentage of 

 soil moisture on different dates from May 1 to .Inly 24 on 2 plats of alfalfa, one sown 

 broadcast and the other drilled; a plat of bare summer fallow, and a plat of wheat. 

 The percentage of moisture was in nearly all cases highest on the hare summer fallow. 



Contributions to our knowledge of the aeration of soils, E. Buckingham 

 ( U. S. Depl. Ayr., Bureau of Soils />'"/. ..'■'>, />]>. ■'>.'). — "The ohject of this paper is to 

 add to our information regarding the aeration of soils, primarily the escape of car- 

 honic-acid gas from its seat of formation in the soil, and the entrance of oxygen to 

 take its place. The specific points treated are: (1) The relative importance of diffu- 

 sion and of changes in barometric pressure; (2) the influence of texture, structure," 

 and compactness; (3) the actual amounts of carbonic acid leaving and of oxygen 

 entering the soil under definite conditions of temperature, porosity, and composition 

 of the soil atmosphere. 



"The experimental work deals (1) with the mixing of carbonic acid and air by dif- 

 fusion through layers of soil of known area, thickness, and porosity when the total 

 pressure is kept the same on both sides of the soil layer, and (2) witli the rate of flow 

 of air through the same layer of soil in precisely the same physical state under the 

 influence of a slight excess of pressure on one side of the layer." 



The development and operation of the methods used are explained. 



"The soils used were of several types, each in various states of compactness, etc., 

 and while the experimental results are few, hecause of the great time expended in 

 searching for suitable methods of experiment and by the actual measurements even 

 after fairly satisfactory methods had been devised, it is believed that the results are 

 sufficient to warrant some general conclusions," among which are that the rate of 

 diffusion of gas from the soil into the atmosphere, or vice versa, "varies approxi- 

 mately as the square of the porosity of the soil, and that this diffusion follows the 

 laws for the free diffusion of gases. It thus becomes possible to calculate the rate of 

 aeration in any particular soil from results obtained in experiments on free diffusion. 



"Tables are given showing the rate of escape (and, consequently, for a condition 

 of equilibrium, the rate of formation as well) of carbon dioxid in the soil when the 

 porosity of the soil and the concentration of the carbon dioxid at any given depth 

 are known." 



The results indicate also " that the aeration of soils is almost entirely due to diffu- 

 sion phenomena, changes in barometric pressure having very little influence in 

 comparison." 



Ohio soil studies, I, A. D. Selby and J. W. Ames (Ohio Sta. Bui. 150, pp. 81- 

 145, pis. 5, dgm.8. 10). — Complete mechanical and chemical analyses of samples of 

 soils (first 6 in.) and subsoils (second 6 in.) from the experimental plats of the sta- 

 tion farm at Wooster, from the farm of the State University at Columbus, and from 

 the test farms at Strongsville, Neapolis, Germantown, and Carpenter are reported, 

 and the significance of the results is discussed, the origin, geological relations, and 

 general character of the soils and the methods of analysis used being fully described. 

 The average results of the mechanical analyses are given in the following table: 



«The term "structure" is, for brevity, used with the meaning "state of granula- 

 tion." 



