620 EXPERIMENT STATION RECORD. [Vol. 38 



receiving 7 tons of manure annually. Corn in rotation yielded 44.2 bu. per 

 acre, and corn in rotation receiving 7 tons of manure annually, 54.55 bu. per 

 acre. Manure has maintained oat and timotliy yields better than crop I'ota- 

 tion, while Vi^heat grown continuously and manured annually has yielded 

 slightly more than wheat grown continuously and receiving commercial fer- 

 tilizers. Corn grown in rotation has been maintained at about the same level 

 of yields by heavy applications of manure as by heavy applications of commer- 

 cial fertilizers. The return from manure has been greater on corn, oats, wheat, 

 and timothy grown continuously than on these crops grown in rotation. 



Soil moisture studies by Miller and Duley led to the conclusion that the 

 effects of loosening the soil on increased absorption was more important than 

 that of decreased evaporation. 



Cooperative work with the U. S. Department of Agriculture in soil mapping, 

 and with agencies outside the station in soil and crop experiments is briefly 

 noted. 



Studies in soil reaction as indicated by the hydrogen electrode, J. K. 

 Plummer {IJ. S. Dept. Agr., Jour. Agr. Research, 12 (1918), No. 1, pp. 19-31).— 

 This article reports experiments made at the North Carolina Experiment Sta- 

 tion with the hydrogen electrode as a means of indicating soil reaction on a 

 number of untreated soils in suspension. " The soils experimented with repre- 

 sent a wide range in texture of those common to the area of the southeastern 

 portion of the United States, extending from and including the Appalachian 

 Mountains to the Atlantic Ocean. The H-ion concentration varies from almost 

 ' true neutrality ' to rather excessive ' true acidity ' in the soils. 



" With the Morgan apparatus for extracting film water from soils [E. S. R., 

 37, p. 717], it is shown that its reaction is the same as the free water, differing 

 only in intensity. 



" The effects of certain fertilizers on the H-ion concentration of long-time- 

 treated plats of three soils have been measured with the following results: 

 (1) Ammonia sulphate has materially increased the H-ion concentration of all 

 plats which have received applications of this material. The acidity thus 

 developed extends often to the subsoil. (2) Sodium nitrate has slightly 

 reduced the acidity of the plats to which it has been applied. (3) Potassium 

 sulphate increases the ' true acidity ' when applied to soils, though not as 

 greatly as ammonium sulphate. (4) Acid phosphate does not appear to have 

 affected in either direction the H-ion concentrations of field soils. (5) Lime 

 materially increases the OH-ion concentration of field plats to wliich it has 

 been added. 



" The acidity developed from ammonium sulphate is more intense in the film 

 than in the free water of three soils. Monocalcium phosphate does not change 

 in any way the soil-film water until excessive amounts are added." 



Hydrogen-ion concentration measurements of soils of two types: Caribou 

 loam and Washburn loam, L. .T. Gillespie and L. A. Hurst (Soil Sci., 4 

 {1911), No. 4, pp. 313-^19). — Studies on the hydrogen-ion concentration of 

 Caribou loam and Washburn loam soils from Aroostook County, Me., are re- 

 ported. 



It was found that these soils possess broadly differing biological character- 

 istics before cultivation. " Cultivated soils of the Caribou loam type exhibit, 

 when examined by the colorimetric method, considerably greater hydrogen-ion 

 concentrations than do soils of the Washburn loam type. The average hydrogen- 

 ion exponent for the Caribou loam was found to be 5.2 ; that of the Washburn 

 loam 5.93. The possibility is indicated that the relative freedom of the Caribou 

 loam from potato scabs may be due to its greater hydrogen-ion concentration." 



