816 EXPERIMENT STATION RECORD. 



" Ry neutralization of the acid liydroxyls at (a) the acid clay would become 

 neutral. The absorption of phosphoric acid can be explained by the basic 

 hydroxyls at (b). By prolonged treatment of neutral clay, i. e., salts of argillic 

 acid, with large quantities of water, charged with carbon dioxid, renewed from 

 time to time, an acid clay may be produced. On the other hand, the reverse 

 action can take place, according to the law of mass, i. e., neutral salts may 

 be decomposed by acid clay, the base being absorbed and the acid set free. 

 This takes place to a certain extent even with potassium eWorld and am- 

 monium sulphate. Hence, acid soils, fertilized with neutral salts, will often 

 produce worse results than when not fertilized at all." 



Certain typical acid soils were studied in some detail with special refer- 

 ence to the determination and correction of acidity and the relation of 

 acidity to the biological activities in the soil. It was found that the acidity 

 could best be determined " by treatment with sodium or potassium acetate 

 and titration of the acetic acid set free. The butyric ferment was found In 

 alkaline soils and in all acid soils tested, even to a depth of 18 in. in a very 

 stiff acid clay soil. A measure for the relative content of the butyric ferment 

 in soils can be obtained by comparing the amount of gas developed with 

 different soils when placed with nitrogen-free glucose culture solution in a 

 suitable apparatus." A simple apparatus for this purpose is described. "Azo- 

 tobacter was found not only in moderately alkaline soils, but also in soils of 

 considerable acidity. When, however, these acid soils consisted of a vei*y stiff 

 clay with deficient aeration it was absent. Liming of acid soils had a very 

 favorable effect on the gi-owth of Azotobacter. The limed soils yielde<l a 

 luxuriant tilm of Azotobacter much sooner than the unlimed check plat did. 

 This increase of Azotobacter is in accord with the observations that the 

 nitrogen-fixing power of soils is increased by liming." 



Soil acidity, H. O. Buckman (Cornell Countryman, 10 (1913), No. 9, pp. 

 277-279). — This article comments briefly on so-called soil acidity, describing two 

 forms, active and inactive or negative acidity. It states that for practical 

 purposes soil acidity may be considered simply as a lack of basic matter In 

 the soil. Field and laboratory tests for determining soil acidity and for esti- 

 mating the necessary amount of lime treatment are also noted. 



Preliminary note on the occurrence of acidity in highland soils, A. A. Meg- 

 GiTT and A. G. Birt (Ann. Rpt. Agr. Expt. Stas. Assam, 1912, pp. Sl-Ifl). — 

 Previously noted from another source (E. S. R., 2S, p. 813). 



The permeability of the soils of Eg-ypt, Audebeau (Compt. Rend. Acad. Sd. 

 [Paris], 157 (.1913), No. 3, pp. 231-233; abs. in. Rev. 8ci. [Paris], 51 (1913), II, 

 No. 5, pp. 15Jt, 155; Bui. Soc. Nat. Agr. France, 73 (1913), No. 5, pp. 342-3^5).— 

 The author states that from the viewpoint of the pe^'meability of its soils Egypt 

 is a vast mosaic. He classes the soils as permeable soils, soils of average or 

 only light permeability, permeable soils with impermeable subsoils, soils more 

 or less impermeable at the surface overlying permeable subsoils in underground 

 communication with irrigation canals, and impermeable soils. He states that 

 in the north of the Delta the clay strata are more plastic and impermeable than 

 in the rest of the country, and that in most cases there is no communication 

 between the upper alluvium and the deep sands. Only a considerable develop- 

 ment of drainage and the use of mechanical means for elevating water will 

 permit the rapid reclamation of the uncultivated lands in the north of Lower 

 Egypt. 



Concerning the south and center of Lower Egypt and also Upper and Central 

 Egypt the author smggests the use of systems of drainage canals situated lower 

 than and bordering on the lands irrigated and that the lands be irrigated by 

 means of mechanical lifting devices throughout the greater part of the year. 



