SOILS FERTILIZERS. 121 



to a certain degree improve the structure and thus increase production. In 

 compact stiff soils, without granular structure, the loosening process is aided, 

 to the benefit of plant growth, by the mechanical action of roots and by a strong 

 modification of the moisture conditions. Roots apparently seldom make prac- 

 tical use of the so-called "root holes" as a means of spreading in heavy soils. 

 The growth of roots as regards their mechanical action varies in loose and 

 compact soils. The beneficial combination of self -loosening and root action ex- 

 plains the frequent permanent improvement of the soil structure under the 

 continued influence of roots, as In grass lands, and also the prevention of per- 

 manent puddling of the soil by rain. 



Further studies of the influence of vegetation on the penetration and move- 

 ment of water in the soils showed a beneficial infiuence, especially in meadow 

 and pasture lands where there Is a marked surface spreading of the roots. 

 Although in these cases the lateral percolation of the water was somewhat re- 

 tarded by the roots, loss of water through evaporation was also retarded and a 

 comparison of soils with and without vegetation showed that the water movement 

 w«s much more rapid in the former. However, in grain lands covered with 

 crops only part of the year, an injury resulted and the soil became hard and 

 compact, making frequent cultivation necessary. 



The influence of subsoil loosening' on soil yield, Augstin (III us. Landw. 

 Ztg., 33 {1913), Xo. 32, pp. 303, 30.'f, figs. iJ).— The opinion is expressed that the 

 entire breaking up of a subsoil destroys capillarity, induces too much ventilation 

 and drainage, and causes soluble plant foods to leach away. Cropping experi- 

 ments on soil which had been completely subsoiled and on soil in which the 

 subsoil had been broken only in a small furrow 3 cm. wide under each furrow 

 were in favor of the latter method. Less power was expended in plowing by 

 this method and it is stated that the looseness of subsoil lasts longer. 



The minimum water capacity of soils and its cause, A. Moskovic (JfUf. 

 Landic. Lclirkanz. K. K. Hochsch. Bodonkia. Wicn, 2 (1013), No. 1, pp. 209-2J,3, 

 figs. 3). — The author reviews the results obtained by several other experi- 

 menters and gives the results of a number of his own experiments made to 

 determine the cause and limitations of the minimum water capacity of soils. 



On tlie basis of these results the author concludes that the minimum water 

 capacity of soils is the maximum amount of water which is independent of 

 gravity, or that amount which is adsorbed by a permeable soil under certain 

 fixed conditions of vapor and air pressure and temperature when a surplus of 

 water is added. He further concludes that under similar conditions of vapor 

 and air pressure, temperature, stratification, and size of grain every soil except 

 alluvial soil has a constant minimum water capacity. The difference between 

 minimum and absolute water capacity of the soil increases as the soil becomes 

 coarser grained. The minimum water capacity of the soil is determined 

 by the adsorbed or condensed water, so that the greater the condensing surface 

 presented within a soil the higher is the minimum water capacity. However, 

 since the adsorptive power of different soil constituents varies, the minimum 

 water capacity is not proportional to the surface presented but only to the free 

 surface tension. In porous soils the larger part of the water not adsorbed 

 drains away below, but nonporous soils, such as fine grained sands if the grains 

 are of suitable shape, form pores with closed walls which retain large quan- 

 tities of water, vso that such fine sands in spite of their small adsorptive power 

 show a high minimum water capacity. The minimum water capacity of a soil 

 is not altered by crumbling but is increased by puddling, which increases the 

 surface tension. 



Quantitative investigations on the reaction of aqueous extracts of soils, 

 T. Saidel {Bui Sect. Sci, Acad, Rounmne, 2 {1913-14), No. 1, pp, 38-44; abs. 



