1020] SOILS — FERTILIZERS. 515 



spots' may be iliie to a concentration of salts caused by the evaporation of a 

 t,'round water seeuis more liliely." 



Velocity of nitrification in soils of tlie y;enoraI f«Ttilizcr series, G. C. 

 GiVK.N anil (I. J. KiiUMANN, JK. (J'( iinsi/lraiiiu Slu. /{pi. niK!, pp. Jf.',5-4.')1, fig. 

 1). — Nitrification studies of soils of the Kfueral fertilizer series at the station, 

 usln;,' ainnioniuni suli)liate, showed that nitrilication proceeiled more rapidly 

 and to a t;reater extent in a soil well supplied with lime, was only somewhat 

 retarded in an acid s(,il, and was benelited by soil orj^anic matter. There was 

 little correlation between uitrifieaMon and the yield of the rotation crops used, 

 except perhaps in the case of the corn crop. It is thou;:ht that cases of exces- 

 sive deficiency in plant nutrients may be I'evealed by a nitrilication test. 



The coagulation of clay and the protective action of humus acids, S. 

 OoEN {Jour. /ADuiir., 67 (J91D), \o. S, pp. 177-^08, fi(/s. 6').— Kxperlnients on 

 the coagulation of clay and clay suspensions by electrolytes and the i)rotective 

 action of humus afrainst such coa^rulation are reported. It is concluded that 

 humus has a protective action aj^ainst the coagulation of clay by electrolytes, 

 the nature of which, however, is as yet unknown. 



Further studies on the freezing-point lowering of soils and plants, M. I\I. 

 McCooL and C. E. Millar (Soil ScL, i) (1920), No. 4, pp. 217-233, fig.H. 5).— In a 

 repetition of certain phases and continuation of other phases of experiments, 

 previously noted (E. S. II., 37, p. 116) as conducted at the Michigan Experi- 

 ment Station, the amount of water that froze readily, or at — 1..5° C. (29.3° F.) 

 and at lower temperatures in the leaves of several crops, was determined. Wide 

 variations in the amount of water that easily froze in the plants studied were 

 found, the greatest taking place in those having low freezing-point depressions. 

 The differences were much less striking when lower temperatures were employed, 

 although larger amounts of water were found to freeze. However, subjection 

 to very low temperature (—15°) resulted in the freezing of no more water at 

 —4° when sub.sequent determinations were made at that temperature. 



The concentration of the cell sap of the roots of the plants used in these 

 investigations was Influenced quite decidedly by the concentration of the soil 

 solution in which the plants were grown. The effect of the concentration of 

 the .soil solution was not so marked on the concentration of the cell .sap of the 

 leaves. The.se results substantiate the conclusions drawn from the previous 

 work. Marked increases in the concentration of the soil solution induced by 

 the addition of full nutrient solutions of varying strength, the water content 

 of the soil remaining constant, did not measurably alter the ajuounts of water 

 that froze at — 2.5 and — 4°, respectively. 



Corn and barley plants grown in soils of high, medium, and low water con- 

 tent iMKSsessed more easily freezable water when grown in the soil of higher 

 water content. When the water content varied and the concentration of the 

 soil solution was maintained practically constant by the addition of a nutrient 

 solution, more water froze at — 2.5° in the leaves of the plants grown in the 

 soils of low water content. There was very little difference in the amount of 

 water that froze at — 4°. The.se results are somewhat at variance with the 

 results obtained when both the water content of the soil and the concentration 

 of the soil solution varied. 



Hydrogen-ion concentration measurements of soils in connection with 

 tlieir " lime requirements," .1. S. Jokfe {Soil Sci., 9 {1920), No. J/, pp. 261- 

 266, figs. 2). — Experiments conducted at the New Jersey Experiment Stations 

 are reported. In which an attenipt was made to establish a correlation between 

 the lime requirement of sandy soils as determined by the Veitch method and 

 the curve of hydrogen-ion concentration values resulting from lime-water treat- 

 ment. 



