1917] SOILS FERTILIZERS. 623 



in excess of the actual requirement of the soil for lime as .tndgred by economic 

 standards; hence a correcting value seems advisable. The correcting value for 

 the soils of Canterbury Plains Is about 0.1 per cent. The greater acidity and 

 higher lime requirement of .soils of the Southland Plains appears to be due to a 

 combination of lack of natural underdrainage and high rainfall, which prevents 

 aeration and oxidation of organic matter, so that ' sour ' humus accumulates in 

 the soil." 



Causes of acidity of soils which are acid througrh exchang'e of ions, H. 

 Kafpen {Landw. Vers. Stat., 89 (.1916), pp. S9-80; ahs. in Jour. Chem. Soc. 

 [London'i, 110 (1916), No. 650, I. p. 876; Chem. Abs., 11 (1917), No. 8. p. 1008).— 

 Experiments with two pine-forest soils and a soil on which the vegetation con- 

 sisted of a fe\^ bilberry bushes are reported. 



The forest soils, which were covered with a layer of humus from 2 to 3 cm. 

 (0.79 to 1.18 in.) deep, showed considerable activity when treated with a normal 

 solution of potassium chlorid, while the third soil failed to react The latent 

 activity of the forest soils is attributed to the action of humic acids on the 

 mineral soil and the production of aluminum and Iron salts. It is shown that 

 the true acidity of humus extracts is approximately the same as that of acetic 

 acid of the same strength, and that latent acidity can be produced by treating 

 mineral soils with raw humus. The same result was obtained with only par- 

 tially humified vegetable substances. It is also thought possible that latent 

 acidity can arise from the production of soluble aluminum and iron compounds 

 in the humus itself and the penetration of the soluble salts into the mineral soil 

 below the humus. 



Movement and distribution of moisture in the soil, F. S. Habeis and H. W. 

 TxJKPiN (U. S. Dept. Agr., Jour. Agr. Research, 10 (1917), No. S, pp. llS-155, 

 figs. 31). — Field and laboratory soil moisture experiments conducted at the Utah 

 Experiment Station under irrigation and dry-farming conditions, and represent- 

 ing several thousand moisture determinations, are reported. The field studies 

 included the effect of fallow, kind of crop, manure, irrigation water, surface 

 mulches, cultural methods, and seasonal conditions on the movement and dis- 

 tribution of soil moisture. The laboratory studies included the effect of the 

 initial percentage of moisture, gravity, soil type,, source of supply, etc. 



In field soils the moisture content of the fallow soils averaged greater than 

 that of the cropped soiLs. Unmanured Irrigated land showed less difference in 

 moisture between cropped and fallow than did the manured. Irrigation in- 

 fluenced the top feet of the cropped plats proportionately more than the fallow, 

 but water did not appear to penetrate the fallow plats below 7 ft. as readily 

 as it did the cropped ones. 



Under dry-farming conditions the difference in moisture between cropped 

 and fallow plats was not noticeable until after June 16. Cropped plats showed 

 more fluctuation than fallow ones. Wheat, corn, potatoes, and peas drew most 

 of their moisture from the first 4 ft. in depth. The wheat land contained less 

 moisture in the fall than the other cropped soils, with corn following. 



The increase in moisture due to applications of from 5 to 7.5 in. of irriga- 

 tion water was felt to depths of 10 ft. in 24 hours, although most of the increase 

 was in the first 4 ft. 



The effect of mulches in preventing moisture loss under both irrigation and 

 dry farming was noticeable several feet below the surface of the ground, but 

 the surface foot showed the greatest benefit from mulches. A straw mulch 

 proved considerably better than a 2-in. soil mulch. Mulches on irrigated plats 

 appeared to influence the moisture content of the soil to greater depths than did 

 those under dry-land conditions. A dry-farm plat kept free from weeds in 



22397°— 17— No. 7 3 



