SOILS FERTILIZEES. 725 



plants and an economical use of tlie water in so far as the production of foliage 

 alone is concerned, but the resulting large transpiring surface may cause the 

 death of the plants before they reach maturity. The same amount of free 

 water distributed through a greater depth may induce a slower growth, allow 

 a longer lease of life, and so permit of the production of seed, while if the 

 same amount be distributed through a still greater depth the content of free 

 water may everywhere be too low to permit of the development of roots, thus 

 rendering the free water nonavailable. 



" The loss of water from the subsoil of dry lands under crop seems to take 

 place almost entirely through transpiration. In the absence of plants the loss 

 from the subsoil is small. The stored moisture of the different depths of 

 subsoil in the field becomes available to the plants by the roots being developed 

 to these depths, but little moisture being elevated to the roots by capillarity. 

 However, in the case of subsoils saturated in cylinders or pots and comparable 

 to such field subsoils as are only a few feet above the water table, the content 

 of free water is so high that large amounts of moisture may be elevated to the 

 roots by capillarity. The amount of water retained by a soil saturated in pots 

 or cylinders is far in excess of the amount retained by a similar soil saturated 

 in a field where the water table is at a considerable depth below the surface, 

 as in ordinary dry land soils. 



" To obtain a basis for comparing the available moisture in soils, either the 

 hygroscopic cocfBcient or the wiitiug coefficient may be used. In general the 

 one may prove as satisfactory as the other, but in considering the germination 

 of seeds and the development of roots, and hence the whole of the earlier por- 

 tion of the life of annual crop plants, the wilting coefficient appears the prefer- 

 able; while in considering the production of seed in the case of annual crop 

 plants and the maintenance of life and even the growth of perennial plants, the 

 hygroscopic coefficient appears much the preferable. 



"In the case of ordinary dry land soils, the water table being at a consid- 

 erable depth below the surface, the maximum amount of soil water available 

 to plants, for growth and for the maintenance of life, is approximately equal 

 to the free water— the difference between the total water and the hygroscopic 

 coefficient — in those portions of the soil and the subsoil occupied by the roots. 

 For some plants the available water appears to be somewhat greater and for 

 others somewhat less than the free water." 



Investigations on moisture and soil types in Sulphur Spring Valley. 

 R. W. Clothier (Arizona Sta. Bui. 70, pp. 736-776, pis. 2, figs. 2). — Rainfall 

 records of the valley are said to indicate that a little less than two-thirds of 

 the annual rainfall occurs during the growing season and a little more than 

 one-third during the winter. The summer rainfall is always local in character, 

 sometimes torrential, but frequently falls in light showers. The author believes 

 that no rain less than i in. is retained by the soil except possibly by the most 

 sandy soils, but that small showers of i in. or more are effective if they fall 

 at intervals of not more than 2 days. 



Attempts were made to conserve the rainfall in the soil by deep plowing, 

 intertillage of crops, and by fallowing the land and harrowing or disking It 

 after every rain. During the 3 years' experiments the winter rainfall was much 

 below normal, but in 1900 the summer rainfall was normal and in 1910 and 

 1911 above normal. The total amount of rain penetrating the soil during the 

 3-year period is estimated at 29.97 in. It was found impossible to save any 

 considerable amount of the natural rainfall from one summer's rainy season to 

 the next by the methods of tillage used. The moisture determinations at the 

 close of each season showed an accumulation of several inches of water in the 



