726 EXPERIMENT STATION RECORD. 



upper 4 ft. of soil, but this was all lost in most cases before the beginning of 

 the next rainy season. 



Where water was applied in larger amounts than afforded by the natural 

 rainfall as by flooding, by run-off, or by supplemental irrigation, there was 

 some moisture saved in the subsoil until the next year. This occurred espe- 

 cially in the lighter soil underlaid by a heavier soil at a depth of about 4 ft. 

 The author suggests as one of the reasons of failure to conserve moisture by 

 these methods the great daily range of temperature which prevails throughout 

 the year in southern Arizona where there is often a difference of 60° between 

 day and night temperature. Such conditions are said to destroy the protecting 

 effect of a dust mulch. 



Investigations of soil moisture conditions in light and heavy soils show that 

 much rainfall was lost by run-off in heavy soils, since water penetrated them 

 veiy slowly and although they were found to have a great absorptive power 

 the water was held relatively near the surface causing evaporation losses. 

 Light soils allowed quick penetration to such depths that comparatively little 

 water was lost by run-off, but the rapid capillary movement in light soils is 

 said to account for the loss of a considerable part of the rain water. 



[Effect of ashes from Mt. Katmai on Alaskan soils], C. C. Geobgeson 

 (Alaska Stas. Rpt. 1912, pp. 40-42, 67-71, pJs. 2).— The soil of Kodiak Island, 

 Alaska, was covered to an average depth of 18 in. with ashes from Mt. Katmai 

 90 miles away during the eruption of June 6 and 7, 1912. These ashes were of 

 3 grades, (1) a fine rather heavy gray sand, (2) a yellow deposit not unlike 

 yellow clay dust, and (3) an exceedingly fine gray powder which had evidently 

 been blown to great heights and which continued to settle through the atmos- 

 phere for days. 



" The ashes had no poisonous or deleterious effect upon plants beyond that 

 of smothering them. This point established, it did not seem improbable that the 

 station land could be rehabilitated by seeding the proper grasses and legumes. 

 To ascertain how grains and grasses would behave in the ashes, small areas 

 were seeded in July to wheat, rye, barley, and oats. Small patches were also 

 seeded to various cultivated grasses and clovers. Part of the seeded patches 

 were fertilized with stable manure and part were seeded on the bare ashes. 

 The seeds germinated, but the growth was very slow in all cases. On the bare 

 ashes the grasses and grains did very poorly. The plants remained alive, but 

 their growth was stunted. Evidently the ashes were wholly destitute of nitro- 

 gen. Where the manure was worked into the surface of the ashes, on the other 

 hand, the growth was almost normal, indicating that fertilizers were needed." 



The beneficial results from a top-dressing of sodium nitrate very clearly indi- 

 cated the need of nitrogen. " It was further observed that when a layer of the 

 ashes was worked in with the original top soil the growth of vegetables and 

 grains was, if anything, better than when grown in the soil without any ashes." 



" From the observations made during the season and the tests carried out, it 

 is reasonable to believe that, with sufficient manure or sodium nitrate to nour- 

 ish the plants until their roots grow down into the soil below the ashes, grasses 

 and grains can be grown successfully. Where the ashes settle or pack down 

 enough to allow the mixing of ash and soil below by means of a plow, the 

 growing of crops is assured." 



Soil fertility, J. W. Nkal (Alaska Stas. Rpt. 1912, pp. 48-50. pi. 1).—The 

 soil around the Fairbanks Station, on which the experiments here reported 

 were made, is described as a silty clay deficient in humus and available plant 

 food in the hilly and upland regions except where the land is timbered and a 

 large amount of vegetation has decomposed and been incorporated with the soil. 

 The conditions are generally such that the primary need is for available plant 



