WATER SOILS. 481 



which several reports of progress have been made.' The importance 

 of water in phint growth is discussed, and the warming eft'ect of irriga- 

 tion water in the fall and spring and its cooling effect in summer is 

 jjointed out. 



It is shown that irrigation water properly applied is a powerful means 

 of oxidation and of purification of the soil from harmful products. 

 This oxidation results in the formation of carbon dioxid, which largely 

 increases the solution of lime. The observations on the extent of oxi- 

 dation and solution of lime in peaty, calcareous, loam, and sandy soils 

 are reported. The action is greater in summer than at other seasons, 

 hence the need of greater caution in the use of water at this time. 



The fertility which the water contains is a very important factor in 

 irrigation, especially during the growing season. The benefit derived 

 from this source is due chiefly to the fertility taken up directly by the 

 plant and to much less extent to that absorbed by the soil. The benefit 

 is greater on poor soils tban on those of better quality. In fact, on rich 

 soils there is a loss of fertility by irrigation. The amount of the differ- 

 ent constituents so removed does not depend upon their absorbability, 

 nitrate apparently being taken up in as large quantities as ammonia, 

 potash, and phosphoric acid. The benefit to be derived from the use of 

 irrigation water depends, therefore, largely upon the fertility of the soil 

 and the vigor and extent of plant growth. The poorer the soil and the 

 larger and more vigorous the plant growth the greater the benefit from 

 the fertilizing constituents of the irrigation water. 



As compared with the other soils experimented with, the sandy soil 

 gave the best results from irrigation. This was especially true when 

 sewage and similar materials which require free access of oxygen for 

 their decomposition were used. 



Ordinary brook and river water generally furnish sufficient lime, pot- 

 ash, and nitrogen for irrigated meadows. Of phosj)horic acid, 36 lbs. 

 per acre in the form of superphosphate or 54 to 72 lbs. in the form of 

 Thomas slag may be used with advantage, the first in the spring, the 

 latter in the fall. Occasionally potash and nitrogen may be needed, but 

 the latter should be applied very sparingly. 



Methods of the mechanical analysis of soils, M. Whitney 

 {U. S. l>rpt. A(/r., Division of Agricultural Soils Bid. l,pp.J2I). — This is 

 a detailed description of the methods in use in the Division of Soils of 

 this Department "for the mechanical analysis of soils and for the deter- 

 mination of the amount of moisture in arable soils.'' The bulletin "is 

 intended partly for the instruction of the observers and special agents 

 of the Division, and partly for the information of workers in tlie agri- 

 cultural colleges and experiment stations and other institutions or 

 organizations which are interested in similar lines of work and who 



'Landw. .Tahrb., 6 (1877), p. 287; 8 (1879), p. 505; 9 (1882), pp. 151, 158; 11 (1885), 

 p. 177; 22 (1893), p. 801. 



