TI1E ABSORPTIVE PROPERTIES OF SOILS 369 



in which they may readily be used by the plant, these 

 materials which would otherwise be lost. 



275. Substances usually carried in drainage water. - 

 However, some material is always lost in drainage water, 

 of which, among the bases of the soil, those most likely to 

 be found are calcium, sodium, magnesium, and potassium; 

 and of the acids, carbonic, nitric, sulfuric, and hydrochloric. 

 Nitric acid and lime undergo the most serious losses. 

 The former may be curtailed to a great extent by keeping 

 crops growing on the soil during all the time that nitri- 

 fication is going on, and if the crop does not mature, or 

 if for any other reason it is not desired to harvest the 

 crop, it should be plowed under, to return the nitrogen in 

 the form of organic matter. A crop used for this purpose 

 is called a catch crop. Rye is used rather commonly as 

 a catch crop, as it continues growth until late in the fall 

 and resumes growth early in the spring, conserving ni- 

 trates whenever nitrification is likely to occur, and 

 it may then be plowed under to prepare the land for 

 another crop. Rye also has the advantage of small 

 cost for seed. 



The loss of calcium cannot well be prevented, and 

 the use of commercial fertilizers always greatly increases 

 such loss. The only remedy is the application of some 

 form of calcium to the soil. 



276. Drainage records at Rothamsted. Drainage 

 water from a series of plats at the Rothamsted Experi- 

 ment Station, which have been manured in various 

 ways and planted to wheat each year since 1852, have 

 been analyzed at certain times, and the results of these 

 analyses, as compiled by Hall, 1 give some idea of the loss 



1 Hall, A. D. The Book of the Rothamsted experiments, 

 pp. 1237-239. New York, 1905. 



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