SUBSTANCES REMOVED IN DRAINAGE WATER 303 



likely to be found are soda, magnesia and lime, and of 

 the acids nitric, carbonic, hydrochloric and sulfuric. 

 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 of the time that 

 nitrification 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 nitro- 

 gen in the form of organic matter. A crop used for this 

 purpose is called a "catch crop." Rye is used quite 

 commonly as a catch crop, as it continues growth until 

 late in the fall, and resumes growth early in the spring, 

 conserving nitrates whenever nitrification may 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 in- 

 creases such loss. The only remedy is the application 

 of some form of calcium to the soil. 



169. 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 analysed at certain times, and the results of these 

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

 of salts from cultivated soils. The drainage water was 

 obtained from the tile drains, one of which extended 

 under each plat from one end to the other, and opened 

 into a ditch, so that the water could be collected when 

 desired. The analyses shown in the accompanying table 



