232 POWER 0* SOIL TO ABSORB SALTS [chap. vin. 



of ammonium salts every other year seems to leave no 

 residue for the following year, may perhaps be set down 

 to the different texture of the two soils. The ammonium 

 salts are converted which are washed down into the 

 subsoil ; at Woburn they can rise again by capillarity, 

 as the soil, though sandy, is still fine in texture; at 

 Rothamsted the soil is too close-grained to admit of 

 any considerable movement of the subsoil water back 

 to the surface. 



The experiments recorded above and the results 

 of the examination of drainage waters go to show 

 that nitrate of soda should only be employed when 

 there is a crop in possession of the ground and ready 

 to seize upon the salt as soon as it becomes diffused 

 through the soil. Only on dry soils can it be safely 

 applied as early as the sowing of the seed ; in wet 

 climates sulphate of ammonia will often be preferable 

 it the soil is warm enough to induce reasonably quick 

 nitrification, and when large quantities of nitrate are 

 wanted they should be put on by successive applications 

 of not more than 1 cwt. per acre at a time. 



