IX.] FERTILISERS DESTROYING THE TEXTURE 251 



humus in a flocculent form. If now underdrainage be 

 brought into practice the soluble salts can be washed 

 through, and a very fertile soil results, owing to the 

 presence of the finely divided humus and calcium car- 

 bonate. Where underdrainage is hardly practicable 

 because of the expense, irrigation water should be 

 used in as limited amounts as possible, and every 

 care should be taken to keep the surface tilled and 

 under crop, so as to minimise evaporation from the 

 bare ground. In humid countries like our own, 

 damage due to the accumulation of salts are rare; 

 the author has, however, seen one case where the 

 vegetation of a lawn was destroyed during a hot dry 

 spell of weather by continuously applying water in 

 quantities which never washed down into the subsoil, 

 but evaporated every day. An efflorescence practically 

 identical with white alkali is sometimes seen on green- 

 house borders, which are constantly watered, but never in 

 sufficient quantities to cause percolation ; and gardeners 

 again are familiar with the check of growth which 

 sometimes occurs in the case of plants long in one 

 pot and constantly watered with hard water. The 

 remedy is to water from time to time so heavily as 

 to cause abundant percolation and thus wash all the 

 salts out. 



Closely related to some of the phenomena presented 

 by alkali soils are certain secondary effects upon the 

 texture of the soil which are produced by the action of 

 some of the salts used as artificial manures. A good 

 friable texture in a heavy soil depends upon the clay 

 particles being generally flocculated and gathered 

 together into little aggregates, which give the soil a 

 coarser grain until they are resolved into their ultimate 

 particles by incautious working when the clay is in a wet 

 state. It has already been shown that acids and most 



