already very porous and upon, arid, which already have thu 

 percentage of lime demanded as plant-food, in these its 

 mechanical effect is not called for. 



53. One is often asked what can be done to correct the 

 objectionable brackness or alkalinity of some of our soils, 

 so that some kind of an orchard crop can be obtained from 

 them. Once for all let it be stated that ordinary lime has 

 no curative effect ; what is wanted is gypsum, that is, 

 sulphate of liiue. The brackness known locally as zwart- 

 brak is due to carbonate of soda, a substance actually 

 poisonous to plants. The sulphate of lime exchanges con- 

 stituents with it, and you get sulphate of soda and carbonate 

 of lime as the result. Now although sulphate of soda is 

 not a desirable thing for one's soil, yet it is not nearly so 

 mischievous as the carbonate would be. Hence it is quite 

 possible for a cultivator whose circumstances oblige him to 

 work on an area which is more or less zwart-brak to make 

 a very tolerable culture off it by dint of a generous appli- 

 cation of gypsum. Before many years are past, the few 

 places where gypsum deposits are known to exist will have 

 a future before them. 



Green-manuring and Snatch-crops in the Orchard, 



54. There is yet another method of adding to the manurial 

 constituents of the soil which should not pass without 

 notice. This is the raising of a quickly growing annual 

 crop between the rows of trees and turning it in with the 

 plough or cultivator to decompose under the surface soil. 

 Xitrogen and organic matter form the principal gains deriv- 

 able from this so called green-manuring upon the large 

 scale on corn lands ; they scarcely apply to the smaller scale 

 of orcharding. Thus, short of complete rotation of crops, 

 there is no better way of checking wire-worm in corn -hinds 

 than by raising a snatch of rape or colza as early in the 

 season as is possible, and turning it under just before it 

 flowers. The insects that harbour in an orchard however, 

 are very different from the wheat-grower's wire-worm, and 



