50 AGRICULTURE 



return in a district of heavy rainfall ; in fact 

 in districts where the rainfall is low, sands 

 may be practically barren. On the other 

 hand, no soil is so suitable for purposes of 

 irrigation, no matter whether the water that 

 is used is comparatively pure, or whether 

 it is of the nature of sewage. To get the 

 best returns from irrigation the water must 

 filter through the body of the soil, and escape 

 into the drains or the sub-soil. In this way 

 the water is brought more directly into 

 contact with the roots of plants, and the 

 substances held in suspension are more com- 

 pletely separated and retained in the body 

 of the soil. 



Sandy soil, although poor in itself, is well 

 fitted for intensive agriculture or, as it is 

 otherwise called, high farming. But a first 

 necessity in adapting soil for intensive agri- 

 culture is the provision of an abundant supply 

 of humus, and this is usually most easily 

 secured by liberal dressings of farmyard 

 manure. Another way of adding to the stock 

 of decomposing vegetable matter in soil is 

 through the agency of green manure, that 

 is to say, by the growth of a quick-growing 

 crop, capable in a short time of forming a 

 large quantity of herbaceous material, which 

 can be dug or ploughed into the soil, and 



