FARM IRRIGATION 237 



to be had at that time it profits nothing that the 

 soil is replenished with moisture in winter, unless 

 it can be husbanded by the methods of "dry farm- 

 ing." 



Irrigation to Enrich the Land. A secondary 

 object of irrigation, in some cases, is to carry to the 

 crops fertilising material dissolved in water. In 

 sewage irrigation this is the principal object; but 

 fields are often flooded with the water of rivers 

 chiefly for the purpose of enriching them with the 

 fine soil and plant food held by the water. Even 

 though the water of a stream may seem quite pure 

 and be very acceptable for drinking, it may contain 

 sufficient plant food in solution, or in the mud it 

 carries, to make it worth while to distribute this 

 water on land solely for the sake of securing the 

 plant food it contains, which is mostly left in the 

 soil when the water evaporates or seeps down. 

 Many meadows in England and Scotland are 

 irrigated chiefly for the fertilising value of the 

 water. Occasionally, also, the fertilisers that are 

 to be applied to irrigated land are dissolved in the 

 water and distributed by it. 



Another object is to correct " alkali." Occasion- 

 ally irrigation is practised to change the texture 

 of the soil, as, for example, to fill an open, 

 sandy soil with the sediment of a muddy stream. 

 But the chief and almost the only object of 

 irrigation in this country, as applied to farm- 

 ing, is to supply water, with the incidental benefit 

 of adding fertility. 



HOW FAR THE NATURAL SUPPLY OF WATER WILL GO 



How dry a region or a soil must be in order to 

 make irrigation necessary, or in other words, the 



STATE NORMAL SCkuA^, 



UOS HliES CHU. 



