IRRIGATION 



73 



be conducted to the garden by gravity, so there would be 

 no expense for pumping. In many more instances a lift 

 of 5 to 15 feet would put the water on land admirably 

 adapted to garden crops. Near the cities water can usu- 

 ally be secured at reasonable prices, and at some places 

 for as low as 4 or 5 cents a thousand gallons. The late 

 W. W. Rawson, the well-known New England gardener, 

 claimed that an intensive grower could well afford to 

 pump water at a cost of 10 cents a thousand gallons. If 

 it were a matter of saving a crop from almost total loss 

 it might pay to use water at double this cost. 



117. Functions of water. — Before entering into a prac- 

 tical discussion of the subject of irrigation the student or 

 the reader should fully realize what an important part 

 water plays in the growth of plants. ( i ) It is a powerful 

 solvent of plant foods. No' matter how fertile a soil may 

 be naturally, or how much manure or fertilizer may be 

 added, such foods are valueless without water to dissolve 

 them. Both stable manures and fertilizers often fail to 

 give increased yields because of insufficient soil moisture. 

 (2) Water not only serves as a solvent, but it holds in 

 solution organic acids which are more powerful solvents 

 than water alone. (3) Water is essential to the life of 

 friendly bacteria. (4) Water serves as a vehicle in the 

 distribution of plant foods in the soil. 



Its functions in the plant are equally important, (i) 

 Water enters largely into the composition of all garden 

 products. Many vegetables contain over 90 per cent of 

 water. (2) Water is also a medium in the conveyance of 

 food in the plant, so that enormous quantities transpire 

 from the leaves. Several hundred pounds of water are 

 required to produce every pound of dry matter. It is 

 claimed that a well-developed hill of cucumbers will use 

 half a barrel of water in three days. (3) The transpira- 

 tion of water has an important relation to the fixation of 

 carbon from the atmosphere. 



