IRRIGATION AND ROTATION OP CROPS. 



9 



when if water could be applied to growing crops it would im- 

 prove them. It will seldom if ever pay to irrigate ordinary 

 farm crops, if it is necessary to pump the water used. In 

 order to have irrigation practical for farm crops the water should 

 be carried and distributed on the land by the force of grav- 

 ity. It may pay to pump water to irrigate some garden crops 

 if the conditions are favorable and the work is done intelli- 

 gently. In this section irrigation should be used to supple- 

 ment the rainfall which should ordinarily be kept from run- 

 ning off the surface of the land by every possible precaution. 



Mulching the surface of the soil is practicable only around 

 trees and in the case of a very few garden crops, such as 

 strawberries and raspberries. The intelligent use of mulch 

 on land in well known cases has caused the soil under it to 

 hold an amount of water equal to thirty-three per cent more 

 than was retained in soil near by not mulched, the amount in 

 one case being equal to an increase of over two quarts of water 

 to every cubic foot of soil, or to an increase of over 680 barrels in 

 the upper one foot of soil of one acre. If this amount of water 

 had been applied at the critical stage in the growth of some 

 crops suffering for moisture, it might have made a success of 

 what would otherwise have been a failure. Where practicable 

 it is always desirable to have a good mulch on land that i3 

 watered, since it retards evaporation and px^vents the surtacrt 

 soil from baking. 



Cultivation of the land prevents evaporatioxi and so saves 

 the moisture in it. In one instance the amount of increase 

 of water in a good soil due to cultivation was equal to thirty- 

 three per cent of what it contained when not cultivated. This 

 increase, however, is somewhat more than was found in other 

 trials, but in every instance there has been a marked increase 

 in the drought resisting qualities of the soil due to continued 

 cultivation. In some experiments made by Professor Levi Stock- 

 bridge in 1878, it was clearly shown that on one occasion in 

 eight days of very dry summer weather thorough cultivation 

 of the land resulted in saving 256 barrels of water in an acre 

 of heavy loam by preventing evaporation from its surface. 

 These facts show the great value of cultivation as an aid in 



