IRRIGATION 119 



where there is sufficient rainfall to start the grain, irrigation 

 is not practiced until the grain is six or eight inches high. It 

 is generally considered better, however, if it is found neces- 

 sary to irrigate near the time of planting, to irrigate before 

 planting rather than after. 



On light soils with free underdrainage it may not be 

 possible to retain the moisture through the winter season, 

 in which case irrigation should be practiced near the time of 

 planting. It is to be noted, however, that in some localities 

 it may be advisable to irrigate after planting, in order that 

 the time of planting may not be delayed. The principal 

 danger in irrigation after planting lies in the formation of 

 crusts. When the crust forms it must be either softened 

 with a subsequent irrigation or broken up mechanically by 

 means of special rollers or peg-tooth harrows. 



It is considered best not to furnish so much water as to 

 grow a large straw crop. Heavy straw crops make a large 

 demand upon the soil moisture, and are not essential for 

 large crops of grain. Grain is also likely to be of more value 

 when grown on straw that does not have a rank growth. It 

 is customary, then, to dispense with as much irrigation during 

 the growing season as is possible without lowering the 

 vitality of the grain. 



In some localities only one irrigation is necessary, and this 

 is given at the time when grain is in the milk stage. It 

 seems quite important that the grain be supplied with 

 abundant moisture at this time. In other localities where it 

 is quite dry and where the conditions of soil and climate 

 require it, two or more irrigations may be given. 



Alfalfa. One of the great crops of the irrigated land in 

 the United States is alfalfa. Like grain, if an ample supply 

 of moisture is given to the soil before the seed is sown, 

 there will be little need of another early irrigation. If the 



