CEREALS UNDER IRRIGATION 435 



in March, as early as weather conditions will permit, and 

 when the grain is a few inches high, to drill the alfalfa 

 into it. For the good of the alfalfa, the grain is cut for 

 hay before it is mature, which gives the alfalfa time to 

 make good growth before cold weather (Scofield and 

 Rogers, 1909). 



A good method of seeding alfalfa into the grain is to 

 drill it across the grain rows after the latter is up, drilling 

 it much shallower than the grain. As to the rate of seed- 

 ing nurse crops, Knorr (1914) recommends 3 pecks of 

 wheat, 5 to 6 pecks of oats, and 4 pecks of barley. 



In the Columbia River Basin, rye is most commonly 

 used to start alfalfa, because it is hardier than other 

 cereals and will resist the blowing sand. The land is 

 irrigated after the hottest weather, usually the last of 

 August. Immediately after, while the soil is moist, 50 

 to 60 pounds of rye and 15 to 20 pounds of alfalfa to the 

 acre are sown together with a drill, the latter being pro- 

 vided with a grass seeder attachment for the alfalfa. 

 The seed should be covered about 2 inches deep. The 

 following spring the rye is clipped 2 or 3 times after 

 jointing, to prevent it from smothering the alfalfa. 

 Sometimes the rye is sown alone in October, and the 

 alfalfa drilled into the grain early in the spring (Hunter, 

 1909). 



472. The alkali menace. The fact has been men- 

 tioned that in the Great Plains and Western area, there 

 is a large percentage of mineral salts in the soil (246). 

 These occur in proportionally larger quantities, even, as 

 the humus content becomes less. In normal quantities 

 in the soil, they are essential in cereal production, but 

 some of them, when accumulated in excess, become de- 

 structive to all crops, though in varying degrees to dif- 



