Seeding Rates for Small Grains in Arizona

Wheat and barley are the two major small grain crops in Arizona. These crops can produce yields near maximum at a wide range of seeding rates due to yield component compensation. Grain yield is determined by plants per unit area, tillers per plant, kernels per head, and kernel weight. At a low seeding rate, the plant will compensate for fewer plants per unit area by producing more tillers per plant and larger heads. At a high seeding rate, fewer tillers are produced compared to a low seeding rate, and the heads are smaller. Therefore, grain yields near maximum can be produced at a wide range of seeding rates if conditions are favorable (see Fig. 1). Weed control can be a problem at low seeding rates and lodging may be a problem at high seeding rates. The optimum seeding rate for small grains depends on a variety of factors which will be discussed.