Because of the lack of moisture during the crops' peak demand, some producers have invested in irrigation systems. The cost of maintaining and using these systems is high, so it is imperative to manage moisture in the most efficient way possible. The following discussion should help Missouri soybean producers understand the crop's need, the soil's ability to hold and supply water, and the agronomic practices that can result in maximum economic yields under irrigation.
Irrigation usually improves soybean yields on drought-prone soils and in exceptionally dry seasons.
Responses of soybeans to irrigation in southeast Missouri, 1967-1974. In research sponsored by the grower check-off program, yields of 10 varieties grown in southwest Missouri during the dry years of 1983 and 1984 averaged 29 and 13 bushels more per acre respectively under irrigation. In 1985, when plentiful rains occurred during the seed-fill period, yields increased by only about 1 bushel per acre. The economics of achieving these yield increases are of paramount importance. The type of irrigation system and the water source greatly affect cost.