Soybean Irrigation Serially Timed During Stages R1 to R6. I. Agronomic Responses1

Abstract

AbstractPrevious research has shown that irrigation timing during the reproductive development of soybean [Glycine max (L.) Merr.] J genotypes is a crucial determinant in ultimate yield response. To obtain more detailed information on this relationship we evaluated the agronomic responses of 16 soybean cultivars to nine irrigation treatments in a 3‐year field experiment. The experiments were conducted in 1980, 1981, and 1982 near Mead, NE on a Sharpsburg silty clay loam (fine, montmorillitic, mesic Typic Arguidoll). In treatments T1 thru T7, only a single irrigation was applied, which coincided with the average R stages 1.1, 2.5, 3.7, 4.7, 5.6, 5.9, and 6.4, respectively. “Check” treatments included T0, which was not irrigated, and T8, which received a total of seven irrigations coincident with those for T1 thru T7. Averaged over years and cultivars, the seed yield responses (kg/ha) were: T0: 3470c, T1: 3595abc, T2: 3530bc, T3: 3740a, T4: 3670ab, T5: 3630abc, T6: 3575bc, T7, 3560bc, and T8: 3540bc. The irrigation treatment X cultivar interaction was significant, primarily because T3 (R3.7) or T4 (R4.7) generally resulted in the highest yields for indeterminate cultivars, whereas T8 resulted in the highest yields for determinate cultivars. Averaged over irrigation treatments and years, the determinate cv. Hobbit was the highest yielding, both with and without irrigation. Significant increases in plant height, nodes/plant, and lodging occurred with the T1, T2, T3, and T8 treatments, but only with the indeterminate cultivars. Precise irrigation timing and proper cultivar choice seem to be crucial if high yields with minimum lodging are to be attained.