Response of Solid‐Seeded Soybean to Flood Irrigation. II. Flood Duration

Flood‐irrigated soybean [ Glycine max (L.) Merr.] can be exposed to extended periods of soil‐saturated conditions, depending on the producers method of application, watering capacity, and field size. Field studies were conducted on a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf) soil in southwest Louisiana during 1982 to 1984 to evaluate the effects of flood duration on solidseeded (i.e., nonbedded narrow rows) ‘Ransom’ soybean. Soybean was flooded at the V6 (vegetative), R2 (bloom), or R2 + R5 (bloom and pod fill) growth stages. Within each timing treatment, water was applied to a standing depth of 0.076 m and allowed to stand for 0 (nonflooded control), 1, 2, 4, or 8 d. Soybean stand density did not change as flood duration increased. Yields for individual timing treatments were generally similar when flood periods were 0, 1, or 2 d. When water was held longer than 2 d postflowering, significant yield reductions were noted in all years and were as much as 1390 and 1520 kg ha −1 in 1982, when water was applied at R2 or R2 + R5, respectively. In 1982 and 1984, when water was applied at R2 + R5, average yield reductions associated with increasing flood duration from 2 to 4 d and from 2 to 8 d were 20 and 10% higher, respectively, compared with R2 only. Increasing flood duration at V6 from 4 to 8 d decreased yields in 1982 and 1984 an average of only 340 kg ha −1 . For those 2 yr, with flood periods of 4 or 8 d, yields for soybean flooded at V6 were substantially higher than yields from the R2 or R2 + R5 treatments. Increased numbers of both seeds per pod and seeds per plant accounted for the higher yields in the V6 treatment. When flood irrigating solid‐seeded soybean after flowering, attempts should be made to remove standing water within 2 d to avoid yield reductions.