Impact of Tillage, Raised Seedbeds, and Fungicides for Soybean Production in Mississippi

J.B. Blessitt, D.H. Poston, T.W. Eubank, R.T. Coleman

In the Yazoo-Mississippi Delta, soybean varieties with little flood tolerance are often planted flat on poorly-drained, heavy-clay soils. Field experiments were conducted near Elizabeth, MS in 2006 to compare disease occurrence, yield, and net returns of soybeans grown using no tillage, surface tillage, and deep tillage production systems and compare yield and net returns for soybean planted flat and on raised beds. The test location had been in continuous no-till soybean production for eight years. The soil type was a Sharkey silty clay loam, and the field was known to have surface and internal drainage problems. Compared to no-till plots, deep tillage increased soybean yield 730 kg/ha. There was no significant yield response to shallow tillage. Soybean yield with Pioneer 94B73, a flood-tolerant variety, was higher than with Asgrow AG4403 which generally performs better on well-drained soils. Disease levels were not affected by tillage, but were significantly reduced by pyraclostrobin fungicide. Fungicide increased soybean yield 410 kg/ha. Planting the flood-tolerant P94B73, using deep tillage, and applying a fungicide resulted in a 1540 kg/ha yield advantage over planting the flood-susceptible AG4403 no-till with no fungicide. In a separate study, soybean yield with raised beds was 580 kg/ha higher than with flat plantings. The flood-tolerant variety outperformed the flood-susceptible variety and a fungicide increased yield. Planting a flood-tolerant variety on raised beds and treating with a foliar fungicide resulted in an 1180 kg/ha yield advantage over planting a flood-susceptible variety flat and not treating with a foliar fungicide. These findings indicate that long-term, no-till monoculture soybean production systems may not be economically sustainable in the Yazoo-Mississippi Delta and implementing methods to improve surface and/or internal drainage can be profitable.