No‐Till Soybeans in Forage Grass Sod1

Abstract No‐till planting of soybeans [Glycine mar (L.) Merr.] is a widespread practice in the midwestern and southern U.S.A. However, the vast majority of this hectarage is double‐crop soybeans planted in wheat (Triticum aestivum L.) or another small grain after grain harvest. Occasionally, soybeans have been planted in a chemically‐controlled winter cover crop. Little work has been reported on the possible merits of planting soybeans in a grass sod, which would offer the advantages of reduced soil erosion hazards and greater flexibility in soybean production systems. Field studies were designed to investigate the success of no‐till soybean production in forage sod. The soils representing different sites and experiments were Weir silt loam (Typic Ochraqualf), Stoy silt loam (Aquic Hapludalf), Alford silt loam (Typic Hapludalf), and Ebbert silt loam (Argiaquic Argialboll). Soybeans were planted in a tall fescue (Festuca arundinacea Schreb.) sod for 4 years at the Carbondale location, and for 2 years in Kentucky bluegrass (Poa pratensis L.) at the Belleville location in southern Illinois. When rainfall was adequate, no‐till soybean production in grass sods was highly successful, with yields as much as 4,308 kg/ha in tall fescue in 1977 and 4,704 kg/ha in tall fescue and 4,119 in Kentucky bluegrass in 1979. In the 2 years of plentiful moisture, adjusted herbicide rates allowed persistence or autumn regrowth of up to 40% of the forage grass, which could be an important factor regarding autumn and winter grazing and erosion control. The best herbicide treatments in these studies for allowing a combination of soybean yield and forage grass persistence or regrowth was paraquat (1, 1′‐dimethyl‐4,4′‐bipyridinium ion) alone at 0.6 kg/ha, paraquat at 0.6 kg/ha in combination with metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] at 3.4 or 4.5 kg/ha or with mefluidide{N‐[2,4‐dimethyl‐5‐[[trifluoromethyl) sulfonyl] amino] phenyl] acetamide} at 0.6 kg/ha. Another promising combination was glyphosate [N‐(phosphonomethyl) glycine] at 1.1 kg/ha plus metribuzin [4‐amino‐6‐tert‐butyl‐3(methylthio)‐as‐triazin‐5 (4H)‐one] at 1.1 kg/ha. All of these treatments resulted in no‐till soybean yields exceeding 4,000 kg/ha, when growing season rainfall was adequate, and tall fescue maintenance or regrowth resulting in 25 to 40% sod cover in the autumn.