Double and Monocropped Wheat and Soybeans Under Different Tillage and Row Spacings¹

Abstract

In wheat [Triticum aestivum (L.) Thell] producing regions with adequate frost‐free days to permit double‐cropping, water is often the most limiting factor in producing the second crop. To more fully utilize climatic resources and land after the harvest of wheat grain, a field study was conducted on a Wynona silty clay loam (Cumulic Haplaquolls) to analyze the effects of tillage and row spacings on soil water content and yields of monocropped (MC) and double‐cropped (DC) wheat and soybeans [Glycine max (L.) Merr.]. Double‐cropped wheat (DCW) yielded 2,210 compared to 2,530 kg/ha for monocropped wheat (MCW). Conventional tillage double cropped soybeans (CT‐DCS) in 50‐cm rows yielded 1,610 compared to 1,460 kg/ha in 75‐cm rows. No‐tillage double‐cropped soybeans (NTDCS) in 50‐cm rows yielded 1,730 compared to 1,550 kg/ ha in 75‐cm rows. Conventional tillage monocropped soybeans (CT‐MCS) in 50‐cm rows yielded 2,010 compared to 1,880 kg/ha in 75‐cm rows. Water content in 120 cm of soil profile was not significantly affected during the soybean growing period by tillage and row spacings; however, lack of moisture in the soil‐seed environment resulted in poorer stands and lower yields for CT‐MCS in 1976. Water storage efficiency under wheat from the fully ripe stage of growth to late September averaged 28% for MCW. More grain production and more effective use of annual precipitation and soil stored water were achieved when wheat and soybeans were DC.

Cropping system influences on extractable water for mono- and double-cropped soybean

“…These soybean, then, efficiently utilized water deeper in the profile. Crabtree and Rupp ( 1980) also concluded that the double-cropping of wheat and soybean used water stored in a 120-cm profile more efficiently than the monocropping of either crop. Cropping system had no significant effect upon extractable water in the 76-cm soybean plots ( Table 2).…”

“…This shading likely slowed soil evaporation. Crabtree and Rupp (1980) found that an extensive crop canopy limited evaporative water loss. Crop canopy enlargement does, however, increase soil water loss due to plant transpiration (Taylor and Ashcroft, 1972).…”

“…Numerous authors (Sanford and Hairston, 1984;Crabtree et al, 1987;Daniels and Scott, 1991) have warned that high-yielding wheat could leave a water-depleted profile for the subsequent soybean crop, severely reducing yields (Roder et al, 1989). Also, water in the soil at the seeding depth must be sufficient at soybean planting to assure adequate germination and a stand (Crabtree and Rupp, 1980;Wesley and Cooke, 1988). Other actively transpiring plants, such as weeds, growing in areas planted with soybean will compete for water (Whisler et al, 1982;Banks et al, 1985 ).…”

“…Soybean yields generally increase in the southeastern United States when soybean is (1) planted relatively early (Coale and Grove, 1990), and (2) grown in narrower rows (Crabtree and Rupp, 1980;Mason et al, 1982;Coale and Grove, 1990). Under severe drought stress, however, narrower row spacings may decrease yields ( Alessi and Power, 1982).…”

Producing Soybean and Wheat Cropping Systems in Rainfed Environments

“…Grower interest has increased dramatically in crops serving as alternatives to complement winter wheat in continuous, winter wheat monocrop areas. Reasons may be agronomic, environmental, or economic (2,3,4,5,18). Soybean can be produced as an early-season or doublecrop with winter wheat in cropping systems, representing multiple cropping and increasing the number of crops harvested per unit area of land for a given time period.…”