Wheat Response to Row Spacing in Relay Intercropping Systems

Relay intercropping of soybean [ Glycine max (L.) Merr.] or cotton [ Gossypium hirsutum L.] into standing wheat [ Triticum aestivum L.] allows for earlier planting of the summer crop than with sequential double‐crop systems. Relay intercropping has been evaluated using modifications of standard planting and harvesting equipment as well as specifically designed equipment. In most relay intercropping systems, wheat is drilled in the fall in a row pattern that provides traffic‐tire lanes as guides for planting the summer crop. Also, row spacing for wheat in relay intercropping is usually wider than for conventionally planted wheat. This field study, conducted during 1991‐1992 and 1992‐1993 near Blackville, SC, on a Varina loamy sand (clayey, kaolinitic, thermic Plinthic Paleudults), compared the yield and yield component response of soft red winter wheat produced with two different intercropping production schemes to the yield and yield component response of conventionally planted wheat. Yields of wheat planted in skip‐row schemes designed to allow for relay intercropping of either soybean or cotton were not significantly different from yield of conventionally planted wheat under the given experimental conditions. For conventionally planted wheat, wheel traffic on certain rows reduced yields by as much as 50% compared with nontraffic rows. In the schemes designed to allow for relay intercropping, wheat grown with wider‐spaced rows (0.31‐0.61 m) compensated with respect to yield on an area basis compared with wheat grown with conventionally spaced rows (0.15‐0.20 m).