Field research (2003–2005) evaluated the effect of wheat row spacing (19 and 38？cm) and cultivar on double-cropped (DC) soybean response, 38-cm wheat on relay-intercrop (RI) response, and wheat cultivar selection on gross margins of these cropping systems. Narrow-row wheat increased grain yield 460？kg , light interception (LI) 7%, and leaf area index (LAI) 0.5 compared to wide rows, but did not affect DC soybean yield. High yielding wheat (P25R37) with greater LI and LAI produced lower (330？kg？ ) soybean yields in an RI system than a low yielding cultivar (Ernie). Gross margins were 267？ greater when P25R37 was RI with H431 Intellicoat (ITC) soybean compared to Ernie. Gross margins were similar for monocrop H431 non-coated (NC) or ITC soybean, P25R37 in 19- or 38-cm rows with DC H431 NC soybean, and P25R37 in 38-cm rows with RI H431 ITC soybean in the absence of an early fall frost. 1. Introduction Claypan soils cover approximately 4 million hectares in the Midwestern U.S. These soils are poorly drained partially because of an argillic claypan layer 15 to 24？cm below the soil surface, and they are highly erodible due to slopes up to 20% and surface water runoff [1, 2]. Conservation tillage systems are recommended to reduce soil loss [3]. Due to economic considerations and relatively strong corn and soybean prices, cropping systems have shifted from a rotation of corn (Zea mays L.) soybeans [Glycine max (L.) Merr.] and wheat (Triticum aestivum L.) to a rotation of corn and soybeans. Small grains such as wheat are important crops to increase water infiltration, organic matter, soil structure, and to reduce soil erosion from surface water runoff [4–6]. No-till soybeans, double-cropped after wheat, had 75% of the runoff of monoculture, conventional tilled soybeans in upland silty soils [5]. Some farmers have used double-cropped soybean production to increase wheat profitability [7–9]. In the absence of government programs, a risk and return analysis in southeast Kansas favored double-cropped wheat-soybeans over monocropped wheat or soybeans [10]. Relay-intercrop production has been proposed in the Midwest to reduce production risks of double-cropping. Double-cropping soybeans after wheat is risky above latitude due not only to low rainfall and dry soils at planting, but also to a relatively short growing season that can be limited by early frost which reduces grain quality and yield [11, 12]. Relay-intercrop production involves overlapping growth cycles of two or more crops. This production system is common with legumes seeded into small grains; however,
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