Management Effects on Harvest Losses and Yield of Double-Crop Soybean
Soybean [Glycine max (L.) Merr.] double cropped with wheat [Triticum aestivum (L.) em Thell] may be more subject to harvest losses than a full season crop due to reduced lowest pod height (LPH). The objective of this field study was to determine the effects of wheat stubble heights (WSH) of 0,15, and 30 cm; soybean planting rates of 37, 65, and 92 seeds m−2; and soybean cultivars of differing maturity [Pella, early Maturity Group (MG) III, Douglas, mid-MG IV, and Mitchell 450, late MG IV] on LPH, harvest losses, and yield. Clipped wheat residues were removed, and soybean planting was done without tillage on a Maury slit loam (Typic Paleudalfs). Increases in WSH and soybean planting rate had no effect on soybean harvest losses, which averaged 0.4, 2.0, and 6.6% for soybean cutting heights (SCH) of 5, 10, and 15 cm, respectively, and reached 16.5% at the 15 cm SCH for Pella in 1986. The latest maturing cultivar had the highest LPH and incurred the smallest harvest losses. Its yield performance in these years, however, was not competitive with the earlier maturing cultivars (2.06, 2.03, and 1.72 Mg ha−1 for Pella, Douglas, and Mitchell 450, respectively). Increasing WSH from 0 to 15 cm improved mean soybean yield by 16.9% in 1986, but had no effect in 1985. Although the use of a later maturing cultivar resulted in greater LPH, its yield was less than earlier cultivars. Increased WSH and soybean planting rate were not supported as strategies to reduce soybean harvest losses.
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