Yield Loss and Management of Volunteer Corn in Soybean

Abstract

Volunteer corn is often overlooked as a weed in soybean. To aid in management decisions, this study determined soybean yield loss attributed to volunteer corn and efficacy of various herbicides at several rates and timings. A hyperbolic equation estimated (R2= 0.88) incremental yield loss (I) of 39.7% at low density when maximum yield loss (A) was constrained to 71%, the highest yield loss observed in these trials, revealing a more competitive plant than many common midwestern weedy species. Clethodim applied at 51 g ai ha−1at V4 soybean resulted in > 90% volunteer corn control with < 5% soybean yield loss, whereas if applied at 12.7 g ai ha−1volunteer corn control was 15%, but soybean yield was 50% greater than the nontreated control. On the basis of these data, the partial volunteer corn control improved soybean yield. Timing of glufosinate application influenced volunteer corn control. Glufosinate applied to 15-cm-tall corn resulted in 33% control, whereas applications to 36- to 91-cm corn resulted in > 70% control. Glufosinate combined with grass herbicides improved control to > 85%, with concomitant yield increases. Results demonstrated that volunteer corn substantially reduced soybean yield at low densities and yield increased when volunteer corn was controlled with various herbicides. On the basis of these results, and current soybean grain and herbicide prices, soybean yield gains from volunteer corn control could increase net return by > $150 ha−1.