Using weed cover to predict yield loss in soybeans

Andrew Crescent Seibert, Purdue University

Abstract

Crop producers commonly apply herbicides to safeguard against crop yield losses, without knowing how the weeds might actually affect yields. This study investigated using weed cover as an early-season predictor of crop yield loss. Weed cover was photographically recorded throughout the growing season. The effects of weed species, weed density, and row spacing on cover development and crop yield loss were recorded with weeds and soybeans (Glycine max L.) grown near West Lafayette, IN, on a Chalmers silty clay loam (fine-silty, mixed, mesic Typic Endoaquoll). In 1992, which had a favorable growing season, weed density affected weed cover and soybean yield, but not in 1993, which was wetter than normal. Weed species had no effect on soybean yield in either year. Soybean in 25-cm rows yielded higher than in 76-cm rows in both 1992 and 1993. Weed cover development was not affected by row spacing. Weed cover was not associated with reduced soybean cover until soybean cover was near 100%. On June 27, 1992, when soybeans were at V6/R1, weed cover accounted for 48% of grain yield variability. Weed cover measurements after June 27 continued to account for about half of grain yield variability in 1992. In 1993, weed cover accounted for 1–13% of yield variability where weeds were propagated, and 16–33% in plots with natural weed infestations. Weed cover was not a better predictor of yield loss than other weed parameters reported previously, although it may be easier to quantify, especially as remote sensing technology advances.

Degree

Ph.D.

Advisors

Vorst, Purdue University.

Subject Area

Agronomy

COinS