2019 journal article

The Influence of Postemergence Herbicide Timing and Frequency on Weed Control and Soybean Yield

CROP FORAGE & TURFGRASS MANAGEMENT, 5(1).

By: D. Mahoney n, D. Jordan n, A. Hare n, R. Leon n, M. Vann n, N. Burgos*, K. Jennings n

co-author countries: United States of America 🇺🇸
Source: Web Of Science
Added: December 9, 2019

Core Ideas Optimizing herbicide timing and frequency for weed control in soybean is critical. Two or more postemergence herbicide applications were required in twin- and narrow-row soybean. Herbicide programs generally provided similar soybean yield. More intensive herbicide programs did not reduce economic returns. Understanding optimal herbicide timing and frequency is critical for mitigating weed seed return to the soil seedbank and maximizing crop yields. Research was conducted over 2016–2018 in North Carolina to determine postemergence-only herbicide application timing and the frequency necessary for adequate weed control, soybean [Glycine max (L.) Merr.] yield, and economic return in twin- and narrow-row soybean. Predominant weeds included common ragweed (Ambrosia artemisiifolia L.), large crabgrass [Digitaria sanguinalis (L.) Scop.], Palmer amaranth (Amaranthus palmeri S.Watson), and Texas millet [Urochloa texana (Buckley) R.D.Webster]. Four postemergence timings included early (EPOST), mid-postemergence, late, and very late postemergence (VLPOST) applications in various combinations. An untreated control was included for comparison. Regardless of planting pattern, broadleaf weed control was 9 to 48% higher when herbicides were applied two or more times than with single EPOST or VLPOST-only applications. Generally, two to three applications were needed to provide 100% annual grass control, whereas single applications only provided 71 to 92% control. Applying herbicides increased yield by 21 to 46% when compared with untreated soybean. In treated soybean, yield following the VLPOST treatment was generally lower than under other regimes. Trends for economic return were similar to those of yield. The data illustrate that multiple postemergence applications are needed for adequate weed control and do not adversely affect net returns. Although yields were protected with the EPOST-only treatment, caution must be taken to mitigate returning weed seed to the soil seedbank, as control for this treatment was lower than when herbicides were applied multiple times.