Weed Community Composition in Simple and More Diverse Cropping Systems

Huong T X Nguyen,Matt Liebman

doi:10.3389/fagro.2022.848548

Abstract

Weed communities in three cropping systems suitable for the Midwestern USA were studied from 2017 to 2020 to examine how crop diversification and the intensity of herbicide use affected weed community diversity, stand density, and aboveground mass. A baseline 2-year cropping system with corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) grown in alternate years was diversified with cool-season crops, namely oat (Avena sativa L.), red clover (Trifolium pratense L.), and alfalfa (Medicago sativa L.) in 3-and 4-year systems. Herbicide was not applied in the cool-season crops. Changing weed management regime from broadcast to banded application and interrow cultivation in corn and omitting herbicide in cool-season crops of the 3- and 4-year rotations resulted in an overall reduction of herbicide a.i mass. The reduction in the mass of herbicide active ingredients was associated with increases in weed stand density, aboveground mass, and community diversity. Increased weed abundance under herbicide mass reduction was not associated with crop yield loss. In the cool-season crops phases of the 3- and 4-year rotations, weed emergence was increased but weed growth was not, as compared with the warm-season crop environments. The dominance of aggressive weed species such as common waterhemp (Amaranthus tuberculatus (Moq ex DC) J.D. Sauer) and common lambsquarter (Chenopodium album L.) tended to be greater in corn and soybean phases of the rotations than in oat, red clover, and alfalfa.

Highlights

The composition of weed communities found in agricultural fields is strongly affected by the types of crops grown and their attendant management practices (Mohler, 2001; Légère et al, 2005; Culpepper, 2006; Smith and Gross, 2007)
Diversification of cropping systems led to increased weed community aboveground mass and stand density, increased weed community diversity and species richness, and decreased weed community evenness
Increased weed abundance was not associated with reduced crop yield

Summary

INTRODUCTION

The composition of weed communities found in agricultural fields is strongly affected by the types of crops grown and their attendant management practices (Mohler, 2001; Légère et al, 2005; Culpepper, 2006; Smith and Gross, 2007). Cropping system diversification strategies that are designed to reduce reliance on external inputs, including herbicides, can balance productivity, profitability, and environmental quality goals (Davis et al, 2012; Hunt et al, 2017, 2019, 2020; Bowles et al, 2020; Tamburini et al, 2020; Beillouin et al, 2021) They can increase cropping systems’ overall resilience to growing environmental adversity (Bowles et al, 2020) and can be effective in suppressing weeds (Weisberger et al, 2019). We hypothesized that diversified cropping systems, with reduced use of chemical herbicides, would provide weed control equal in effectiveness to the conventional approaches applied in the 2year corn and soybean system. We hypothesized that the weed communities in the more diverse cropping systems would be more diverse, more even, and more species-rich than those in the 2-year corn and soybean system, reflecting a broader range of crop species and their attendant management practices in the more diverse rotations. We hypothesized that including oat, red clover, and alfalfa in rotations with corn and soybean would reduce the density and aboveground mass of noxious weed species in corn and soybean when the rotations cycles returned to corn and soybean

MATERIALS AND METHODS

RESULTS

DISCUSSION

DATA AVAILABILITY STATEMENT