Conservation Management and Crop Rotation Effects on Weed Populations in a 12-Year Irrigated Study

Abstract

Potato, dry bean, and sugar beet production have increased markedly in recent years on irrigated cropland in Alberta, Canada. Concerns exist about declining soil quality and increased soil erosion when these low-residue crops are grown in sequence in short-duration rotations. A 12-yr rotation study was conducted to determine the merits of adopting various conservation practices (reduced tillage, cover crops, composted manure) and longer-duration rotations to develop a more sustainable production system for these row crops. This article reports on weed density and weed seedbank data collected in the study. Weed densities recorded prior to applying postemergence herbicides indicated that conservation compared with conventional management treatments had greater weed densities in 30 to 45% of the cases in 3-, 4-, and 5-yr rotations. In contrast, a 6-yr conservation rotation that included 2 yr of timothy forage resulted in similar or lower weed densities than rotations with conventional management practices. Residual weed densities recorded 4 wk after applying postemergence herbicides were only greater in conservation than conventional rotations in 2 of 12 yr, regardless of rotation length. Weed seedbank densities at the conclusion of the 12-yr study were similar for 3- to 6-yr rotations under either conservation or conventional management. These findings indicate that implementing a suite of conservation practices poses little risk of increased weed populations in the long term. This knowledge will facilitate grower adoption of more sustainable agronomic practices for irrigated row crops in this region.

Conservation Management Practices and Rotations for Irrigated Dry Bean Production in Southern Alberta

“…Pynenburg et al (2011) reported that high weed pressure in the presence of white mold increased disease severity for dry bean in Ontario. In our study, narrow‐row dry bean often had higher weed populations (Blackshaw et al, 2015) than wide‐row due to reliance on herbicides for weed control in the absence of inter‐row cultivation and this may have contributed to higher white mold incidence.…”

“…In 2003 the wide‐row 4‐CONV rotation (30 plants m −2 ) had significantly higher plant density than narrow‐row 3‐, 4‐, and 6‐CONS (14–24 plants m −2 ). This was likely due to higher weed populations in the narrow‐row treatments (Blackshaw et al, 2015). Since inter‐row cultivation was not possible with narrow rows, weed control based solely on herbicides was a challenge, especially in the early years of the experiment.…”

On-farm evaluation of integrated weed management in no-till rainfed crops in semi-arid Morocco

“…However, in crop/livestock integrated production systems, weed weeds are an important challenge since most weeds are considered as free forage for livestock and the weedy fallow is widely practiced (El Brahli and Mrabet, 2000). Abandoning the plow induces a qualitative and quantitative change in the flora which is why no-tillage crop production relies primarily on herbicides, particularly glyphosate, for weed management (Aibar, 2006;Blackshaw et al, 2015;Loss et al, 2015).…”

“…Integrated weed management systems have the potential to provide long-term management of weeds (Blackshaw et al, 2005;Holm et al, 2006;Harker and O'Donovan, 2013;Blackshaw et al, 2015). Agronomic factors such as crop diversification and rotations, combined with herbicides, need to be evaluated for their potential to manage weeds in no-till system in semi-arid Morocco.…”

Weed Dynamics in No-Till Rainfed Crops in Chaouia, Semi-Arid Morocco

“…Such increased use of herbicides may be considered by small farmers a major problem of no-till farming particularly in a time when the use of agrochemicals is considered by the general public as threat for human health and the environment (Friedrich, 2005). management under CA may include the combination of applied soil herbicides, crop rotation, and competitive crop varieties with weeds (Anderson, 2015;Blackshaw et al, 2005Blackshaw et al, , 2015Gulden et al, 2011;Harker & O'Donovan, 2013;Holm et al, 2006).…”