Cover Crop for Early Season Weed Suppression in Crops: Systematic Review and Meta‐Analysis

Abstract

W eeds occurring during early crop growth need to be removed because these are known to be most competitive with crops (Knezevic et al., 2002; Norsworthy and Oliviera, 2004; Tursun et al., 2016; Osipitan et al., 2016). Uncontrolled weeds at this early growth stage could cause irreversible and substantial crop yield losses (Knezevic et al., 2002, Adigun et al., 2014). If weeds are controlled at this time, crops can get a head start, achieve canopy closure, and compete effectively with later emerging weeds (Rajcan and Swanton, 2001). Typical early season weed control options include pre-plant, pre-emergence, and early post emergence herbicide applications in no-till cropping systems or mechanical cultivation in tilled systems. Herbicides provide an easy and cost-effective way of controlling weeds in crops and result in increased crop vigor and yield. Conversely, they are also a potential threat to the environment (e.g., pesticides residues in surface and/or groundwater) and in some areas, the development of resistant weed biotypes has reduced the utility of herbicides. In tillage-based cropping systems, mechanical operations such as plowing, harrowing, disking, and cultivating are used. Tillage for weed control has been utilized for a long time (Abdin et al., 2000) as it reduces weed density. At the same time, weed seeds receive a brief exposure to sunlight, due to soil inversion after tillage that can trigger their germination. There are still concerns about the negative impact of tillage on soil health and topsoil erosion (Loaiza Puerta et al., 2018). Cover crops have been documented to improve soil quality and minimize environmental degradation while providing a level of weed suppression in crops

Impact of Cover Crop Management on Level of Weed Suppression: A Meta‐Analysis

“…A report showed that most studies that evaluated weed suppression by cover crops were conducted at sites with what appeared to be adequate annual rainfall (³750 mm) or with irrigation provided where rainfall was inadequate to optimize cover crop biomass production necessary for weed suppression (Osipitan et al, 2018). A report showed that most studies that evaluated weed suppression by cover crops were conducted at sites with what appeared to be adequate annual rainfall (³750 mm) or with irrigation provided where rainfall was inadequate to optimize cover crop biomass production necessary for weed suppression (Osipitan et al, 2018).…”

“…Weed suppression using cover crops in conservation tillage systems was comparable with chemical and mechanical weed control in many situations, particularly at early stages of crop growth according to a recent meta-analysis study (Osipitan et al, 2018). The level and duration of weed suppression provided by…”

Advancing cover cropping in temperate integrated weed management

“…2 Even low seeding rates of fast emerging cover crops can suppress weeds during fall and spring, and provide early season weed control in the subsequent main crop. 17,18 Mixtures of cover crops performed better under dry and warm conditions than the before-mentioned single cover crop species. 19 Cover crop mixtures better compensate temporal and spatial variation in growing conditions, and thus tend to outperform single species in the long term by ensuring that at least some species grow every year at every site.…”

“…Avena strigosa also produced a very dense root system in the upper soil surface and reduced root biomass of weeds and volunteer crops by 97% . Even low seeding rates of fast emerging cover crops can suppress weeds during fall and spring, and provide early season weed control in the subsequent main crop …”

“…This allows them to efficiently compete with weeds and volunteer crops for water, light and nutrients. Even perennial weeds such as Cirsium arvense , Cyperus esculentus and Elymus repens were significantly suppressed by these cover crops …”