Abstract
AbstractCover crops are grown as potential ways to improve soil fertility, soil structure, and biodiversity, while reducing weed/pest burdens. Yet, increased costs (in both time and fuel), farmer knowledge requirements, and yield uncertainty (green bridge effect and variable crop establishment) have led to hesitation among farmers. This study was conducted at the field scale (covering an area of nearly 20 hectares) to determine whether different cover crop mixtures affected soil properties and ecosystem services on a heavy clay soil. Measurements of soil chemistry, physics, biology, weed abundance, and subsequent crop performance were taken within a minimum tillage management system, across three cover crop mixtures (commonly sold to UK farmers). The cover crop mixtures included oats (Avena sativa), radish (Raphanus sativus), phacelia (Phacelia tanacetifolia), vetch (Vicia sativa), legumes, buckwheat (Fagopyrum esculentum) and a bare stubble control followed by a spring oat crop. Soil physics (penetrometer and bulk density) and chemistry (N, P, K, Mg, Ca, and organic matter) varied little across treatments, although there was significantly lower Mg in the cover crop including legumes and an increase in NO3 within this treatment. Soil biology and botanical composition were also assessed, monitoring earthworm and mesofauna abundance; and sown and unsown (weed) biomass. Epigeic earthworms were found to have significantly larger abundance in cover crop mixtures with radish present, although other meso‐ and macrofauna did not differ. Significant weed suppression was found during both the cover crop growing period and as a legacy in the subsequent crop, leading to significant yield increases and economic benefits in some treatments. Our study confirms that cover crops are providing benefits, even on heavy clay soils, including improvements in nutrient leaching risk reduction, weed suppression, and crop yield, coupled with wider ecosystem benefits. We therefore consider cover crops to have a role in sustainable management of arable rotations.
Highlights
Cover crops have been highlighted as a method to reduce nutrient losses (Cooper et al, 2017), increase soil organic carbon (Ladoni, Basir, Robertson, & Kravchenko, 2016), and change fauna abundance and diversity (Blubaugh, Hagler, Machtley, & Kaplan, 2016; Frasier et al, 2016) as well as reduce anthropogenic inputs (Wittwer, Dorn, Jossi, & Heijden, 2017)
One of the cover crop mixtures (C + P + R + L) was sold as a biodiversity increasing mix, but our results show that there were no differences found between mixtures there was in comparison with the bare stubble control
A different suppressive ability was found among the cover crop treatments—C + P + R had significantly less weed biomass than the C + P + R + L treatment with C + P intermediate (Figure 4a). This is likely to be due to the combination of plant species and seed rate of these species when compared with the other cover crop treatments (C + P + R + L had 28% of seed sown as legume or buckwheat seeds, but the proportion of grown biomass this equated to was
Summary
Cover crops have been highlighted as a method to reduce nutrient losses (Cooper et al, 2017), increase soil organic carbon (Ladoni, Basir, Robertson, & Kravchenko, 2016), and change fauna abundance and diversity (Blubaugh, Hagler, Machtley, & Kaplan, 2016; Frasier et al, 2016) as well as reduce anthropogenic inputs (Wittwer, Dorn, Jossi, & Heijden, 2017). Implementation of cover crops has yield uncertainty in the performance of the following crop—partly due to the green bridge effect (Acharya et al, 2016; a living host for plant herbivores and/or plant pathogens, where they can reside over the winter, ready to take over in the spring crop), as well as difficulties in the timing of establishment (and variability in establishment) of the subsequent crop These problems are exacerbated on a heavy clay soil that is more prone to waterlogging, takes longer to dry CROTTY and STOATE out and warm up in the spring, reducing the time available to establish the spring crop. The investigation will consider whether cover crops are an economically viable option on a heavy clay soil in a temperate climate
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