Assessing the farm-scale impacts of cover crops and non-inversion tillage regimes on nutrient losses from an arable catchment

Abstract

The efficacy of cover crops and non-inversion tillage regimes at minimising farm-scale nutrient losses were assessed across a large, commercial arable farm in Norfolk, UK. The trial area, covering 143 ha, was split into three blocks: winter fallow with mouldboard ploughing (Block J); shallow non-inversion tillage with a winter oilseed radish (Raphanus sativus) cover crop (Block P); and direct drilling with a winter oilseed radish cover crop (Block L). Soil, water and vegetation chemistry across the trial area were monitored over the 2012/13 (pre-trial), 2013/14 (cover crops and non-inversion tillage) and 2014/15 (non-inversion tillage only) farm years. Results revealed oilseed radish reduced nitrate (NO3¬¬-N) leaching losses in soil water by 75–97% relative to the fallow block, but had no impact upon phosphorus (P) losses. Corresponding reductions in riverine NO3¬¬-N concentrations were not observed, despite the trial area covering 20% of the catchment. Mean soil NO3¬¬-N concentrations were reduced by ~77% at 60–90 cm depth beneath the cover crop, highlighting the ability of deep rooting oilseed radish to scavenge nutrients from deep within the soil profile. Alone, direct drilling and shallow non-inversion tillage were ineffective at reducing soil water NO3¬¬-N and P concentrations relative to conventional ploughing. Applying starter fertiliser to the cover crop increased radish biomass and nitrogen (N) uptake, but resulted in net N accumulation within the soil. There was negligible difference between the gross margins of direct drilling (£731 ha-1) and shallow non-inversion tillage (£758 ha-1) with a cover crop and conventional ploughing with fallow (£745 ha-1), demonstrating farm productivity can be maintained whilst mitigating diffuse pollution. The results presented here support the wider adoption of winter oilseed radish cover crops to reduce NO3¬¬-N leaching losses in arable systems, but caution that it may take several years before catchment-scale impacts downstream are detected

The legacy of cover crops on the soil habitat and ecosystem services in a heavy clay, minimum tillage rotation

“…The abundance of slugs and snails did not differ between treatments, including the bare stubble control. The highest abundance was found in the C + P + R treatment, while the lowest was in the C + P + R + L treatment, disputing the assertion that radish as a cover crop increases slug numbers (Cooper et al, ). Few differences were found between treatments for the mesofauna (Table ).…”

“…Cover crops have been highlighted as a method to reduce nutrient losses (Cooper et al, ), increase soil organic carbon (Ladoni, Basir, Robertson, & Kravchenko, ), and change fauna abundance and diversity (Blubaugh, Hagler, Machtley, & Kaplan, ; Frasier et al, ) as well as reduce anthropogenic inputs (Wittwer, Dorn, Jossi, & Heijden, ). However, proving to the average farmer their usefulness has not been achieved to date (Bouma, ).…”

“…Cereals and grasses include oats ( Avena sativa ), rye ( Secale cereale ), and ryegrass ( Lolium perenne ), which generally produce more biomass (ground cover and rooting system) than other cover crop types (Maltais‐Landry, Scow, & Brennan, ). Brassicas, such as radish ( Raphanus sativus ), mustards, and turnips, also provide a good ground cover and have been found to reduce nitrate leaching due to the deep rooting system which is able to scavenge more nutrients from depth (Cooper et al, ). Legumes, including vetch ( Vicia sativa ), crimson and berseem clover ( Trifolium incarnatum ; T. alexandrinum ), and lucerne ( Medicago sativa ), fix nitrogen from the atmosphere and have been found to improve litter quality (due to their lower C:N ratios) (Frasier, Quiroga, & Noellemeyer, ) leading to increases in soil organism biodiversity (Crotty, Fychan, Scullion, Sanderson, & Marley, ) and mineralization (Frasier et al, ).…”

Traditional agriculture: a climate-smart approach for sustainable food production

“…pea, vetch and clover) or non-leguminous (e.g. rye, sorghum and brassicas) (Cooper et al 2017). Rye, oat, pea, vetch, clover, sun hemp, velvet bean and sorghum are among the prominent cover crop species that are grown to enhance soil fertility and soil carbon sequestration (Wang et al 2010).…”

“…Cover crop refers to the crop that is grown to cover the ground for reducing soil erosion and nutrient loss (Reeves 1994;Dabney et al 2001). They are usually non-cash crops sown in the autumn to provide winter ground cover (Cooper et al 2017). Replacement of a bare fallow period through cover cropping is a sustainable strategy for reducing runoff and soil erosion (Reeves 1994;Alvarez et al 2017).…”