Traditional and cover crop-derived mulches enhance soil ecosystem services in apple orchards

Applied Soil Ecology

Volume 178, October 2022, 104569

Authors

Sean M. Webber,, Alison P. Bailey, Theresa Huxley, Simon G. Potts, Martin Lukac

Abstract

Organic mulches are a traditional method of groundcover management in temperate commercial orchards, now largely replaced by herbicides and synthetic fertilisers. As a potential contribution to improving orchard sustainability, we hypothesised that the addition of organic mulches would: (H1) improve soil fertility and lead to greater tree growth and yields; (H2) support a larger and more biologically active community of soil organisms, assessed as increased soil respiration and greater earthworm numbers and biomass; and (H3) increase leaf litter decomposition and burial, potentially reducing the risk of apple scab disease (Venturia inaequalis). Cuttings from two legume-based cover crop mixtures grown in the alleyway spaces between tree rows and two traditional mulch materials, straw and compost, were trialled alongside a bare soil business-as-usual control for two years, using a randomized complete block design in a conventionally managed commercial ‘Gala’ apple orchard in the UK. Compared to the control, the compost mulch significantly increased both soil carbon and nitrogen by over 50 %. The straw mulch effectively suppressed weeds by about 90 % and increased soil moisture by about 5 %. Cover crop cuttings increased moisture levels and increased earthworm numbers and mass by 1.7 and 1.8 times greater respectively in the double-rate ‘legume-grass’ cuttings treatment. Increasing the quantity of cover crop cuttings produced more positive effects; the cumulative addition of cuttings can benefit several soil-derived ecosystem services. This study took place in a commercial apple orchard, the findings may therefore be applicable to other orchard and row-grown perennial crops.