Effects of soil surface management practices on soil and tree parameters in a ‘Cripps Pink’/M7 apple orchard 1. Mineral nutrition

Abstract

Effects on soil, leaf and fruit element concentrations of organic (compost, straw mulch and hand weeding) and integrated (inorganic fertilisers and herbicide usage; IP) soil surface management practices in the tree rows, in combination with weed covers, cover crops and straw mulch in the work rows, were investigated in a seven-year trial. The trial took place on a gravelly soil in a ‘Cripps Pink’/M7 apple orchard in the Elgin area, South Africa. The organic treatments promoted higher phosphorus (P) and potassium (K) concentrations in the soil, leaves and fruit than the IP treatments. Leaf and fruit nitrogen (N) levels were normal in both the organic and IP treatments. Compost application rates that supply adequate N therefore deliver excessive amounts of P and K. Use of such composts should be based on P and K contents, supplementing where necessary with N. In both the IP and organic treatments, element concentrations were higher in the tree rows than the work rows. Treatments applied to the work rows did not affect soil and tissue element concentrations consistently. Standardisation of compost composition is required, as is balanced delivery of N, P and K.

Keywords: compost, cover crops, organic, straw mulch, weed control

South African Journal of Plant and Soil 2013, 30(3): 163–170