Effects of soil surface management practices on soil and tree parameters in a ‘Cripps Pink’/M7 apple orchard 2. Tree performance and root distribution

Abstract

Effects of integrated production (IP) and organic-acceptable soil surface management practices were investigated in a ‘Cripps Pink’/M7 apple orchard in the Elgin area, South Africa. Work row treatments included cover crops, weeds and straw mulch. In the IP tree rows, weeds were controlled with herbicide and nitrogen (N) was supplied in inorganic form. Tree rows in the organic treatments received mineral nutrients in compost, and a straw mulch was used to control weeds. Tree and soil parameters were determined over a seven-year period. Compost usage in the organic treatments led to high soil phosphorus (P) and potassium (K) concentrations, but less acidity, than in the IP treatments. Stem circumferences, pruning weights and root numbers were generally greater in the organic than the IP treatments. Conversely, yields and yields per cm2 stem area were mostly lower in the organic, than in the IP, treatments. To improve yields in organic apple orchards the balance between vegetative growth and flowering and bearing structures must be improved, mainly through better control over orchard nutrition. Such control will be facilitated if composts are standardised with regard to mineral nutrient contents, ratios between N, P and K, and delivery rates.