Use of organic applications to increase productivity of high density apple orchards

Minimizing use of agrochemicals in fruit growing is a goal of integrated fruit production (IFP). Recently, a range of locally available organic materials have been advocated for possible orchard use. Over the past decade, a series of randomized, replicated field trials were established in grower and research orchards in British Columbia to test the effectiveness of these materials when applied to the surface as mulches or mixed to 30 cm depth as soil amendments. Mulch application most consistently affected tree growth, as indicated in a long term field trial where cumulative yield after 5 crop years was increased by surface application of shredded paper, alfalfa and biosolid mulches. Soil nutrient status and soil biological activity were altered by surface mulching and at another site trees were buffered against moisture stress. Initial growth stimulation from mulching was not sustained at a site where excessive irrigation reduced N availability. Rotovation of a biosolid-amendment to 0.3 m depth prior to planting improved the P-nutrition and initial growth of apple. Amendment treatment did not always affect apple tree performance. Effects were not observed at sites with strong fertigation regimes or fertile soils or when sites had overriding growth limitations unaffected by treatment (e.g. replant disease, K deficiency).