ORGANIC MULCH IN APPLE TREE ROWS AS AN ALTERNATIVE TO HERBICIDE AND TO IMPROVE FRUIT QUALITY

The objective of this study was to examine organic mulches as an alternative for herbicides in organic fruit orchards, in order to improve yield, fruit quality and soil properties. In March 2002, the 1-1.2 m wide apple tree rows at Michurin Research Institute of Horticulture were mulched with sawdust or pine bark at ca. 25-30 t dry matter (DM) ha^-1 or grass clippings, with between-tree herbicide (glyphosate) and/or manual weeding serving as control treatment. Grass alleyways in all the treatments were regularly mowed. Over the 4 years of the experiment, the herbicide-treated control reduced the weed cover to 2-25% and their dry mass to 3-27%, compared with the manual-weeded control values. The three organic mulches decreased the number of emerged weeds to 5-30%, compared with the manual-weeded control and was comprised of 25-30 weed species (making organic mulches an ecological alternative to herbicide). The three organic mulches improved soil properties, conserved soil moisture and increased N, P, and K content, compared with manual weeding. Apple trees with mulch developed a shallower root system. The three organic mulches, compared with manual weeding, enhanced vegetative growth, measured as length of one-year shoots, leaf area for leaves taken from bourse shoots (by 27 versus 12%) and tree trunk cross-section area (by 23 versus 13%). With the mulches, yield and fruit mass were increased by 35 and 17% compared with manual weeding.