Evaluation of orchard floor management systems for apple under organic protocol: Effect on soil organic matter and nitrogen, nematode community, root architecture and development, and rootstock performance

Orchard floor managements systems (OFMS) play the fundamental role in establishing the soil conditions for tree growth. Organic growers rely on the soil food web to provide nutrient availability for the plant. A change in soil biology by changing or modifying OFMS could reflect on the food web, the plant root responses, and ultimately the tree production.; With this experiment we evaluated the effect of three different OFMS on soil nitrogen, food web structure, tree root dynamics and architecture, and responses of three rootstocks. The experiment was conducted in an organically certified (Organic Crop Improvement Agency - OCIA) orchard of "Pacific Gala". Three rootstocks were evaluated: M.9 NAKB 337 (dwarfing), M.9 RN 29 (semi-dwarfing), and Supporter 4 (semi-vigorous). Three OFMS were used: Mulch of alfalfa hay (MU), propane Flaming (FL), and strip tilling at each side of the tree row while natural vegetation was allowed to grow undisturbed on the tree row (Swiss Sandwich System, SS). The effect of OFMS was evaluated by measuring SOM and N content at 2 depths (0-10 and 0-30 cm). The effect on soil biology structure was measured by the relative percentage of the populations categorized by feeding habit. Root infections by mycorrhizae and number of root feeders' nematodes in the roots were also measured. Fine root responses to the soil conditions were measured by minirhizotrons only in MU and SS, while the response of the root Dario Stefanelli distribution was measured by trenching in the soil profile in all the treatments. These last two measurements were performed only on M.9 NAKB 337 rootstock.; The Mulch treatment had the highest values of SOM and N with no differences between the SS and FL treatments. These parameters are still growing in MU while they seem stabilized in FL and SS. This had an effect on the structure of the soil biology. Mulch presented the highest number of bacterial feeding nematodes (85% against 60% of SS and FL) with continued increases. Swiss Sandwich and FL had higher fungal feeders, which play an important role in nutrient release in depleted soils and higher root feeding nematodes, both in soil and in roots, but the trees did not suffer. Flame and SS presented the highest number of mycorrhizal infection in roots. A positive linear correlation between root infection % and number of spores in the soil was found. (Abstract shortened by UMI.)...