Tree establishment and growth using forage ground covers in an alley-cropped system in Midwestern USA

摘要

The integration of forage crops in an alley-cropped system was examined as a method of encouraging tree planting to increase farm income, improve soil quality, and enhance biodiversity on Midwestern U.S. farms. Crop and tree performance were evaluated in an alley-cropped system using four forage intercrops grown in tree alleyways to simulate a potential hay crop – oat (Avena sativa L.) and red clover (Trifolium pratense L.); oat, red clover, and red fescue (Festuca rubra L.); oat, red clover, and orchardgrass (Dactylis glomerata L.); and oat and hairy vetch (Vicia villosa Roth) – compared to a herbicide, mowing and control (no management) treatment. Five tree species, divided into fast-growing hardwoods of two poplar (Populus spp.) clones [Crandon (P. alba L. × P. grandidentata Michx.) and Eugenei (P. deltoids Bartr. × P. nigra L.)], and silver maple (Acer saccharinum L.) were compared with two high-value, slow-growing hardwoods planted from seed and as seedlings: red oak (Quercus rubra L.) and black walnut (Juglans nigra L.). Tree survival in the first year was greater for the fast-growing species, and by the fourth year, tree height among the four forage treatments was equivalent for all upland locations. The oat/hairy vetch ground cover was associated with the shortest trees in the bottomland site. Herbicide-treated trees were taller than the average of the four forage treatments for all four planting conditions. Tree height in the mowing and the control treatments was not significantly different for all four planting conditions. The nutritive value of the forage crop was excellent in the second year of tree establishment, with crude protein content and digestibility at 17 and 71%, respectively, in the oat/red clover/red fescue treatment, suggesting the viability of forage crops as alternatives to herbicides in alley-cropped systems.