The 2011 ASHS Annual Conference

Ground cover can improve the sustainability of tree production systems by reducing nutrient lost, increasing soil organic matter content, and maintaining nutrients balance. However, part studies have mainly focus on N nutrition with only little attention accorded to other essential macronutrients. Therefore, this research project aims to evaluate the effect of three different ground covers, alfalfa (Medicago sativa), Dutch white clover (Trifolium repens) and perennial rye (Lolium perenne) and management practices on plant and soil macronutrients (P, K, Ca, Mg) in Fraser fir production system. Management included banding (B) and no-banding (noB) treatments of each species of cover crop and a control or bare-ground (BG) treatment where all weeds were removed. Ground covers were mowed every 21 days and returned to the ground as green mulch. Parameters measured included tree growth, foliar macronutrient concentration, soil macronutrient concentration, and cover crop biomass and macronutrients content. Results indicated that the highest macronutrient content was found in alfalfa, while perennial rye had the lowest. Ground cover treatments did not affect tree foliar Mg and P concentration significantly; however, lower Ca and K concentration were found in ground cover treatments compared to bare ground treatments, which might due to competition between ground cover and trees. Soil macronutrient concentration at 0-15 cm depth and 15-30 cm depth differ among treatments, however not significantly. We concluded that ground cover species and management practices should be selected carefully in order to avoid competition between trees and ground covers. More studies of mineralization and macronutrient flows are needed to help tree growers decide on strategies for using ground cover in tree production systems.