INFLUENCE OF TILLAGE AND SIDEDRESS NITROGEN ON SNAP BEAN FOLLOWING A HAIRY VETCH COVER CROP

Use of conservation tillage practices and legume winter cover crops are management options that can effectively control soil erosion and supply nitrogen (N), via fixation and mineralization, to subsequent crops. This study was conducted to investigate the effects of tillage on snap bean (Phaseolus vulgaris L.) production in the Mountain region of Georgia and to determine whether sidedress N fertilizer is required to maintain snap bean yields in conventional and no-tillage soil management systems that utilize a winter cover crop of hairy vetch (Vicia villosa Roth). Snap beans were grown following hairy vetch near Blairsville, Georgia during 1992 and 1993. Hairy vetch contained 75 to 80 kg N/ha when the cover crop was killed in the spring. Treatments imposed on snap beans comprised a factorial combination of spring tillage (conventional or no-tillage) and sidedress N (0 or 56 kg N/ha) applied three weeks after planting (WAP). Conventional tillage tended to increase the concentration of inorganic N in the 0- to 30-cm soil layer relative to no-tillage, but the effect was significant only at five WAP in 1992. Sidedressing with 56 kg N/ha at three WAP resulted in significantly higher concentrations of inorganic N in the 0- to -15 cm soil layer at five WAP in both years. Despite treatment differences in soil inorganic N concentration, there were no significant effects of tillage or sidedress N on plant stand or shoot and pod dry weight. While total yields of marketable pods were not significantly affected by tillage or sidedress N treatment, early yield in 1993 was 44% greater for no-tillage, a growing season considerably drier than that of 1992. Use of hairy vetch eliminated the need for sidedress N in conventional and not-illage snap bean production. These results suggest that adoption of resource-conserving vegetable production systems based on no-tillage soil management and use of hairy vetch winter cover crops could result in improved water quality, sustained soil productivity, and greater production efficiency in the southern Appalachians.