TILLAGE AND COVER CROP EFFECTS ON MAIZE YIELD AND SOIL NITROGEN

Tillage and spring kill cover crop may affect crop N-accumulation and subsequent N release to the soil, thereby influencing maize (Zea mays L.) uptake and yield. We examined the influence of three tillage practices [conventional tillage with mouldboard plough (MP) as using traditionally tillage, chisel tillage (CT), shallower rototiller tillage (ST)], one cover crop management systems [common vetch (Vicia sativa L.)] on cover crop N accumulation, soil N, and maize biomass yield and N uptake. An experiment was conducted on a clay-loam soil from 2005 to 2008 in a semi-arid region in Mediterranean conditions. Cover crop N accumulation was higher with MT than ST and CT due to increased biomass yield over all year average. However, maize biomass yield and N uptake were found higher in ST than in MT and CT. Soil N at 0-30 cm depth at maize planting was higher in ST followed by CT and MT. Similarly, soil N was determined higher in ST at the end of establishment year followed by MT and CT, respectively. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.