| Abstrakt: |
Few studies have compared N utilization by maize (Zea maysL.) under conventional tillage (CT) and no‐tillage (NT) in the Appalachian region. Silage production (TDM) and fertilizer N and soil N uptake, were investigated in a 3‐yr study on a Gilpin silt loam (fine‐loamy, mixed, mesic Typic Hapludult) in West Virginia previously cropped to pasture. 15N‐depleted N fertilizer was band‐applied, within‐row, at 0, 56, 112, and 224 kg N ha−1, 4 wk after planting. Tillage method did not affect silage production, N concentration or total N uptake at any N rate. Maximal silage production under NT (13.2 Mg ha−1) was calculated to require just 24 kg ha−1more fertilizer N than under CT (12.6 Mg ha−1). Fertilizer N uptake (kg ha−1) was similarly unaffected by tillage method, with annual fertilizer N use efficiencies (% recovery) of 55, 54, and 49% under NT, and 57, 57, and 48% under CT, at application rates of 56, 112, and 224 kg ha−1, respectively. Similar percentages for cumulative fertilizer N use efficiencies, which account for any labeled N carried over from year to year, suggest that there was little residuum available to the crop, particularly at near‐optimal N rates. Soil N uptake decreased by 17% with N additions below (56 kg ha−1) or above (224 kg ha−1) the optimum, but was generally unaffected by tillage method. These similarities between NT and CT for maize silage production and N use, despite using a management system contrived to show differences, emphasize the importance of edaphic and climatological factors in predicting N responses under various tillage methods. Nonetheless, these results show that reasonably high levels of silage can be produced without excessive fertilizer N requirements ( ≈ 170 kg N ha−1) or losses (< 50%) when pastures are converted to NT maize. |
Plný text