Sweet corn production and efficiency of nitrogen use in high cover crop residue

In the humid, temperate mid-Atlantic area of the USA, crop production that leaves the soil uncovered can lead to undesirable soil and nutrient losses to the surrounding Chesapeake Bay watershed. To cope with this issue, winter annual cover crops could provide soil cover both during winter months and, as surface residue in no-tillage cropping systems, during summer months. Legume cover crops such as hairy vetch can produce abundant biomass and N by the time summer crops are planted in spring. Although N mineralized from a legume cover crop can contribute to meeting the N requirement of crops such as corn, it also may not be used efficiently by crops and could be lost into the local environment. This research was conducted to determine whether hairy vetch or a hairy vetch-rye mixture that was allowed to produce high levels of biomass with a high N content (200 to 250 kg/ha) could meet the N requirements of no-tillage sweet corn and to determine the efficiency of N use relative to that of fertilizer N. Our results show that marketable yield of sweet corn was approximately doubled by hairy vetch in 2 of 3 years compared to an unfertilized, no-cover crop control. However, in 2 of 3 years, hairy vetch and the vetch-rye mix reduced yield by 19 and 34%, respectively, compared to a no-cover crop control with fertilizer N. Reduced plant population that reduced the number of ears per ha accounted for the yield reduction by these cover crops compared to the fertilized no-cover crop control. Fertilizer N was 1.5 to 2 times more efficient than hairy vetch at producing sweet corn ear mass per unit of N input but combinations of fertilizer N with cover crops were less efficient than either alone. Results suggest that growing sweet corn without tillage in high biomass levels of cover crops can interfere with crop establishment, reduce the efficiency of crop production, and allow for potentially high N losses into the environment.