Optimizing vetch nitrogen production and corn nitrogen accumulation under no-till management

Legume cover crops can often meet much of the N demand of a crop. There may be, however, an asynchrony between N mineralization from the cover crop residues and crop N uptake, resulting in potentially substantial N loss. We hypothesized that manipulation of hairy vetch (Vicia villosa Roth.) termination and corn (Zea mays L.) planting dates would regulate the quantity of N available from the vetch, the mineralization rate from the vetch residues, and the relative rate of N uptake in the corn. Field experiments were implemented in 2007 and 2008 to study the integrative effects of delaying vetch termination/corn planting through the establishment of three termination/planting dates within the month of May (an early, middle, and late date). Greater vetch biomass was found as the termination date was delayed, with a 360 and 35% biomass gain in 2007 and 2008, respectively, over 4 wk. The soil N content, for all termination dates, followed a similar availability trend across the season in both years, but the quantity of inorganic N in the soil varied depending on termination date. The average corn grain yield in 2007 was 8.0 Mg ha^-1 under vetch fertilization, with no difference among vetch biomass levels, and in 2008, ranged between 4.4 and 7.6 Mg ha^-1, with significant differences depending on vetch biomass level. Our study concluded that although vetch N availability can be manipulated through termination date, the dependence on climate for vetch biomass levels and N release will complicate year-to-year predictability.