Increased animal production and concomitant land application of manure create conditions conducive for significant environmental losses of manure-N. Scavenger cover crops have shown some promise in mitigating off-field losses. In this study, we tested the effects of oat (Avena sativa) and winter rye (Secale cereal) cover crops on N losses in soils with a history of manure management during the volatile spring season. Undisturbed cores were taken from replicated plots planted to oats, winter rye or fallow at three points during the spring season. After a simulated rainfall, emissions were collected for a subsequent 96-hour incubation period. Nitrous oxide emissions in cover crop treatments showed no significant difference over a control plot during the early spring season. However, as temperatures warmed, winter rye was found to decrease average N2O emissions by approximately 70% when compared to either the oat or fallow treatment. Furthermore, nitrate concentrations found in leachate at 55 cm were dramatically lower in rye plots, while the winter-killed oat showed no decrease in nitrate leaching when compared to a control. These stark contrasts in oat and rye treatments were likely the result of the re-growth of the rye during the sampling period. Stimulation of N losses in manured fields could in fact be hastened during the spring season with the use of oats as a fall cover crop, while rye appears to have a positive effect on N-cycling during the same period.
– Assess the nitrogen dynamics associated with the addition of winter forage cover crops (winter rye and oats) on manured soils. This study will assess the effect of these cover crops with respect to leaching losses and denitrification as compared to a control factor.
– Through the use of 15N isotope enrichment as labelled biomass, the study allows for the partitioning of residue N. Isotope enrichment allows one to trace its movement within a given system, which then allows for an analysis of the interactions between treatments. This step assesses the management aspect of this study. Under the use of different cover crops, this step measures the effectiveness of applying cover crops.
– Demonstrate the potential for winter rye and oats as forage cover crops in the temperate Northeast while investigating the associated tradeoffs between N sinks and losses.