Balancing Nitrogen Sinks and Sources Using Cover Crops On Manured Fields

View the project final report

• 2010 annual report

Commodities

• Agronomic: corn, oats, rye

Practices

• Crop Production: cover crops, crop rotation, nutrient cycling, tissue analysis
• Soil Management: green manures, nutrient mineralization, organic matter, soil analysis, soil quality/health

Nitrous oxide losses pose a significant threat as both a potent greenhouse gas (GHG) and a destructive influence on the ozone layer. The EPA estimates that N2O losses from agricultural soil management is the fifth largest source of GHG, greater than combustion from aviation, and the dominant agricultural source. In 2008, a CO2 equivalent of 233.5 Tg was emitted as N2O from agricultural sources with 17.1 Tg coming from manured fields. As dairy farms become increasingly concentrated and meat consumption increases, N2O will steadily increase thereby intensifying the damaging effects it has on the atmosphere. Cover crops may serve as a potential solution to the increased denitrification on manured fields. Certain forage crops act as storage facilities for residual N in the soil system removing the nutrient from potential loss pathways such as denitrification and leaching. In the northeastern US, a variety of cover crops have been effective in capturing residual nitrogen within the soil profile yet a primary question remains unanswered: Do cover crops reduce nitrogen losses sufficiently to significantly reduce N losses through denitrification? Using 15N isotope enrichment, this study will attempt to answer this question by reconstructing a partial nitrogen budget based on leaching losses, denitrification and maize uptake with the use of two cover crops: winter rye (Secale Cereale) and oats (Avena Sativa).

- 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.