Double cropping and manure management mitigate the environmental impact of a dairy farm under present and future climate

Authors: CASTANO-SANCHEZ, JOSE - New Mexico State University; KARSTEN, HEATHER - Pennsylvania State University; Rotz, Clarence - Al

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2021
Publication Date: 11/23/2021
Citation: Castano-Sanchez, J.P., Karsten, H.D., Rotz, C.A. 2021. Double cropping and manure management mitigate the environmental impact of a dairy farm under present and future climate. Agricultural Systems. 196:103326. https://doi.org/10.1016/j.agsy.2021.103326.
DOI: https://doi.org/10.1016/j.agsy.2021.103326

Interpretive Summary: Dairy farms contribute to environmental concerns primarily through manure nutrient losses. Manure application to cropland often results in losses of nitrogen and phosphorus contributing to eutrophication of lakes and coastal waters with implications for human health through respiratory issues and drinking water contamination. Projected changes in temperature, precipitation, and atmospheric carbon dioxide present a challenge and perhaps opportunity for future agricultural production. Projected changes may exacerbate environmental impacts of dairy farms, but also improve production with proper adaptation. We evaluated whole-farm production, environmental and economic impacts of double cropping corn and rye silages along with subsurface application of manure on a representative dairy farm using recent historical and projected mid-century climate. We found that double cropping benefited greatly from the projected increase in growing season length providing additional forage that is less susceptible to summer droughts. Placing manure below the soil surface countered projected increases in nutrient losses by midcentury due to increased temperatures and storm intensities. Our results suggest that use of this more intensive crop rotation along with improved manure application technology can help mitigate dairy farm environmental impacts now and even more in the future without significantly increasing total production costs.

Technical Abstract: Strategies are needed to reduce the environmental impacts of dairy farms, and these may become more important as our climate continues to change. Double cropping small grain and corn silages provides a strategy that can benefit dairy farms in the northeastern U.S. as they adapt to a longer growing season. Subsurface application of manure may also reduce nitrogen (N) and phosphorus (P) losses as the region faces warmer temperatures, greater precipitation, and more intense storms. Our objective was to evaluate whole-farm production, environmental and economic impacts of adopting these strategies on a representative dairy farm in central Pennsylvania under recent historical and projected midcentury climate. Farm management strategies were simulated using the Integrated Farm System Model to determine effects on crop yields, feed production, volatile, leaching and denitrification losses of N, sediment erosion, sediment-bound and soluble losses of P, farm-gate life cycle greenhouse gas emissions, fossil energy use, and production costs. Double cropping increased and stabilized feed production by providing forage from a winter rye crop with less dependency on the summer crops of corn silage and cool season grasses. Summer crops are susceptible to summer droughts, which are expected to increase in this region due to warmer temperatures and increased evapotranspiration. Double cropping was most beneficial in the midcentury climate due to the projected increase in growing season length. Double cropping and subsurface injection of manure reduced soluble and total P runoff, ammonia volatilization, and total N losses. Double cropping using broadcast manure application had a neutral environmental and economic impact on the farm. Adoption of these strategies provided a feasible adaptation and mitigation approach for future climate by reducing projected increases in soluble P runoff and ammonia emission caused by warmer temperatures and more intense storms while maintaining and potentially reducing total farm production costs. Whole-farm simulation provides a tool for evaluating potential benefits and tradeoffs of novel technologies and strategies as agriculture adapts to changes in climate. Although these results are specific to a dairy farm in central Pennsylvania, they generally apply to dairy farms throughout the Northeast U.S. and climates where similar changes in temperature and precipitation are projected by mid-century. Our analyses suggest that use of a more intensive crop rotation (double cropping winter small grain and corn silage) along with improved manure application technology (subsurface injection) can help mitigate dairy farm environmental impacts now and even more in the future.