Abstract
Introducing cover crops is a form of ecological intensification that can potentially reduce local, regional and global environmental impacts of soybean cropping systems. An assessment of multiple environmental impacts (global warming potential, eutrophication, soil erosion and soil organic carbon variation) was performed on a continuous soybean system in the U.S. upper Midwest. Four sequences were assessed and compared: a soybean cropping system with winter camelina, field pennycress, or winter rye as cover crop, plus a control (sole soybean). Cover crops were interseeded into standing soybean in Year 1, while in Year 2 soybean was relay-cropped into standing camelina or pennycress. Rye was terminated before sowing soybean. When compared with the control, sequences with cover crops showed lower eutrophication potential (4–9% reduction) and soil erosion (5–32% reduction) per ha year−1, in addition to a lower global warming potential (3–8% reduction) when the cover crop was not fertilized. However, when the economic component was included in the assessment, and the results expressed per USD net margin, the sequences with cover crops significantly reduced their performance in all categories of impact considered. A further optimization of field management for camelina and pennycress is recommended to make the cropping system more sustainable.
Highlights
Higher values of greenhouse gases (GHGs) in fertilized sequences can partially be ascribed to higher values of field nitrous oxide (N2 O) emissions generated by the conversion of available soil ammonium (NH4 + ) by nitrification and denitrification processes carried out by microorganisms in soil [68,69]
Relay-cropping new winter cover crops such as winter camelina and field pennycress with soybean in the U.S upper Midwest is a new practice of temporal and spatial ecological intensification that can have multiple potential benefits for the agricultural sector, including an improvement of the ecosystem services provided by the cropping system
Overall, decreased eutrophication potential and soil erosion rate than the control per ha year−1 were estimated in camelina and pennycress at all locations, in addition to a lower global warming potential when the cover crop did not receive additional N-fertilization
Summary
New varieties and hybrids with a higher harvest index and shorter life cycle, and irrigation are some of the key elements that allowed a drastic increase in productivity in agriculture [1]. Such a process has widened the ecological footprint of agricultural production by accelerating natural resource depletion (e.g., soil organic carbon and soil erosion), increasing environmental pollution (e.g., water contamination and eutrophication processes) and reducing biodiversity of agroecosystems. The magnitude of the environmental impact associated with the agricultural intensification has become a threat to sustain the crop productivity itself [2]
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