Does the legacy of long-term crop rotation influence crop residue decomposition dynamics and potential soil N2O flux?
Peer Reviewed StatusNon-Peer Reviewed
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Research has demonstrated that including winter wheat and under-sown red clover into corn-soybean rotations has the potential to improve soil health indices and N use efficiency. Yet, the mechanisms that explain these benefits are poorly understood. One hypothesized explanation is, that by including wheat/red clover in corn-soybean rotations, the soil N supply improves or that the soil N cycle tightens; thereby lowering potential N loss. To address this hypothesis, in Oct 2017 we collected soil cores (10 cm deep, 8 cm diam.) from the second-year corn phase of a 39-yr long-term trial where the following rotations had been maintained: corn-corn-soy-soy (CCSS) or corn-corn-soy-wheat/red clover (CCSWrc), under conventional tillage (CT) or no-till (NT). For each rotation legacy, the soil samples were sieved (2 mm) and air-dried prior to establishing 50 g soil microcosms that were amended with 15N-enriched corn stover or roots (1 and 0.2 g of dried and ground biomass, respectively). Natural abundance and unamended controls were included in the randomized complete block, replicated design. The microcosms were incubated for 14 d at 70% water-filled pore space inside 1L mason jars. Soil and gas samples were periodically collected to measure crop residue decomposition dynamics (via CO2 fluxes and 15N mineralization) and 15N2O fluxes. The results demonstrated higher residue-derived stover N mineralization, and significantly higher N2O stover emissions (by more than a twofold) from the CCSWrc vs the CCSS legacy (P=0.0075). Corn stover and root residues showed distinct N2O patterns, where corn roots (but not stover) appeared to stimulate soil-primed N2O emissions. Overall, our findings indicate that crop residues are processed differently by soil microorganisms depending on the long-term crop rotation legacy.
Part OfSoils and Crops Workshop
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