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Organic agroecological systems “produce goods using methods that preserve the environment and improve soil health” but can be a substantial source of greenhouse gases if not managed properly. We designed a laboratory incubation to monitor N and C transformations in soils resulting from different 15N labelled additions (urea vs beet top residues), water filled pore space (40, 60 and 80%) and prior tillage management (clean vs no tillage) during a simulated freeze-thaw.
Non-metric multidimensional scaling analysis (NMS) of amendment (N source) and water filled pore space (%) effects on reactive N species and C mineralization estimated by the amount of cumulative carbon dioxide evolved on 7 d at 10 degree C (pre-freeze). The proportion of total variance in the parameter matrix represented by Axes 1 and 2 is indicated in parentheses. Linear correlations between axis scores and variables significant at p < 0.05 are indicated in the form of arrows along the 2 NMS axes. (Adapted from Bhowmik et al 2017; SBB)
We found that there was sufficient available nitrate in beet top tissue (cover crop) to stimulate denitrification in soil with cover crop incorporation under conditions that limit ammonification and nitrification (10 degree C late fall air temperature). (Bhowmik et al 2017; Soil Biology & Biochemistry)
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