Egboluche, N. P. 2020. Cover crops and cover crop residues regulate rates of soil microbial decomposition and plant available nitrogen. Thesis, Michigan State University, East Lansing, MI.

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Changes in soil microbial community and activities can influence the nutrient cycling and its availability to plants. I conducted a one-year soil incubation study to: evaluate the effects of short- and long-term N additions on the soil microbial activities and how cover crop residue mixtures influence ecosystem functions. Two legume residues, Vicia villosa – hairy vetch (V) and Pisum sativum – field pea (P) with C:N ratio 12.8 and 10.5 respectively and two non-legume residues, Pennisetum glaucum – pearl millet (M) and Lolium multiflorum – rye grass® with C:N ratio 37.8 and 14.3 respectively were used in this study. Soils amended with V and R had greater inorganic N compared to M and P residues while in soils with residue mixtures I observed non-additive synergistic (NAS) effect on inorganic N at the initial and final stage of the incubation period. Long-term N addition increased inorganic N but was apparent with short-term N fertilizer. Addition of both short- and long-term N increased β-1,4,-glucosidase (BG), β-D-1,4-cellobiohydrolase (CBH), phenol oxidase (PO), peroxidase (PER) and acid phosphatase (PHOS) with the exception of Leucine-aminopeptidase (LAP) and urease enzyme activities. There was non-additive antagonistic (NAA) effects on cellulase, total oxidase, β -1,4,-N-acetyl glucosaminidase (NAG) and NAS effects on LAP, urease and PHOS enzyme activities. The addition of residues likely stimulated microbial growth, but the NAA effect of residue mixtures on C acquisition enzyme (cellulase and total oxidase) activities suggests development of C limitation.

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