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.

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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