Soil enzyme activities in heavily manured and waterlogged soil cultivated with ryegrass (Lolium multiflorum)

Abstract

Extended waterlogging (WL) conditions can alter soil enzyme activities and their role in maintaining healthy soils. We assessed the effects of soil moisture regimes (field capacity (FC) and WL) and phosphorus (P) rates (0, 15, 30, 45 kg available P ha–1) on (i) soil enzymes and microbial biomass carbon (MBC), nitrogen (MBN), and P (MBP), and (ii) dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). The treatments were tested in a four–month greenhouse experiment using intact soil columns under annual ryegrass (Lolium multiflorum). Waterlogging decreased the activity of β–glucosidase and acid phosphomonoesterase, but increased N–acetyl–β–glucosaminidase in soils. These changes were associated with changes in MBC, DOC, TDN, but not MBP. Anoxic conditions in WL soil promote the activity of anaerobes and contribute to the reduction of Fe oxyhydroxides and the release of DOC, TDN, and P in the soil solution. The activity of the extracellular enzymes decreased in WL with additions of slurry indicating adequate supply of C, N, and P. Our results also showed that both enzyme activities and microbial biomass were restricted in the upper soil layer with limited downward movement along the soil profile. We can conclude that since these enzymes control the hydrolysis of cellulose, phosphomonoester, and chitin, respectively, soil moisture influences the direction and magnitude of C, N, and P in manured and waterlogged soil cultivated with ryegrass.