2008 Joint Annual Meeting (5-9 Oct. 2008): Amidohydrolases Activities of an Ultisol: Effects Of Tillage, Cropping And Nitrogen Sources.

Agricultural practices impact soil properties and quality via factors that include sufficient plant residues and nutrients to maintain soil organic matter levels and sufficient soil cover using crops, thereby creating a stable environment for biological activity. Soil enzyme activities provide valuable information on the impact of soil management on biological processes such as nutrient cycling. In this study we evaluated the effects of management practices on the activity of three soil amidohydrolases (L-asparaginase, L-glutaminase, and urease). The treatments comprised of one or a combination of management practices that included three tillage methods, two sources of nitrogen, three levels of nitrogen, use or non use of cover crop (Secale cereale L.), and a bare fallow (control). The three tillage methods were conventional-till, no-till, and mulch-till. The two sources of nitrogen were poultry litter and ammonium nitrate. Activity of the amidohydrolases under the different treatments increased with respect to the control (BF). However, the activity of L-glutaminase, was highest for all treatments, followed by urease, and then L-asparaginase. A significant increase in activity was observed with the addition of poultry manure. The activities of the three amidohydrolases were significantly correlated with soil organic carbon (SOC), pH, and microbial biomass nitrogen (MBN). The results suggest that the management practices affect soil biological and biochemical properties, which in turn affect the mineralization of organic N in the soil through the action of these enzymes.