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ARS Home » Southeast Area » Raleigh, North Carolina » Soybean and Nitrogen Fixation Research » Research » Publications at this Location » Publication #228997
Title: Activities of N-Mineralization Enzymes Associated With Soil Aggregate Size Fractions of Three Tillage Systems

Author
item MURUGANANDAM, SUBATHRA - NC STATE UNIV
item Israel, Daniel
item ROBARGE, WAYNE - NC STATE UNIV

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2008
Publication Date: N/A
Citation: N/A

Interpretive Summary: This research provides basic understanding of how nitrogen mineralization processes in soil are impacted by tillage methods. It provides some understanding of why no till soil management has beneficial effects on crop production. It has potential to improve efficiency of nitrogen use in soils subject to no till management.

Technical Abstract: Nitrogen mineralization occurring near the soil surface of agro-ecosystems determines the quantity of plant available N, and soil enzymes produced by microorganisms play significant roles in the N mineralization process. Tillage systems may influence soil microbial communities and N mineralization enzymes through alterations in total soil C and N. Soil aggregates of different sizes provide diverse microhabitats for microorganisms and therefore, influence soil enzyme activities. Our objective was to test the hypothesis that activities of N mineralization enzymes increase with aggregate size and in no-till compared to tilled systems. Potential activities of N-acetyl glucosaminidase (NAG), arylamidase, L-glutaminase, and L-asparaginase were measured in five aggregate size fractions (<0.25, 0.25-0.5, 0.5-1, 1-2, and 2-4 mm) obtained from soils of three long-term (22 yr) tillage systems (no-till, chisel, and moldboard). All enzyme activities were significantly (p<0.05) greater in no-till than in tilled systems and positively correlated (p<0.005) with potential N mineralization. Potential activities of NAG, L-glutaminase, and arylamidase were significantly greater (p <0.05) in the intermediate (0.5-1 mm) aggregate size than in other size fractions. All enzyme activities were positively correlated with total soil C (p<0.0001), N (p<0.05), and microbial biomass C (p<0.05). Although, aggregate size had significant effects on N-acetyl-glucosaminidase, arylamidase and L-glutaminase activities the magnitudes were small compared to the magnitudes of the tillage effects. Fungal biomarkers (18:2'6c and 16:1'5c) determined by PLFA method were significantly greater in the no-till than in tilled systems and positively correlated with all enzyme activities. This suggests that no-till management enhances activities of N mineralization enzymes by enhancing the proportion of fungal organisms in the soil microbial community.