ACTIVITY AND THERMODYNAMIC PARAMETERS OF UREASE IN SOILS AMENDED WITH ORGANIC RESIDUES

Al-Ansari & Et Al

doi:10.36103/ijas.v50i3.695

Abstract

An experiment was conducted to study the thermodynamic parameters (Q10, Ea, Ha, Sa and Ga) of urease in loamy sand and silty clay soils treated with different sources of organic residues (cow residue, alfalfa leaves, wheat straw and poultry residue). Residues were mixed with soil at rate of 2%. The amended soils were incubated at 30°C for 30 days to undergo biochemical, chemical and physico-chemical reaction. Amended soils were incubated at 10, 20, 30, 40, 50, 60, 70 and 80°C. Urease activity was assayed and thermodynamic parameters were calculated. Results indicated that urease activity of amended soil was higher than that of control soils at various temperatures of incubation. Urease activity increased by increasing temperature of incubation from 10 to 40°C. Q10, Ea, Ha, and Sa values of silty clay soil were in the order of : poultry manure > cow manure > alfalfa residue > wheat residue > control soil. However, in loamy sand soil the order was cow manure > alfalfa residue > wheat residue > control > poultry manure. Order of Ga was control > wheat residue > alfafa residue > cow manure > poultry manure at both soils. Except at poultry manure, all thermodynamic parameters values were higher in loamy sand soil as compared with their values in silty clay soil.

Highlights

Al-Ansari & et al INTRODUCTION Soil enzymes mediate biological reaction involve in nutrient cycling in soil, and can be used as potential indicators of soil quality(11,19,24)
Enzymes activity in soil significantly correlated with organic residue (39) and soil microbial biomass (36, 38)
Organic residues influence microbial population since, they provide the soil with carbon and other nutrients essential for microbial growth

Summary

INTRODUCTION

Soil enzymes mediate biological reaction involve in nutrient cycling in soil, and can be used as potential indicators of soil quality(11,19,24). The constant A is a factor related to the Moyo et al(26) attributed the variation in Ea frequency of collisions of the reactants (e.g. values for soil urease reported in literatures to substrate) with the enzyme The collisions factors such as pH, urea concentration, or frequency is influenced by the concentration of water content other than temperature and to the reactant molecules and their kinetic energy various assay techniques used which could (14). Lai and Tabatabai (20) indicated activation energies should be were significantly affected by organic residues compared only under similar conditions such source( table 2)and ranged between 47.10 in as pH , choice of buffer , substrate loamy sand soil treated with cow manure and concentration and temperature of incubation. Lai and Tabatabai (20) reported values in range 13.5-39.1 kJ mol-1 for urease by the association with the soil organic and inorganic minerals complexes, the higher the barrier to be overcome during formation of enzyme-substrate complex

Cow manure Alfalfa residue Control Mean

Findings

Alfalfa residue