Cellulase activity of soils and the effect of tillage management on enzyme activities in soils

Abstract

APPENDIX 215 carbon side chain. It is formed by polycondensation (chemical reaction) of phenolic compounds and free radicals. Thus, it does not show a specific order. In addition, it is very inert (Paul and Clark, 1989). Hemicelluloses are various polymers of hexoses, pentoses, and sometimes, uronic acids. In the pure state, hemicelluloses are easily decomposed. In nature, however, they are frequently complexed with other substances that may make the breakdown more difficult. Enzymatic degradability of cellulose is closely related to its structure, forms, and its association with lignin and hemiceUulose. As Eriksson (1981) and Schwald et al. (1988) indicated, the resistance of native cellulose to enzymatic hydrolysis is due, in part, to its intrinsic properties and to the fact that its association with lignin, the polysaccharides, hemiceUulose and pectin, hinder access by cellulolytic enzymes. In addition, hydrogen bonding holds the cellulose molecules together. As a result, these fibers are composed of crystalline or highly ordered regions and less ordered, amorphous regions. This results in differences in reactivity and adsorption of the substrate by the cellulolytic enzyme due to its accessibility, degree of polymerization, or variation in crystal structure. Biodégradation of Cellulose Cellulose in soils is derived mainly from photosynthesis of higher plants.

Arylamidase Activity of Soils

“…These results agree with findings of other researchers that have also reported the enzyme activities are correlated with the organic C content of soils (Speir, 1977;Dick, 1984). Results of arylamidase activity were significantly affected by tillage and residue management practices which agree with those reported by others for other soil enzymes (Dick, 1984;Deng andTabatabai, 1996 a,b, 1997). Thus, the results may surest this enzyme is also a potential tool for soil quality research focused on monitoring the changes influoiced by soil management practices.…”

Amino acid composition of soil organic matter and nitrogen transformations in soils under different management systems

“…There were also signiticant relationships between aspartase activity and amidase activity (r = 0.44*, P < 0.05), urease activity (r = 0.80***, P < 0.001), L-asparaginase activity (r = 0.94***, P < 0.001), and L-glutaminase activity (r = 0.88***, P < 0.001) in the 27 surface soils studied (Figures 20-23; Table 41, Appendix). Such significant relationships are expected considering that similar relationships have been reported for other soil enzymes (Deng, 1994;Tabatabai, 1981a, 1991b,d;Speir, 1977).…”

“…Frankenberger and Tabatabai (1991b) Soils may also become enriched with several trace elements from fertilizers, municipal, and industrial wastes (Berrow and Webber, 1972;Charter et al,, 1993;Guisquiani et al, 1994). The inhibiting effect of trace elements added to soils on enzyme activities have been demonstrated by several investigators (Al-Khafaji and Deng, 1994;Frankenberger and Tabatabai, 1981b;Frankenberger and Tabatabai, 1991b;Frankenberger and Tabatabai, 1991d;Fu and Tabatabai, 1989;Juma and Tabatabai, 1977;Tabatabai, 1977). The term "trace element" is used here to refer to elements, that when present in sufficient concentrations, are toxic to living systems.…”

“…Crop rotations, organic and inorganic soil amendments are known to regulate soil microbial biomass and enzjmiatic actions responsible for residue decomposition, organic matter turnover, and nutrient cycling (Biederbeck et al, 1984;Doran and Smith, 1987;McGill et al, 1986). Recent studies by Deng (1994) showed that the activities of 14 soil enzymes involved in C, N, P, and S cycling in soils were affected by tillage and residue management practices. However, the review of literature revealed no information on the relative distributions of aspartase activity in soils and on the influence of various cropping systems, tillage, and residue management on its activity in soils.…”

“…reported a significant correlation between L-asparaginase activity and amidase (r = 0.82), and urease (r = 0.79) activities in 26 surface soil samples. In a study byDeng (1994) values for correlation coefficients (r) for linear regressions among the activities of 14 enzymes involved in C, N, P, and S cycling in soils ranged from 0.33 to 0.96.…”