Soil is a fundamental resource and it is crucial to manage its quality in order to enhance agricultural productivity and environmental quality. Soil enzymes catalyze several biochemical reactions which result in the transformation of organic matter, and the release of inorganic nutrients for plant growth and nutrient cycling. Soil enzyme activities are useful biological soil quality indicators since they are operationally practical, very sensitive, integrative, easy to measure and more responsive to soil tillage and structure than other soil variables. There are several enzymes in soil, but those involved in hydrolases and the degradation of main litter components are used most often for evaluating soil quality. This paper reviews the roles of soil enzymes such as β-glucosidase, phosphatase and urease, as well as the implications of their activities for soil quality.

We herein report a simple large scale green synthesis route for the synthesis of silver nanoparticle (Ag-NP) multi walled carbon nanotubes (MWCNTs) hybrid nanocomposite (Ag-MWCNTs). The as-synthesized hybrid nanocomposite were characterized using UV-Vis absorption spectroscopy, Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD) and high resolution transmission electron microscopy (HR-TEM). Raman spectroscopy analysis showed an increase in the D/G ratio of Ag-MWCNTs hybrid nanocomposites when compare with that of functionalized MWCNTs (F-MWCNTs) attributed to the presence of Ag-NPs on the surface of the F-MWCNTs. The as-synthesized Ag-MWCNTs nanocomposites showed strong antibacterial efficacy against Escherichia coli compared to the Ag-NPs and MWCNTs. The catalytic potential of the Ag-MWCNTs hybrid nanocomposite was investigated for the first time by studying the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride at 299 K at various reaction times. The reaction follows first order kinetics with a rate constant of 5.18×10⁻¹ s⁻¹. It is believed that, the large scale synthesis of such hybrid nanocomposites via simple method using non-toxic reagent will not only enhance its antibacterial efficacy, durability and biocompatibility, it will also minimize its biotoxcity and environmental impacts.

The best management options for cover cropping are largely unknown, including the growth patterns of cover crop (CC) species, optimum termination stages and termination methods. A greenhouse experiment was conducted to explore the following: (i) Effect of two termination stages (vegetative and flowering) on the chemical composition (N and C:N) of four CCs; (ii) Short-term impacts of living CCs and residues on soil pH, total N, urease and phosphatase activities at the two termination stages, and under two termination methods (slash and spray). Species tested as CCs were, vetch (Vicia dasycarpa L.), field pea (Pisum sativum L.), oats (Avena sativa L.), rye (Secale cereal L.) and a control (no CC). The experiment was set up in a randomized block design with three replications. Soil was sampled at kill and one year after CC kill. Delaying termination from vegetative till flowering stage decreased N in the tissue of P. sativum, A. sativa, V. dasycarpa and S. cereal by 59%, 65%, 44% and 56%, respectively, while their C:N ratios increased. Cover crop presence had no effect on soil pH. Living CCs had no significant effect on soil N concentration. The activities of urease and phosphatase were stimulated by all the living CC species. Unlike urease, all CC residues had a positive impact on phosphatase activity at one year. Only P. sativum and V. dasycarpa residues increased soil N concentration in the short-term. Compared to flowering, termination at vegetative stage improved soil N concentrations and phosphatase activity at both sampling times. Termination method had no effect on soil N, urease and phosphatase activity at one year. The significant interaction (P < 0.05) of sampling time, CC and termination stage effects on soil N concentration and phosphatase activity observed in this study indicates that these management approaches can optimize CC benefits and improve soil chemical and biological properties.

The soil pollution as a product of xenobiotics, industrial action, agricultural chemicals, or inappropriate disposal of waste can change the natural environment of soil indices and trigger life-threatening situations. Soil enzyme activity is the suitable bio-indicator or parameter for monitoring soil pollution due to their sensitivity that quickly responds to any soil disturbances. Also, they are known to play an essential role in maintaining soil health and a quality environment. This study aimed to determine the levels of enzyme activity in soil from polluted and unpolluted sites and study the relationship between the physicochemical properties and soil enzyme activity to manage soil pollution. Four selected enzymes (Urease, Invertase, Catalase, and Phosphatase) were examined for their activity from forty samples using the assay method for 24 h; the colorimetry spectrophotometer measured their activity. The obtained data revealed that Invertase activity was a predominant enzyme in all soil samples. Whereas, the urease activity had obtained in low amounts for all collection sites, especially on Site A1. Soil pH had discovered to range between 5.8 and 8.51, moisture content values recorded to vary from 0.12% to 9.09%, and soil organic carbon recorded to fluctuate between 0.08% and 1.54%. Urease and phosphatase activity correlated positively with all soil physicochemical properties except for moisture content, which correlated negatively (r = −0.297; p ≥ 0.05). The invertase activity negatively associated all soil physicochemical properties, excluding the moisture content that correlated positively and significantly with invertase activity. We noted that the dumpsite soil contains low enzyme activity levels, which might attribute to the type of waste disposed off. Also, only the phosphatase activity reported correlating positively with all examined physicochemical parameters entirely.