SOIL β-GLUCOSIDASE ACTIVITY UNDER WINTER WHEAT CULTIVATED IN CROP ROTATION SYSTEMS DEPLETING AND ENRICHING THE SOIL IN ORGANIC MATTER
β-glucosidase (E.C. 3.2.1.21), an enzyme involved in cellulose degradation, plays an important role in the soil organic carbon cycle. Cellulose is the most abundant organic compound in the biosphere so a product of its enzymatic hydrolysis is important as an energy source for soil microorganisms. Since β-glucosidase is very sensitive to different factors, determination of its activity might be helpful in soil quality monitoring. The objective of the study was to assess the effect of various doses of farmyard manure (FYM) and mineral nitrogen on β-glucosidase activity in soil samples taken under winter wheat cultivated in crop rotation systems depleting soil from organic matter (A) and enriching soil in organic matter (B). Soil samples were taken in 2002 from a two-factor fertilization experiment carried out as randomized sub-blocks cropped with winter wheat cultivated on lessive soil. The experiment was located at the Experimental Station of the Institute of Tillage and Soil Science in Grabowo on the Vistula River. All fertilization combinations included FYM (0, 20, 40, 60 and 80 t.ha–1) and nitrogen fertilization (0, 40, 80 and 120 kg ha–1). The activity of β-glucosidase was determined according to Eivazi, Tabatabai (1988). The enzyme activity ranged 3.604-7.041 mM pNP g–1 h–1 in soil samples taken from crop rotation A and between 4.931-7.445 mM pNP g –1 h –1 in those collected from the crop rotation enriching the soil in organic matter. These data were closely related to the applied FYM and nitrogen fertilization doses. Moreover, β-glucosidase activity depended significantly on sampling dates. Enzyme activity was closely connected with soil organic carbon and total nitrogen content, which was confirmed by highly significant correlation coefficients between these parameters (r=0.611-0.770 for C org, and r=0.844-0.912 for N og ; p<0.01 and p<0.001).
ASSESSING SOIL QUALITY THROUGH SOIL CHEMICAL PROPERTIES AND ENZYME ACTIVITIES IN SEMIARID AREA , IRAN
Semiarid ecosystems are more sensitive to environmental changes than other terrestrial ecosystems, which makes their monitoring very important. Determining soil quality is critical to precise monitoring of semiarid area, and its evaluation involves the assessment of soil properties. In this study, the soil chemical properties and enzyme activities were measured and compared in order to determine soil quality. Four plots were chosen in the cold and warm sites in the Khabr national park and Ruchun wildlife refuge with grazed and not grazed areas. Samples of surface soil (0–10 cm) were collected in spring and autumn. The results showed that chemical properties of the soils were significantly affected by site (soil organic carbon, total nitrogen, available phosphorus and soil moisture) and season (pH, total nitrogen, available phosphorus and soil moisture) but not by grazing. All assayed enzyme activities were significantly influenced by site and season. Alkaline phosphatase activity was affected by grazing, too. Soil chemical properties (soil organic carbon, total nitrogen, and available phosphorus content and soil moisture) and enzyme activities (acid phosphatase, alkaline phosphatase, invertase, β-glucosidase, urease and arylsulfatase) showed higher value at cold sites. The positive correlation between all assayed enzymes and soil organic carbon (r= 0.189-0.639) indicated the important role of soil organic carbon availability in soil enzyme activities. Seasonal variation was observed in soil chemical properties except for electrical conductivity. In addition, temporal variation was observed in enzyme activities with more activity in spring samples except for arylsulfatase activity. According to more value in nutrient content and enzyme activities, it can be concluded that soil at cold sites have higher quality than warm sites. In conclusion, the warm sites with poor soil quality need more concern to be protected.
Effects of heavy metal contamination of soils on micronucleus induction in Tradescantia and on microbial enzyme activities: a comparative investigation.
The aim of this study was to investigate correlation between genotoxic effects and changes of microbial parameters caused by metal contamination in soils. In total, 20 soils from nine locations were examined; metal contents and physicochemical soil parameters were measured with standard methods. In general, a pronounced induction of the frequency of micronuclei (MN) in the Tradescantia micronucleus (Trad-MN) assay was seen with increasing metal concentration in soils from identical locations. However, no correlations were found between metal contents and genotoxicity of soils from different locations. These discrepancies are probably due to differences of the physicochemical characteristics of the samples. Also, the microbial parameters depended on the metal content in soils from identical sampling locations. Inconsistent responses of the individual enzymes were seen in soils from different locations, indicating that it is not possible to define a specific marker enzyme for metal contamination. The most sensitive microbial parameters were dehydrogenase and arylsulfatase activity, biomass C, and biomass N. Statistical analyses showed an overall correlation between genotoxicity in Tradescantia on the one hand and dehydrogenase activity, biomass C, and the metabolic quotient on the other hand. In conclusion, the results of the present study show that the Trad-MN assay is suitable for the detection of genotoxic effects of metal contamination in soils and furthermore, that the DNA-damaging potential of soils from different origin cannot be predicted on the basis of chemical analyses of their metal concentrations.