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).
Soil microbiological and biochemical properties affected by plant growth and different long-term fertilisation
Abstract The purpose of this study was to measure the effects of plant growth on soil microbial biomass C (C mic ) and soil enzyme activities. In a pot experiment using spring barley and sugar beet, we investigated the response of C mic , hot water extractable C and N fractions (C hwe , N hwe ), and enzyme activities involved in C, N and P cycling in a loess-derived Chernozem from Bad Lauchstadt (Central Germany). The study site has been receiving the same fertilisation treatments for 100 years. The soil originated from plots fertilised with 15 t ha −1 farmyard manure (FYM) year −1  + mineral fertiliser (NPK), or 15 t ha −1 FYM year −1 , or NPK or from an unfertilised control. Pots were sampled monthly, and alkaline phosphatase- (AP), β-glucosidase- and protease-activities were analysed. At the beginning and the end of study, levels of C mic , C hwe and N hwe were also measured. All three enzyme activities and C mic were significantly and positively correlated with C org and C hwe . Results suggest that the enzyme activities measured originated mostly from microorganisms and that C hwe is an important C source for soil microorganisms. β-Glucosidase and AP activities were higher in summer months than at other times. In contrast, protease activity changed only slightly during the growing period.
Acid and alkaline phosphatase dynamics and their relationship to soil microclimate in a semiarid woodland
The seasonal dynamics of acid and alkaline phosphatase activity (mg p-nitrophenol released g ˇ1 soil h ˇ1 ), soil water potential and temperature, and the relationship of phosphatase activity to plant and soil microbial processes underneath Juniperus monosperma canopies and Hilaria jamesii-dominated intercanopy areas were studied in a northern Arizona pinyon‐juniper ecosystem. Alkaline phosphatase activity was significantly higher in soils under junipers (126.523.9 mg p-nitrophenol g ˇ1 soil h ˇ1 ) than in intercanopy soils (106.624.0 mg p-nitrophenol g ˇ1 soil h ˇ1 ), and significantly exceeded acid phosphatase activity by a factor of 6. Seasonal high phosphatase activities were up to 2.4 times greater than seasonal lows. Activities were maximal in summer and winter. Juniper soils were cooler than intercanopy soils except during the coldest months of the year, when they were up to 2.78C warmer. Intercanopy soils were up to 6.28C warmer than juniper soils, and had the highest (30.020.38C) and the lowest average temperatures (2.320.28C). Soil microclimate explained as much as 20% of the variation in acid and alkaline phosphatase. Temperature and water potential together were better predictors of phosphatase activity than either one alone. The soil water potential classˇ0.1 MParc >ˇ0.5 MPa was the most frequent best predictor of phosphatase activity, especially alkaline phosphatase. The winter peak in alkaline phosphatase activity is attributed to a buildup of phosphatase released into the soil from dying soil organisms, and the desorption and reactivation of previously accumulated phosphatase. # 2000 Elsevier Science Ltd. All rights reserved.