共查询到20条相似文献，搜索用时 31 毫秒
1.
Effect of tillage and residue management on enzyme activities in soils 总被引：14，自引：3，他引：14
Recent interest in soil tillage and residue management has focused on low-input sustainable agriculture. In this study we investigated the effect of three tillage systems (no-till, chisel plow, and moldboard plow) and four residue placements (bare, normal, mulch, and double mulch) on the activities of four amidohydrolases (amidase, L-asparaginase, L-glutaminase, and urease) in soils from four replicated field-plots. Correlation coefficients (r) for linear regressions between the activities of each of the enzymes and organic C or pH and between all possible paired amidohydrolases were also calculated. The results showed that the effects of tillage and residue management on pH in the 28 surface soil (0–15 cm) samples were not significant. The organic C content, however, was affected significantly by the different tillage and residue-management practices studied, being the greatest in soils with notill/double mulch treatment, and the least with no-till/bare and moldboard/normal treatments. Within the same tillage system, mulch treatment resulted in greater organic C content compared with normal or bare treatment. The activities of the amidohydrolases studied were generally greater in mulch-treated plots than in non-treated plots, and were significantly correlated with organic C contents of soils, with r values ranging from 0.70*** to 0.90***. Linear regression analyses of enzyme activities on pH values (in 0.01 M CaCl2) of the 28 surface soils showed significant correlations for L-asparaginase, L-glutaminase, and urease, with r values of 0.74***, 0.77***, and 0.72***, respectively, but not for amidase (r=0.24). The activities of the four amidohydrolases studied in the 40 soil samples tested were significantly intercorrelated, with r values ranging from 0.72*** to 0.92***. The activities of the four amidohydrolases decreased with increasing soil depth of the plow layer, and were accompanied by a decrease in organic C content. 相似文献
2.
Enzyme activities in a limed agricultural soil 总被引：11，自引：2，他引：9
This study assessed the effect of eight lime application rates, with four field replications, on the activities of 14 enzymes
involved in C, N, P, and S cycling in soils. The enzymes were assayed at their optimal pH values. The soil used was a Kenyon
loam located at the Northeast Research Center in Nashua, Iowa. Lime was applied in 1984 at rates ranging from 0 to 17,920 kg
effective calcium carbonate equivalent (ha–1), and surface samples (0–15 cm) were taken after 7 years. Results showed that organic C and N were not significantly affected
by lime application, whereas the soil pH was increased from 4.9 to 6.9. The activities of the following enzymes were assayed:
α- and β-glucosidases, α- and β-galactosidases, amidase, arylamidase, urease, l-glutaminase, l-asparaginase, l-aspartase, acid and alkaline phosphatases, phosphodiesterase, and arylsulfatase. With the exception of acid phosphatase,
which was significantly (P<0.001) but negatively correlated with soil pH (r=–0.69), the activities of all the other enzymes were significantly (P<0.001)and positively correlated with soil pH, with r values ranging from 0.53 for the activity of α-galactosidase to 0.89 for alkaline phosphatase and phosphodiesterase. The
Δ activity/Δ pH values ranged from 4.4 to 38.5 for the activities of the glycosidases, from 1.0 to 107 for amidohydrolases
and arylamidase, 97 for alkaline phosphatase, 39.4 for phosphodiesterase, and 11.2 for arylsulfatase. This value for acid
phosphatase was –35.0. The results support the view that soil pH is an important indicator of soil health and quality.
Received: 3 May 1999 相似文献
3.
Increasing numbers of vegetable growers are adopting conservation tillage practices and including cover crops into crop rotations. The practice helps to increase or maintain an adequate level of soil organic matter and improves vegetable yields. The effects of the practices, however, on enzyme activities in southeastern soils of the United States have not been well documented. Thus, the objectives of the study were to investigate the effects of cover crops and two tillage systems on soil enzyme activity profiles following tomato and to establish relationships between enzyme activities and soil organic carbon (C) and nitrogen (N). The cover crops planted late in fall 2005 included black oat (Avena strigosa), crimson clover (Trifolium incarnatum L.), or crimson clover–black oat mixed. A weed control (no cover crop) was also included. Early in spring 2006, the plots were disk plowed and incorporated into soil (conventional tillage) or mowed and left on the soil surface (no-till). Broiler litter as source of N fertilizer was applied at a rate of 4.6 Mg ha−1, triple super phosphate at 79.0 kg P ha−1, and potassium chloride at 100 kg K ha−1 were also applied according to soil testing recommendations. Tomato seedlings were transplanted and grown for 60 days on a Marvyn sandy loam soil (fine-loamy, kaolinitic, thermic Typic Kanhapludults). Ninety-six core soil samples were collected at incremental depths (0–5, 5–10, and 10–15 cm) and passed through a 2-mm sieve and kept moist to study arylamidase (EC 3.4.11.2), l-asparaginase (EC 3.5.1.1), l-glutaminase (EC 3.5.1.2), and urease (EC 3.5.1.5) activities. Tillage systems affected only l-glutaminase activity in soil while cover crops affected activities of all the enzymes studied with the exception of urease. The research clearly demonstrated that in till and no-till systems, l-asparaginase activity is greater (P ≤ 0.05) in plots preceded by crimson clover than in those preceded by black oat or their mixture. Activity of the enzyme decreased from 11.7 mg NH4+–N kg−1 2 h−1 at 0–5 cm depth to 8.73 mg NH4+–N kg−1 2 h−1 at 5–10 cm and 10–15 cm depths in the no-till crimson clover plots. Arylamidase activity significantly correlated with soil organic C (r = 0.699**) and soil organic N (r = 0.764***). Amidohydrolases activities significantly correlated with soil organic N but only urease significantly correlated with soil organic C (r = 0.481*). These results indicated that incorporation of cover crops into rotations may increase enzyme activities in soils. 相似文献
4.
Prediction of potentially mineralizable N as an important N pool from soil amidohydrolases was investigated. Composite soil samples were collected from plots of a field experiment in which 0, 50 and 100 Mg cow manure ha−1 year−1 had been applied for five consecutive years. The soils were treated with corn shoots or roots or remained untreated in a factorial combination with the manure treatments, with three replications. The mineralized inorganic N was measured periodically in 20-week incubations and potentially mineralizable N (N0) was calculated based on a first-order kinetic model. Urease, l-glutaminase and l-asparaginase activities were measured before and after incubation. The values of N0 ranged from 208.6 in the controls to 388.4 in soils that had received 50 Mg ha−1 year−1 of cow manure and were amended with corn shoots. Corn residue amendment in the manure treated soils, increased the values of N0 or changed the N mineralization kinetic pattern from a first-order to a zero-order model. According to a relative sensitivity index, l-asparaginase was the most sensitive enzyme to the treatments. Multiple regression analysis revealed that 92% of N0 variations can be described by the activities of urease and l-asparaginase and therefore the soil amidohydrolase activities have the potential to evaluate potentially mineralizable N. 相似文献
5.
ABSTRACT This study investigated the relationship between a recently proposed alkaline hydrolysis method for estimating the chemical index of nitrogen (N) mineralization potential of soils and the activities of arylamidase and four amidohydrolases involved in hydrolysis of organic N (ON) in soils. Nitrogen mineralization was studied in 13 soils from uncultivated fields in Iowa, USA, by direct steam distillation of 1 g field-most soil treated with 1 M KOH or 1 M NaOH. The distillate was collected in boric acids, which was changed every 5 min for a total of 40 min. The NH4 +-N in the distillate was determined by titration with 0.005 M H2SO4. The cumulative amounts of N hydrolyzed were fitted to the first-order exponential equation to determine the “potentially hydrolyzable N (Nmax )” for the soils. The activities of arylamidase, L-asparaginase, L-glutaminase, amidase, and L-aspartase were assayed at their optimal pH values. Results showed that estimated Nmax values were strongly correlated with the activities of arylamidase and amidohydrolases. The activities of arylamidase and the amidohydrolases were significantly correlated, indicating that the activities of the two groups of enzymes are coupled in mineralization of ON in soils. Based on the specificity of enzyme reactions and the strong relationship between estimated Nmax values and the activities of arylamidase and amidohydrolases, we concluded that similar amide-N bonds were susceptible to enzymatic and alkaline hydrolysis, and that alkaline hydrolyzable ON can be used as an index of N mineralization in soils. 相似文献
6.
This study was carried out to investigate the long‐term influence of lime application and tillage systems (no‐till, ridge‐till, and chisel plow) on the activities of phosphatases and arylsulfatase in soils at four research sites in Iowa, USA. The activities of the following enzymes were studied: acid and alkaline phosphatases, phosphodiesterase, and arylsulfatase at their optimal pH values. With the exception of acid phosphatase, which was significantly (P < 0.001) but negatively correlated with soil pH (r ranged from –0.65** to –0.98***), the activities of other enzymes were significantly (P < 0.001) and positively correlated with soil pH, with r values ranging from 0.65** to 0.99*** for alkaline phosphatase, from 0.79*** to 0.97*** for phosphodiesterase, and from 0.66*** to 0.97*** for arylsulfatase. The Δ activity/Δ pH values were calculated to determine the sensitivity of each enzyme to changes in soil pH. Acid phosphatase was the most sensitive and arylsulfatase the least sensitive to changes in soil pH. Activities of the enzymes were greater in the 0 – 5 cm depth samples than those in 0 – 15 cm samples under no‐till treatment. With the exception of acid phosphatase, enzyme activities were mostly significantly (P < 0.001) and positively correlated with microbial biomass C (Cmic), with r values ranging from 0.28 (not significant) to 0.83*** and with microbial biomass N (Nmic), with r values ranging from 0.31 (not significant) to 0.94***. Liming and tillage systems significantly affected the activities of some enzymes but not others, as was evident from the specific activity values (g of p‐nitrophenol released kg–1 Corg h–1). 相似文献
7.
《Applied soil ecology》2006,34(3):258-268
The potential negative impact of agricultural practices on soil and water quality is of environmental concern. The associated nutrient transformations and movements that lead to environmental concerns are inseparable from microbial and biochemical activities. Therefore, biochemical and microbiological parameters directing nitrogen (N) transformations in soils amended with different animal manures or inorganic N fertilizers were investigated. Soils under continuous corn cultivation were treated with N annually for 5 years at 56, 168, and 504 kg N ha−1 in the form of swine effluent, beef manure, or anhydrous ammonia. Animal manure treatments increased dehydrogenase activity, microbial biomass carbon (Cmic) and N (Nmic) contents, and activities of amidohydrolases, including l-asparaginase, urease, l-glutaminase, amidase, and β-glucosaminidase. Soils receiving anhydrous ammonia demonstrated increased nitrate contents, but reduced microbiological and biochemical activities. All treatments decreased Cmic:organic C (Corg) ratios compared with the control, indicating reduced microbial C use efficiency and disturbance of C equilibrium in these soil environments. Activities of all enzymes tested were significantly correlated with soil Corg contents (P < 0.001, n = 108), but little correlation (r = 0.03, n = 36) was detected between Cmic and Corg. Activities of amidase and β-glucosaminidase were dominated by accumulated enzymes that were free of microbial cells, while activities of asparaginase and glutaminase were originated predominately from intracellular enzymes. Results indicated that soil microbial and biochemical activities are sensitive indicators of processes involved in N flow and C use efficiency in semiarid agroecosystems. 相似文献
8.
Effects of liming and tillage systems on microbial biomass and glycosidases in soils 总被引：7，自引：0，他引：7
This study was undertaken to investigate the long-term influence of lime application and tillage systems (no-till, ridge-till and chisel plow) on soil microbial biomass C (Cmic) and N (Nmic) and the activities of glycosidases (- and -glucosidases, - and -galactosidases and -glucosaminidase) at their optimal pH values in soils at four agroecosystem sites [Southeast Research Center (SERC), Southwest Research Center (SWRC), Northwest Research Center (NWRC), and Northeast Research Center (NERC)] in Iowa, USA. Results showed that, in general, the Cmic and Nmic values were significantly (P <0.001) and positively correlated with soil pH. Each lime application and tillage system significantly (P <0.001) affected activities of the glycosidases. With the exception of -glucosidase activity, there was no lime×tillage interaction effect. Simple correlation coefficients between the enzyme activities and soil pH values ranged from 0.51 (P <0.05) for the activity of -glucosidase at the NWRC site (surface of the no-till) to 0.98 (P <0.001) at the SWRC site. To assess the sensitivity of the enzymes to changes in soil pH, the linear regression lines were expressed in activity/pH values. In general, their order of sensitivity to changes in soil pH was consistent across the study sites as follow: -glucosidase>-glucosaminidase>-galactosidase>-galactosidase>-glucosidase. Lime application did not significantly affect the specific activities (g p -nitrophenol released kg–1 soil organic C h–1) of the enzymes. Among the glycosidases studied, -glucosidase and -glucosaminidase were the most sensitive to soil management practices. Therefore, the activities of these enzymes may provide reliable long-term monitoring tools as early indicators of changes in soil properties induced by liming and tillage systems. 相似文献
9.
Influence of long-term residue management on soil enzyme activities in relation to soil chemical properties of a wheat-fallow system 总被引：1，自引：1，他引：1
Summary Soil enzyme activities (acid and alkaline phosphatase, arylsulfatase, -glucosidase, urease and amidase) were determined (0- to 20-cm depth) after 55 years of crop-residue and N-fertilization treatment in a winter wheat (Triticum aestivum L.)-fallow system on semiarid soils of the Pacific Northwest. All residues were incorporated and the treatments were: straw (N0), straw with fall burn (N0FB), straw with spring burn (N0SB), straw plus 45 kg N ha–1 (N45), straw plus 90 kg N ha–1 (N90), straw burned in spring plus 45 kg N ha–1 (N45SB), straw burned in spring plus 90 kg N ha–1 (N90SB), straw plus 2.24 T ha–1 pea-vine residue and straw plus 22.4 T ha–1 of straw-manure. Enzyme activities were significantly (P<0.001) affected by residue management. The highest activities were observed in the manure treated soil, ranging from 36% (acid phosphatase) to 190% increase in activity over the control (N0). The lowest activities occurred in the N0FB (acid phosphatase, arylsulfatase and -glucosidase) and N90 treated soils (alkaline phosphatase, amidase and urease). Straw-burning had a significant effect only on acid phosphatase activity, which decreased in spring burn treated soil when inorganic N was applied. Urease and amidase activity decreased with long-term addition of inorganic N whereas the pea vine and the manure additions increased urease and amidase activity. There was a highly significant effect from the residue treatments on soil pH. Arylsulfatase, urease, amidase and alkaline phosphatase activities were positively correlated and acid phosphatase activity was negatively correlated with soil pH. Enzyme activities were strongly correlated with soil organic C and total N content. Except for acid phosphatase, there was no significant relationship between enzyme activity and grain yield.Journal Paper No. 8072 of the Agricultural Experimental Station, Oregon State University, Corvallis, OR 97331, USA 相似文献
10.
Dirk Landgraf 《植物养料与土壤学杂志》2001,164(6):665-671
The response of microbial biomass carbon (Cmic), nitrogen (Nmic), basal respiration, and the metabolic quotient to 3 years of a natural succession fallow were studied in a field experiment on sandy soil in Northeast Saxony/Germany from 1996 to 1998. Soil samples were taken from Eutric Cambisol and Mollic Cambisol every six weeks during the vegetation period at soil depths of 0—10 and 10—30 cm. The Cmic content in the topsoils increased with time of succession in both soil types. This trend was more distinct in the Mollic Cambisol (70.7 μg g—1 in June 1996 to 270.9 μg g—1 in October 1998 at 0—10 cm) than in the Eutric Cambisol (69.7 μg g—1 in June 1996 to 175.0 μg g—1 in October 1998 at 0—10 cm). By contrast, the Nmic content slightly decreased in the Eutric Cambisol from 18.9 μg g—1 to 17.7 μg g—1 during the same time period. In the Mollic Cambisol, the Nmic increased from 18.8 μg g—1 in spring 1996 to 35.5 μg g—1 in fall 1998, however to a lower extent than the Cmic. Subsequently, the (C:N)mic ratio increased from 4.3 to 5.8 at soil depth of 0—10 cm and from 3.5 to 6.5 at 10—30 cm during the 3‐year‐study at the Eutric Cambisol. In the Mollic Cambisol, the enhancement of (C:N)mic ratio was more pronounced (i.e. from 4.3 to 6.7 at 0—10 cm and from 3.5 to 7.2 at 10—30 cm). Most likely this results from a shift in microbial populations towards a dominance of soil fungi. The already low basal respiration of, on average, 0.26 mg CO2 g—1 (24h)—1 (0—10 cm) in June 1996 decreased with time of succession fallow to 0.15 and 0.22 mg CO2 g—1 (24h)—1 in October 1998 in the Eutric and the Mollic Cambisol, respectively. Thus, the metabolic quotient as an indicator for the efficiency of organic matter turnover in soil was very low in both soils. During the summer months, the metabolic quotients reached minimum levels of ≤ 0.1 μg CO2 C (g Cmic)—1 h—1, probably because of low soil moisture contents. Correlation analyses revealed close relationships between Nmic and total N, Nmic and water content, and Nmic and pH values. These relationships became even more pronounced with the time period of natural succession. For the samples from fall 1998, highly significant correlations were determined between Nmic and total N (coefficients were rs = 0.91***), Nmic and water content (rs = 0.91***), and Nmic and pH value (rs = 0.76***). The values for all biological parameters studied were larger in the Mollic than in the Eutric Cambisol. This indicates higher turnover rates of different C and N fractions in the Mollic Cambisol. In general, set aside of formerly agricultural managed sandy soils resulted in greater Cmic : Nmic ratios and thus, in a change in the microbiological community structure as well as in reduced C and N turnover rates (i.e. low metabolic quotient) under the climatic conditions of the East German lowlands. 相似文献
11.
The relationships of soil microbial biomass C (Cmic) or N (Nmic) with mean annual precipitation and temperature were studied along a climatic transect in the Mongolian steppe. Soil organic C (Corg) and total N (Nt), respiration rate, Cmic and Nmic at depths of 0–5 and 5–10 cm decreased with increasing aridity. The contents of Corg and Nt in the 0- to 5-cm soil layers decreased linearly with precipitation reduction along the transect. Cmic and Nmic changes with precipitation were not linear, with higher changes between 330 and 128 mm mean annual precipitation. Cmic/Corg and Nmic/Nt increased with increasing aridity. The metabolic quotient qCO2 of 0- to 5-cm soil layers was low between 330 and 273 mm precipitation. The relationship between the qCO2 of the 0- to 5-cm soil layers and the mean annual precipitation was well fitted with a quadratic function y =0.0006x2 –0.40x +86.0, where y is the qCO2 (µmol CO2-C mmol–1 Cmic) and x is the mean annual precipitation (mm). Corg, Nt, Cmic, Nmic and respiration rate decreased exponentially with increasing mean annual temperature in both the 0- to 5- and 5- to 10-cm soil layers, and change rate was lower when the mean annual temperature was higher than 2.6°C. The close relationships of the mean annual precipitation or temperature with soil Corg, Nt, Cmic, Nmic, Cmic/Corg and qCO2 indicate that each parameter can be calculated by determining the other parameters in this specific climatic range. 相似文献
12.
Effect of di-(2-ethylhexyl) phthalate (DEHP) on microbial biomass C and enzymatic activities in soil
Xinhong Wang Xing Yuan Zhiguang Hou Jing Miao Hui Zhu Chuantao Song 《European Journal of Soil Biology》2009,45(4):370-376
The effects of di-(2-ethylhexyl) phthalate (DEHP) at five different doses from 10 to 1000 mg kg−1 soil on biological properties were investigated over a period of 56 days. Meanwhile, the dissipation of DEHP was also monitored. The results indicated that the microbial biomass C (Cmic) fluctuated at around 70 mg kg−1 soil for the control, whereas the Cmic varied significantly for the soil samples contaminated by DEHP. The catalase activities in all five treatments were stimulated at most time, and the activities of phosphatase in the soils treated by DEHP with 500 mg kg−1 or 1000 mg kg−1 were significantly higher than the other treatments from the 20th day. Urease was more sensitive and inhibited significantly during the initial period of incubation. Additionally, the dose–response relationship of invertase was presented in the later phase of incubation. The activities of urease and invertase might indicate soil perturbations caused by the introduction of DEHP. The dissipation of DEHP was found to follow the pseudo first-order kinetics behavior. 相似文献
13.
A. Berner I. Hildermann A. Fließbach L. Pfiffner U. Niggli P. Mder 《Soil & Tillage Research》2008,101(1-2):89-96
Conservation tillage (no-till and reduced tillage) brings many benefits with respect to soil fertility and energy use, but it also has drawbacks regarding the need for synthetic fertilizers and herbicides. Our objective was to adapt reduced tillage to organic farming by quantifying effects of tillage (plough versus chisel), fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators and crop yield. The experiment was initiated in 2002 on a Stagnic Eutric Cambisol (45% clay content) near Frick (Switzerland) where the average annual precipitation is 1000 mm. This report focuses on the conversion period and examines changes as tillage intensity was reduced. Soil samples were taken from the 0–10 and 10–20 cm depths and analysed for soil organic carbon (Corg), microbial biomass (Cmic), dehydrogenase activity (DHA) and earthworm density and biomass. Among the components tested, only tillage had any influence on these soil fertility indicators. Corg in the 0–10 cm soil layer increased by 7.4% (1.5 g Corg kg−1 soil, p < 0.001) with reduced tillage between 2002 and 2005, but remained constant with conventional tillage. Similarly, Cmic was 28% higher and DHA 27% (p < 0.001) higher with reduced than with conventional tillage in the soil layer 0–10 cm. In the 10–20 cm layer, there were no significant differences for these soil parameters between the tillage treatments. Tillage had no significant effect on total earthworm density and biomass. The abundance of endogeic, horizontally burrowing adult earthworms was 70% higher under reduced than conventional tillage but their biomass was 53% lower with reduced tillage. Wheat (Triticum aestivum L.) and spelt (Triticum spelta L.) yield decreased by 14% (p < 0.001) and 8% (p < 0.05), respectively, with reduced tillage, but sunflower (Helianthus annuus L.) yield was slightly higher with reduced tillage. Slurry fertilization enhanced wheat yield by 5% (p < 0.001) compared to compost fertilization. Overall, Corg, Cmic, and DHA improved and yields showed only a small reduction with reduced tillage under organic management, but long-term effects such as weed competition remain unknown. 相似文献
14.
Tillage impacts on soil biological activity and aggregation in a Brazilian Cerrado Oxisol 总被引：3，自引：1，他引：3
Mechanized agriculture is increasing rapidly in the Cerrado region of Brazil, causing concerns about water quality, off-site impacts, and sustainability. Our objective was to determine the impact of tillage on soil biological activity and aggregate stability in an Oxisol typical to the region. Three different tillage practices common to the Cerrado region (no-till, disk harrow, and disk plow) and an area under native vegetation were examined. Five different soil enzyme activities, C- and N-mineralization, organic C, total N, and aggregate distribution were determined. Total N, acid phosphatase, arylamidase, and C- and N-mineralization were the most sensitive to changes in tillage management. For each of these analyses, the no-till system had greater concentrations or activities (18–186%) than disk plow in the 0–5 cm layer. Significant differences observed in the 0–5 cm depth did not necessarily translate into total profile differences to a depth of 30 cm. No-till had significantly greater levels of total N, and C- and N-mineralization (20–127%) than the disk harrow system. Total N ranged from 1.8 to 2.2 kg m−3; C- and N-mineralization (24-day incubation) ranged from 2.8 to 6.8 and 0.04 to 0.10 kg m−3, respectively, among tillage systems and soil depths. Enzyme activities in all treatments were more strongly correlated with total soil N than with soil organic C (SOC), contrary to the norm in temperate soils where the stronger correlation is with SOC. Mean weight diameter of water stable aggregates was related to SOC (r = 0.73) and total N (r = 0.92), indicating that soil organic matter does play a significant role in stabilizing aggregates in Oxisols. Results indicated the importance of reducing tillage as a means of increasing soil biological activity of the topsoil in the Cerrado region of Brazil. By understanding the effects of tillage on soil biological properties, management systems can be implemented that improve natural nutrient cycling processes and soil structure, resulting in increased agricultural sustainability of tropical ecosystems. 相似文献
15.
l-Asparaginase activity of soils 总被引：1，自引：0，他引：1
Summary A simple, precise, and sensitive method to assay l-asparaginase (l-asparagine amidohydrolase, EC 3.5.1.1) activity in soils is described. This method use steam distillation to determine the NH
inf4
sup+
produced by l-asparaginase activity when soil is incubated with buffered (0.1 M THAM, pH 10) l-asparagine solution and toluene at 30°C for 2 h. The procedure developed gives quantitative recovery of NH
inf4
sup+
-N added to soils and does not cause chemical hydrolysis of l-asparagine. The optimum buffer pH for NH
inf4
sup+
-N released by l-asparaginase activity in soils was 10. This enzyme was saturated with 50 mM
l-asparagine, and the reaction rate essentially followed zero-order kinetics. The d-isomer of asparagine was also hydrolyzed in soils, but at only 16% of the activity of the l-isomer at a saturating concentration of the substrate. The optimal temperature for the soil l-asparaginase reaction occurred at 60°C and denaturation began at 65°C. The Arrhenius equation plot for l-asparaginase activity in three selected soils was linear between 10 and 50°C. The activation energy values of this enzyme ranged from 20.2 to 34.1 (average 26.6) kJ mol-1. Application of three linear transformations of the Michaelis-Menten equation showed that the K
m values of l-asparaginase in nine soils ranged from 2.6 to 10.0 (average 6.1) mM and the V
max values ranged from 9 to 131 g NH
inf4
sup+
-N released g-1 soil 2 h-1. The temperature coefficients (Q
10) for soil l-asparaginase activity ranged from 1.12 to 1.70 (average 1.39). Steam sterilization (121°C for 1 h), formaldehyde, and NaF decreased the activity but the presence of toluene increased the amount of NH
inf4
sup+
released. Treatment of soils with dimethylsulfoxide completely destroyed l-asparaginase activity. The use of sulfhydryl reagents indicated that a free sulfhydryl moiety was required to maintain the active enzyme. l-Asparaginase activity in soils was increased by 13 to 18% in the presence of THAM buffer prepared to contain 5 mM Ca2+ and Mg2+, respectively. 相似文献
16.
Soil carbon sequestration with continuous no-till management of grain cropping systems in the Virginia coastal plain 总被引：3，自引：1，他引：2
John T. Spargo Marcus M. Alley Ronald F. Follett James V. Wallace 《Soil & Tillage Research》2008,100(1-2):133-140
Carbon sequestration in agroecosystems represents a significant opportunity to offset a portion of anthropogenic CO2 emissions. Climatic conditions in the Virginia coastal plain and modern production practices make it possible for high annual photosynthetic CO2 fixation. There is potential to sequester a substantial amount of C, and concomitantly improve soil quality, with the elimination of tillage for crop production in this region. The objectives of our research were to: (1) measure C sequestration rate with continuous no-till management of grain cropping systems of the Virginia middle coastal plain; (2) determine the influence of biosolids application history on C content and its interaction with tillage management; and (3) evaluate the impact of continuous no-till C stratification as an indicator of soil quality. Samples were collected from 63 sites in production fields using a rotation of corn (Zea mays L.)–wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.)/soybean double-crop (Glysine max L.) across three soil series [Bojac (coarse-loamy, mixed, semiactive, thermic Typic Hapludults), Altavista (fine-loamy, mixed semiactive, thermic Aquic Hapludults), and Kempsville (fine-loamy, siliceous, subactive, thermic Typic Hapludults)] with a history of continuous no-till management ranging from 0 to 14 years. Thirty-two of the sites had a history of biosolids application. Five soil cores were collected at each site from 0–2.5, 2.5–7.5 and 7.5–15 cm and analyzed for bulk density and soil C. Bulk density in the 0–2.5 cm layer decreased and C stratification ratio (0–2.5 cm:7.5–15 cm) increased with increasing duration of continuous no-till due to the accumulation of organic matter at the soil surface. A history of biosolids application resulted in an increase of 4.19 ± 1.93 Mg C ha−1 (0–15 cm). Continuous no-till resulted in the sequestration of 0.308 ± 0.280 Mg C ha−1 yr−1 (0–15 cm). Our results provide quantitative validation of the C sequestration rate and improved soil quality with continuous no-till management in the region using on-farm observations. 相似文献
17.
This study was carried out to investigate the effect of tillage and residue management on activities of phosphatases (acid
phosphatase, alkaline phosphatase, phosphodiesterase, and inorganic pyrophosphatase) and arylsulfatase. The land treatments
included three tillage systems (no-till, chisel plow, and moldboard plow) in combination with corn residue placements in four
replications. The activities of these enzymes in no-till/double mulch were significantly greater than those in the other treatments
studied, including no-till/bare, no-till/normal, chisel/normal, chisel/mulch, moldboard/normal, and moldboard/mulch. The effect
of mulching on activities of phosphatases was not as significant as on activities of arylsulfatase. The lowest enzyme activities
were found in soil samples form no-till/bare and moldboard/normal treatments, with the exception of inorganic pyrophosphatase,
which showed the lowest activity in no-till/bare only. Among the same residue placements, no-till and chisel plow showed comparable
arylsulfatase activity, whereas the use of moldboard plow resulted in much lower arylsulfatase activity. The activities of
phosphatases and arylsulfatase were significantly correlated with organic C in the 40 soil samples studies, with r values ranging from 0.71*** to 0.92***. The activities of alkaline phosphatase, phosphodiesterase, and arylsulfatase were
significantly correlated with soil pH, with r values of 0.85***, 0.78***, and 0.77***, respectively, in the 28 surface soil samples studied, but acid phosphatase and inorganic
pyrophosphatase activities were not significantly correlated with soil pH. The activities of phosphatases and arylsulfatase
decreased markedly with increasing soil depth and this decrease was associated with a decrease in organic C content. The activities
of these enzymes were also significantly intercorrelated, with r values ranging from 0.50*** to 0.92***.
Received: 4 October 1995 相似文献
18.
Summary Topsoils (0–75 mm) from four soil types with different sulphate retention capacities were collected from stock camp and non-camp (main grazing area) sites of grazed pastures in New Zealand which had been annually fertilized with superphosphate for more than 15 years. These soils were analysed for different S fractions and incubated at 30°C for 10 weeks using an open incubation technique in order to assess the extent of S mineralization and the release of soluble soil organic S from camp and non-camp soils during incubation. The soils were preleached with 0.01 M KCl, followed by 0.04 M Ca(H2PO4)2 before being incubated. Pre-incubation leachates and weekly 0.01 M KCl leachates were analysed for mineralized S (i.e., hydriodic acid-reducible S) and total S. Soluble organic S was estimated as the difference between these two S fractions. Results obtained show higher cumulative amounts of all three S fractions in leachates over a 10-week incubation period in camp than in non-camp soils, suggesting that higher mineralization occurred in camp soils. Cumulative amounts of mineralized S from camp and non-camp soils showed a linear relationship with duration of incubation (R
20.985***), while the cumulative release of soluble organic S followed a quadratic relationship (R
20.975***). A significant proportion (14.6%–40.8%) of total S release in KCl leachates was soluble organic S, indcating that organic S should be taken into account when assessing S mineralization. Mineralized S and soluble organic S were best correlated with 0.01 M CaCl2-extractable soil inorganic S (R
2=0.767***) and 0.04 M Ca(H2PO4)2-extractable soil inorganic S(R
2=0.823***), respectively. Soil sulphate retention capacity was found to influence amounts of mineralized S and soluble organic S, and thus periodic leaching with KCl to remove mineralized S from soils may not adequately reflect the extent of soil S mineralization in high sulphate-retentive soils. In low (<10%) sulphateretentive soils, increasing the superphosphate applications from 188 to 376 kg ha–1 year–1 increased S mineralization but not amounts of C-bonded and hydriodic acid-reducible soil S fractions. 相似文献
19.
Denitrification rates are often greater in no-till than in tilled soils and net soil-surface greenhouse gas emissions could be increased by enhanced soil N2O emissions following adoption of no-till. The objective of this study was to summarize published experimental results to assess whether the response of soil N2O fluxes to the adoption of no-till is influenced by soil aeration. A total of 25 field studies presenting direct comparisons between conventional tillage and no-till (approximately 45 site-years of data) were reviewed and grouped according to soil aeration status estimated using drainage class and precipitation during the growing season. The summary showed that no-till generally increased N2O emissions in poorly-aerated soils but was neutral in soils with good and medium aeration. On average, soil N2O emissions under no-till were 0.06 kg N ha−1 lower, 0.12 kg N ha−1 higher and 2.00 kg N ha−1 higher than under tilled soils with good, medium and poor aeration, respectively. Our results therefore suggest that the impact of no-till on N2O emissions is small in well-aerated soils but most often positive in soils where aeration is reduced by conditions or properties restricting drainage. Considering typical soil C gains following adoption of no-till, we conclude that increased N2O losses may result in a negative greenhouse gas balance for many poorly-drained fine-textured agricultural soils under no-till located in regions with a humid climate. 相似文献
20.
《European Journal of Soil Biology》2008,44(4):419-428
We measured soil microbiota and enzyme activities in order to compare conventional (CCS: chemical fertilisers, plant rotation with cereals dominating) and organic (OCS: green and farmyard manure, plant rotation including leguminous plants) cropping systems in a long-term field experiment. During the 3-year study period, strawberry was grown on the whole area and peat amendment was applied to a set of plots. Activities of 12 different enzymes, phospholipid fatty acids (PLFA) and microbial biomass (Cmic and Nmic) were measured twice each year. Dry weight (dw), water holding capacity (WHC) and pH were also measured. The enzyme activities were generally higher, arylsulphatase, phosphomonoesterase (PME) and esterase activities consistently, in the OCS than in the CCS. Other enzyme activities displayed higher activities either during 1 or 2 years or seasonally. Peat amendment increased PME, phosphodiesterase (PDE), leucine aminopeptidase (AP), chitinase, cellobiosidase, α-glucosidase and esterase activities but decreased arylsulphatase and initially alanine AP activities, whereas β-glucosidase and β-xylosidase activities were increased only during the 3rd year. Microbial biomass was higher in the OCS than in the CCS but peat addition decreased Cmic and Nmic at least initially. Both the OCS and peat addition increased soil PLFA content. Peat treatment also affected soil microbial structure as revealed by PLFA patterns, whereas the cropping system had no impact. 相似文献