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  • 1
    Electronic Resource
    Electronic Resource
    Factors affecting l-asparaginase activity in soils (1991)
    Springer
    Biology and fertility of soils 11 (1991), S. 1-5 
    Details
    ISSN: 1432-0789
    Keywords: Organic N ; Urease ; Amidase ; Asparaginase ; Soil enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Studies on the distribution of l-asparaginase in soil profile samples revealed that its activity generally decreases with sample depth and is accompanied by a decrease in organic C content. Statistical analyses indicated that l-asparaginase activity was significantly correlated (** P〈0.01) with organic C (r=0.86**) and total N (r=0.78**) in the 26 surface soil samples examined. There was no significant relationship between l-asparaginase activity and the percentage of clay or sand. There was, however, a significant correlation between l-asparaginase activity and amidase (r=0.82**) and urease (r=0.79**) activities in the surface samples studied. The effects of 21 trace elements, 12 herbicides, 2 fungicides, and 2 insecticides on l-asparaginase activity in soils showed that most of the trace elements and pesticides, at the concentrations used, inhibited the reaction catalyzed by this enzyme. The degree of inhibition varied among soils. When the trace elements were compared, at the rate of 5 μmol g-1 soil, the average inhibition of l-asparaginase in three soils showed that Ag(I), Cd(II), Hg(II), Ni(II), Pb(II), and V(IV) were the most effective inhibitors (average inhibition ≥20%). The least effective inhibitors (average ≤10%) included Cu(I), Ba(II), Co(II), Sn(II), Zn(II), Al(III), Se(IV), As(V), and Mo(VI). Other trace elements that inhibited l-asparaginase activity in soils were Cu(II), Mn(II), As(III), B(III), Cr(III), Fe(III), Ti(IV), and W(VI). When the pesticides were compared, at the rate of 10 μg active ingredient g-1 soil, the average inhibition of l-asparaginase activity in three soils ranged from 4% with Merpan to 46% with Malaspray. Other pesticides that inhibited l-asparaginase activity in soils (average inhibition in parentheses) were Aatrex (17%), Alanap (21%), Amiben (18%), Banvel (12%), Bladex (24%), 2,4-D (17%), Dinitramine (19%), Eradicane (16%), Lasso (40%), Paraquat (33%), Sutan (39%), treflan (7%), Menesan (18%), and Diazinon (33%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335825
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  • 2
    Electronic Resource
    Electronic Resource
    l-Asparaginase activity of soils (1991)
    Springer
    Biology and fertility of soils 11 (1991), S. 6-12 
    Details
    ISSN: 1432-0789
    Keywords: Soil enzymes ; Organic N ; Enzyme kinetics ; Asparaginase ; N mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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 μg 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335826
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  • 3
    Electronic Resource
    Electronic Resource
    Decomposition of different organic materials in soils (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 175-182 
    Details
    ISSN: 1432-0789
    Keywords: Crop residues ; Animal manures ; Sewage sludges ; Carbon mineralization ; Rate constant ; Global CO2 ; Sustainable agriculture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory experiments were conducted to evaluate organic C mineralization of various organic materials added to soils. A soil sample was mixed with organic material to approximate a field application of 9 g organic C kg-1 soil (0.9% or 50 Mg ha-1). The organic materials used were four crop residues [corn (Zea mays L.), soybean (Glycine max L. Merr.), sorghum (Sorghum vulgare Pers.), and alfalfa (Medicago sativa L.)], four animal manures [chicken (Gallus domesticus), pig (Sus scrofa), horse (Equus caballus), and cow (Bos taurus)] and four sewage sludges [Correctionville (Imhoff tank), Charles City (holding tank), Davenport (secondary digester), and Keokuk (primary digester)]. The soil-organic material mixture was incubated under aerobic conditions at room temperature (20±2°C) for 30 days. The CO2 evolved was collected in standard KOH solution by continuously passing CO2-free air over the soil. Results showed that, in general, the amounts of CO2-C released mereased rapidly initially, but the pattern differed among the organic materials used. More than 50% of the total CO2 produced in 30 days of incubation was evolved in the first 6 days. Expressed as percentages of organic C added, the amounts of CO2 evolved ranged from 27% with corn to 58% with alfalfa. The corresponding percentages for animal manures ranged from 21 to 62% with horse and pig manures, respectively, and for sewage sludges they ranged from 10 to 39% for Charles City and Keokuk sludges. All CO2 evolution data conformed well to a first-order kinetic model. Potentially, readily mineralizable organic C values and first-order rate constants (k) of the organic matter-treated soils ranged from 1.422 g C kg-1 soil with ak value of 0.0784 day-1 to 6.253 g C kg-1 soil with ak value of 0.0300 day-1. The half-lives of the C remaining in soils ranged from 39 to 54 days for plant materials. The corresponding half-lives for the C remaining from animal manures and sewage sludges ranged from 37 to 169 days and from 39 to 330 days, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647664
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of tillage and residue management on enzyme activities in soils (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 202-207 
    Details
    ISSN: 1432-0789
    Keywords: Amidase ; Urease ; L-Asparaginase ; L-Glutaminase ; Tillage systems ; Residue management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00382513
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  • 5
    Electronic Resource
    Electronic Resource
    Arylsulfatase activity of microbial biomass in soils as affected by cropping systems (1999)
    Springer
    Biology and fertility of soils 29 (1999), S. 46-54 
    Details
    ISSN: 1432-0789
    Keywords: Key words Arylsulfatase activity ; Chloroform-fumigation method ; Biomass enzymes ; Crop rotations ; N fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The impacts of crop rotations and N fertilization on different pools of arylsulfatase activity (total, intracellular, and extracellular) were studied in soils of two long-term field experiments in Iowa to assess the contibution of the microbial biomass to the activity of this enzyme. Surface-soil samples were taken in 1996 and 1997 in corn, soybeans, oats, or meadow (alfalfa) plots that received 0 or 180 kg N ha–1 before corn, and an annual application of 20 kg P ha–1 and 56 kg K ha–1. The arylsulfatase activity in the soils was assayed at optimal pH (acetate buffer, pH 5.8) before and after chloroform fumigation; microbial biomass C (Cmic) and N (Nmic) were determined by chloroform-fumigation methods. All pools of arylsulfatase activity in soils were significantly affected by crop rotation and plant cover at sampling time, but not by N fertilization. Generally, the highest total, intracellular, and extracellular arylsulfatase activities were obtained in soils under cereal-meadow rotations, taken under oats or meadow, and the lowest under continuous cropping systems.Total, intracellular, and extracellular arylsulfatase activities were significantly correlated with Cmic (r〉0.41, P〈0.01) and Nmic (r〉0.38, P〈0.01) in soils. The averages of specific activity values, i.e., of arylsulfatase activity of the microbial biomass, expressed per milligram Cmic, ranged from 315 to 407 μg p-nitrophenol h–1. The total arylsulfatase activity was significantly correlated with the intracellular activity, with r values 〉0.79 (P〈0.001). In general, about 45% of the total arylsulfatase activity was extracellular, and 55% was associated with the microbial biomass in soils, indicating the importance of the microflora as an enzyme source in soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050523
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  • 6
    Electronic Resource
    Electronic Resource
    Enzyme activities in a limed agricultural soil (2000)
    Springer
    Biology and fertility of soils 31 (2000), S. 85-91 
    Details
    ISSN: 1432-0789
    Keywords: Key words Soil quality ; Glycosidases ; Amidohydrolases ; Arylamidase ; Phosphatases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050628
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of tillage and residue management on enzyme activities in soils: III. Phosphatases and arylsulfatase (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 141-146 
    Details
    ISSN: 1432-0789
    Keywords: Key words Tillage systems ; Crop residues ; Acid phosphatase ; Alkaline phosphatase ; Phosphodiesterase ; Inorganic pyrophosphatase ; Arylsulfatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract 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***.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050222
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  • 8
    Electronic Resource
    Electronic Resource
    Sulfate adsorption by variable charge soils: Effect of low-molecular-weight organic acids (1998)
    Springer
    Biology and fertility of soils 26 (1998), S. 157-163 
    Details
    ISSN: 1432-0789
    Keywords: Key words Sulfate adsorption ; Organic acids ; Organic anion adsorption ; Effect of pH ; Ionization of organic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sulfate (SO4 2–) movement and transport in soils has received considerable attention in recent years. In most soils, SO4 2– coexists with a variety of natural organic compounds, especially organic acids. Studies were conducted to assess the effect of low-molecular-weight organic acids (eight aliphatic and five aromatic acids) on SO4 2– adsorption by variable charge soils from Chile and Costa Rica. The effects of type of organic acid, pH, type of soil, and organic acid concentration were investigated. In one experiment, a 1.0 g soil sample was equilibrated with 25 ml 0, 0.5, 1.0, 2.0, 4.0, or 6.0 mM K2SO4 in 1 mM NaCl in the presence or absence of 5 mM citric acid. In the second set of experiments, the adsorption of 2 mM SO4 2– in soils at pH 4 or pH 5 in the presence or absence of one of 13 organic acids at a concentration of 2 mM or 5 mM was studied. Results showed that citric acid significantly decreased SO4 2– adsorption by the two soils. Sulfate adsorption decreased with increasing pH of the equilibrium solution. Aliphatic acids, with the exception of cis-aconitic acid, decreased the amount of SO4 2– adsorbed by the two soils, with oxalic, tartaric, and citric acid showing the greatest effect. The differences in pH values of the equilibrium solutions in the presence and absence of organic acids were significantly, but negatively, correlated with the amount of SO4 2– adsorbed, suggesting chemisorption of SO4 2– and the release of hydroxide ions. The ionization fraction values of the organic acids at the equilibrium pH were correlated with the amounts of SO4 2– adsorbed, suggesting that the protonation of surface hydroxyl groups of the mineral phase increased as the strength of the ionization of the acid increased, thus creating more positively charged surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050361
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of active nitrogen pools in soils under different cropping systems (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 302-309 
    Details
    ISSN: 1432-0789
    Keywords: Key words Biomass carbon ; Biomass nitrogen ; Cropping systems ; Nitrogen mineralization constants ; Active nitrogen pools
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Studies were conducted to evaluate the relationships among different active N pools of organic matter in soils at two long-term cropping systems in Iowa. Results indicated that multi-cropping systems, particularly meadow-based systems, enhanced bioactivities of soils. Mono-cropping systems, particularly soybean, reduced soil microbial biomass and enzyme activities. The mineralizable N pool (potential N mineralization;N o) was more sensitive to changes in the size of the microbial biomass N (Nmic) than to changes in organic N. One unit change in organic N did not lead to substantial changes in N o, but 1 unit change in Nmic resulted in three or more units change in N o. The active N pools and turnover rate were more sensitive to changes in organic C than to changes in microbial biomass C (Cmic). A unit change in organic C resulted in 10.6 units change in N o, but a unit change in Cmic resulted in only 0.8 unit change in N o. Cmic or Nmic are better indexes than organic C or N for the estimation of N o or N availability, because biomass values are more highly correlated with cumulative N mineralized during 24 weeks of incubation, with r values ranging from 0.57 (P〈0.001) to 0.88 (P〈0.001).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000252
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of pH on nitrogen mineralization in crop-residue-treated soils (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 115-119 
    Details
    ISSN: 1432-0789
    Keywords: Acid rain ; N turnover ; N immobilization ; Soil pH ; Minimum tillage ; N mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This study compares N mineralization in soils treated with crop residues [corn (Zea mays L.), soybean (Glycine max (L.) Merr.), sorghum (Sorghum vulgare Pers.)] or alfalfa (Medicago sativa L.) at three adjusted soil pH values (4, 6, and 8); pH was adjusted with dilute H2SO4 or KOH. A sample of soil (20 g) was treated with 0.448 g plant material (equivalent to 50t ha−1), mixed with 20 g silica sand adjusted to the pH of the soil, and packed in a leaching tube. The soil-sand mixture was leached with 100 ml 5 mM CaCl2 adjusted to the same pH as that of the treated soil to remove the initial mineral N, and incubated at 30°C. The leaching procedure was repeated every 2 weeks for 20 weeks. Results from three soils showed that N mineralization increased as the soil pH increased. In one soil (Lester soil), significant amounts of NH 4 + -N accumulated at pH 4 during the first 12 weeks. Treatment with corn and soybean residues resulted in a marked reduction in N mineralization, especially at pH 4. The percentage of organic N mineralized from sorghum residue and alfalfa added to soils increased as the soil pH increased; the values ranged from 7.7% to 37.0% for sorghum and from 17.2% to 30.1% for alfalfa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257645
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