首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 250 毫秒
1.
Studies to determine the kinetic parameters of the rhodanese-catalyzed reaction in soils showed that the Km values of thiosulfate and cyanide for this enzyme are similar to those for the same enzyme isolated from other biological systems. Application of the three linear transformations of the Michaelis-Menten equation indicated that the apparent Km constants of thiosulfate and cyanide varied among the soils used, but the results obtained by the three plots were similar. By using the Lineweaver-Burk plot. the Km values of S2O3?2 and CN? for rhodanese activity in five soils ranged from 1.20 to 10.3 (av 5.46) and from 2.48 to 10.20 (av 5.81) mM, respectively. The Vmax values ranged from 511 to 1431 (av 759) nmoles SCN? produced · g?1 soil · h?1. The activation energy values ranged from 21.6 to 34.0 (av 28.0) kJ · mole?1, and the average Q10 for temperatures ranging from 10 to 60 C ranged from 1.25 to 1.45 (overall average. 1.37).  相似文献   

2.
Inorganic pyrophosphatase activity in three soils decreased when exchangeable and soluble metals were removed by leaching with in NH4OAc (pH 8). The effect of added metal ions at various concentrations in the leached soils showed that, at certain concentrations, Ba2+, Ca2+, Co2+, Mg2+, Mn2+, Ni2+ and Zn2+ promoted, K+ and Na+ had no effect, and Fc2+ and Cu2+ decreased pyrophosphatase activity. At high concentrations (>50 mM). Co2+, Mn2+, Ni2+ and Zn2+ inhibited pyrophosphatase activity in two soils. The concentration of metal ion needed for optimum activity of pyrophosphatase varied among the soils. The efficiency of the metal ions at optimum concentrations (average percentage increase for three soils in parentheses) in promoting pyrophosphatase was Ca2+ (47) > Mg2+ (42) > Ba2+ = Co2+ (29) > Ni2+ (27) > Zn2+ (20) > Mn2+(16). Pyrophosphatase activity in two leached soils adjusted to 50, 75, 100 or 150 mM PPi and Ca2+ or Mg2+ concentrations from 0 to 250 mM was at an optimum when the metal ion: PPi ratio was 1:1. Soil pyrophosphatase in the presence of 200 mM CaCl2 or MgCl2 was protected against inactivation by heat (90 C for up to 30 min).  相似文献   

3.
A method to assay pyrophosphatase activity in soil is described. It involves the determination of orthophosphate (Pi) released by pyrophosphatase activity when soil is incubated with 70 mm pyrophosphate (PPi) solution, citrate buffer (pH 5.8) and toluene at 37°C for 2 h. The Pi released is determined by a procedure that involves separation of Pi from PPi and formation of a Pi-molybdate complex. The method is precise and is not complicated by fixation of Pi in soil.  相似文献   

4.
Many farmlands are periodically flooded or ponded by excessive precipitation resulting in changes to soil chemical and biochemical properties. In this study, one set (eight treatments with four replications) of field-moist surface soils (0–15 cm) and their air-dried counterparts obtained from a long-term liming experiment were incubated at 30 °C under waterlogged conditions for 10 days, and the amounts of net NH4 +-N released (soluble and exchangeable) were determined after extraction with 4 M KCl. Another set of three surface soils were used to evaluate the effect of six heavy metals on the NH4 +-N release under waterlogged conditions. Results showed that increasing the liming rate from 0 to 17,930 kg ha?1 effective calcium carbonate equivalent increased the average soil pH from 4.98 to 7.06, averages of the amounts of NH4 +-N released ranged from 1.6 to 5.2 mg N kg?1 field-moist soil, and the corresponding amounts released in air-dried soils ranged from 18.9 to 32.9 mg N kg?1 soil. This increase of the amount NH4 +-N released in air-dried soil samples is presumably due to a slaking effect. At 5 mmol kg?1 soil, all six heavy metals inhibited the NH4 +-N released. The relative effectiveness of the heavy metals in inhibition of the NH4 +-N released varied among the three soils. Lead(II) was the most effective inhibitor of NH 4 +-N release in Clarion and Harps soils and Cd(II) in Harps soil. Cobalt(II), Cu(II), and Cd(II) were the least effective inhibitors of NH4 +-N release in Clarion, Harps, and Okoboji soils, respectively.  相似文献   

5.
Significance of microbial biomass and non-exchangeable ammonium with respect to the nitrogen transformations in loess soils of Niedersachsen during the growing season of winter wheat. I. Change of pool sizes Nitrogen transformations in loess soils have been examined by laboratory and field experiments. After straw application (· 8 t · ha?1), N in microbial biomass (Nmic) increased by about 20 mg · kg?1 soil (· 90 kg N · ha?1 · 30 cm?1) after 9 days of incubation (20 °C). Another laboratory experiment yielded an increase of about 400 mg of NH4+-N · kg?1 fixed by minerals within 1 h after addition of 1 M NH4+-acetate. Defixation of the recently fixed NH4+ after addition of 1 M KCl amounted to only 60 mg · kg?1 within 50 days. In a field experiment with winter wheat 1991, an increase in Nmic of about 80 kg N · ha?1 · 30 cm?1 was observed from March to June. After July, growth of the microbes was limited by decreased soluble carbon concentrations in the rhizosphere. Different levels of mineral N-fertilizer (0, 177 and 213 kg N · ha?1) did not affect significantly the microbial biomass. The same field experiment yielded a decrease of non-exchangeable ammonium on the “zero”-fertilized plot in spring by 200 kg N · ha?1 · 30 cm?1. The pool of fixed ammonium increased significantly after harvest. After conventional mineral N-fertilizer application (213 kg N · ha?1). NH4+-defixation was only about 120 kg N · ha?1 · 30 cm?1 until July.  相似文献   

6.
Though engineered covers have been suggested for reducing landfill methane emissions via microbial methane oxidation, little is known about the covers' function at low temperature. This study aimed to determine the methane consumption rates of engineered soil columns at low temperature (4–12°C) and to identify soil characteristics that may enhance methane oxidation in the field. Engineered soils (30 cm thick) were mixtures of sewage sludge compost and de-inking waste, amended with sand (SDS soil) or bark chips (SDB soil). At 4–6°C, we achieved rates of 0.09 gCH4 kgTS?1d?1 (0.02 m3 m?2d?1) and 0.06 gCH4 kgTS?1d?1 (0.009 m3 m?2d?1) with SDS and SDB soils, respectively. With SDS, good movement and exchange of oxygen in porous soil moderated the slowdown of microbial activity so that the rate dropped only by half as temperature declined from 21–23°C to 4–6°C. In SDB, wet bark chips reduced the soil's air-filled porosity and intensified non-methanotrophic microbial activity, thus reducing the methane consumption rate at 4–6°C to one fourth of that at 21–23°C. In conclusion, soil characteristics such as air-filled porosity, water holding capacity, quantity and stabilization of organic amendments that affect the movement and exchange of oxygen are important variables in designing engineered covers for high methane oxidation at low temperature.  相似文献   

7.
Treatment of a soil under permanent pasture with carbaryl (a broad spectrum carbamate biocide) resulted in a 2-fold increase in the volume of surface runoff. This was attributed to a 3-fold reduction in infiltration rate as a result of litter accumulation at the soil surface in the absence of surface-casting earthworm activity. The amounts of dissolved inorganic P (DIP), NH+4-N, and NO?3-N in surface runoff from pasture treated with carbaryl (1.18, 9.53 and 4.25 kg ha?1 yr?1, respectively) were appreciably greater than those from untreated pasture (0.31, 1.63 and 0.52 kg ha?1 yr?1). This was attributed to the large amounts of DIP, NH+4-N, and NO?13-N released from decomposing litter. Following incubation at 4°C for 18 days the release of DIP, NH+4-N and NO?3-N from litter was 160, 1600 and 950 μg g?1, respectively. Losses of particulate P and sediment in surface runoff were lower in the absence (0.31 and 290 kg ha?1 yr?1, respectively) than in the presence (0.56 and 1120 kg ha? yr?1) of surface casts, pointing to the importance of surface casts as a source of sediment. Surface casts accounted for 45 and 75%, respectively, of the annual loading of particulate P and sediment in surface runoff. Nevertheless, the total loss in surface runoff of P and N forms was increased substantially when the production of earthworm casts was eliminated  相似文献   

8.
Weathering of piled material in the field is a popular method to treat spent mushroom substrate (SMS) before reuse. During the weathering process, rainfall and snowmelt pass through SMS piles and a large amount of solutes is released in the leachate. To investigate solute release patterns, the field weathering process was simulated under controlled conditions in the laboratory. Fresh SMS was packed in an acrylic column (20 cm i.d.) to 150 cm height and leached intermittently with a cumulative total of 230 cm of deionized water over 180 days. Leachate was collected and analyzed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), electrical conductivity (EC), and inorganic salts. Solute release patterns were described using first order models, and total released solutes were calculated. The SMS leachate had DOC, DON and EC values ranging from 450 to 15,500 mg L?1, 50 to 1,700 mg L?1, and 3 to 50 dS m?1, respectively. The major inorganic cations were K+, Na+, Ca2+, Mg2+ and NH4+, and anions were Cl? and SO42?. Release of DOC, DON, and bivalent cations Ca2+ and Mg2+ were described by a first order Exponential Rise to Maximum model, while releases of monovalent ions Cl?, K+, Na+ and NH4+ were described as a first order Sigmoidal Logistic process, and SO42? release was best modeled by a Sigmoidal Chapman equation. Following six months and 230 cm applied water, 3.1 kg of DOC, 0.58 kg of dissolved N, and 8.6 kg of inorganic salts were leached per cubic meter of bulk SMS (220 kg oven dry mass). Weathering of SMS involves a significant removal of nutrients from the composted material, which can contribute to pollution of soil and groundwater.  相似文献   

9.
ABSTRACT

Soil degradation due to salinization and sodication is the paramount threat in Indo-Gangetic plains. The studies on reclamation and management of such soils can provide a pragmatic solution for improving fertility and productivity of these soils. Lack of organic matter and poor availability of nutrients are the major factors for low productivity of sodic soils. Rice-wheat is a major cropping system in Indo-Gangetic alluvial plain region even in reclaimed sodic soils and farmers used inorganic fertilizers only to get higher yields. In this study, we used different organic sources of amendments in conjunction with different nitrogen (N) doses supplied through inorganic fertilizers to investigate the combined effect of organic and inorganic amendments on soil fertility and the productivity of rice- wheat system in sodic soils. Salt tolerant varieties of rice and wheat were grown in sodic soil (pH: 9.30, EC: 1.12 dSm?1 and exchangeable sodium percentage, ESP: 52) during 2014–15 to 2016–17 in a field experiment with 13 treatment combinations of organic and inorganic amendments (T1- (control) 100% of recommended dose of N (RDN), T2-municipal solid waste compost (MSWC) @10 t ha?1 + 50%RDN, T3- MSWC @10 t ha?1 + 75% RDN,T4- MSWC @10 t ha?1 + 100%RDN, T5-Vermicompost (VC) @10 t ha?1 + 50% RDN, T6- VC @10 t ha?1 + 75% RDN, T7-VC@10 t ha?1 + 100% RDN, T8- Farm yard manure (FYM) @ 10 t ha?1 + 50% RDN,T9- FYM@10 t ha?1 + 75%RDN, T10- FYM@10 t ha?1 + 100% RDN, T11-Pressmud (PM) @10 t ha?1 + 50% RDN, T12-PM@10 t ha?1 + 75%RDN, and T13- PM @ 10 t ha?1 + 100% RDN). Use of organic amendments supplemented with reduced dose of N through inorganic fertilizer has significantly improved soil bio-physical and chemical properties. Application of VC@10 t ha?1 + 100% RDN (T7) decreased soil bulk density, pH, EC, ESP and Na content to 2.0, 4.2, 26.5, 42.8, and 56.6% respectively and increased soil organic carbon by 34.6% over control (T1). Soil fertility in terms of available N, P, K, Ca, and Mg increased by 20.5, 33.0, 36.4, and 44%, respectively, over control (T1). Soil microbial biomass carbon, nitrogen, and phosphorus also improved significantly due to combined use of organic amendments and inorganic fertilizers over the only use of inorganic fertilizers. Decreasing in soil sodicity and increasing soil fertility showed significant increase (P < 0.05) in crop growth, growth indices, and grain yields of rice and wheat. The study revealed that combined use of VC or MSW compost @10 t ha?1 in conjunction with 75% RDN through inorganic fertilizers in sodic soils proved sustainable technology for restoration of degraded sodic soils and improving crop productivity.  相似文献   

10.
Plant availability of potassium (K) in soils is controlled by dynamic interactions among its different pools. Potassium quantity–intensity (Q/I) parameters were determined to relate them to bean plant indices in a pot experiment. The results showed that the activity ratio at equilibrium (ARk) ranged from 0.015 to 0.358 (mmol L?1)0.50, the potential buffering capacity (PBC) ranged from 7.54 to 26.32 mmol kg?1/(mmol L?1)0.50, the labile K (Δk°) ranged from 9.1 to 112.2 mg kg?1, and the K adsorbed at specific sites (Kx) ranged from 6.51 to 69.69 mg kg?1. The results of pot experiment showed that some K Q/I parameters were significantly correlated with some plant indices. Also, the correlation study showed that readily exchangeable K was significantly correlated with K Q/I parameters except Kx. The results of this research show that the K Q/I method can be used for estimating of soil K availability for bean.  相似文献   

11.
Abstract

The pyrophosphatase (PPi) enzyme catalyzes the hydrolysis of pyrophosphate to orthophosphate. The PPi activity was determined in 14 hill‐land soils of the Appalachian Region. The top two horizons from each soil were sampled and stored in a field‐moist state at 4°C (4°C) and in an air‐dry (AD) state prior to determination of PPi activity. Each soil type had its own level of PPi activity. The mean PPi activities of surface and subsurface horizons stored at 4°C were 1.3 and 1.7 times higher than those of AD samples. The average PPi activities of surface horizons were 6.2 and 4.6 times higher than subsurface horizons stored at AD and 4°C. respectively. The PPi activities were positively correlated with organic C, N, forms of S and P. exchangeable cations, original moisture by weight and volume, and percent air‐filled porosity. In both surface and subsurface horizons, significant positive correlationships were observed between PPi activities and Mn content, indicating the need for Mn in the activation of PPi. High PPi activities in surface horizons might induce a greater rate of hydrolysis of applied pyrophosphate (polyphosphate) fertilizers to orthophosphate and lead to undesirable fixation of P in acid soils.  相似文献   

12.
Acetylene reduction by non-symbiotic, heterotrophic micro-organisms in a range of soils containing different concentrations of heavy metals was determined using intact soil cores. The suitability of this method for the soils used in this investigation was established. Samples were collected seasonally, and were incubated under standard conditions (darkness: 15°). Mean values of metal concentrations in the soil (μg g?1) were: Cd: 1–200; Pb: 60–8000; Zn: 70–26000, Cu: 20–40. Rates of acetylene reduction were generally low, from 2800 to 50000 nmol C2H4, m?2 day?1. Assuming a 3:1 ratio of C2H2 reduction to N2 fixation, this represents a rate of 0.3 to 5.0 g N fixed ha?1 day?1 in the surface 150 mm of soil. No consistent effect of heavy metal concentration was found. The most important factors determining activity were soil moisture content and possibly inorganic nitrogen concentration. It thus appears that the bacteria in polluted soils are capable of adapting to potentially toxic concentrations of heavy metals, or that these metals are present in the soils tested in unavailable or non-toxic forms.  相似文献   

13.
THE REACTION OF FLUORIDE WITH SOILS AND SOIL MINERALS   总被引：4，自引：0，他引：4  
The reaction of sodium fluoride solution with soils and soil minerals at constant pH has been assessed as a possible single-value characteristic in the classification of soils, particularly those containing significant amounts of poorly ordered inorganic material. A suitable method involves reaction of the soil or clay at 25°C with 0·85 M sodium fluoride at pH 6·8, the amount of OH? released after 25 min being taken as the single-value characteristic. There was a statistically significant correlation between the amount of OH? released and the amount of alumina extracted with cold 5 per cent sodium carbonate solution from both freely drained and poorly drained Scottish soils. The multiple correlation coefficients were improved for freely drained soils by including the dithionite-extracted ferric oxide and the silica soluble in 5 per cent sodium carbonate solution. The procedure is not suitable for surface soils, because of interference by organic matter, or for carbonate-containing soils unless carbonate is removed.  相似文献   

14.
Abstract

A method for assaying the soil lipase activity is described. It involves the titrimetric estimation of the amount of lauric acid released by the lipase activity when the soil is incubated with Tween 20 in the presence of toluene at 30°C for 18 h under agitation. The method is simple and precise and incubation without agitation is also possible. The method has been applied to six different kinds of soils. The lipase activity in the cultivated soils ranged from 22.5 to 75.5 mmol min?1 g?1 of dried soil. The K m value for Tween 20 was 1.8 × 10?4 m. The optimum pH was approximately 7.5. The hydrolysis of liveen 20 in soil was inhibited by glycerol which was the essential moiety of glyceride. The inhibition by glycerol was found to be competitive. These results indicate that Tween 20 is a potential substrate for the assay of the glyceride hydrolytic activity in soils.  相似文献   

15.
Summer solarization of six wet field soils of four different textures raised soil temperatures by 10–12°C at 15cm depth. Soil solarization increased concentrations of NO?3N and NH+4N up to six times those in nontreated soils. Concentrations of P, Ca2+, Mg2+ and electrical conductivity (EC) increased in some of the solarized soils. Solarization did not consistently affect available K+, Fe3+, Mn2+, Zn2+, Cu2+, Cl? concentrations, soil pH or total organic matter. Concentrations of mineral nutrients in wet soil covered by transparent polyethylene film, but insulated against solar heating, were the same as those in nontreated soil. Increases in NO?3N plus NH+4N were no longer detected in fallowed soils 9 months after solarization. No significant correlation between mineral-nutrient concentration in plant tissue and plant growth was found. Fresh and dry weights of radish, pepper and Chinese cabbage plants usually were greater when grown in solarized soils than in nontreated soils. Fertilization of solarized soils sometimes resulted in greater plant growth responses than observed in solarized but nonfertilized soils.  相似文献   

16.
Abstract

A long‐term soil incubation and column nutrient leaching study was conducted to determine nitrogen (N)‐mineralization rates of selected Florida Histosols with drained and intermittent‐flooded conditions. Five surface soils from the Everglades Agricultural Area (EAA) were packed in columns (5‐cm i.d. containing the 0‐ to 15‐cm depth of each soil) and leached with 0.01M CaC12 followed by distilled water every 25 d for 1 yr. Drained columns were treated with a minus‐nitrogen‐phosphorus (NP) solution followed by applying ‐0.97 MPa tension to remove excess solution. Flooded columns received the same minus‐NP solution, but were flooded to a depth of 3 cm. Both treatments were incubated for 25‐d periods, solution sampled, and treatments reapplied. Because flooding conditions could not be maintained during the sampling period, this treatment is referred to as intermittent flooded. The ammonium‐nitrogen (NH4 +‐N) released from drained soils accounted for less than 6% of the total soluble N released from all soils, compared to more than 30% released from flooded soils. There were no differences in the amounts of soluble organic N from drained and intermittent flooded soils. Total soluble N from the surface 15‐cm of drained soils ranged from 217 to 509 kg‐ha‐1yr‐1, with 50 to 67% released as nitrate‐nitrogen (NO3 ‐‐N). In contrast, total soluble N released from flooded soils ranged from 168 to 345 kg‐ha‐1yr‐1, with less than 3% released as NO3 ‐‐N.  相似文献   

17.
Adenosine deaminase activity in six soil samples was measured. One g of moist soil was incubated with 0.02 M adenosine in 0.1 M phosphate buffer (pH 7.6) and toluene in a shaking water bath (30°C) for 72 h. Inosine and NH2 + were detected in the filtrate as degradation products of adenosine; inosine was identified by paper chromatography, and NH2 + was determined by Nessler’s method.

The adenosine deaminase activity in soils was completely inhibited by autoclaving (120°C, 15 min).

The relation between substrate concentration and reaction rate followed the Michaelis-Menten equation.

The optimum pH for adenosine deaminase activity in soils ranged from about 7 to 8.

The adenosine deaminase activity in soils ranged from about 1.51 to 4.33 munit (nmol per min) per g of dry soil at 30°C.  相似文献   

18.
Determining potassium (K) fertilizer requirement using sorption isotherms is considered more accurate than conventional soil K tests. A total of 59 surface soil samples were used to establish K exchange isotherm. To evaluate K requirement sorption test, a glasshouse experiment using perennial ryegrass (Lolium perenne, cv. Roper) was carried out on 10 soil samples. The experiment was laid out as a completely randomized design with four replications and four K levels (K0, K20, K40, K80). Concentrations of K in solution established by adding K in the pots estimated from the sorption curve ranged from 20 to 80 mg K l?1 including check treatment (no K). Dry matter yield of ryegrass in most soils approached maximum as adjusted K levels were increased to 20 mg K l?1. The amounts of K required to bring the soils to 20 mg l?1 in soil solution varied among soils and ranged from 99 to 399 mg kg?1, on average 205 mg kg?1 soil. It was found that a useful regression model for the prediction of standard K requirement (K20) included the combination of plant available K extracted by NH4OAc (Av-K) and clay content: K20 = ?41 ? 0.63 Av-K + 9.0 Clay (R2 = 0.61, p < 0.001, n = 59).  相似文献   

19.
Accurate estimation of the available potassium (K+) supplied by calcareous soils in arid and semi‐arid regions is becoming more important. Exchangeable K+, determined by ammonium acetate (NH4OAc), might not be the best predictor of the soil K+ available to crops in soils containing micaceous minerals. The effectiveness of different extraction methods for the prediction of K‐supplying capacities and quantity–intensity relationships was studied in 10 calcareous soils in western Iran. Total K+ uptake by wheat grown in the greenhouse was used to measure plant‐available soil K+. The following methods extracted increasingly higher average amounts of soil K+: 0.025 M H2SO4 (45 mg K+ kg?1), 1 M NaCl (92 mg K+ kg?1), 0.01 M CaCl2 (104 mg K+ kg?1), 0.1 M BaCl2 (126 mg K+ kg?1), and 1 M NH4OAc (312 mg K+ kg?1). Potassium extracted by 0.01 M CaCl2, 1 M NaCl, 0.1 M BaCl2, and 0.025 M H2SO4 showed higher correlation with K+ uptake by the crop (P < 0.01) than did NH4OAc (P < 0.05), which is used to extract K+ in the soils of the studied area. There were significant correlations among exchangeable K+ adsorbed on the planar surfaces of soils (labile K+) and K+ plant uptake and K+ extracted by all extractants. It would appear that both 0.01 M CaCl2 and 1 M NaCl extractants and labile K+ may provide the most useful prediction of K+ uptake by plants in these calcareous soils containing micaceous minerals.  相似文献   

20.
We estimated the total inorganic fluxes of nitrogen (N), sulfur (S), chloride (Cl?, sodium (Na+, calcium (Ca2+, magnesium (Mg2+, potassium (K+ and hydronium (H+. The resistance deposition algorithm that is programmed as part of the CALMET/CALPUFF modeling system was used to generate spatially-distributed deposition velocities, which were then combined with measurements of urban and rural concentrations of gas and particle species to obtain dry deposition rates. Wet deposition rates for each species were determined from rainfall concentrations and amounts available from the National Acid Deposition Program (NADP) monitoring network databases. The estimated total inorganic nitrogen deposition to the Tampa Bay watershed (excluding Tampa Bay) was 17 kg-N ha?1 yr?1 or 9,700 metric tons yr?1, and the ratio of dry to wet deposition rates was ～2.3 for inorganic nitrogen. The largest contributors to the total N flux were ammonia (NH3 and nitrogen oxides (NO x at 4.6 kg-N ha?1 yr?1 and 5.1 kg-N ha?1 yr?1, respectively. Averaged wet deposition rates were 2.3 and 2.7 kg-N ha?1 yr?1 for NH4 + and NO3 ?, respectively.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号