摘要:

Using the quantity-intensity (Q/I) approach, we evaluated the effect of different levels of phosphorus on zinc equilibria in four soils having widely different characteristics. Although these soils showed marked differences in their Q/I parameters, plots of ΔZnexonARZnremained unchanged on treatment with low to high rates of P (0 to 1200 ± P g-1soil), and the Q/I isotherms of Zn-(Ca + Mg) exchange equilibria for a soil at different P levels were superimposable. It was apparent from these studies that applying P to the soil did not decrease Zn intensity in the soil solution.Zinc buffer capacity of the studied soils was in the increasing order of Gangtok acid soil, Gurdaspur neutral soil, Ludhiana alkaline soil, and Bhatinda calcareous soil; the reverse was true for the Zn intensity values.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Kinetic descriptions of the effect of clay minerals on the activity of enzymes are needed for a better understanding of the interaction of enzymes and clays in soil. We used a model clay-enzyme system to study the kinetics of inhibition f acid phosphatase and pyrophosphatase activities in homogenized corn roots by Na-homoionic montmorillonite, illite, and kaolinite clays. The adherence of the inhibition data to the partial noncompetitive kinetic model in the presence of montmorillonite or illite suggested that corn-root acid phosphatase and pyrophosphatase bind to the clay to form a complex whose maximum rate of activity (Vmax) is smaller by a factor of β, but whoseKmvalues remain unchanged. The β values determined for the inhibition of acid phosphatase by montmorillonite and illite were 0.33 and 0.53, respectively. The corresponding β values for inhibition of pyrophosphatase were 0.42 and 0.32. The inhibition of acid phosphatase and pyrophosphatase activities by kaolinite could be explained by a partial competitive inhibition model. TheVmaxvalues measured remained the same in the presence of kaolinite, but the apparentKmvalues were increased by a factor of α. The α values determined for acid phosphatase and pyrophosphatase were 4.6 and 3.2, respectively. The partial noncompetitive and partial competitive models predict a limit to the amount of inhibition observed in the presence of the various clay minerals. This indicates that a clay-enzyme complex may form whose activity is reduced but not totally eliminated and suggests that the formation of a clay-enzyme complex may be a mechanism by which a certain proportion of enzyme activity in soil may become stabilized. Shaking of the samples during incubation did not change the type of kinetics observed, but did change the values of the kinetic constants.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We investigated in phosphorus (P) status of 12 well-drained to moderately well-drained soil profiles along an east-west transect in the Niger Delta area of Nigeria, by determining available P estimated by the methods of Bray and Kurz no. 1, Bray and Kurtz no. 2, Olsen and Truog, and the various P fractions. Total P in the six profiles of soils developed on Coastal Plain sands (CPS) ranged from 281 to 1469 ppm mean, 821), and total P in the four profiles of soils developed on Meander Belt deposits (MBD) and Sombreiro Warri deposits (SWD) ranged from 63 to 293 ppm (mean, 133). The two profiles in the transitional zone between CPS and SWD had total P of 326 to 595 ppm (mean, 441). Organic P ranged from 11 to 338 ppm and constituted 3 to 44% of total P. Inactive inorganic P accounted for 9 to 65% of total P. The relative abundance of the various active inorganic P forms was, in decreasing or der, Fe-P, Al-P, and Ca-P, except in three of the profiles of MBD-SWD region, where Ca-P was nearly equal to or slightly higher than Al-P. The results showed high availability of P in CPS soils, medium availability of P in the transitional zone, and low P in the MBD and SWD regions. The distribution of P fractions indicated a low degree of development of the soils, especially the MBD and SWD soils.Total P was significantly correlated positively with percentage of clay and negatively with pH and percentage of sand. Fe-P and Al-P had significant correlation with total P, percentage of sands, percent-age of clay, and available P extracted by the methods of Bray and Kurtz no. 1, Bray and Kurtz no. 2, and Truog.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

A fertile agricultural soil was amended with primary papermill sludge at rates from 0 to 267 g/kg soil. Samples incubated at 12 and 25°C displayed N immobilization proportional to the rates of sludge addition. Prior to 50 d of incubation, N immobilization was pronounced at both temperatures. Between 50 and 100 d, net mineralization began in the 33-g/kg treatment at 12°C and in the 33-g/kg and 67-g/kg treatments at 25°C. By day 150, net mineralization was evident in the 67-g/kg rate at 12°C and in the 133-g/kg treatment at 25°C. By the end of the incubation, extractable N levels were reduced from approximately 3 to 80% of the controls incubated at 12°C and from approximately 1 to 84% of the controls incubated at 25°C. A highly significant negative relationship between extractable N and sludge addition was determined at day 250. Statistical analyses indicated significant differences in the polynomial regression equations for each temperature. Total carbon mineralized was significantly increased with incremental sludge addition. Mineralized Carbon (as a percentage of added sludge C) ranged from approximately 7% in the 267-g/kg rate to approximately 24% in the 17-g/kg rate incubated at 12°C, and from 17% in the 267-g/kg rate to 65% in the 17-g/kg rate incubated at 25°C. Organic matter determined on day 250 indicated that the 133− and 267-g/kg rates significantly increased organic matter content at both incubation temperatures. Results suggest that, with proper management, papermill sludge could be useful in conservation of soil N and organic matter.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

In a study of the volatilization loss of nitrogen in a submerged field (pH 7.6) at two levels of soils salinity, 3 to 4 dS m-1(SW1) and 7 to 8 dS m-1(SW2), the losses were in the order: ammonium sulfate > prilled urea > lac-coated urea > urea briquettes (placed) > sulfur-coated urea > urea in paper packet (placed) in SW1, and ammonium sulfate > prilled urea > laccoated urea > sulfur-coated urea > urea briquettes (placed) > urea in paper packet (placed in SW2. Except for placed fertilizers, with the increase in soil salinity from SW1to SW2, the volatilization loss increased from 17.8 to 37.3% for ammonium sulfate, from 14.6 to 26.1% for prilled urea, from 12.0 to 23.4% for lac-coated urea, and from 8.4 to 16.3% for sulfur-coated urea. Volatilization loss was measured in the field following a simple method. The study showed that volatilization loss (V,kg N ha-1d-1) could be predicted fairly satisfactorily from the partial pressure gradient of NH3(atm × 10-6) between the floodwater and the atmosphere (ΔPi), ignoring the influence of kind of fertilizer (N source) and soil salinity level. The relationship was of the formV= 0.424 + 0.038 ΔPi(r= 0.73), significant atP= 0.01.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

This paper presents a statistical procedure, multivariate analysis of variance (MANOVA), that can be used in conjunction with adsorption data. A hypothetical example used to compare MANOVA with simple analysis of variance (ANOVA) shows that, even when ANOVA does not detect significant differences due to treatments, it is possible that MANOVA may because of the multidimensional analysis. Data from an actual field study are analyzed using MANOVA to demonstrate that differences in P adsorption can be due to inherent variability as well as treatments.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Growth of some plant species on some soils may results from their adaptation to soil-desiccation contraction forces, which constrict roots. This constriction was simulated by placing the roots of ‘Eureka,’ ‘Olaf,’ or ‘SD 2256’ spring wheat plants between rigidly held, 13-mm-OD plastic tubes that were inflated with air. If water transport is inhered, the effect or root constriction on plant growth should parallel growth at low, in comparison with high, soil water. This aspect ws studied in the greenhouse and found to be correct in some cases. In others, stresses from high evapotranspiration probably masked the effect of the constricting force. Heading was accelerated in some Eureka plantings by a root constricting force of 0.6 MPa or by allowing the soil to dry between waterings. Olaf produced more spikes but less straw and tended to produce less grain than SD 2256. Straw and grain weights tended to be larger, but not significantly larger, for plants treated either with pressure or with high soil water. Fewer main roots, seminal plus nodal, were produced with root constriction, but the grain and straw yields were not reduced.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The coefficient of linear extensibility (COLE), used to estimate the shrink-swell hazard of natural soil fabric, requires that intact soil clods be collected when near saturation or be rewetted. Clods must be coated with saran, and significant laboratory equipment is needed to determine the clod shrinkage. A shrink-swell test is needed that can be used in a nonlaboratory setting to evaluate the shrink-swell potential of soils prior to the design of buildings, septic tank subsurface absorption systems (ST-SAS), and other structures. A technique for estimating COLE by extruding a soil paste in the shape of a rod (COLErod) and measuring shrinkage with drying is evaluated as an estimator for COLE determined with the standard technique COLEstd) for a group of Ultisols with a range of physical, chemical, and mineralogical properties. The COLE values of 39 discrete samples were determined by both techniques. The samples were collected from B and C horizons of eight soil types at multiple sites per soil type. COLErodis a highly significant estimator (r2= 0.55,p< 0.001) of COLEstd. Variability is probably due to loss of soil fabric when determining COLErod, as well as limited precision with both techniques. COLErodagreed well with the similar linear shrinkage test (r2= 0.96,p< 0.001), further suggesting that the COLErodmethodology is acceptable.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We investigated the fate in soil of 2,6-diethylaniline (2,6-DEA), an intermediate in the microbial metabolism of certain acetanilide herbicides. At a concentration of 100 ppm in a soil-water slurry (10g moist soil in citrate-phosphate buffer, pH 5.2), 2,6-DEA was converted to a number of products. These products were extracted with acetone from the soil fraction of the slurry. The two major products isolated with HPLC were identified as a dimer of 2,6-DEA,N-(2,6-diethylphenyl)-2,6-diethyl-p-benzoquinone monoimine (M-1), and a tetramer (M-2). Varying the pH values of the citrate-phosphate buffers used in the preparation of the soil slurries had a significant effect on the quantity of the products. The highest yields of both M-1 and M-2 were obtained at pH 3.8. The yield of the two products decreased with rising pH values. Sterilization of the soil by gamma irradiation did not inhibit the formation of products M-1 and M-2. However, 1-h autoclaving for 3 consecutive days completely destroyed the ability of the soils to catalyze the transformation of 2,6-DEA. Addition of EDTA to the incubation mixture for a final concentration of 0.6% (wt/vol) decreased the formation of M-1 and M-2, and the addition of the same concentration of NaN3or Na2S2O4completely inhibited the transformation of 2,6-DEA. Our results support the assumption that physicochemical factors play a significant role in the oligomerization reaction of an aniline in the soil.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We conducted laboratory studies to investigate the effects of low temperature and accelerated soil-solution contact on soil adsorption of labile organic chemicals. We measured the kinetics of adsorption and degradation of14C-aniline,14C-benzoic acid,14C-phenol, and14C-diuron in the solution phase at 3 and 22°C. In the initial stages of reactions, the adsorption of all four chemicals was instantaneous at both temperatures under accelerated soil and solution mixing. A steady state was observed after the onset of equilibrium for the adsorption reaction for all compounds within 10 to 30 min. Its length varied according to the expected order of susceptibility to microbial degradation, i.e., diuron > aniline > phenol ≥ benzoate. It was apparent that the steady-state period without or in combination with low temperature could be advantageously used to obtain adsorption measurements in microbially active systems. Minimal interference from solute transformations in the solution phase would be expected from soil micro-organisms. A mechanistic sorption-catalyzed degradation model was evaluated to uncouple mathematically these processes. The model described satisfactorily the disappearance of labile chemicals in soil suspensions. Numerical analysis allowed the concurrent determination of adsorption, desorption, and biodegradation rate coefficients.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID