摘要:

Some chemical properties and lignin-related phenolic acids were measured in tropical uncultivated and cultivated Malaysian peats and compared with those of a subfrigid uncultivated Japanese peat. The phenolic acids were identified by gas-liquid chromatography combined with mass spectrometry and determined by gas-liquid chromatography. The total amount of phenolic acids was 13 to 14 mg/g soil C in the Malaysian peat, similar to the 11 mg/g soil C in the Japanese peat. The ratio of the total amounts of substituted hydroxybenzoic acids, viz. 4-hydroxybenzoic + vanillic + syringic to substituted hydroxycinnamic acids, viz.p-coumaric + ferulic, was smaller in the tropical peat soils than in the subfrigid peat. Sinapic acid was not detected in any of the peats. The effect of a laccase fromTrametes versicoloron these phenolic acids was determined. The substituted hydroxycinnamic acids decomposed more readily with the laccase than did the substituted hydroxybenzoic acids and were transformed to measurable reaction products. A reaction product from HCA was identified astrans-4-hydroxy-3-(trans-4′-cinnamyloxy) cinnamic acid. The possibility of these phenolic acids being polymerized in the tropical peats soils, in particular, is discussed.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

A simple procedure is presented for the determination of field scale soil surface temperature using meteorological and surface energy measurements. An advectionaridity evaporation model, in conjunction with the surface energy budget, is used to solve for the sensible heat flux. The calculated sensible heat flux and Monin-Obukhov surface layer similarity theory for temperature are employed to obtain the field scale temperature. A theoretical model to define the scalar roughness length is applied. The model correlated well (r2= 0.91) with infrared surface temperature measurements. Error analysis indicated that the procedure conserved the higher statistical moments and the maximum daily observed surface temperature.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Three methods for assessing soil hydraulic properties were conducted and their results compared for two soils in Western Massachusetts. The methods compared are: the Instantaneous Profile Method, the Guelph Permeameter, and laboratory determination using intact soil cores. The saturated hydraulic conductivity and unsaturated conductivity function, as well as the moisture retention relationship when possible, were determined and the results compared with respect to their ranges of applicability and the respective limitations of each method. We found close agreement for the moisture retention relationships determined by the instantaneous profile method and the soil cores for the ranges of pressures and moisture contents they have in common. In addition, there was also close agreement between the K(Φ) relationship measured using the instantaneous profile method and that predicted using the van Genuchten and Mualem models. The field saturated conductivity results determined using the Guelph Permeameter were one to three orders of magnitude less than the saturated conductivity results determined from soil cores and those determined by the instantaneous profile method. The unsaturated K(Φ) relationship using Gardner's definition of matric potential and the results from the Guelph permeameter predicted hydraulic conductivity values three to four orders of magnitude less then the other two methods at 200 cm of pressure.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The phosphate ion adsorption capacity from aqueous solutions of three Argentinean soil samples is studied. The experimental methods employed are described in detail. The physisorption of nitrogen, argon, and carbon dioxide is analyzed, and the surface characterization reached is correlated with the adsorption of phosphate ions.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Phosphorus (at rates equivalent to 0, 100, 200, 300, and 400 kg P ha-15 cm−1) ha and N (at rates equivalent to 0 and 200 kg N ha-15 cm−1) were added to a sludgetreated soil obtained from an experimental field. The P- and N-treated soils were packed in containers and used to grow Swiss chard (Beta vulgaris) in a glasshouse. Concentrations and activities of Cd2+and Zn2+ions and the distribution of Cd and Zn complexes in the soil saturation extracts were determined. Results indicated that P additions up to 400 kg ha-15 cm−1did not affect the yield of or the Cd and Zn uptake by Swiss chard grown on this sludge-treated soil. The yield of Swiss chard grown on the soil treated with 200 kg N ha-15 cm−1was significantly greater than that of the control. The Cd and Zn uptake by Swiss chard, however, did not increase in proportion with the yield increment. With the increased yield, the uptake of Cd was increased by 50%, but the uptake of Zn remained unchanged. Potassium, PO4, and NO3concentrations in soil saturation extracts increased with amounts of P and N added as both were added as K salts. Total Cd and Zn concentrations, Cd and Zn activities, and overall distribution of Cd and Zn complexes of the soil saturation extracts, however, were not significantly affected by P and N treatments. The plant uptake of Cd and Zn in this sludgetreated soil was probably limited by the rate of Cd and Zn desorption from solid phase.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Results of a series of experiments show that impact of acidization on clays increases with decreasing pH and increasing temperature. Experiments using acidic buffers with pH values ranging from 1.0 to 5.0 were performed to simulate the laboratory removal of carbonates from calcareous soils. Impact of acidization was measured by relative changes in X-ray diffraction (XRD) peaks of three clays (a smectite, an illite, and a kaolinite). Results show that dissolution of carbonates at pH < 5.0 causes serious changes in XRD peaks, as does dissolution at temperatures over 40°C. Buffers with high buffer capacities also cause changes in XRD responses, although these can be corrected by uniform saturation of interlayers. Results of experiments using pH = 5 buffers are similar to those using various forms of EDTA. The results indicate that removal of carbonates from calcareous soils with buffered acids for careful analysis of clays should be done at relatively high pH at room temperatures.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Excessive application of Cu to Florida citrus has resulted in accumulation of Cu, causing Cu toxicity. Maintaining soil pH levels at 6.5 to 7.0 has been recommended to minimize the Cu toxicity problem. In this study, the role of Ca, independent of pH, on Cu toxicity was investigated. Cleopatra mandarin and rough lemon rootstock seedlings were grown in Myakka sand (sandy, siliceous, hyperthermic, Aeric Haploquods) treated with a factorial combination of four Cu rates (0, 50, 100, and 200 mg Cu/kg), two Ca sources (CaCO3and CaSO4), and four Ca rates (0, 200, 400, and 800 mg Ca/kg). Increasing the rate of Ca from 0 to 800 mg/kg increased the soil pH (1:1, soil:water) by 1.5 unit and decreased the pH by 0.3 unit when using CaCO3and CaSO4, respectively. Top and root growth were greater for seedlings grown in CaCO3- compared with CaSO4- amended soil. Increasing rates of Ca application, as either CaCO3or CaSO4, increased top and root growth of both rootstocks at some Cu rates. The effects of increasing rates of Cu on top and root weights in the absence of Ca amendment (i.e., “pure-effect” of Cu) were much greater on Cleopatra mandarin than on rough lemon rootstock. Fibrous root Cu content for both rootstocks was highly correlated with soil Cu extractable by Mehlich 3 (r2= 0.883 to 0.891) and with root weight (r2= 0.256 to 0.521). Increasing rates of Ca, applied either as CaCO3or CaSO4, significantly decreased concentrations of Cu in the fibrous roots. The results demonstrate that increased Ca availability in the rooting environment ameliorates the effects of Cu phytotoxicity. The concentration of Cu in fibrous roots is a better index of Cu phytotoxicity than is that in the leaves.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The internal N cycle in soils of native and established prairies is highly conservative of N, whereas that of cultivated soils has a greater potential for loss of N to denitrification and leaching. In addition to rapid plant uptake of inorganic N, the efficiency of the N cycle in prairie soils has been partly attributed to the quality and quantity of available C substrate to allow for microbial immobilization of N. In this study we investigate soluble or “free” anthrone-reactive carbon (ARC), as a measure of hexose sugars, soluble organic C, and soluble amino-N status of prairie and cultivated soils as possible measures of instantaneously available C and N.Soils were collected from 11 adjacent prairie and cultivated sites in July 1991. Field moist soil samples were analyzed for biomass C, KCl extractable NH4+, NO3−, and amino-N, and K2SO4-soluble organic C and ARC. Soil samples were also air-dried and analyzed for total C and N.Prairie soils were generally higher in total C, total N, biomass C, soluble amino-N, and soluble ARC than their cultivated counterparts. Total soluble organic C was not consistent among sites, but ratios of soluble C to inorganic N gave a better indication of the status of the internal N cycle than did the total C:N ratios.The prairie soils were lower in NO3−and total inorganic N than cultivated soils and had higher NH4+:NO3−ratios. This may reflect the tight internal N cycle in prairie soils. Net production of NO3−in systems where an available C source is limiting results in the accumulation of NO3−. Conditions of high NO3−and low levels of soluble ARC may be representative of a perturbed internal nitrogen cycle.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Changes in equilibrium infiltration rates (ie) of bare tilled and untilled soils were investigated by simulating five 150-min rain storms every 24 hours at a constant rate of 70 mm h−1on tilled and untilled micro-catchments. Decreases iniein the tilled soils were more strongly associated with initial tillage-induced surface roughness than with total porosity and water transmission characteristics of the sublayers. Regression analysis indicated that the changes iniecould be predicted by an exponential function which relatedieto accumulated rainfall.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID