摘要:

Crop growth in Oxisols is known to be limited by high soil acidity and low levels of basic cations. Five greenhouse experiments were conducted to evaluate the effects of soil pH on the growth and nutrient uptake of upland rice(Oryza sativaL.), wheat(Triticum aestivumL.), corn(Zea maysL.), common bean(Phaseolus vulgarisL.), and cowpea(Vigna unguiculataL. Walp.). Six levels of soil pH (4.1, 4.7, 5.3, 5.9, 6.6, and 7.0) were achieved by addition of various levels of CaCO3. Crop species responded differently to pH, reflecting the genetic diversity among species. Higher dry matter accumulation in roots and tops of rice, corn, and cowpea was observed at acidic pH ranges indicating that these species are tolerant to soil acidity. However, increasing soil pH enhanced dry matter accumulation in roots and tops of wheat and common bean, reflecting their intolerance to soil acidity. In all of the crop species, uptake of calcium (Ca) and magnesium (Mg) decreased with a decrease in soil pH. Overall uptake of zinc (Zn), manganese (Mn), and iron (Fe) in all species increase with a decrease in soil pH. Higher pH in an Oxisol might induce micronutrient deficiencies; therefore, one has to avoid overliming. In general, increasing soil pH decreased the uptake of nitrogen (N), phosphorus (P), and potassium (K) in rice, but uptake of these elements increased in wheat, corn, and common bean. In order to achieve the full genetic potential of any given species on an Oxisol, one needs to consider the species tolerance to soil acidity and its nutrient demand.

ISSN:0010-3624    

DOI:10.1080/00103629809370142

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soil pH in southwestern Australia (WA) is usually measured either in water (pHw) or 0.01M CaCl2(pHCa). There are no published relationships to convert one pH to the other. This has been done in this paper for 236 WA soils: pHCa=0.918 pHw‐0.3556, r2=0.9401. It is, therefore, concluded that, for the majority of soils within WA, it is likely that the linear model proposed for all soils would give the best relationship.

ISSN:0010-3624    

DOI:10.1080/00103629809370143

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Red fir (Abies magnificaA. Murr.) woody debris decomposing for 17 years in untreated (Control) and nitrogen‐fertilized plus widely thinned (NT2) plots was examined by13C nuclear magnetic resonance (NMR). Total carbon (C) and total N concentrations were also determined. Combined data of wood and bark showed correlations between carboxylic, aromatic, O‐alkyl and aliphatic C fractions, and C fractions with C/N, but phenolic and methoxyl correlations were non‐significant. Wood mass losses averaged 38% for both Controls and NT2. Bark mass losses were 61% for Controls and 66% for NT2, but these were not significantly different at p<0.05; bark sloughing added considerable variance. Wood in Controls decreased O‐alkyl (66 to 50%) and aromatic (16 to 13%), increased carboxyl (1.5 to 6.5%) and aliphatic (2.0 to 15.5%), and decreased Cm/Lm, i.e., carbohydrate/lignin monomers (2.78 to 1.82). In NT2 plots, open crowns allowed greater drying of the forest floor during warm, dry summers. The C/N averages were slightly lower in NT2 than in Controls for wood (167 versus 188), and the same for bark (45 and 43), but differences were not significant at p<0.05. Decompositional pathways in different environments, by brown‐rot and whiterot fungi, are discussed.

ISSN:0010-3624    

DOI:10.1080/00103629809370144

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

No‐tillage induces the stratification of soil nutrients because of the return of crop residues to soil surface, fertilization and the lack of soil mixing. In this research we have attempted to develop a phosphorus (P) balance on soybean, to study the relative importance of the causes of P stratification. An experiment was performed on a Typic Hapludoll located in mid Buenos Aires province, Argentina. The treatments were fertilized and unfertilized. Soybean biomass and P concentration in grains, stubble and roots were determined. In both treatments the P stratification was produced by the enrichment of the surface layer and the impoverishment of the deeper layers. In the non‐fertilized plots the soil lost P (7.5 kg P ha1) meanwhile in the fertilized plots (20 kg P ha‐1added) the soil gained P (6.6 kg P ha‐1). The accumulation of plant residues alone is enough to redistribute P in soils, but fertilization was the main factor in P stratification.

ISSN:0010-3624    

DOI:10.1080/00103629809370145

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

City sewage sludge was applied to the surface layer (0–10 cm) of two sandy soils, slightly calcareous with 8.9% CaCO3and moderately calcareous with 26.7% CaCO3, at the rates of 0, 25, 50, 75, and 100 Mg ha‐1. The effects of sewage sludge and its rates on total soluble salts, pH of soils and concentration and movement of some heavy metals within soils were investigated. Soil samples were packed at bulk density of 1.5 g cm‐3in PVC columns and incubated for 19 weeks. The results indicated that total soluble salts (EC) of the treated layer increased with increasing sewage sludge rates. Soluble salts also increased with an increase in soil depth for both soils. The pH values of treated layers in two soils decreased with increasing sewage sludge rates. With increasing sewage sludge rates, concentrations of heavy metals [cobalt (Co), nickel (Ni), cadmium (Cd), and leaf (Pb)] increased in the treated layers compared to the untreated layers and their mobility was restricted mostly to the upper 30‐cm depth. Movement of Co and Pb in both the soils was predominately limited up to a depth of 40 cm for Co and 5 cm for Pb below the treated soil layer. Nickel and Cd movement was mostly limited to a depth of 10 cm in slightly calcareous soil and 5 cm in moderately calcareous soil. Metal movement in the respective soils is ranked as Co>Ni=Cd>Pb and Co>Ni=Cd>Pb. The low concentrations of heavy metals and the restricted mobility with soil depth, suggest that this material may be used for agricultural crop production without any toxic effect on plants.

ISSN:0010-3624    

DOI:10.1080/00103629809370146

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Accurate determination of trace levels of cadmium (Cd) in soil extracts can become problematic in an extractant such as acid oxalate which releases a substantial amount of an interfering element, especially iron (Fe) along with trace levels of Cd from soils. The most common technique to identify the chemical interference is to check the recoveries of the element of interest (e.g., Cd), by adding a known concentration to the extract and analyzing. This study evaluated several published methods {solvent extraction with MIBK (methyl iso‐butyl ketone) following reaction with APDC (ammonium pyrrolidine; matrix modification with palladium/magnesium nitrate [Pd/ Mg(NO3)4J; monoammonium phosphate (NH4H2PO4); nitric acid (HNO3) + molybdenum (Mo) + hydrogen peroxide (H2O2) or palladium nitrate [Pd(NO3)2/ammonium nitrate (NH4NO3)]} recommended for analyzing trace levels of Cd in soils using graphite furnace atomic absorption spectrophotometry (GFAAS). None of these methods were found suitable for analyzing trace levels of Cd extracted by acidified ammonium oxalate [(NH4)2C2O4] extracts or mixed acid digests. The recovery of added Cd in these extracts was consistently below 80% and relative standard deviations were in the range of 1–17%. A simple method for analyzing trace levels of Cd, based on iodide complexation and extraction into MIBK, was developed and is recommended for soil extracts encountering chemical interference especially from Fe. The recoveries of Cd were found to be 100±10% and the coefficient of variance was minimal.

ISSN:0010-3624    

DOI:10.1080/00103629809370147

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The purpose of this research was to study kinetics and statics of strontium (Sr) adsorption by native zeolites (clinoptilolite containing tuffs) and to evaluate the effectiveness of zeolites as adsorbents in removing strontium from the “phosphogypsum‐soil‐plant”; system. The concentrations of Sr in the initial solutions of SrCl2were similar to those found in native waters and water extracts of alkali soils (I‐180 mg L‐1). Natural zeolites rapidly adsorbed Sr in large amounts over a wide range of concentrations. The presence of Ca in the solutions of phosphogypsum did not prevent the adsorption of Sr by zeolites. A new approach for establishing the dose of adsorbent based on the experimental determination of the optimum ratio of zeolite to phosphogypsum is suggested. The 20:1 ratio of phosphogypsum to zeolite was found to give the optimum level of Sr adsorption at the lowest rate of zeolite in the given rate of concentration.

ISSN:0010-3624    

DOI:10.1080/00103629809370148

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The organic carbon (C) oxidation efficiencies of the Walkley‐Black and modified wet combustion procedures were evaluated in soil samples taken from different ecological zones and diverse parent materials in Nigeria. Dry combustion using a C analyzer was the standard to evaluate the efficiency of the modified wet combustion method. The efficiency of the Walkley‐Black method was later compared to that of the modified wet combustion procedure. The results indicated that the modified wet combustion and the dry combustion procedures were highly correlated (r=0.99**)‐Significant correlation (r=0.96**) was also found between the Walkley‐Black and the modified wet combustion procedures. There was no correlation between the C data obtained using the modified wet digestion method and the%DCB‐Fe2O3. These results suggest the absence of strong organo‐mineral complexes in these soils. Organic C recoveries by the Walkley‐black method were not affected by fine‐grinding (<0.5 mm) of the soil samples. It is suggested that both the modified wet combustion and the Walkley‐Black methods may be used without a correction factor in Nigerian soils. The modified wet combustion procedure was also found to be an adequate substitute for the dry combustion procedure.

ISSN:0010-3624    

DOI:10.1080/00103629809370149

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An experiment was conducted to determine the value of fly ash collected from flue gases of the Kwinana coal fired power station in Western Australia, as an amendment for sandy soils and as a replacement for phosphorus or potassium fertilizers. The results showed large increases in clover dry matter production (49% to 278%), attributed to improvements in nutrient and water retention from the fly ash. The fly ash provided a substantial amount of the phosphorus needed by the clover, although application of phosphorus fertilizer further increased dry matter production in the presence of fly ash. No evidence was obtained from plant growth or tissue analysis that the fly ash provided potassium to the pasture. The maximum yield was achieved when 501 ha‐1of fly ash was applied to the soil. However, only 10 to 401 ha‐1was required to achieve 75 to 90% of the maximum production. Although a statistically significant increase in cadmium and mercury concentration could be attributed to fly ash, the increase was small and within the range of natural variation of levels found at the sites.

ISSN:0010-3624    

DOI:10.1080/00103629809370150

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We applied fluorogenic methylumbelliferyl compounds to measure enzyme activities (ß‐glucosidase, cellobiohydrolase, and ß‐xylosidase) in a wetland peat. The enzyme activities showed substrate saturation around 400 μM and approximate linearity for at least 100 minutes incubation time. The effects of phenolics and toluene on the enzymes were small. All enzyme activities increased with increasing incubation temperature. Beta‐glucosidase and ß‐xylosidase showed optimal activities in an acidic condition (pH 5), while cellobiohydrolase had the highest activity in a neutral pH. The method would be effective in samples with low enzyme activities and interferences from organic compounds.

ISSN:0010-3624    

DOI:10.1080/00103629809370151

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor