摘要:

Heating samples of clays to various temperatures is a common pretreatment for identification of clay minerals by X‐ray diffraction (XRD). The exchangeable cations in the interlayer region of smectitic clays can rehydrate when the sample is cooled after the heat treatments. Because the basal spacings (d(001)) of smectites are a function of the hydration state of the interlayer cations, they can be easily misinterpreted if the hydration state is not controlled during the XRD analysis. In this report a method for preventing the rehydration of interlayer cations during XRD analysis is described, and its effectiveness is demonstrated on selected samples of clays.

ISSN:0010-3624    

DOI:10.1080/00103628809368044

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Plant available selenate was measured in a soil extract by electrothermal atomic absorption spectroscopy. Selenate in soil was first extracted with potassium sulfate then extracted into toluene fron an iodide‐sulfuric acid media. Aliquots of the toluene were injected into the graphite furnace for selenium determination. Quantities of extractable selenium measured using the electrothermal atomic absorption method compared favorably with the results of determinations using a fluorometric technique on aliquots of the soil extract. The simplicity of the procedure allowed for the precise determination of soil selenate in a brief period of time.

ISSN:0010-3624    

DOI:10.1080/00103628809368045

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Soil and sediment samples were digested in HF and Si was determined by the ammonium molybdate‐oxalic acid procedure. Results were compared with three Standard Reference Materials from the United States Bureau of Standards. It was found that more than 0.05 % HF in the digests significantly suppresses Si color development. The ratio Si/Fe was more important than absolute Fe concentrations, and Si/Fe below 1 intensified Si color development. It is recommended that HF and Si/Fe should be maintained at below 0.05 % and 1, respectively.

ISSN:0010-3624    

DOI:10.1080/00103628809368046

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An accurate and precise ion Chromatographie (IC) method is described for determination of total S in soils and plant materials. It involves ignition of a mixture of soil and NaHCO3or plant material and NaHCO3containing Ag2O at 550°C for 3 h. The residue is dissolved in 1MHOAc, diluted with deionized water, filtered, and analyzed for S02‐4by a Dionex model 2002i ion Chromatograph. Results by the IC method of seven Iowa soils, three Chilean soils, and 10 plant materials agreed closely with those obtained by the methylene blue method after alkaline oxidation with NaOBr. In general, the IC method was more precise than the methylene blue method. The method is simple and requires a minimum of analytical skill. A single operator can analyze 30–40 soil or plant samples in a normal working day.

ISSN:0010-3624    

DOI:10.1080/00103628809368047

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Growing evidence of positive crop responses to gypsum or phosphogypsum (PG) application in acid soils strongly support the use of these amendments as an ameliorant of subsoil acidity. Although gypsum improves Ca availability in subsoils, its role in alleviation of Al toxicity needs careful attention. In the current study, either PG, CaSO4.2H2O or CaCl2.2H2O was added (to supply 12 mM Ca) to solutions containing 40 μM Al at pH 4.1 + 0.1. Solution pH was gradually raised to 4.5, 4.8 and then to 5.3 at various time intervals during 25 d aging of the solutions at 25 + 1OC.

ISSN:0010-3624    

DOI:10.1080/00103628809368048

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Growth and chemical composition of crop plants may be subject to alteration by systemic compounds employed for pest control. A field study was implemented to examine the effects of aldicarb on growth, chemical composition, and nutrient diagnosis of a potato crop at various growth stages. Aldicarb use resulted in increased dry matter production of leaves, stems, and tubers, and final fresh tuber weight during the second year of the study. Higher tuber yields were likely due to greater photosynthetic capacity because the increase in leaf dry matter production with time was greater in the aldicarb treatment than in control. Leaf nutrition was not influenced by aldicarb; however, leaf nutrient content varied greatly with growth stage. Similar nutrient status evaluations were generated by DRIS, regardless of pesticide treatment or growth stage. DRIS was able to diagnose nutrient limitations as early as tuber initiation

ISSN:0010-3624    

DOI:10.1080/00103628809368049

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Cadmium, Zn and Mn in eleven paired soils (one which had a history of sludge application and a control from adjacent land where sludge had not been used) were partitioned into five fractions: exchangeable, adsorbed, organically bound, carbonate bound and sulfide, by the use of KNO3, H20, NaOH, EDTA and HNO3, respect‐ively. The data indicate that the major portion of the total metals was found in the carbonate, sulfide and organic fractions. Addition of CaCO3caused an increase in the exchangeable + soluble fractions of added Cd in the soils, but had little effect on native or sludge derived Cd.

ISSN:0010-3624    

DOI:10.1080/00103628809368050

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Swiss chard (Beta vulgarisvar. cicla) and corn (Zea maysL.) were used as biological indicators of Cd, Zn and Mn availability in 12 soils amended with and without sludge, CdSO4and CaCO3. Soil Cd, Zn and Mn were partitioned into six fractions: soluble, exchangeable, adsorbed, organically bound, carbonate bound and sulfide bound, by the use of H2O, KNO3, H2O, NaOH, EDTA and HNO3, respectively. The data indicate that the major portion of total Cd was found in the carbonate, residual and organic fractions. Addition of CaCO3caused an increase in the soluble and exchangeable fractions of Cd in the soils. The concentrations of Cd in the saturation extracts of the limed soils were significantly greater than those of the unlimed soils; however, this was not reflected in greater plant uptake of Cd from limed soils.

ISSN:0010-3624    

DOI:10.1080/00103628809368051

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Selected chemical properties of an artificially acidified agricultural soil from northern Idaho were evaluated in a laboratory study. Elemental S and Ca(OH)2were used to manipulate the soil pH of a Latahco silt loam (fine‐silty, mixed, frigid Argiaquic Xeric Argialboll), which had an initial pH of 5.7. A 100 day incubation period resulted in a soil pH manipulation range of 3.3 to 7.0. Chemical properties evaluated included: N mineralization rate, extractable P, AI, Mn, Ca, Mg and K and CEC. N mineralization rate (assessed by anaerobic incubation) decreased with decreasing soil pH. Nitrification rate also decreased as NH4+‐N accumulated under acid soil conditions. Sodium acetate extractable P was positively linearly correlated (R2= 0.87) with soil pH over the entire pH range evaluated. Potassium chloride extractable Al was less than 1.3 mg kg‐1of soil at pH values higher than 4.4. Consequently, potential Al toxicity problems in these soils are minimal. Extractable Mn increased with decreasing soil pH. Soil CEC, extractable Mg, and extractable K all decreased with increasing soil pH from 3.3 to 7.0. Extractable Ca levels were largely unaffected by changing soil pH. It is likely that the availability of N and P would be the most adversely affected parameters by soil acidification

ISSN:0010-3624    

DOI:10.1080/00103628809368052

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The effects of Ca and K levels on barley (cv. Johnston) yield were studied in soil media containing high levels of Mg. The dry matter yield of barley decreased with increasing concentrations of Mg in soils, but the decrease was small. Dry matter yield was positively related to concentration of K in the soil. However, additions of fertilizer Ca or K did not increase dry matter yield, indicating that depressed yield associated with high Mg levels was not due to reduced availability of Ca or K. In commercial agriculture, applications of either Ca or K to such soils are unlikely to prove beneficial in increasing crop yields.

ISSN:0010-3624    

DOI:10.1080/00103628809368053

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor