摘要:

A trial was carried out with compost and compost/peat mixtures to test several extraction methods for the estimation of availability of phosphorus (P). The test plant wasDendranthema grandiflorumAll composts had a high pH and salt content. Amounts of P extracted by different extraction methods decreased in the order: Formate < CAL < NH4‐acetate < CaCl2/DTPA < CaCl2. Dilution of compost with peat decreased pH and increased availability of P. The better availability of P caused by dilution with peat was not reflected by the Formate‐, CAL‐, and NH4‐acetate method. These acid and well‐buffered extraction solutions overestimate P, and are therefore not suited to estimate availability of P in composts and compost/peat mixtures. Weak extraction solutions, like CaCl2and CaCl2/DTPA, gave results which showed a good correlation with P content of plants and P uptake. The advantage of the latter method compared with CaCl2is the extraction of amounts of P comparable to amounts taken up by the plants. Therefore of all the extraction methods tested, the CaCl2/DTPA method showed the best suitability to estimate the availability of P in composts and compost/peat mixtures.

ISSN:0010-3624    

DOI:10.1080/00103629409369172

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

For two series of potted plants that had been regularly liquid fertilized from above, the pH of a pour‐through (PT) extract of the intact rootball was always higher (mean 0.53; range 0.24–1.26 units) than the pH of the whole rootball as determined by saturated media extracts (SME). Rootball pH increased from the top to base. pHPTwas close to the PTSMEof the basal part of the rootball. In contrast, pHPT of media newly filled into pots was always lower than pHSME. Equations linking pH determined by PT, SME, 1:1.5, and 1:5 extraction procedures are presented. The results indicate that caution is needed in interpreting pH data obtained by the PT technique.

ISSN:0010-3624    

DOI:10.1080/00103629409369173

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We compared sequential and separate extraction procedures for estimating non‐crystalline and crystalline aluminum (Al) and iron (Fe) in a floodplain forest soil. We used 0.2M acid ammonium oxalate (pH 3.0) to estimate non‐crystalline Al and Fe, dithionite‐citrate‐bicarbonate to estimate crystalline Fe, and 0.1M sodium hydroxide (NaOH) to estimate crystalline Al. Both separate and various combinations of sequential extractions were compared, as well as variations in soil:solution ratio, extraction time, extraction temperature, and the use of field‐moist versus dried soils. A sequential oxalate/NaOH extraction, using 0.4 g dry weight equivalent of field‐moist soil and a soil:solution ratio of 1:100, gave the best estimate of non‐crystalline Al and Fe and crystalline Al, while a separate 16 hour DCB extraction at room temperature, using 0.8 g dry weight equivalent of field‐moist soil and a soil:solution ratio of 1:50, gave the best estimate for non‐crystalline plus crystalline Fe. A sequential oxalate/NaOH extraction followed by a separate DCB extraction is a relatively simple procedure for estimating amounts of non‐crystalline and crystalline Al and Fe in large numbers of soil samples.

ISSN:0010-3624    

DOI:10.1080/00103629409369174

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

To gain information on soil factors which may limit productivity of tobacco on Coastal Plain soils in Maryland, studies were conducted on Monmouth sandy loam soils in 1982 to 1984 and in 1988. The 1982–1984 study involved the application of dolomitic lime in 1982 at rates of 0, 3.6, 7.3, and 14.6 M ton/ha which achieved pH values of 4.4, 4.7, 5.0, and 5.3, respectively, in combination with annual applications of supplemental molybdenum (Mo) at rates equal to 0, 0.28, 0.55, and 1.1 kg/ha. The 1988 study involved lime application rates of 6.0, 17.0, and 25.0 M ton/ha to achieve pH values of 5.0, 5.6, and 6.0, respectively, in combination with Mo rates equal to 0, 0.5, and 1.0 k/gha. Studies were also conducted in 1988 involving the application of 0, 0.55, and 1.10 kg/ha supplemental Mo without lime additions to two sites having pH values of 5.0 and 5.5, respectively. Cured leaf yields, total nitrogen (N) and alkaloid levels were measured in all studies. Leaf Mo levels were monitored in the 1988 studies. Applications of 14.6 M ton/ha of lime in 1982 induced significant yield increases which averaged 13.8% over controls in the 3‐year study. No significant benefits from supplemental Mo were found at the 0 and 3.6 M ton/ha lime treatments (< pH 4.7) in the 1982–84 study or in any of the 1988 studies. However, 1.1 kg/ha Mo applied in combination with 7.3 and 14.6 M ton kg/ha lime increased yields by 16 to 22% above the control treatments in the 1982–84 study, and by 17.8% and 18.7% when applied in combination with 6.0 and 25.0 M ton/ha, respectively, in 1988. In 1988, leaf Mo increased with increased Mo rates, especially at higher pH values. Treatment effects on total N and alkaloid levels were non‐significant in most instances suggesting that N metabolism activities in the control plants were not being limited by plant available Mo (0.10 μg/g) in the soil.

ISSN:0010-3624    

DOI:10.1080/00103629409369175

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Plant uptake of selenium (Se) on western United States mine lands is a concern in reclamation efforts due to the potential growth of vegetation that may be considered toxic to wildlife and domestic animals if consumed over time. A study was designed to determine if sewage sludge from Rock Springs and Kemmerer/Evanston, Wyoming, at rates of 25, 50, and 100 Mg/ha, would enhance or decrease Se uptake by yellow sweet clover (Melilotus officinalis)and thick spike wheatgrass(Agropyron dasystachyum)grown on mine backfill material (i.e., overburden material that has been displaced). Results indicated that increased sludge amendments significantly decreased plant Se levels. Changes in backfill chemical and physical characteristics were believed to have caused a reduction in Se bioavailability (as determined by AB‐DTPA extraction), even though total Se concentrations of the sludge‐amended backfill treatments were greater with increasing sewage sludge additions. Land application of sewage sludge is therefore recommended as a viable method for mine land reclamation efforts.

ISSN:0010-3624    

DOI:10.1080/00103629409369176

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Water‐soluble zinc (Zn) fertilizers are rapidly converted to insoluble forms in calcareous soils resulting in lower efficiency of such fertilizers. A knowledge of distribution of native and applied Zn in such soils is necessary for understanding the fate of applied Zn fertilizers and finding ways to increase their efficiency. This experiment was conducted to obtain such information in selected highly calcareous soils of Iran. A sequential extraction method was used to fractionate the Zn forms of surface horizons (0–20 cm) of 20 highly calcareous soils [16 to 58% calcium carbonate (CaCO3) equivalent; pH 7.9 to 8.5] which had previously received 0, 10, or 20 mg Zn/kg as zinc sulfate (ZnSO4) and had been under one corn(Zea maysL.) crop in the greenhouse. The forms determined were exchangeable (EXZN), sorbed (SRZN), organic (ORZN), carbonate (CRZN), residual (RSZN), and sum of forms (SMZN). The native SMZN ranged from 32.4 to 66.7 mg/kg with a mean of 49.9 mg/kg. Application of 10 and 20 mg Zn/kg as ZnSO4increased the mean to 57.7 and 62.7 mg/kg, respectively. Concentration of different forms of Zn in the soils was determined to be in the following order: RSZN >>> CRZN > SRZN > EXZN > ORZN. The concentration of native EXZN+SRZN+ORZN forms constituted less than 5% of SMZN, while concentration of CRZN alone ranged from 4.37 to 16.05% with a mean of 8.36%. Application of ZnSO4, while significantly increased the concentration of all forms of Zn, had a pronounced effect on CRZN. Averaged over all soils, 58 and 60% of the applied ZnSO4was converted to CRZN for the 10 and 20 mg Zn/kg, respectively. Regression equations relating different Zn forms to soil physical and chemical properties indicated that the Zn forms are significantly influenced by soil properties.

ISSN:0010-3624    

DOI:10.1080/00103629409369177

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Selenite adsorption by a variety of oxides consisting of iron (Fe), aluminum (Al), titanium (Ti), manganes (Mn), and silicon (Si), and by two humic acids were investigated in order to grasp selenite behavior and fixation mechanisms in soil. It was found that selenite was apparently adsorbed even by the Mn oxides on which surface negative charge was dominant in normal pH range (pH <4). No selenite adsorption was observed in the silicon dioxide (SiO2) and the two humic acids. A sequential extraction of adsorbed selenite with competitive anions showed the differences of binding force or stability of adsorbed selenite among the minerals. While the goethite fixed selenite strongly, selenite adsorbed on the Mn oxide was easily released to the liquid phase with other anions, such as phosphate. Each mineral had its inherent characteristic in ligand exchange reactions accompanied with selenite sorption. Selenite sorption by the Mn and the Ti oxides resulted in large increase of surface negative charge, while only a little increase in the Fe and Al oxides. Proton consumption with selenite sorption was extremely smaller for the Mn oxide than for the others.

ISSN:0010-3624    

DOI:10.1080/00103629409369178

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Little research has been conducted on magnesium (Mg) nutrition of taro [Colocasia esculenta(L.) Schott cv. ‘Bun Long']. In this study, we evaluated the effects of varying levels of Mg (0.0, 0.05, 0.1, 0.2, 0.4, and 0.8 mM) on taro plants grown hydroponically for 33 days. Magnesium treatment effects were evaluated for dry matter biomass, leaf area, and N, P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn, and B concentrations of old and young leaves. Dry matter of leaves (young, old, and total), roots, corms, petioles, and total biomass were significantly higher in all plus‐Mg treatments than in the zero‐Mg treatment. These same biomass parameters were not different among treatments with Mg (0.05 to 0.8 mM). Leaf area (young, old, and total) did not differ significantly with varying levels of Mg. A quadratic model described the relationship between Mg levels in leaves and solution Mg (r2= 0.99). Young and old leaf Mg concentrations did not differ. Total leaf Mg concentration ranged from 0.07% to 0.42% for the lowest and highest Mg levels in solution, respectively. Leaf Mg effects on total leaf DM was best fit using segmented regression (r2= 0.95), with a corresponding critical leaf Mg concentration (95% of maximum predicted leaf DM) of 0.14%. No significant interactions were observed between Mg and other mineral nutrients. Critical leaf Mg concentration is based on the vegetative growth stage of taro and could be a key index for taro producers who emphasize vegetable leaf, rather than corm production.

ISSN:0010-3624    

DOI:10.1080/00103629409369179

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The adoption of polyacrylamide (PAM) in reducing irrigation‐induced erosion in California's San Joaquin Valley has been stymied by the lack of information about its toxicity and environmental fate. A review of the literature was conducted to bring to the forefront knowledge of polyacrylamide, its effectiveness in controlling erosion and its environmental fate. Polyacrylamide is a water‐soluble, high molecular weight synthetic organic polymer that primarily interacts with the clay fraction of soils. The degree of interaction depends on both the properties of the polymer and properties of the soil. It is effective in stabilizing soil aggregates, reducing soil erosion, and increasing water infiltration, and also has an indirect significant impact upon crop growth and yield. For the most part, polyacrylamide is resistant to microbial attack, and its degradation is mainly through physical breakdown. Polyacrylamide has been shown to be non‐toxic to humans, animals, fish, and plants; the only concern has been the toxicity of its residual monomer (acrylamide) content, which is a known neurotoxin to humans. The residual monomer is bio‐degradable and does not accumulate in soils. The major source of acrylamide that is released into the environment if from the use of polyacrylamide products, so the FDA regulates the residual monomer content of PAM used in food contact products. If the acrylamide content is kept to a minimum, PAM itself does not pose any environmental threat, and thus, can be used effectively as a soil conditioner.

ISSN:0010-3624    

DOI:10.1080/00103629409369180

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A study was conducted to evaluate conventional steam‐distillation techniques for N‐isotope analysis of inorganic forms of N in soil extracts. Extracts obtained with 2 M KCl from 10 diverse soils were treated with: (i) (15NH4)2SO4and KNO3, (ii) (NH4)2SO4and K15NO3, or (iii) KNO3and Na15NO2. Steam distillations were performed sequentially to determine NH4+‐N and NO3‐‐N, and were also carried out to determine (NO3‐+ NO2‐)‐N or (NH4++ NO3‐+ NO2‐)‐N; a pretreatment with sulfamic acid was used to determine NO3‐‐N in the presence of NO2‐‐N. Recovery of added N ranged from 95 to 102%. Significant isotopic contamination was observed in sequential distillation of unlabeled NO3‐‐N following labeled NH4+‐N; otherwise, analyses for15N were usually within 1% of the values calculated by isotope‐dilution equations.

ISSN:0010-3624    

DOI:10.1080/00103629409369181

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor