摘要:

The mechanism of specific phosphate adsorption by hydroxy‐lated mineral surfaces comprises two aspects: the phosphate‐hydroxyl surface reaction and the configuration of the adsorbed phosphate ion. Evidence pointing to ligand exchange as the mechanism of the phosphate‐surface hydroxyl reaction include kinetics of adsorption and desorption; hydroxyl ion release; infrared spectroscopy, and stereochemical calculations. Data pertaining to the coordination of adsorbed phosphate on hydroxy‐lated mineral surfaces have not been conclusive overall. Isotopic exchange experiments and studies of desorption kinetics do not provide definitive information on surface coordination. Measurements of hydroxyl ion release and crystallographic calculations provide support for the existence of both monodentate and bidentate surface complexes of phosphate ions. Infrared spectroscopic investigations suggest a binuclear complex on dried, phosphated goethite. However, these studies cannot be extrapolated automatically to soil minerals, since the addition of water favors formation of a monodentate surface complex. Further research is needed to establish the configuration of adsorbed phosphate ions.

ISSN:0010-3624    

DOI:10.1080/00103628509367646

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Plant analyses methods have expanded immensely to document plant mineral element deficiency and toxicity disorders and to note mineral element interactions. Experiments were conducted to determine the feasibility of using cation exchange papers for the extraction of cationic elements from solutions to be analyzed by x‐ray fluorescence. The cationic elements Al, Fe, Mn, Zn, and Cu were effectively extracted from solutions by one exchange resin paper disk if solutions were passed several times through the exchange resin paper. Calcium and Mg were extracted from solutions if two or three separate exchange papers were used, and K was not extracted from solutions with the use of up to five separate exchange papers. The relatively high concentrations of K in solutions and the relatively low exchange capacity of ion exchange resin papers apparently prevented the effective removal of K from solution. The detectability limits on the exchange resin disks by this technique were <2.8 μg Al, 0.5 μg Fe, 0.10 μg Mn, 0.10 μg Zn, and 0.08 μg Cu. Extraction of cationic elements from solutions for x‐ray analysis appeared practical and relatively rapid for Al, Fe, Mn, Zn, and Cu, less practical for Ca and Mg, and impractical for K.

ISSN:0010-3624    

DOI:10.1080/00103628509367647

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Significant correlations have been found between the nitrate concentration in young corn (Zea maysL.) stalks and available soi 1 N and relative grain yield when N availability is a yield limiting factor. To successfully use nitrate tissue testing as an indicator of the N status of plants, the effects of factors other than soil or fertilizer N on the nitrate concentration in the tested tissue must be understood. Diurnal effects on stalk nitrate content were studied in a greenhouse experiment, in which stalk samples were collected every two hours for 24 hours, and in a field study, where plants in an N‐fertilizer response experiment were sampled at sunrise and at mid‐day. A significant diurnal cycle was observed for stalk nitrate content in the greenhouse, with a peak at 0800 h and a low at 1400 h, but no diurnal effect was found in the field study, possibly due to plant stress from other environmental factors. In a second greenhouse study, stalk samples from seedlings in direct and 66% shaded natural light were collected for two consecutive days and measured for nitrate content to ascertain the consequences of sampling on overcast days. Significant accumulations of nitrate occurred in stalks of plants sampled after two consecutive days of shading. Stalk samples from three standard hybrid corn trials in central Pennsylvania were measured for nitrate content to determine if hybrid differences existed. Hybrid differences in stalk nitrate were significant in only one of the three sites studied, and the variation in that one may have been due to differences in drought tolerance as well as nitrate metabolism. The results suggest that sampling strategies should be designed to minimize the effects of irradiance level on nitrate accumulation, but that differences in nitrate accumulation among corn varieties may not be a major concern in using nitrate tissue tests to predict N availability.

ISSN:0010-3624    

DOI:10.1080/00103628509367648

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Shoot dry weights ofIlex vomitoriaAit. ‘Schellings Dwarf’,Pittosporum tobiraThunb., andJuniperus chinensisL. ‘Blue Vase’ fertilized with Sref 20N‐2P‐8K and Step (micronutrient formulation) or Osmocote 18N‐3P‐10K and Micromax (micronutrient formulation) were not different when grown in a 1 sedge peat: 1 cypress sawdust: 1 cypress shavings (v/v/v) medium with or without superphosphate.PhotiniaXfraseriDress shoot and root dry weights decreased if supersphosphate was added to the growing medium and fertilized with Sref and Step, but were not different when fertilized with Osmocote and Micromax. Shoot tissue P levels ofP. XfraseriandP. tobiraincreased with the addition of superphosphate regardless if Osmocote and Micromax or Sref and Step were used, but there was no corresponding increase in shoot dry weight. Water soluble P levels of the superphosphate amended medium with Sref and Step decreased about 70 ppm during the 6‐month experimental period.

ISSN:0010-3624    

DOI:10.1080/00103628509367649

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Soil series of extensive acreage were selected to evaluate their S‐supplying power under greenhouse conditions using alfalfa in one study and corn and grain sorghum as test crops in a second study. The soils were divided into two major groups by textural classification for statistical evaluations. The addition of sulfur significantly increased dry matter yields and sulfur content of the plant material on all soils through the course of these studies. Significant predictors of sulfur uptake include extractable SO4‐S and organic matter. Organic matter was a significant predictor of the percent yield response above the check yields on soils receiving S applications using corn and grain sorghum as test crops. Based on this equation, yield response would be expected in this greenhouse study with an organic matter content of 2.6% or less.

ISSN:0010-3624    

DOI:10.1080/00103628509367650

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Automated methods for determining ammonium, nitrate, and nitrite in a single soil extract containing 2MKCl and 5 mg/L phenylmercuric acetate are presented. The ammonium method is also suitable for Kjeldahl, soil and plant digests. Amino acid interferences with the ammonium method are reported. Ammonium is determined by a salicylate‐isocyanurate method, while nitrite is determined by the colorimetric reaction of N‐(l‐naphthyl)‐ethylenediamine dihydrochloride with sulfanilamide. Nitrate is determined in the same manner as nitrite after the sample has been passed through a Cu2+/Cd reduction column. The difference between the Cu2+/Cd reduced sample and nitrite sample value is nitrate.

ISSN:0010-3624    

DOI:10.1080/00103628509367651

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effect of soil test levels of K (1N,NH4OAc) on yields of soybean (Glycine maxMerr) reproductive growth, seed size and numbers were evaluated for early, medium, and late maturing cultivars on a Maury silt loam (Typic Paleudalf). Relative yields were near maximum when extractable K was approximately 210 pp2m. Concentrations of K in uppermost, fully expanded leaves at flower initiation at the high production level were approximately 2.0 to 2.15%.

ISSN:0010-3624    

DOI:10.1080/00103628509367652

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A study has been made of the effect of rapid pH change upon the absorption of zinc by six soils with diverse organic matter contents. At pH values more than one pH unit above the soil pH, organic matter and zinc in soil solution increased considerably. Addition of calcium caused reprecipitation of organic matter and zinc, suggesting that zinc at high pH is primarily absorbed on organic matter where it is selectively retained as an organic complex.

ISSN:0010-3624    

DOI:10.1080/00103628509367653

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628509367645

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor