摘要:

Zinc toxicity of peanuts (Arachis hypogaeaL.), resulting from excessive amounts of Zn applied to previous crops, has been observed for many years in a limited number of peanut fields in Georgia. A tentative critical value of 12 mg/kg of Mehlich No.1 extractable soil Zn has been reported, but soil pH should be considered in establishing a more precise critical value since availability of soil Zn is affected greatly by soil acidity. A 3‐year study was conducted on a Tifton loamy sand (thermic, Plinthic Paleudults) to evaluate the relationship between soil pH and soil Zn on concentration of Zn in peanut leaves. Factorial treatments were 0, residual, medium, and high rates of Zn and soil pH levels near 5.5, 5.9, 6.2, and 6.8. Pod yields were not affected by treatments and Zn toxicity was not observed. Leaf Zn was affected more by soil pH than by soil Zn, but correlation coefficients were highest where both soil pH and soil Zn were included in the determination. A regression equation, based on soil pH and soil Zn, showed that an increase in soil Zn from 1.0 to 10.0 mg/kg increased leaf Zn 202 mg/kg at soil pH 4.6 and only 9 mg/kg at pH 6.6. Data from growers’ fields, in which samples were collected from eight healthy and toxic areas, indicated that a leaf Ca:Zn ratio of 50 or less was required for Zn toxicity of peanuts rather than high concentrations of leaf Znper se.

ISSN:0010-3624    

DOI:10.1080/00103629009368383

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The total porosity of a container medium is often inaccurate when determined from a water release curve because the use of the total porosity value and bulk density in the equation, Total porosity = (1 ‐ bulk density/particle density) x 100, gives an unrealistic value for particle density. The inaccuracy seems to be caused by incomplete saturation of the medium sample at zero suction. Total porosity should be calculated using bulk density and particle density, rather than equating total porosity with the zero suction value on the water release curve. The zero suction value is a measure of effective porosity since it does not take into account trapped air in the medium.

ISSN:0010-3624    

DOI:10.1080/00103629009368384

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A study was conducted to determine the elemental composition of two plant fractions (leaves and stems) of several forage species in three sheep farms of the paramo in Colombia. The elemental composition of the forage species, and the relationship between soil chemistry and the elemental composition of the forages were also determined. Sampling periods corresponded to the end of the rainy season (May‐June 1987), and the middle end of the dry season (February 1988). Leaves were higher (P<0.05) than stems in the following: calcium, phosphorus, magnesium, potassium, iron, molybdenum, crude protein, and IVOMD. Overall percentage of deficiencies were related to the requirements for sheep as follows: calcium (88%, 13%), phosphorus (50%, 27%), magnesium (85%, 41%), potassium (13%,3%), sodium (94%, 96%), iron (10%, 4%), copper (82%, 65%), manganese (7%, 0%), zinc (46%, 42%), cobalt (92%, 85%), selenium (77%, 65%), crude protein (45%, 8%) for stems and leaves, respectively.

ISSN:0010-3624    

DOI:10.1080/00103629009368385

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Total soil P was determined in six soils differing in pH, and in organic matter, total Fe, clay and sand contents. This study was undertaken to determine whether replacement of a sand bath.digestion procedure by an Al‐block digestion procedure affected the efficacy of an alkaline NaOBr method for determining total soil P. An Al digestion block was used for soil oxidation with NaOBr‐NaOH and the results were compared with a sand bath NaOBr method and a HC1O4 method. Temperature variability was very low in the digestion block (S.D.= ±1.4°C) when compared with the sand bath (S.D.= +20.1°C). The digestion block resulted in a greater precision in total P determination when compared to the sand bath (S.D.= ±3.7 vs. ±5.6, respectively). Linear relationships were obtained with the sand bath digestion technique (R2= 0.981) and with the HC1O4method (R2= 0.982). Using an Al digestion block for NaOBr‐NaOH oxidation of soils for total P determination allows for a simple, precise alternative to sand bath digestion and to potentially hazardous HClO4procedures.

ISSN:0010-3624    

DOI:10.1080/00103629009368386

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper describes a method for quantifying oxalate in soil HC1 extracts using reversed‐phase ion‐pairing high performance liquid chromatography with UV detection at 220 nm. The method was adapted from a procedure for determining urinary oxalate (6). The mobile phase was 10 percent KH2PO4and 5 mM TBA adjusted to pH 2.0 with H3PO4. The analytical column was a totally porous, reversed‐phase silica based C‐8 column (Hibar Li‐Chrosorb™). An important step in this method was the pre‐ treatment of each soil extract with a reversed‐phase C‐18 column (SPICE™ C‐18). Sample pre‐treatment removed complex, non‐polar and low polarity compounds often present in soil extracts.

ISSN:0010-3624    

DOI:10.1080/00103629009368387

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Nine soil surface treatments and one planting‐hole treatment were tested for their effectiveness in stimulating growth and preventing chlorosis of pin oak (Quercus palustris) seedlings planted in calcareous soil. Planting‐hole acidification was highly effective, especially in combination with a surface treatment of either sulfuric acid or aluminum sulfate. Ammonium sulfate lowered soil pH but was detrimental to the seedlings. Nutrient concentrations in uniformly chlorotic leaves were different from those in interveinally chlorotic leaves, but both types were characterized by low zinc.

ISSN:0010-3624    

DOI:10.1080/00103629009368388

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103629009368372

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor