摘要:

A procedure is described to fractionate, identify and quantify organic selenium compounds at μg/kg levels in soil extracts. The fractionation is based first on the different solubility of humates and fulvates at low pH, followed by adsorption chromatography with XAD‐8 resin. The latter uses a pH gradient to elute the acidic and basic hydrophobic fulvates as well as hydrophilic fulvates. The neutral hydrophobic fulvates were retained on the column and determined by difference from the total extractable selenium. A 0.1MNaOH/0.1 M Na4P2O7solution extracted 33% of the total soil selenium. In the soil studied, organic selenium was 20% of total extractable selenium. One of the hydrophilic fulvates has been identified as selenomethionine by gas chromatography‐mass spectrometry. The quantity of organic selenium and the presence of selenomethionine suggests that organoselenium compounds could be an important source of plant available selenium

ISSN:0010-3624    

DOI:10.1080/00103628909368079

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The influence of inorganic N on the development of mycorrhizal symbiosis inLeucaena leucocephala(Lam.) de Wit was studied in an Oxisol subjected to simulated erosion. The plants were grown in pots containing soil samples inoculated with the VAM fungusGlomus aqgregatumand amended with 0, 25, 50 or 100 ppm N. The extent of VAM colonization of roots increased with increasing levels of N in both eroded and uneroded soils. However, the level of infection was significantly higher in the eroded soil than in the uneroded one. Mycorrhizal activity monitored in terms of P content of leucaena subleaflets increased significantly in the eroded soil when it was amended with 25 ppm N and became similar to that observed in the uneroded soil. Nodule dry matter production and shoot N concentration increased significantly with N application upto 50 ppm. Above this level of N, nodule dry weight declined while N concentration did not change. Application of 25 ppm N to the eroded soil also significantly increased shoot and root dry weights while no change was observed in the uneroded soil. A further increase in N level did not improve yield. The results illustraste the potential benefits of starter N in the establishment of mycorrhizal and nodulatedLeucaena leucocephalain eroded soils

ISSN:0010-3624    

DOI:10.1080/00103628909368080

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Four ryegrass (Lolium multiflorumLam.) cultivars were grown in 1/5 Steinberg nutrient solution supplemented with six Al levels (0, 37, 74, 148, 296, or 592 umol L‐1) at pH initially adjusted to 4.2. Average net Fe influx was stimulated at low nutrient solution Al levels. This stimulation was larger for more Al‐tolerant cultivars Marshall and Gulf. Decreases in average net Mn and Zn influxes were brought about by increasing Al levels in the nutrient solution. The average net influx of Fe, Mn, and Zn was positively correlated with the root tolerance index (relative root yield of plants grown with and without Al added to the nutrient solution). For more Al‐tolerant cultivars, increased total uptake of Fe and Cu was brought about by increased nutrient solution Al levels up to 74 umol L‐1. Decreases in total uptake of Mn and Zn were generally noted with increased nutrient solution Al levels. Percentage inhibition of total Fe, Mn, Zn, and Cu uptake was negatively correlated with the mean pH of the Al‐containing nutrient solutions. The higher average net influx and the smaller percentage inhibition of total Fe uptake at nutrient solution Al levels up to 74 umol L‐1can be used as indicators in ranking ryegrass cultivars as more Al‐tolerant

ISSN:0010-3624    

DOI:10.1080/00103628909368081

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A greenhouse experiment using three soils of different pH levels (4.37, 5.78, 6.44) was conducted to determine the effects of rhizosphere on pH, total Zn and labile Zn in water extracts of soils grown to oats and rice. Zn concentrations were determined using a linear sweep cathodic stripping voltammetry technique.

ISSN:0010-3624    

DOI:10.1080/00103628909368082

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Application of 11.2 kg B/ha and/or of 224 kg N/ha reduced the number of table beet (Beta vulgarisL. cv Detroit Dark Red) roots with B deficiency compared to low rates or no N or B application in three field experiments. In two of the three experiments, the 224 kg/ha N rate decreased B concentration in leaves when no B was added yet B deficiency of roots was reduced compared to the 56 kg/ha N rate. B application increased B concentration in leaves. Calcium concentration in leaves was higher at 224 kg N/ha than for 56 kg N/ha. Nitrogen concentration in leaves was increased by increasing the rate of N while K concentration was decreased at the higher N rate. Average number of roots with B deficiency was significantly higher for the Morse strain than for the Harris strain of ‘Detroit Dark Red’ in one experiment where the two strains were compared. There were no differences between the two strains in leaf B concentration but Ca concentration was higher in the Morse strain than for the Harris strain. Yields were higher at the 224 kg/ha rate of N than at 56 kg N/ha but were not consistently affected by B and K applications. There was no clear relationship of leaf N, Ca and K concentrations to B deficiency of roots

ISSN:0010-3624    

DOI:10.1080/00103628909368083

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A study developing a DRIS application to evaluate foliar nitrogen (N), phosphorus (P.), potassium (K), calcium (Ca), and magnesium (Mg) nutrition, was conducted on a 3‐year‐old Fraser fir [Abies fraseri(Pursh) Poir.] Christmas tree plantation in Watauga county, North Carolina. Preliminary DRIS norms and index equations were developed from premium grade Christmas trees for the five nutrients analyzed. In contrast to most crops where growth or yield are assessed. Fraser fir Christmas tree performance was evaluated by conventional grading procedures based on tree quality. Preliminary evaluation of DRIS performance on the 79‐tree data set suggested that assessments of nutritional balance as well as an examination of individual nutrient concentrations are needed to diagnose the nutrient status of Fraser Fir Christmas trees

ISSN:0010-3624    

DOI:10.1080/00103628909368084

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Precise P fertilizer recommendations depend on the concentration of P removed by a given soil test extractant and the effect of other soil properties. Soybeans were grown several years on five Oxisols with a number of established soil P levels. A model was developed to maximize net return as a function of the P extracted by three methods and the optimum P fertilizer rate at each site. To account for site effects, other soil properties were then evaluated in individual combinations with extractable P by multiple regression. Mehlich‐3, Bray‐1, and resin extractable P accounted for 67, 57, and 62% of the variation in optimum P fertilizer rate, respectively. When clay content or surface area was included, the percentages increased to 84, 84, and 95%.In general, other soil properties reflecting P sorption, such as P adsorption maximum, P buffering coefficient, and measurements of clay type, were less effective than percentage clay or surface area. Two additional studies were conducted for one season to validate this approach. The results were excellent on one soil, but underestimated the optimum P rate on another. There was a difference in clay type between the two sites, indicating that perhaps the approach developed should be restricted to kaolinitic soils which predominate in the region

ISSN:0010-3624    

DOI:10.1080/00103628909368085

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

‘Dodd’ pecan seedlings were exposed to 3 levels of soil aeration for 30 days; 100%, 5%, and 0% of the container surface exposed to the atmosphere. These treatments resulted in about 21%, 13.5%, and 3% soil O2and 0.3%, 5%, and 13% soil CO2for 100%, 5%, and 0% of the container surface exposed, respectively. Restricting soil aeration induced partial stomatal closure, and decreased leaf number, leaf area, and leaf, trunk and root dry weights. The decrease in root dry weight associated with reduced soil aeration exceeded the decrease in top dry weight by about 50%. Translocation of N and P to the leaves was reduced when soil aeration was restricted, but root N and P concentrations were increased compared to trees grown in well aerated soil. Leaf elemental concentrations of Ca, Mg, and Mn were lower when trees were exposed to reduced soil aeration. Zinc and Fe concentrations were greater in the roots of trees with low aeration, but leaf and trunk concentrations of Zn and Fe were not affected

ISSN:0010-3624    

DOI:10.1080/00103628909368086

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The standard Kjeldahl method does not recover nitrate‐N quantitatively. A simple and effective modification to the standard Kjeldahl procedure is proposed which includes nitrate‐N in the total nitrogen determination in dry soil and plant material, The method involves the nitration of a phenolic compound, such as phenyl acetate, followed by subsequent recovery of the nitrogen as ammonium by standard Kjeldahl analysis

ISSN:0010-3624    

DOI:10.1080/00103628909368087

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The lowest acceptable pH values for spring wheat (Triticum aestivum. cv. Waverly), winter wheat (cv. Stephens) and lentils (Lens culinaris. cv. Chilean) were determined in two greenhouse studies using a Latahco silt loam (fine‐silty, mixed, frigid Argiaquic Xeric Argialboll). The soil pH was adjusted to values ranging from 3.7 to 7.0 with additions of elemental S or Ca(OH)2prior to planting. Parameters evaluated included germination rate, stand vigor, N and P plant uptake, and plant biomass production for winter wheat and lentils in study 1, and seed germination rate, stand vigor, number of seed, seed yield, nodulation status, root mass, and stem diameter of spring wheat and lentils in study 2. Significant correlations were observed between evaluated parameters and soil pH for lentils in both studies. Although not always statistically significant, good correlations between evaluated parameters and soil pH were observed for both spring and winter wheat. Nitrogen and P availability did not limit plant growth at pH values at or above 3.7. Germination rates were not affected by soil pH. Growth of winter wheat, spring wheat, and lentils was severly reduced, as indicated by stunted growth and necrotic leaves, at pH values below 3.7, 3.7, and 4.5, respectively. Nodulation of lentil roots byRhizobium leguminosarumwas affected by pH with highest numbers of nodules observed above pH 5.5 and no nodulation observed below pH values of 4.0. The lowest acceptable pH values for lentil and wheat crops were similar to reported values obtained in field studies in northern Idaho (5.6 for lentils; 5.2 for wheat). In these greenhouse studies, low soil pH may have reduced biomass production by interfering with plant nutrition and by probably increasing plant disease problems. The data presented in this paper are important because they show that the acidic surface 30 cm of agriculturally important soils in northern Idaho control potential crop yield, and that the less acid subsoil is of only minor importance

ISSN:0010-3624    

DOI:10.1080/00103628909368088

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor