摘要:

Difficulty has been experienced in establishing a suitable aluminum (Al) index to predict Al toxicity to plants grown in nutrient solutions with a wide range of properties. In the present study, relationships were evaluated between root length and (i) concentration of total Al, (ii) concentration of monomeric Al, and (iii) the sum of the activities of monomeric Al species (SaAlmono) in solution. Results are reported for soybean (Glycine max(L.) Merr.), subterranean clover (Trifolium subterraneumL.), alfalfa (Medicago sativaL.), and sunflower (Helianthus annuusL.). Total Al concentration in solution, comprising polymeric and monomeric Al species, was a poor index of Al toxicity, confirming the hypothesis that only monomeric Al is toxic to root growth. In solutions with widely differing composition, the concentration of monomeric Al also proved unsatisfactory due to ionic strength effects on the activities of monomeric Al species. SaAl monowas the best index of Al toxicity, accounting for 72 to 92 % of the variation in root length depending on the plant species. Root length was reduced by 50% at SaAl monoof 7–16 μM in soybean, 13 μM in subterranean clover and alfalfa, and 11 μM in sunflower.

ISSN:0010-3624    

DOI:10.1080/00103628609367789

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Effects of varying additions of phosphorus (0, 0.8, 8 and 80 μM P) on the concentrations of total and monomeric aluminum (Al) and on calculated sum of activities of monomeric Al species (SaAl mono) were investigated during 21 d of aging in deionised water containing 40 μM Al with either 0 or 1500 μM calcium (Ca). These P and Ca treatments were also maintained in deionised water without the addition of Al. The concentrations of total and monomeric Al decreased with an increase in P additions at the 8 and 80 μM P although the effect was negligible at the 0.8 μM P. The effects of increase in P additions on the monomeric Al were almost instant as evident from 12 to 49 percent decrease in its concentration after only an hour of aging. However, marked effects of P on the total Al were observed after 3 d of aging. On 21 d of aging in solutions with 8 and 80 pH P, the concentrations of total and monomeric Al decreased by 17 to 34 percent and 20 to 60 percent, respectively. The presence of Ca had negligible effects on the concentrations of either total or monomeric Al at the varying P additions. However, the calculated SaAl monofor a given P concentration treatment over Al mono 21 d of aging were considerably lower in solutions with 1500 μM Ca than with 0 Ca. At each P concentration treatment, SaAl monowere considerably lower than the concentration of monomeric Al in solutions with 1500 μM Ca, while in solutions with 0 Ca the above difference was negligible. During the 21 d of aging, in solutions containing 40 μM Al, the measured P concentrations in the 0.8, 8 and 80 μM nominal P concentration treatments decreased by 44, 37, and 19 percent respectively, at the 0 Ca treatments and 50, 56 and 24 percent respectively, at the 1500 μM Ca treatments.

ISSN:0010-3624    

DOI:10.1080/00103628609367790

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A simple and rapid procedure for the determination of nitrate in fresh leaf tissue, suitable for use by relatively untrained operators is presented. The method requires only 4 reagents and can be carried out in less than 20 min from start to finish. A 400 mg sample of fresh leaf tissue is macerated briefly with 5 drops of 10 N sulphuric acid, diluted with 10.0 ml of water and filtered. Nitrate‐N is estimated on an aliquot of the filtered extract by reducing the nitrate to nitrite by shaking with powdered zinc in ammonium hydroxide solution for 3 min. The reduced mixture is allowed to settle (5 min) and an aliquot is withdrawn through a cotton‐wool plug thus removing any particles of the zinc. The filtered aliquot is then reacted with a single colour reagent to yield a pink azo‐dye, the intensity of which is directly proportional to the amount of nitrate.

ISSN:0010-3624    

DOI:10.1080/00103628609367791

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This study had two principal objectives. The first was to verify whether five solutions evaluated for extracting multiple plant nutrients from soils could also be utilized to determine soil nitrate levels. The second goal was to ascertain whether nitrate could be determined potentiometrically in these solutions using the nitrate‐sensitive electrode and colorimetrically as nitrite using an automated copper—cadmium reduction procedure. The following five solutions having possible multi‐element extraction capability were studied: 1, 0.25NHOAc; 2, O.5NHOAc; 3, 0.25NHOAc + 0.015NNH4F (Kelowna extractant); 4, Kelowna + 0.001NEDTA; and 5, Kelowna + 0.005MDTPA. Reference soil nitrate values were obtained by steam distillation after reduction of NO3to NH4with Devarda alloy in 2NKCl extracts. The procedures were evaluated by comparing analytical values obtained with the electrode on colorimetric method with those obtained by steam distillation by means of linear correlation and regression techniques. Analytical data from soils containing from 6 to 240 ug NO3‐N/mL were utilized for the comparison. The potentiometric method was tried with solutions 1, 2, and 3, while the colorimetric procedure was verified with solutions 3, 4, and 5. Results indicated that nitrate was determined accurately by potentiometric means provided extracts were diluted with 0.05% w/v Ag2SO4to suppress chloride‐ion interference. Acetate, carbonate and bicarbonate ions did not appear to affect nitrate electrode readings at the prevailing extracting solution pH. Results also indicated that soil nitrate was extracted and determined accurately by colorimetric means using solutions 3, 4, and 5. These conclusions were indicated by the regression parameters calculated for the relationships between the NO3values obtained with the different tested solutions and determination methods and the standard procedure. Accordingly, the slopes, Sy.Xvalues, and correlation coefficients for the relationships varied between 0.97 to 1.02, were lower than 4 ug N/mL soil, and above 0.97**, respectively.

ISSN:0010-3624    

DOI:10.1080/00103628609367792

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Lablab or Hyacinth bean,Lablab purpureus(L.) Sweet, is a drought tolerant grain‐forage legume widely grown within a wide range of neotropical regions of the world. It has been an important cultivated food grain crop for many centuries within extensive warm humid‐subhumid climatic areas and grown on widely different Ultisol and Oxisol soil types. The objective of these studies was to determine soil fertility effects of Ca, P, and K factorial combinations applied to a Typic Eutrustox on growth, nodulation, and nitrogen fixation of Lablab bean. Stem and nodule xylem components were determined along with soil pH and nitrification within the nodule rhizosphere. Highly significant increases resulted with P fertilization for stem, leaf, seed, nodulation, and nitrogenase activity. With the exception of nitrogenase, all were also increased with K additions. Both stem and seed were significantly increased with Ca treatments. Highly significant increases for total plant N content resulted with P, K, Ca, and P x K interaction. Allantoinates were initially dominant components of stem xylem exudate following decapitation but were not detected after 5 days. Amino‐amide composition remained relatively constant. Nitrates increased from 1.6 to 81.8 ug N ml‐1exudate during the 8 day collection period. Soil nitrate levels adjunct to decomposing nodules increased from 4.2 to 1661.1 ug g‐1soil. Initial high levels of ureide transforming enzymes ALTN, ALTC, and URC were not detected after 4 days. Amine‐amide enzymes AST, GS, GOGAT, and GDH were relatively constant with nitrate reductase increasing from 0.12 to 9.35 IU ml‐1xylem exudate during the 8 d period. Nodule xylem export components were dominated by ureides, 429.8 umol, and amines 30.3 umol ml‐1. Enzyme activity levels were highest for AST 22.17 and GS 13.25 IU ml‐1with the ureide enzymes URC 2.24, ALTN 0.26, and ALTC 0.15 IU ml‐1. Nodule exudate composition was K 422.0, P 63.4, Ca 53.8, Mg 42.8, and Na 25.6 ug ml‐1.

ISSN:0010-3624    

DOI:10.1080/00103628609367793

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Field and greenhouse studies were conducted in Idaho in 1985 to document the maximum levels of a salt fluxing residue (slag) material that can be safely applied to agricultural soils without reducing spring wheat (Triticum aestivum) growth. The slag material, which contains significant quantities of Mg and K, was applied to Mission (coarse‐silty, mixed, frigid Andic Fragiochrepts) and Palouse (fine‐silty, mixed, mesic Pachic Ultic Haploxerolls) silt loam soils at rates ranging from 0 to 40,000 kg/ha. Parameters evaluated included: (1) germination, (2) plant vigor, (3) yield, and (4) soil and plant tissue K, Ca and Mg.

ISSN:0010-3624    

DOI:10.1080/00103628609367794

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The effect of liming on mineralization and soil nitrifier activity (NA) was investigated with Brookston clay (pH 5.7) and Haldimand clay (pH 4.7). Liming increased the rate of mineralization in both soils but at a rate about 4‐times greater in Haldimand clay than Brookston clay. A significant increase in N mineralization due to liming occurred in both soils only when pH was raised above 6.0. The rate of mineralization was greater than nitrification in the Haldimand soil resulting in NH4+accumulation. Nitrifier activity increased with liming of Brookston clay, but decreased in Haldimand clay after 15 days of incubation. There was a significant increase in nitrifier activity due to liming from 15 to 60 days in Haldimand clay. After 60 days nitrifier activity in limed treatments increased by five times over the unlimed control.

ISSN:0010-3624    

DOI:10.1080/00103628609367795

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A growth chamber experiment was conducted to compare ammonium thiosulfate, gypsum and elemental sulfur in the form of Agrisul as sources of sulfur for rapeseed (Brassica napusvar. Regent). Rapeseed supplied with ammonium thiosulfate or gypsum produced significantly higher yields than treatments supplied with elemental sulfur. Powdering and mixing of elemental sulfur, as opposed to banding granules, significantly increased dry matter yield of rapeseed. While not always significant, there was a trend towards higher dry matter yields where gypsum granules were mixed as opposed to banded and where ammonium thiosulfate was placed in a band as opposed to being mixed throughout the soil.

ISSN:0010-3624    

DOI:10.1080/00103628609367796

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A short hand notation for depicting inped soil macropores is presented. By utilizing symbols for macropore diameter, facial shape, pore length, inped shape and pore orientation; it is possible to quickly portray inped field macropores. Circles, ellipses, and triangles of differing dimensions are used to symbolize round, elliptical, and irregular facial shaped pores of different diameters. The pore length and orientation are symbolized by line length and line direction. The inped shapes (spherical, tubular, and elongated) are respectively represented by one line, two parallel lines, or three parallel lines within or intersecting the pore shape symbols. Field application of this methodology saves time and is valuable when numerous inped pores need to be depicted.

ISSN:0010-3624    

DOI:10.1080/00103628609367797

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628609367788

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor