摘要:

Recovery of15N‐labeled and non‐labeled NO3‐‐N (100 μg) during total N determination by a semimicro‐Kjeldahl procedure, not modified to include NO3‐‐N quantitatively, was studied in the presence and absence of soils varying in organic C. Recovery of NO3‐‐N was negligible in non‐soil systems, irrespective of whether water was present or not, unless an oxidizable C source, octyl alcohol (0.04 g), was added to the digestion mixture; addition of octyl alcohol resulted in a recovery of 78 and 87 μg NO3‐‐N in the presence and absence of water, respectively. Recovery of 100 μg NO3‐‐N added to soils containing from 0.1 to 3.8 g of C/cg of soil ranged from 34 to 90 pg NO3‐‐N in the absence of water. The recovery of the added NO3‐‐N was in the same order, but not proportional to, the organic C content of these soils. Addition of soil NO3‐‐N, determined by a separate method of analysis, to a regular Kjeldahl‐N value is not a satisfactory method for determining total soil N.

ISSN:0010-3624    

DOI:10.1080/00103628509367655

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Comparisons are made of three methods of Al analysis in micro‐samples (≤ 100 mg) of plant material. Direct current plasma emission spectrometry (DCP), graphite furnace atomic absorption spectrometry (GFAAS), and pyrocatechol violet (PCV) all gave comparable results for the plant materials analyzed.

ISSN:0010-3624    

DOI:10.1080/00103628509367656

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A method of digesting plant tissue samples for multi‐element analysis by inductively‐coupled plasma (ICP) emission spectroscopy was developed which does not require the use of HclO4. A substitute oxidant, H2O2, eliminated the hazards associated with hot, concentrated HClO4. Optimal conditions for pre‐digestion and digestion were investigated.

ISSN:0010-3624    

DOI:10.1080/00103628509367657

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Cassava (Manihot esculenta, Crantz) is perhaps one example of a crop exceptionally adapted to marginal conditions, although it too performs poorly in extreme soil acidity conditions. The differential response of cassava cultivars to high levels of KCl‐extractable soil Al in a Typic Tropudult of Panama is reported in this study. High levels of soil Al reduced plant height and root yields of most cultivars, although some genotypes showed good potential to produce acceptable root yields at Al levels above 5 cmol (p+)/kg. Cultivars showed distinctive leaf area indices (LAI) and leaf area distribution patterns that in some cases appeared to be Al toxicity related. Two possible ways Al might have affected LAI, leaf area distribution and hence root yields are suggested: 1) impairment of its ability to develop and sustain leaf area, and 2) disturbance of its capacity to distribute and accumulate assimilates by roots.

ISSN:0010-3624    

DOI:10.1080/00103628509367658

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The adsorption of Cd and Cu by three different soils was studied in the presence of variable concentrations of calcium chloride. Cadmium adsorption fitted the Freundlich equation while Cu better fitted the Langmuir equation. Increasing ionic strength decreased metal adsorption because of the competition of Ca‐ions for the adsorption sites of the soils.

ISSN:0010-3624    

DOI:10.1080/00103628509367659

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Developmental and environmental effects on mineral nutrient concentration in birdsfoot trefoil (Lotus corniculatusL.) are not well documented. In this study, elemental composition of two birdsfoot trefoil stands were determined from a late vegetative stage through reproductive growth. ‘Norcen’ birdsfoot trefoil was established on a Glyndon silt loam (coarsesilty, frigid Aeric Calciaquolls) in Roseau County, Minnesota (49°N), in 1980, and Norcen and ‘Leo’ birdsfoot trefoil were seeded on a Waukegan silt loam (fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludolls) near Rosemount, Minnesota (45°N), in 1981. Shoot and root samples were taken at approximately biweekly intervals in the year following establishment. Shoots were separated into stems, leaves, umbels, and seed.

ISSN:0010-3624    

DOI:10.1080/00103628509367660

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A tillage system, ‘slit‐till’, has been developed that modifies plowpans and permits root penetration and proliferation into subsoil horizons. Slit‐till also provides a means of placing nutrients into subsoil zones where roots are concentrated. Greenhouse studies determined the effects of calcium nitrate, calcium phosphate, ammonium phosphate, ammonium nitrate, and dolomitic limestone on grain sorghum [Sorghum bicolor(L.) Moench] shoot and root development in a compacted layer of acid subsoil (pH 4.3), subject to a slit‐till treatment, and on chemical properties of soil adjacent to the injection site. Cylinders were prepared by layering A and B horizons of a Marvyn loamy sand (fine‐loamy, siliceous, thermic, Typic Hapludult) to form 56 cm of subsoil and 10 cm of topsoil in polyvinylchloride (PVC) tubing (20 × 66 cm). A 6‐cm‐thick hardpan (bulk density 1760 Mg.m‐3) was created at the top of the subsoil layer. The amendments, 500 μg/g of dolomitic limestone and 15 μg/g each of the other amendments, were injected into a 10 × 10 × 0.4 cm slit. Sorghum shoots and roots were harvested 49 days after plant emergence. Plant height was increased 15% by calcium nitrate, calcium phosphate, ammonium phosphate, and dolomitic limestone, but decreased 15% by ammonium nitrate. Twenty‐nine percent of the roots for the check occurred in the subsoil, but this increased to 49% with ammonium phosphate. Soil pH was increased and exchangeable aluminum was decreased by the dolomitic limestone up to 12 mm from point of injection.

ISSN:0010-3624    

DOI:10.1080/00103628509367661

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Three pretreatments and five dispersing treatments in a factorial design were applied to particle size analysis samples from a Rozellville 2Bt horizon and a Rosholt Bt horizon. The sodium citrate ‐ dithionite pretreatment and calgon, sodium pyrophosphate, and sodium oxalate as dispersing treatments resulted in significantly higher clay concentrations than the other treatments when applied to the Rosholt samples. The same trends were apparent when these dispersing treatments were applied to the Rozellville samples, however, clay concentrations were not significantly higher.

ISSN:0010-3624    

DOI:10.1080/00103628509367662

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628509367654

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor