摘要:

On samples from sandy soils of French Gascony (spodosols), we compared results from analytical determination of organic carbon (C) by wet and dry combustion and of organic matter (OM) by loss‐on‐ignition at 550°C. Results demonstrated that wet digestion systematically underestimated C content. Loss‐on‐ignition an wet digestion measurements were well correlated to C content obtained by dry combustion.

ISSN:0010-3624    

DOI:10.1080/00103629809370106

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The available (0.1M HCl‐ and DTPA‐extractable) and total forms of copper (Cu) and zinc (Zn) were determined in soils developed on various groups of basalts, namely, the Newer, Older, Lateritized‐Older, and Biu (undifferentiated) basalts. The HCl‐, DTPA‐extractable, and total Cu in the soils ranged from 0.40 to 5.60, 0.15 to 2.64, and 15 to 65 mg Cu kg‐1, respectively, with corresponding means values of 2.06, 0.89, and 41 mg Cu kg‐1. Similarly, HCl‐, DTPA‐extractable, and total Zn varied from 3.00 to 6.20, 0.14 to 2.15, and 25 to 265 mg Zn kg‐1with respective mean values of 4.65, 0.52, and 89 mg Zn kg‐1. The soils were high in the total forms of Cu and Zn, generally sufficient in available Cu, but deficient in available Zn. Both the total and available forms of Cu and Zn were little correlated with soil properties in soils of the Lateritized‐Older and Biu basalts, while only the available forms were related mainly to silt, clay, pH, and organic carbon in soils of the Newer and Older basalts. Furthermore, the available forms were correlated with each other, but not with the total forms.

ISSN:0010-3624    

DOI:10.1080/00103629809370107

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of organic amendment with sewage sludge composts of varying heavy metal content on the organic matter content and enzymatic activity of an agricultural soil supporting barley(Hordeum vulgareL.) or lettuce(Lactuca sativaL.) crops was studied. The organic amendments did not improved lettuce growth, the contaminated composts having a negative effect on yield. However, all organic amendments improved barley straw yields although they did not affect grain yields. The addition of the organic materials increased the total carbohydrate content of the soil although this content decreased with cultivation. There was a clearly observed effect of crop type and the degree of heavy metal contamination of the amendment on the most labile carbon (C) fractions (water‐soluble C, carbohydrates, and polyphenolics). In general, soil enzymatic activities were stimulated by addition of sewage sludge compost with low heavy metal content. The compost containing high level of cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) inhibited protease‐BAA activity with respect to the other composts. After cultivation, urease activity increased in soil amended with the high dose of composts, regardless their degree of metallic contamination. Both crop type and metallic contamination contained in the organic materials added influenced phosphatase and ß‐glucosidase activity.

ISSN:0010-3624    

DOI:10.1080/00103629809370108

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The use of safe staining techniques in the evaluation of mycorrhizal colonization is critical to the continued understanding of this important symbiosis. Several procedures being utilized currently involve regulated and/ or toxic chemicals. The integration of unregulated and nontoxic chemicals into these procedures is important to alleviate potential dangers currently used chemicals pose. We eliminated all regulated reagents by combining portions of several previously published staining and root preservation procedures. A block digester for plant tissue digestion was used as a heating unit and proved to be easier to use, quicker and more reliable than either a water bath or a circulating air oven. Optimum clearing time in KOH varied from 8 to 10 min and 30 to 40 min for wheat, sweet corn, and dry bean roots, respectively. We also successfully used both drying and freezing of roots for storage prior to staining. These modified procedures were quick and easy and provided reliable temperature control and excellent staining while protecting individuals and the environment from toxic chemicals.

ISSN:0010-3624    

DOI:10.1080/00103629809370109

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soil organic matter is an active component of agroecosystems. Rapid and precise measurement of organic carbon (Corg) is essential to monitor changes in organic matter and soil quality. A new semi‐micro wet digestion method for the determination of Corgwas developed using rapid microwave energy applied at 500 J mL‐1digestion mixture to enhance oxidation of Corgby K2Cr2O7and conc. H2SO4. This proposed method and three existing methods of soil C determination were compared with the LECO dry combustion carbon analyzer. The r2value for the proposed microwave method regressed against LECO C was 0.9913. The recovery of Corgby the rapid microwave digestion method for spectrophotometric measurement was 91.7±1.2% (conversion factor 1.09) of C measured by the LECO dry combustion method. Compared to the traditional Walkley‐Black's method, the proposed spectrophotometric with microwave digestion method was rapid and more precise, used smaller reagent volumes, and produced less waste.

ISSN:0010-3624    

DOI:10.1080/00103629809370110

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A relatively small range between deficiency and toxic limits of boron (B) necessitates precise evaluation of the availability of extractable boron before applying B in deficient soils. Keeping this in view, laboratory and greenhouse experiments were conducted to assess the availability of native B in soils. For this purpose, 25 acid soils with diverse properties and varying hot water extractable B content, were selected from lateritic and alluvial tracts of Southern West Bengal. A greenhouse pot experiment with four rates of B (0, 0.5, 1.0, and 2.0 mg kg‐1) was conducted in completely randomized design to study the response of soybean (Glycine maxL.) to native and applied B in all 25 soils. The suitability of nine extractants for determining available soil B was assessed by correlating the amount of extractable B in untreated soils with Bray's percent yield, uptake, and tissue B concentration of soybean plants. Optimization of salicylic acid concentration is described and the advantages of this extractant are discussed. The interference of amethyst color (produced by iron and salicylic acid) with the colorimetric estimation of B is studied. Hot CaCl2was found to be the most suitable extractant for the determination of available B in these soils, followed by hot water, salicylic acid, and ammonium acetate. However, salicylic acid appeared to be the most efficient extractant for routine soil analysis for available B, where a large number of samples are analyzed. The critical values in respect to sufficiency of extractable B for soybean plants were 0.51 for hot water, 0.61 for hot CaCl2, 0.27 for ammonium acetate and 0.45 mg kg‐1for salicylic acid. The critical B concentration in soybean plants was 18 mg kg‐1on dry weight basis. Multiple regression equations relating soil properties to native soil B extracted by various extractante were developed. It was observed that organic carbon and clay contributed positively to B extracted by hot water, hot CaCl2, and ammonium acetate, while salicylic acid extractable B showed positive relationships with cation exchange capacity (CEC) and clay. The CEC and Fe2O3were found to have positive influence on tartaric acid extractable B. Implications of the influences of soil properties on the extractable B content of soils are discussed.

ISSN:0010-3624    

DOI:10.1080/00103629809370111

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Few reports highlight the effect of organic matter in improving the properties of saline soils. A laboratory study was conducted to determine the effect of adding farm yard manure (manure), Egyptian clover hay (clover hay), and wheat straw, at 1 and 3% of soil weight on water stability of soil aggregates (WSA), water‐holding capacity (WHC), pH, and electrical conductivity of soil extract (ECe) of a normal, saline, and saline sodic soil. After 90 and 180 days, WSA and WHC increased, while pH and ECe decreased. Soil properties improved most by adding 3% manure to all the soils. Wheat grown in these soils indicated significant differences for various growth and yield variables, especially the root growth, number and area of green leaves, and grain yield. Organic matter added to these soils increased WSA and WHC and decreased pH and Ece. The WHC had no correlation with pH, but was negatively correlated with Ece. Increased WSA caused the leaching of excess ions and reduced their toxicity, while enhanced WHC increased the availability of water to the roots and promoted growth. It is concluded that manure ameliorated salt affected soils and promoted wheat growth better than clover hay and wheat straw.

ISSN:0010-3624    

DOI:10.1080/00103629809370112

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This experiment was conducted at the EPAMIG Experiment Station in São Sebastião do Paraíso (MG) on Red Dusk Latosol, where both sources of potassium (K) (KCl, K2SO4, and KMgSO4) and doses of K (0, 100, 200, and 400 g K hole‐1) on the coffee tree (Coffea arabicaL.), cultivar Catuaí Vermelho, were studied. During 1993 and 1994, 288 samples of leaves, grains, and husks of coffee were utilized and the chloride content was established by the Mohr's, Volhard's, and mercurimetrical methods to correlate with the potentiometric titulation method, considered as a standard. Every year, the effect of sources and doses of K on the chloride contents of each material and investigated methods was evaluated and also for fruits (husk + grain). The mercurimetrical method is the most convenient for the determination of chloride in leaves, husk, and grains due to the simplicity and more accurate determination of the final changing point of the titulation. The highest chloride contents were found in the leaf, hull, fruits, and grains and there was an increase of the chloride content in these portions with an increase of the KCl doses.

ISSN:0010-3624    

DOI:10.1080/00103629809370113

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Banded urea could cause nitrite (NO2‐) accumulation and enhanced denitrification due to ammonia (NH3) toxicity toNitrobacter.Delayed urea hydrolysis with addition of acidic phosphate to urea would reduce these problems. A laboratory experiment was conducted to evaluate effects of triple superphosphate (TSP) on NO2‐accumulation and denitrification. A Ste. Rosalie clay (Typic Humaquept), an Ormstown silty clay loam (Typic Humaquept) and a Chicot sandy clay loam (Typic Hapludalf) were used. Treatments included three rates of TSP (0, 0.22, and 0.44 g P column‐1) and 0.50 g N column‐1with an unfertilized control. Urea and TSP were pelleted and placed on soil columns which were sampled for urea, ammonium (NH4+), NH3, nitrate (NO3‐), NO2‐‐N, and pH analyses. Denitrification was measured on day 7, 14, and 21. Soil pH and NH3concentrations were reduced with added TSP due to delayed urea hydrolysis, and as a result, NO2‐accumulation and denitrification were decreased. With time, differences in denitrification rate decreased between treatments with urea alone and with urea plus TSP, implying that TSP was more effective in the early stages of urea hydrolysis. Application of TSP with urea may improve urea use efficiency through reduced denitrification.

ISSN:0010-3624    

DOI:10.1080/00103629809370114

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Manganese (Mn) in soils occurs mainly as hydrous oxides in the form of nodules, concretions or coatings on the surface of soil particles playing an important role in the retention of nutrients or heavy metals. Boron (B) is one of these elements found to be fixed by Mn‐oxides in a relatively available form. This research was conducted to study B sorption by Mn‐oxides prepared in the laboratory in relation to soil pH. Two Mn‐oxides were prepared as coatings on the surface of quartz sand, pyrolusite and birnessite. Boron sorption experiments carried out with uncoated sand (US), pyrolusite‐coated sand (PS), and birnessite‐coating sand (BS) showed that B sorption was increased in PS and BS in comparison to US. Total B sorption was greater on BS than PS and BS sorbed more unrecoverable B by dilute hydrochloric acid method. In US and PS, B sorption was linearly increased with pH. In BS, maximum B sorption occurred at pH 8.5. The operating mechanisms seems to be H bonds between boric acid and OH groups in pyrolusite and lingand exchange between borate and surface hydroxyls in birnessite.

ISSN:0010-3624    

DOI:10.1080/00103629809370115

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor