摘要:

A study of soil chemical properties of eleven soils present in different geographycal locations where palm trees(Copernicia tectorum) grow in Venezuela gave the following relevant results: 1) ten soils have at least one layer with exchangeable Mg higher than exchangeable Ca (Mg/Ca>1.00; magnesic layer); 2) eight soils have at least one layer with more than 15% exchangeable Na (sodic layer); 3) ten soils have layers with predominance of Na+Mg in the exchangeable complex (Na + Mg >50%, sodic‐magnesic layers); 4) very acid soil pH values (3.75 to 5.00) on the soil surface layers increasing markedly (even to alkaline values) with depth; and 5) all profiles have very low available P values. The common occurrence of these rather unusual chemical properties, especially the first three ones on most of these soils were considered as evidence of their role as fundamental edaphic factors on palm tree adaptation and distribution. These results also indicate that, besides the already described soil physical (high clay content, slow permeability) and environmental conditions (seasonal flooding and drought, and yearly burning), unusual soil chemical properties seem to be also involved with the ecological conditions associated with the presence of palm trees.

ISSN:0010-3624    

DOI:10.1080/00103629009368236

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Studies with 42 soils selected to obtain a wide range in properties showed that air‐dry and moist soils have substantial capacities for sorption of H2S from air (averages, 9.8 and 12.5 g S kg‐1soil, respectively). Soil properties influencing the capacities of air‐dry soils for sorption of H2S included sand and clay contents, DCB‐soluble Mn, exchangeable Na, DCB‐soluble Fe, and total DCB‐soluble metals. The corresponding capacities of moist soils were influenced by sand and clay contents, DCB‐soluble Mn, and surface area. It was possible to closely predict the H2S sorption capacities of both air‐dry and moist soils (R2= 0.804 and 0.918, respectively) from consideration of their properties.

ISSN:0010-3624    

DOI:10.1080/00103629009368237

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Ten easily determined soil parameters related to soil acidity were evaluated for their potential to provide simple, indirect estimates of the exchangeable aluminium percentage (PAL). These parameters were correlated with the PAL in 0.6NBaCl2extracts of soils collected from lime trials on 4 different parent materials. Six rates of lime (0, 0.75, 1.5, 3, 6, 12 t/ha) were added 3–4 years prior to collection of the samples. The soil parameters examined were the pH of soil suspensions with SMP, Woodruff and New Woodruff buffer solutions; the pH of 1, 5 and 10mMCaCl2and 0.6NBaCl2soil extracts, and the aluminium content of 1, 5 and 10mMCaCl2soil extracts. The best correlations with the exchangeable aluminium percentage for all soils considered, were those based on the aluminium content of the 5mMCaCl2extract (r=0.976, n=24) followed by the pH of the 0.6NBaCl2extract (r=0.945, n= 24). Both these methods are suggested as reliable indirect estimates of soil exchangeable alumimium percentage where availability of staff or equipment restrict direct determinations.

ISSN:0010-3624    

DOI:10.1080/00103629009368238

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The sorption of Cu and Zn on soils, as a function of pH, is important to an understanding of their mobility in the soil solution and their availability for plant nutrition. Copper and Zn sorption as a function of the pH were measured for six B horizons of two Orthic Humic Gleysols, two Orthic Humo‐Ferric Podzols, one Orthic Dystric Brunisol and one Orthic Sombric Brunisol. The results show that: 1) for the same amount of metal in solution and the same pH, more Cu is sorbed than Zn and 2) there is a maximum of sorption at or just above pH 5.00 and a large decrease as pH decreases.

ISSN:0010-3624    

DOI:10.1080/00103629009368239

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A mathematical equation which predicts H‐ion activity (HA) of container media from laboratory analysis of components was devised and tested. The equation is based on the weighted sum of HA contributed by each component. Both measured and predicted HA increased linearly with increasing volume percent bark in milled pine bark‐sand media. Regression equations describing measured and predicted HA were not statistically different. The predictive equation was also tested on other 2‐component potting mixtures with no statistical differences occurring between measured and predicted HA. Measured pH and pH values derived from the HA predictive equation were in close agreement.

ISSN:0010-3624    

DOI:10.1080/00103629009368240

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A second rotation forest sand (Mt Burr sand) was separated by a combination of dry sieving and winnowing into different particle sizes rich in either soil or organic matter. These fractions were analysed for % loss on ignition, % organic carbon, total organic nitrogen and mineral nitrogen. Mineralization of soil organic nitrogen and nitrification of ammonium sulphate added to these fractions were studied. Amongst the heavier fractions obtained by sieving, the <125 μm fraction (the finest) contained the highest concentration of organic and exchangeable nitrogen and was the most active in nitrogen transformations. Amongst the lighter fractions obtained by winnowing, the 125 to 500 μm fraction had the highest organic nitrogen content but mineralization of nitrogen was greatest in the 500 to 2000 μm. Nitrification of native and applied ammonium nitrogen was similar in both the 125 to 500 μm and 500 go 2000 μm organic matter fractions.

ISSN:0010-3624    

DOI:10.1080/00103629009368241

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An experiment was conducted in the central region of Malawi to study the relationship of minerals in soil‐plant‐animal systems to enable prediction of mineral status of beef cattle. Soil, forage and tissues (blood, bone and liver biopsy samples) were collected from cows at the same time in February, April, May, October and December for three consecutive years. Brahman x Malawi Zebu cows were supplemented with mono‐ and di‐calcium phosphate, salt and copper (plus cobalt and selenium) boluses.

ISSN:0010-3624    

DOI:10.1080/00103629009368242

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The treatment of soil with SO2caused rapid increases in concentrations of water soluble plus exchangeable (extractable) Mn. The extractable Mn increased with increasing pressure of SO2and time of exposure, and increased with increasing water contents up to field capacity but decreased beyond this point. The addition of peat to a sandy loam increased the effect of SO2on extractable Mn while the addition of lime decreased the effect. Reactive Mn oxides in soils may contribute significantly to SO2sorption by soils.

ISSN:0010-3624    

DOI:10.1080/00103629009368243

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Approximately twenty years before this study, a site that consisted of a mixed oak forest was harvested, cleared, and divided into three treatment areas consisting of approximately 20 acres each. The three areas were planted to oak (forest), grass (grassland) and corn (agricultural) respectively. The influence of pH on the rate of phosphatase activity was determined over a broad range of soil pH in soil sampled from each treatment area. Phosphomonoesterase activities were measured at a pH of 2 through 12 and phosphodiesterase activities determined at a pH of 4 through 12. In the forest soil only a acid phosphomonoesterase was detected whose pH optima was maximal at the measured soil pH of 4.9. A neutral phosphomonoesterase was found in the grassland soil, pH 6.6, with a broad pH optima ranging from 4.6 to 7.0, while the detection of an acid phosphatase and a alkaline phosphatase, with a pH optima of 4.8 and 11.0 respectively, was found associated with the agriculture soil with a measured pH of 7.2. Phosphodiesterase activity was optimum or near optimum at the measured pH of each soil examined. The released phosphatases apparently have different pH optima in relation to maximal activity suggesting the presence of different kinds of phosphomonoesterases and phosphodiesterases and perhaps that the enzymatic reaction in soil is catalyzed by more than one enzyme or by multiple forms of the same enzyme. The results of the study would indicate that a relationship exists between soil pH and (1) the synthesis and release of phosphatases in soil, (2) the complexion of the organisms producing the enzymes and (3) phosphatase stability or conformation. Based upon the results of the study, the analysis of phosphatase activity at the measured soil pH would seem to be a necessary part of any investigation designed to determine the contribution of phosphatase enzymes to the cycling of P.

ISSN:0010-3624    

DOI:10.1080/00103629009368244

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We compared three methods of estimating soil organic carbon (dichromate oxidation with and without external heating and loss‐on‐ignition) with a method for total carbon measured in an automated resistance furnace. In 38 surface (0–150 mm) podzolized sands the concentration of total carbon ranged from 0.39 to 4.57% and was highly correlated with all three methods (r2=0.99, p<0.0001, in each case). Dichromate oxidation with and without external heating recovered 99.1 and 88.8% of total carbon respectively, indicating that all carbon was organically bound, and that the ‘heat of reaction’ was not sufficient for total oxidation of organic carbon. Because the organic carbon content of the organic matter varied from 38% to 55% a mean value of 46% would be more appropriate for these soils than the Van Bemmelen factor of 58% for converting organic matter to organic carbon concentration The loss‐on‐ignition procedure represents a precise technique for the estimation of organic matter and, when calibrated, organic carbon in surface sandy soils.

ISSN:0010-3624    

DOI:10.1080/00103629009368245

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor