Effects of light,macronutrients, and sucrose on germination and development of the endangered fern Adiantum reniforme var. sinense (Adiantaceae)

Effects of light, macronutrients strength of Murashige and Skoog (MS) (1962), and sucrose in the culture medium on spore germination and gametophyte development of the endangered fern Adiantum reniforme var. sinense were investigated. The presence of light was found to be essential for both spore germination and gametophyte growth. Moreover, a medium consisting of 1/4 MS with 15 g/l sucrose was optimal for spore germination and early gametophyte development; whereas, MS medium with 30 g/l sucrose was optimal for further gametophyte development. Increasing amounts of sucrose (45–60 g/l) in the medium delayed gametophyte growth and development. Additionally, sporophyte formation and early growth of gametophytes in a medium consisting of clay and peat (v/v = 1:2) was higher than those in a medium consisting of pure river sand. These findings indicated that requirements for nutrients for spore germination and early gametophyte development of A. reniforme var. sinese were relatively low, but these increased with further gametophyte development, formation and growth of sporophytes.     

Clay dispersion and its relation to surface charge in a paddy soil of the Red River Delta,Vietnam

Dispersion is an important issue for clay leaching in soils. In paddy soils of the Red River Delta (RRD), flooding with fresh water and relatively high leaching rates can accelerate dispersion and the translocation of clay. For the clay fraction of the puddled horizon of a typical paddy soil of the RRD, the effect of various cations and anions as well as humic acid (HA) at different pH values on the surface charge (SC) were quantified and the dispersion properties were determined in test tubes and described by the C₅₀ value. In the <2 µm fraction, dominated by illite, the proportion of 2:1 vs. 1:1 clay minerals is 5:1. The organic‐C content of the clay fraction is 2.2%. Surface charge was found to be highly pH‐dependent. At pH 8 values of –32 and at pH 1 of –8 mmol_c kg^–1 were obtained. Complete dispersion was observed at pH > 4, where SC is > –18 mmol_c kg^–1. The flocculation efficiency of Ca strongly depends on the pH. At pH 4, the C₅₀ value is 0.33, 0.66 at pH 5, and 0.90 mmol L^–1 at pH 6. At pH 6, close to realistic conditions of paddy soils, the effect of divalent cations on the SC and flocculation decreases in the order: Pb > Cu > Cd > Fe^II > Zn > Ca > Mn^II > Mg; Fe^II was found to have a slightly stronger effect on flocculation than Ca. An increase in concentrations of Ca, Mn^II, and Mg from 0 to 1 mmol L^–1 resulted in a change in SC from –25 to approx. –15 mmol_c kg^–1. In comparison, the divalent heavy‐metal cations Pb, Cu, Cd, and Zn were found to neutralize the SC more effectively. At a Pb concentration of 1 mmol L^–1, the SC is –2 mmol_c kg^–1. From pH 3 to 5, the dispersion of the clay fraction is facilitated rather by SO than by Cl^–, which can be explained by the higher affinity of SO to the positively charged sites. With an increase of the amount of HA added, the SC continuously shifts to more negative values, and higher concentrations of cations are needed for flocculation. At pH 3, where flocculation is usually observed, the presence of HA at a concentration of 40 mg L^–1 resulted in a dispersion of the clay fraction. While high anion concentrations and the presence of HA counteract flocculation by making the SC more negative, Fe^II and Ca (C₅₀ at pH 6 = 0.8 and 0.9 mmol L^–1, respectively) are the main factors for the flocculation of the clay fraction. For Fe^II and Ca, the most common cations in soil solution, the C₅₀ values were found to be relatively close together at pH 4, 5, and 6, respectively. Depending on the specific mineralogical composition of the clay fraction, SC is a suitable measure for the determination of dispersion properties and for the development of methods to keep clay particles in the soil in the flocculated state.     

长庆原油脱水过程W/O型乳状液的形成与特性

长庆油田油气储运系统沉降罐内油水过渡层加厚,导致净化油含水过高,影响原油正常生产.以长庆靖安油田脱水过程中沉降罐内产生的中间层乳状液为对象,借助显微镜、色谱、X射线衍射仪和X射线能谱仪等技术手段,研究其宏观特性及其分离出的水、油和固相的特性,揭示中间层乳状液的形成机制及其物理特性的影响因素.测试结果：分离出的水中硫质量浓度为35.82 mg/L、总铁45 mg/L,硫酸盐还原菌（SRB）含量为104～105个/mL,污水粒径中值为85.63 μm,沥青质/胶质质量分数为3.78％,固体中FeS含量较高.结果表明：联合站上游集油系统腐蚀严重,乳状液中原油老化严重,固体物质除了因腐蚀而产生的FeS外,还有大量伴随原油开采地层中的石英、长石和粘土等矿物.（表3,图7,参6）     

Effects of Different Rates of Ca2+ Addition on Respiration and Sorption of Water-Extractable Organic C to a Vertisol Subsoil

It is well known that calcium (Ca²⁺) plays an important role in binding organic matter to clay. However, most previous studies were conducted with either topsoil or pure aluminosilicates. Less is known about the effect of Ca²⁺ on binding of organic matter to clay-rich subsoils, which have lower organic-matter contents than topsoils, and their clays are more strongly weathered than pure aluminosilicates. Two experiments were conducted with a Vertisol subsoil (69% clay): a laboratory incubation and a batch sorption. The mineral substrate in the incubation experiment was pure sand alone or sand amended with 300 g clay kg^?1. Powdered calcium sulfate (CaSO₄) at rates of 0, 5, 10, and 15 g Ca kg^?1 and mature wheat residue at a rate of 20 g kg^?1 were added to this mineral substrate and the water content was adjusted to 70% of water-holding capacity. Carbon dioxide release was measured for 28 days. Cumulative respiration per g soil organic carbon (C) (SOC from clay and residues) was increased by clay addition. Increasing Ca²⁺ addition rate decreased cumulative respiration in the sand with clay but had no effect on respiration in the pure sand. Clay and Ca²⁺ addition had no significant effect on microbial biomass carbon (MBC) per g SOC but clay addition reduced the concentration of potassium sulfate (K₂SO₄)–extractable C per g SOC. For the batch sorption experiment, the subsoil was mixed with 0 to 15 g Ca kg^?1 and water-extractable organic C (WEOC) derived from mature wheat straw was added at 0, 1485, 3267, and 5099 mg WEOC kg^?1. Increasing Ca²⁺ addition rate increased sorption of WEOC, particularly at the greatest concentration of WEOC added, and decreased desorption. This study confirmed the importance of Ca²⁺ in binding organic matter to clay and suggests that Ca²⁺ addition to clay-rich subsoils could be used to increase their organic C sequestration.     

Improved Structural Stability of an Acidic Hardsetting Soil Attributable to Lime Application

Abstract

Lime [calcium carbonate (CaCO₃)] has been used for acid soil amelioration of acid soils in Australia and elsewhere, but its effects on soil physical properties are not clear. Mechanisms responsible for the beneficial changes in the soil physical and structural properties of an acidic hardsetting soil in southern NSW, Australia, as a result of lime application were investigated. Changes in water‐stable aggregation, a mechanical property, were related to changes in physicochemical properties, and soil organic carbon forms as a result of liming. The improved soil structure due to liming can be explained in terms of reduction in SAR (Sodium absorption ratio) and increase in EC (Electrical conductivity) (both lead to less dispersion) as well as increases in labile carbon (less slaking). The combined effects of reduced dispersion and slaking were responsible for the reduced bulk density and tensile strength of the hardsetting surface soil. These beneficial effects of liming on soil structural and physical properties were detectable 4 years after but not 18 years after lime application.     

Soil Ammonium Diffusion Constraints Contribute to Large Differences in Nitrogen Supply to Rice in the Southern United States

This study was to determine if diffusion of soil ammonium may explain why many sandy soils have greater nitrogen (N)–supplying capacity to rice than clay soils. A laboratory procedure using transient-state methods measured the linear movement of soil ammonium (NH₄) in tubes packed with five field soils under aerobic conditions. Ammonium diffusion was measured by sectioning tubes after 48 h of equilibration and then measuring NH₄ by steam distillation. Effective diffusion coefficients, D_e, and NH₄ diffusion distance, d, per day ranged from D_e = 4.6 × 10^?5 cm² d^?1 and 1.5 cm d^?1 for Katy sandy loam to D_e = 2.9 × 10^?7 cm² d^?1 and 0.11 cm d^?1 for League clay. Ammonium diffusion distance d was strongly related to soil clay content and hence was predicted by d = Y × {[100/(% clay)] ? 1}, where Y is set to 0.1. Predicted d and measured d were highly related (R² = 0.99).     

Organic matter determination in arid region soils: loss-on-ignition versus wet oxidation

ABSTRACT

The precise assessment of soil organic matter (SOM) is required when studying soil pedology, chemistry, physics, and fertility. Besides, it is a key for evaluating soil quality, plant growth, and sustainable land management. This research aims to correlate the SOM resulted from loss-on-ignition (LOI) with those from wet combustion (Walkley–Black, WB). A total of 130 soil samples were collected from Egypt and analyzed using WB and LOI. In LOI, samples exposed to the combustion temperatures of 300, 375, 430, and 550°C for 2 and 4 hours. Using RStudio, simple linear regressions were conducted to estimate the most suitable temperature/time combinations. The results showed that applying lower temperatures (300 and 375°C) for 2 hours provided a strong correlation between LOI and WB with R² of 93 and 94% for all dataset and sandy soils, respectively. For clay soils the respective R² values at 300 and 375°C were 83 and 85%. The proposed combinations were valid to estimate SOM content for different soils with correlation up to 0.99 for sandy soils.     

Soil loss,soil degradation and rehabilitation in a degraded land area in Guarapuava (Brazil)

Erosion and soil degradation are environmental impacts recognized worldwide. The degraded areas in the Guarapuava region are small (patchy). However, these areas are important sources of sediment that affects water quality in rural catchments and could threaten farm sustainability because farmers in this region generally have only a small area for cultivation. This paper presents a case study at a field scale that explores key questions concerning the evaluation of soil erosion, the appraisal of soil degradation and area recovery. This study was carried out over seven years (2002–2008). Several different measurement procedures were employed including assessment of soil loss, aggregation distribution, bulk density, total porosity, aggregate water retention and palisade efficiency. The degraded area displayed a very high soil loss (165.2–217.7 t ha⁻¹ y⁻¹). The palisades were efficient for sediment retention because they were able to trap 62–88 per cent of the total sediment that originated in the area during the first year when this management technique was applied. After their installation, the retained sediment was gradually enhanced with respect to its physical, chemical and biological characteristics. The palisades promoted efficient soil recuperation in spite of the degraded conditions of the degraded area (shallow rills and cohesive soil). The use of palisades together with enclosure of the area was the most efficient method for promoting soil recovery and plant succession. These techniques allowed transformation of the area from a loss system towards an accumulation system with respect to sediment, water, nutrients, organic matter and seeds. Copyright © 2010 John Wiley & Sons, Ltd.     

Beta-carotene content of postharvest orange-fleshed muskmelon fruit: Effect of cultivar,growing location and fruit size

The influence of two growing locations (soil types), six fruit sizes, and two years on the postharvestBeta-carotene content of muskmelon (Cucumis melo L. var. reticulatus Naud.) fruit was studied with two different cultivars. Fully abscised commercial size fruit: 9, 12, 15, 18, 23, and 30 (fruit/0.04 M³ shipping box) had highly variableBeta-carotene contents (5.3 to 33.8 µg/g fresh weight) that varied by size class, soil type and cultivar.Beta-carotene content increased with fruit size up to a maximum, though fruit size continued to increase. Find sandy loam soil produced fruit with lessBeta-carotene content than silty clay loam soil. The cultivar Primo contained higherBeta-carotene content levels than cultivar Cruiser. Mesocarp percent moisture content for both Cruiser and Primo at both locations by fruit size was not significantly correlated (r=0.40) withBeta-carotene content. Indicating fruit cell dilution may not contribute to the differences inBeta-carotene content in different fruit size classes.Beta-carotene content of size class 18 fruit from six cultivars grown on the silty clay loam soil for two consecutive years, showed a year, and year by cultivar effect for some cultivars. Whereas, some cultivars did not differ inBeta-carotene content between the two years. This indicates a potential for controllingBeta-carotene content of muskmelon fruit at a constant, high level by careful selection of production cultivar.Mention of a trademark of propriety does not constitute a guarantee or warranty of the product by the US Department of Agriculture or Texas A&M University and does not imply its approval to the exclusion of other products that also may be suitable.     

Re‐visiting potassium‐ and phosphate‐fertilizer responses in field experiments and soil‐test interpretations by means of data mining

Currently, potassium (K)‐ and phosphate (P)‐fertilizer recommendation in Germany is based on standardized soil‐testing procedures, the results of which are interpreted in terms of nutrient availability. Although site‐specific soil and plant properties (e.g., clay and carbon content, pH, crop species) influence the relation between soil nutrient content and fertilizer effectiveness, most of these factors are not accounted for quantitatively when assessing fertilizer demand. Recent re‐evaluations of field observations suggest that even for soil nutrient contents well within the range considered to indicate P or K deficiency, fertilizer applications often resulted in no yield increase. In this study, results from P‐ and K‐fertilization trials (in total about 9000 experimental harvests) conducted during the past decades in Germany and Austria were re‐analyzed using a nonparametric data‐mining procedure which consists of a successive segmentation of the data pool in order to elaborate a modified recommendation scheme. In addition to soil nutrient content, fertilizer‐application rates, nutrient‐use efficiency, and site properties such as pH, clay content, and soil organic matter, have a distinct influence on yield increase compared to an unfertilized control. For K, nutrient‐use efficiency had the largest influence, followed by soil‐test K content, whereas for P, the influence of soil‐test P content was largest, followed by pH and clay content. The results may be used in a novel approach to predict the probability of yield increase for a specified combination of crop species, fertilizer‐application rate, and site‐specific data.