土壤溶质迁移的柱滞留方程

The relationship between magnetic properties and particle size of soils derived from metamorphic rock,basalt,granite,Quaternary red clay,limestone and mudstone from Zhejiang Province,East China was studied,Based on the variations of the mass magnetic susceptibility (χ),anhysteretic remanent magnetization (ARM),and saturation isothermal remanent magnetization (SIRM) with soil particle size,the relationship could be classfied into three groups.For the soils derived from metamorphic rock and basalt,magnetic values were the highest in the gravel and coarse sand fractions and decreased with decreasing soil particle size.The soils derived from sedimentary rock had a bimodal distribution of magnetic values.with peaks in 1-0.5 and 0.005-0.0005mm fractions.The soil developed on granite was characterized by a peak of magnetic value in 0.001-0.0005mm fractions.The soil developed on granite was characterized by a peak of magnetic value in 0.001-0.0005 mm fractions.Frequency-dependent susceptibility(χfd)and ratios of magnetic parameters (ARM/χ,SIRM/χand SIRM/ARM) of soil particle fractions showed that variations in ferrimagnetic grain size paralleled those in particle size,χfd peaked in caly fraction and decreased with increasing particle size,irrespective of soil parent materials.The acquisition curves of IRM and demagnetization paramenter of different soil particles indicated that there were different magnetic minerals assemblages in different particle fractions.     

Protocol to Quantify the Reactivity of Carbonate Limestone for Horticultural Substrates

Abstract

The current method for comparing the reactivity of different limestones used to correct pH in horticultural substrates is based on batch trials, where the limestones are incorporated into the substrate and the pH is measured over time (typically up to 28 days). The objective was to test a laboratory approach to provide a rapid analytical test on reactivity of various limestone sources. To a lime sample, 4M hydrochloric acid (HCl) was added, and the volume of carbon dioxide (CO₂) released into a burette was measured over time. Reagent‐grade calcium carbonate (CaCO₃) and two commercially available pulverized dolomitic limestones were tested. In addition, six particle‐size fractions derived from each of the limestone samples were also evaluated for reaction rate and the corresponding pH responses. In less than 1 min after acid addition, 100% of CaCO₃ reacted, whereas it took 3.9 and 11.5 min, respectively, for 50% of the limestone samples to react, and 14 and 52 min, respectively, for 90% neutralization. Reaction rate increased as the particle size decreased; however, a similar reaction rate was observed for the particle sizes larger than 150 µm (>100 U.S. mesh). Time to 90% reaction was negatively correlated with pH response when 6 g of each lime was incorporated per L of peat substrate. It may be possible to establish a lime reactivity index, for example based on the time required for 50% or 90% reaction, and thereby provide a rapid screening of different limestone sources.     

Potential of Limestone Tailings for Correction and Fertilization of an Oxisol in the Brazilian Savanna

ABSTRACT

Limestone mining industries produce large quantities of by-products that can generate environmental impacts if disposed inappropriately. This study aimed to evaluate the agronomic viability of limestone tailings as soil aciditys and the availability of Ca + Mg in an Oxisol. The experiment was carried out under a randomized complete design, in a 6 × 5 factorial scheme, with four replications. Six sources of limestone [Blended Limestone 1 (BL1), Unblended Limestone 1 (UL1), Blended Limestone 2 (BL2), Unblended Limestone 2 (UL2), Commercial Limestone (CC) and Pure Limestone (PL)] were studied at five application doses (0.0, 0.5, 1.0, 2.0 and 4.0 t ha^?1). During the incubation time of the soil, it was determined the active (pH) and potential acidity (H + Al), as well as the contents of Ca + Mg. It is concluded that the maximum efficiency dose for the limestone sources BL1, UL1, BL2 and UL2 was 4.0 t ha^?1, with responses higher than or equal to commercial limestone. Thus, these sources (BL1, UL1, BL2 and UL2) can be used as soil acidity correctors, since they have adequate reactivity and neutralization power, contributing positively and promisingly in the correction of both active and potential acidity, in addition to increasing the availability of Ca and Mg.     

Reaction Times of Twenty Limestones

Abstract

Particle size and calcium carbonate equivalent characterize agricultural limestone. When agricultural limestone is used for horticultural container substrates, variations in pH among batches of substrate produced with the same limestone rate, as well as pH drift from initial pH, occur. Horticultural endeavors require more detailed characterization of limestone neutralization capacity than is provided for agricultural limestones. Reactivity of twenty limestones encompassing a broad range of calcium and magnesium carbonate were compared. Limestones were wet‐sieved into three particle‐diameter fractions and reacted with ammonium chloride in the presence of steam. Fine particles reacted faster than coarse; however, there was a point beyond which degree of fineness of calcitic limestone no longer affected reactivity. Dolomitic limestones were slower reacting than calcitic. Reactivity within particle fractions of dolomitic and coarse calcitic limestones varied significantly. These results indicate that particle diameter and calcium carbonate equivalent are not the only factors influencing limestone neutralization capacity.     

Relative Neutralizing Value as an Indicator of Actual Liming Ability of Limestone and Byproduct Materials

Methods used to compare the effectiveness of liming materials (e.g., relative neutralizing value, RNV; effective calcium carbonate equivalent, ECCE) were developed for ground limestone. This method is relatively untested on industrial byproducts that could be used when limestone is expensive or unavailable. The objective was to determine if RNV applies to both ground limestones and industrial byproducts. A 42-d incubation study was performed on three acid soils with 11 ground limestones and 9 different byproducts at four rates based on titration and the modified Adams-Evans buffer method. Overall effectiveness, assessed as RNV compared to Ca(OH)₂, averaged 101.5 ± 0.9% for all the evaluated liming materials, except the paper sludge and dolomitic marble. Thus, RNV was a good estimate of neutralizing ability when particle size was accurate. Addition of RNV to packaging would facilitate the commercial use of byproducts as liming materials allowing consumers to compare products by price and properties.     

土石混合介质导气率变化特征试验

土壤中碎石的存在改变了土壤结构和孔隙分布,进而影响土壤通气性能。该文通过对碎石单粒径土石混合介质导气率变化特征研究,旨在探讨单粒径土石混合介质导气内在机理,为进一步研究复杂的野外土石混合介质的导气特性提供基础。为了研究土石混合介质中碎石对导气率的影响,该文通过试验研究,分析土壤颗粒小于2mm的样本(砂土、砂壤土、黏壤土)、碎石质量分数(10%、20%、30%、40%、50%)和碎石粒径(2～3、>3～5mm)对土石混合介质导气率的影响。结果表明:在土壤颗粒小于2mm的样本条件下,土壤导气率呈砂土>砂壤土>黏壤土;在相同碎石质量分数的土石混合介质中导气率呈砂壤土>砂土>黏壤土;碎石的存在改善黏壤土的导气性能,使黏壤土碎石混合介质的导气率大于黏壤土的导气率;降低了砂壤土和砂土的导气性能,且砂土的降低幅度远大于砂壤土;在砂壤土中碎石粒径2～3mm的导气率大于>3～5mm的导气率;在砂土中碎石质量分数30%之内,碎石粒径>3～5mm的导气率稍大于2～3mm的导气率,在40%则相反,但两种粒径下混合介质导气率差异不是很明显。     

浙江中部红壤施用石灰对土壤交换性钙、镁及土壤酸度的影响

为了确定红壤施用石灰后钙、镁移动和土壤酸化速率,监测了耕层（10～20ｃｍ）和底土（20～60ｃｍ）的ｐＨ和交换性Ca2+、Mg2+、Al2+的长期变化。结果表明,耕层交换性Ca2+在施用石灰后的一年半时间达到最高值,此后随着时间的推移而急剧减少;而底土的交换性Ca2+随石灰用量的增加和施用石灰后时间的推移而增加。镁在土壤剖面中的移动比钙快;施用石灰后耕层和底土酸度的降低与交换性Ca2+的增加基本同步。在本试验条件下,不论施用石灰与否都存在着复酸化过程,但施用石灰后复酸化作用更强。     

含岩屑紫色土水分扩散规律

紫色土中存在的岩屑显著影响土壤水分扩散。以往研究主要集中在> 2 mm岩屑上而忽视了<2 mm岩屑的作用。因此,探讨>2 mm岩屑对紫色土水分扩散的影响基础上,明确<2 mm岩屑的作用对完善含岩屑紫色土水分扩散规律的研究具有重要的意义,从而为土壤水动力学模型的构建提供理论依据。以四川盆地紫色页岩发育的暗棕紫泥土和泥岩发育的红棕紫泥土为研究对象,设置3种岩屑粒径(0.25~2,2~5,5~10 mm)和4种岩屑含量(0,30%,50%,70%),利用水平土柱吸渗法测定含岩屑土壤湿润锋变化特征、水分扩散率D(θ)和土壤含水率θ,并拟合D(θ)、Boltzmann参数λ与θ之间的关系。结果表明:对于暗棕紫泥土,岩屑粒径为2~5 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加呈先增加后降低再增加的趋势;岩屑粒径为0.25~2,5~10 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加逐渐增加。对于红棕紫泥土,岩屑粒径为2~5,5~10 mm,随岩屑含量增加,70%岩屑含量的土壤D(θ)明显大于其余3个岩屑含量的土壤,而30%岩屑含量和50%岩屑含量土壤之间的D(θ)无显著差异,且土壤湿润锋前进速率均呈先增加后降低再增加的趋势;岩屑粒径为0.25~2 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加逐渐增加。因此,随岩屑含量提高,土壤水分扩散速率整体呈现增加趋势;且泥岩发育的土壤水分扩散速率高于页岩发育的土壤。     

A new equation to simulate the contact between soil and maize residues of different sizes during their decomposition

The availability of soil nutrients, which are recycled through the decomposition of crop residues, is important for the management of cropped soils. However, knowledge regarding the influence of contact between crop residues and soil on the dynamics of carbon (C) and nitrogen (N) in soil is limited. In particular, the effect of particle size on decomposition is not well-known, and conceptual approaches for modelling the soil-residue contact in a decomposition model remain scarce. Therefore, we analysed and modelled the effect of maize stem particle length on decomposition. We incubated maize stem residues with particle sizes of 0.02, 0.5, 2 and 5 cm in length in a loamy soil at 25 °C over 301 days. We continuously measured the mineralisation of C and N and determined the chemical evolution of the remaining particles. We used the decomposition model CANTIS which takes into account the soil-residue contact, using a contact factor, K_MZ. The decomposition rates of smaller maize particles were higher than those of larger particles during the early phases of decomposition. However, these differences were not maintained after 301 days. These results suggest that a larger size of the maize particles only slowed the rate of mineralisation in the short term but did not modify decomposition in the medium term. We proposed a new formalism for expressing the changes in soil-residue contact with different particle sizes. The contact factor K_MZ was calculated using the standardised specific surface area and can be applied more widely to residues that differ in morphology and density.     

Tracking the Transport of Silver Nanoparticles in Soil: a Saturated Column Experiment

Silver nanoparticles (AgNPs) can enter the environment when released from products containing them. As AgNPs enter soil, they are often retained in the soil profile and/or leached to the groundwater. This research assessed the transport of AgNPs in their “particle form” through the soil profile using a series of columns. Three soil types were put into soil columns: LSH (loam with high organic matter (OM)), LSL (loam with low OM), and Sand (no OM). The results showed that AgNP transport and retention in soil as well as particle size changes are affected by soil organic matter (OM) and the cation exchange capacity (CEC) of soil. OM affected the transport and retention of AgNPs. This was evident in the LSH columns where the OM concentration was the highest and the AgNP content the lowest in the soil layers and in the effluent water. The highest transported AgNP content was detected in the Sand columns where OM was the lowest. CEC had an impact on the particle size of the AgNPs that were retained in the soil layers. This was clear in columns packed with high CEC-containing soils (LSL and LSH) where AgNP particle size decreased more substantially than in the columns packed with sand. However, the decrease in AgNP sizes in the effluent water was less than the decrease in particle size of AgNPs transported through but retained in the soil. This means that the AgNPs that reached the effluent were transported directly from the first layer through the soil macropores. This work highlights the ability to track AgNPs at low concentrations (50 μg kg^?1) and monitor the changes in particle size potential as the particles leach through soil all of which increases our knowledge about AgNP transport mechanisms in porous media.     

Surface-active properties of particle size fractions in two humic acids

The relationships between surface active properties and humic acid (HA) particle sizes were investigated. Two HAs from an Ando soil and a Brown forest soil were separated into 6 particle size fractions by gel permeation chromatography. Surface-active properties characterized by surface excess value (\gT mol cm^-2), cross-sectional surface area per molecule (A nm²), critical micelle concentration (CMC g L^-1), efficiency and effectiveness of water surface tension reduction were obtained by the measurement of the surface tension of HA solutions from different particle size fractions. For the HA from the Ando soil, except for the smallest particle size fraction, increasing particle size enhanced the efficiency of reduction of the water surface tension and decreased the CMC, while the effectiveness of reduction of the water surface tension was about the same. The surface activity of the HA from the Ando soil increased with increasing particle size. This phenomenon was similar to the surface activity of a homologous series of surfactants, which increased with increasing alkyl chain length. For the HA from the Brown forest soil, the smallest particle size fraction and three large fractions showed a high efficiency, namely a high surface activity. The smallest fraction from the Brown forest soil showed the highest efficiency and the lowest CMC value. In both HAs, the smallest particle size fraction showed exceptional surface-active properties compared with the other fractions and three fractions with large particle size showed a higher surface activity than other smaller fractions.     

Factors Influencing the Dissolution of Phosphate Rock in a Range of High P‐Fixing Soils from Cameroon

Abstract

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo‐Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)‐sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg^?1 soil and incubated at 30°C for 85 days. Dissolution of the PRs was determined at various intervals using the ΔNaOH‐P method (the difference of the amount of P extracted by 0.5 M NaOH between the PR‐treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH‐(H₂O)<5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH‐(H₂O)>5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P=At^B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.     

土石混合介质水分入渗特性试验研究

土壤中碎石的存在改变了土壤结构和土壤水分运动规律.为研究碎石含量和碎石粒径对土石混合介质水分入渗特性的影响.利用垂直一维积水入渗试验资料对其进行分析.结果表明:土石混合介质的累积入渗量和湿润锋推进速度均小于细土,碎石含量对累积入渗量和湿润锋的影响存在一个转折点.该转折点因粒级不同而不同;碎石含量对含水量剖面的影响表现为含水量随含石量增加而下降;碎石粒径只对混合介质本身的物理特性有影响,对水分入渗无明显影响.     

Comparison of effects of phosphorus sources on soil acidity,available phosphorus and maize yields at two sites in western Kenya

The effects of farmyard manure (FYM), Tithonia diversifolia (tithonia) and urea when applied alone or in combination with Minjingu phosphate rock (MPR), Busumbu phosphate rock (BPR) or triple superphosphate (TSP) on soil acidity, P availability, maize yields and financial benefits were evaluated at Bukura and Kakamega in western Kenya. A reduction in exchangeable acidity and Al was observed in most tithonia- and FYM-treated soils, but not with inorganic P sources when applied in combination with urea. The effectiveness in increasing available soil P followed the order; TSP > MPR > BPR among inorganic P sources, and FYM > tithonia among organic materials at both sites. At Bukura, a site higher in both available P and Al saturation compared with Kakamega, maize did not respond to inorganic P sources applied in combination with urea. Maize, however, responded when inorganic P sources were applied in combination with FYM or tithonia at this site. At Kakamega, maize responded to TSP but not to MPR or BPR when applied with urea. Application of TSP in combination with tithonia gave the highest maize yields at both sites. Of the tested technologies, only FYM when applied alone at Bukura was economically attractive.     

Biochar particle size and Rhizobia strains effect on the uptake and efficiency of nitrogen in lentils

Abstract

Biochar has attained significant attention as a beneficial soil amendment amongst growers and researchers. However, the impact of particle size of biochar is yet to be investigated. Here in the present study, we studied three particle sizes (<2?mm, 2–5?mm, and >5?mm) of biochar and two rhizobia strains (Rhizobium leguminoserum (RL) and Rhizogold (RG)) for their effect on the uptake and efficiency of nitrogen (N) in lentils. The two years experiment followed a randomized complete block design with split plot arrangement replicated three times. The data revealed that grain N, straw N, N uptake, N recovery efficiency (NRE), and N agronomic efficiency (NAE) were maximum with biochar smallest size (<2?mm). However, the N physiological efficiency, number of branches and plant height decreased with reduced particle size. Furthermore, the smallest particle size showed more number of pod plant^?1. Biofertilizer strain (RL and RG) significantly increased the straw N but not the grain N. Both strains showed increased NRE and NAE, however, the RL demonstrated 7% more grain N than the RG. Both strains (RL and RG) demonstrated 16% and 20% increase in number of branches plant^?1, 62% and 48% in plant height and 2% and 5% in root length, respectively. The RL strain improved the number of branches plant^?1 at the lowest (<2?mm) and medium size (2–5?mm) particles size but both RL and RG strains demonstrated increased plant height under the maximum particle size. These results indicated that a mere increase in surface area with decreasing biochar particle size may not serve for enhancing biofertilizer strains performance since reducing particle size may immobilize the starter N applied. However, reducing particle size effect on N cycling into soil plant system was favorable.     

Changes of soil particle size fraction along a chronosequence in sandy desertified land: a fundamental process for ecosystem succession and ecological restoration

Purpose

Soil is composed of particles of different sizes. A fraction of soil particles with different sizes has many vital effects on soil properties such as soil texture, soil porosity, and soil nutrient content. We intended to explore what change took place in soil particle distribution along the chronosequence of restoration and to address what implication this change has for ecosystem restoration.

Materials and methods

Six restoration ecosystem sites were selected to form a chronosequence in a sandy desertified region, northern China. We examined the relative content of soil particles with different sizes and established an index of enrichment ratio to reflect the change trend of soil particle size fraction.

Results and discussion

It was showed that soil substrate in this region is mainly composed of coarse sand (>0.25 mm) and fine sand (0.25–0.10 mm), the fraction of which are averagely 23.62 and 57.07 %, respectively. These characteristics make soil coarse, loose and erodible, and to be one of the reasons why sandy desertification was quickly developed in this region. In sandy desertification process, the grades of soil particles were air-classified. Fine sand was strongly enriched 1.36 times than average level, while very fine sand (0.10–0.05 mm) and silt and clay (<0.05 mm) were strongly diluted 0.14 and 0.22 times than average level, respectively. Along with the chronosequence of restoration, very fine sand and silt and clay were deposited and markedly enriched. This change in soil particle size fraction along the chronosequence has many fundamental roles for the subsequent restoration succession of sandy land ecosystem, such as promoting plant growth, strengthening soil anti-erodibility, leading to species replacement and community succession.

Conclusions

From this research, it could be concluded that the response of soil particle size fraction to ecological restoration in sandy desertified lands is ecologically valuable, demonstrating that a positive cycle between plant and soil was formed to strengthen the stability of soil-plant system, and the ecosystem has the ability of self-recovering or self-organizing.

     

Increase of Available Phosphorus by Fly‐Ash Application in Paddy Soils

Abstract

Fly ash from the coal‐burning industry may be a potential inorganic soil amendment to increase rice productivity and to restore the soil nutrient balance in paddy soil. In this study, fly ash was applied at rates of 0, 40, 80, and 120 Mg ha^?1 in two paddy soils (silt loam in Yehari and loamy sand in Daegok). During rice cultivation, available phosphorus (P) increased significantly with fly ash application, as there was high content of P (786 mg kg^?1) in the applied fly ash. In addition, high content of silicon (Si) and high pH of fly ash contributed to increased available‐P content by ion competition between phosphate and silicate and by neutralization of soil acidity, respectively. With fly‐ash application, water‐soluble P (W‐P) content increased significantly together with increasing aluminum‐bound P (Al‐P) and calcium‐bound P (Ca‐P) fractions. By contrast, iron‐bound P (Fe‐P) decreased significantly because of reduction of iron under the flooded paddy soil during rice cultivation. The present experiment indicated that addition of fly ash had a positive benefit on increasing the P availability.     

Effect of Medicinal Plants Cultivation on the Physicochemical Properties of Leached Chernozem

For the first time, a nonspecific neutralizing effect of rhizodeposits of medicinal plants has been found in a leached chernozem. The neutralization of actual, exchangeable, and total acidity of the soil takes place against the background of a decrease in the activity of calcium ions in the soil solution. It can be supposed that this effect is due to the release of secondary metabolites of phenol nature in the rhizodeposits. These substances can change the anionic composition of the soil adsorption complex. Plant species with the maximum effect on the composition of the soil adsorption complex have been identified.     

保水剂粒径对秦巴山区土壤水分及烤烟生长的影响

[目的]探究保水剂粒径对秦巴山区土壤水分及烤烟生长的影响,为改善秦巴山区烟田的土壤环境以及促进保水剂在烤烟生产中的应用提供科学支持。[方法]以不施用保水剂为对照,以粉末状(粒径0.18mm)、细颗粒状(粒径0.18～2.25mm)和颗粒状(粒径2.25～3.25mm)的聚丙烯酸钾保水剂为研究材料,监测不同粒径的保水剂对秦巴山区黄棕壤烟田土壤水分、土壤容重及烤烟生长、烤烟品质及经济性状的影响。[结果]不同粒径的聚丙烯酸钾保水剂在烤烟不同生长期均可提高0—40cm土层土壤水分,降低0—40cm土层土壤容重,但对40cm以下土层的土壤水分无显著影响,其中细颗粒状保水剂对土壤水分、土壤容重影响较大。不同粒径的保水剂均可促进烤烟根系生长及茎叶生长,提高烟叶产量与产值,降低下等烟的比例,其中细颗粒状保水剂对烤烟最大叶片、根系生长量、产量及产值影响较大,但粉末状保水剂对上等烟比例影响较大。[结论]不同粒径的保水剂均可提高烤烟品质,其中细颗粒状保水剂对烟碱、总氮、钾及氯的影响较大,粉末状保水剂对总糖和还原糖影响较大。秦巴山区黄棕壤烟田应选用细颗粒状的聚丙烯酸钾保水剂。     

Influence of pH and calcium on the growth,polysaccharide production and symbiotic association of<Emphasis Type="Italic"> Sinorhizobium meliloti</Emphasis> SEMIA 116 with alfalfa roots

The Sinorhizobium -legume interaction is sensitive to a number of environmental factors, soil acidity being one of the most important. In the typic Hapludoll soil of the central-southern region of Córdoba (Argentine) it was found that the nodulation of alfalfa ( Medicago sativaL.) roots was impaired with a reduction in shoot dry matter under conditions of soil acidity (pH 5.5) Our results showed that the addition of lime as dolomitic limestone at a concentration of 1 t ha ^-1to acid soil caused a significant increase in the nodulation of alfalfa roots inoculated with the strain Sinorhizobium meliloti SEMIA 116 (recommended inoculum for alfalfa) in the greenhouse experiments. The success of the lime treatment may be related not only to an increase in the pH values but also to an increase in the Ca concentration, improving the growth of S. meliloti and its nodulation ability under acidic conditions. In this study, we also demonstrated an increment in the bacterial growth rate as well as in the production of exopolysaccharides and lipopolysaccharides under low pH (5.5) and a high Ca concentration (5 mM) in the culture medium.