Relationship between granitic soil particle-size distribution and shrinkage properties based on multifractal method

The mechanical properties of granitic residual soils vary with depth due to changes in soil type and heterogeneity caused by weathering. The purpose of this study was to relate the spatial variation of particle-size distribution (PSD) of granitic soils with soil shrinkage parameters using multifractal theory. The heterogeneity of PSD and pedogenic processes were depicted in detail by multifractal dimensions. The PSD generally increased with the increase of profile depth in accordance with the variation of single fractal dimension (D) ranging from 2.45 to 2.65. The shrinkage limit was greatly influenced by the multifractal dimension parameters, including information dimension (D₁) and capacity dimension (D₀) (Adjusted R²=0.998, P < 0.01), and the maximum linear extensibility (κ_v) was determined by spectral width (△α) and bulk density, with the latter explaining 89% of the total variance of κ_v (P < 0.01). Soil shrinkage characteristic curve was fitted by the modified logistic model (R² > 0.97, root sum of squares < 0.1), and the water variation corresponding to the maximum change rate of linear extensibility was determined by the silt content (R²=0.81, P < 0.01). Overall, the shrinkage of granitic soils was primarily influenced by PSD and soil compactness.     

华北旱地土壤硫施用量指标

Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extractable S was determined using turbidimetric method or inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively. In addition, mineralizable organic S, organic S, N/S ratio, sulfur availability index (SAI) and available sulfur correction value (ASC) in soils were also determined. The S amount extracted by 1.5 g L^-1 CaCl₂ was nearly equivalent to that by 0.25 mol L^-1 KCl (40 ℃), and both of them were slightly smaller than that by 0.01 mol L^-1 Ca(H₂PO₄)₂ solution, as measured by turbidimetric method or ICP-AES. The extractable S measured by turbidimetric method was consistently smaller than that by ICP-AES. All methods tested except that for organic S and N/S ratio produced satisfactory results in the regression analyses of the relationships between the amounts of S extracted and plant dry matter weight and S uptake in the pot experiment. In general, 0.01 mol L^-1 Ca(H₂PO₄)₂-extracted S determined by ICP-AES or turbidimetric method and 0.25 mol L^-1 KCl (40 ℃)-extracted S determined by ICP-AES appeared to be the best indicators for evaluation of soil available S.     

土壤性质与不同土壤Hg形态的关系

Correlation and path analysis methods were used to study the relationship between soil properties and the distribution of different soil Hg fractions with nine representative soils from Chongqing, China. Results showed that clay (< 2 m) could increase water-soluble Hg (r = 0.700*). Soil organic matter (OM) could enhance the increase of elemental Hg (r = 0.674*). The higher the base saturation percentage (BSP), the more the residual Hg (r = 0.684*). Organic Hg, the sum of acid-soluble organic Hg and alkali-soluble Hg, was positively affected by silt (2～20 μm) but negatively affected by pH, with the direct path coefficients amounting to 1.0487 and 0.5121, respectively. The positive effect of OM and negative effect of BSP on organic Hg were the most significant, with the direct path coefficients being 0.7614 and -0.8527, respectively. The indirect effect of clay (< 2 μm) via BSP (path coefficient = 0.4186) was the highest, showing that the real influencing factor in the effect of clay (< 2 μm) on acid-soluble organic Hg was BSP. Since the available Hg fraction, water-soluble Hg, was positively affected by soil clay content, and the quite immobile and not bioavailable residual Hg by soil BSP, suitable reduction of clay content and increase of BSP would be of much help to reduce the Hg availability and Hg activity in Hg-contaminated soils.     

钙盐诱导下土壤锰和铁的释放及其对胡椒的生物有效性

Releases of manganese and iron ions from an albic soil (Albic-Udic Luvisol), a yellow-red soil (Hap-Udic Ferrisol) and a yellow-brown soil (Arp-Udic Luvisol) induced by calcium salt addition and their bioavailability to pepper (Capsicum frutescens L.) were studied in a pot experiment. Addition of Ca(NO₃)₂ decreased soil pH and increased both exchangeable and DTPA (diethylenetriamine pentaacetic acid)-extractable Mn and Fe in soils. Meanwhile, total Mn accumulation in the shoots of Capsicum frutescens L. on the salt-treated soils increased significantly (P< 0.01) compared with the control, suggesting that salt addition to soil induced Mn toxicity in Capsicum frutescens L. Although exchangeable and DTPA-extractable Fe increased also in the salt-treated soils, Fe uptake by the shoots of Capsicum frutescens L. decreased. The effect of added salts in soils on dry matter weight of pepper varied with the soil characteristics, showing different buffer capacities of the soils for salt toxicity in an order of yellow-brown soil > albic soil > yellow-red soil. Fe/Mn ratio in shoots of Capsicum frutescens L. decreased with increasing salt addition for all the soils, which was ascribed to the antagonistic effect of Mn on Fe accumulation. The ratio of Fe/Mn in the tissue was a better indicator of the appearance of Mn toxicity symptoms than Mn concentration alone.     

γ-辐照对施用碱稳定固体土壤中Cu的提取性影响

An incubation experiment was conducted to investigate the microbial biomass associated Cu in four contrasting soils to which an alkaline stabilised sewage sludge cake was applied. The organisms of sludge-amended and control soils were killed using γ-irradiation technique, and the aqueous and acid-extractable Cu concentrations were determined. Addition of the sludge product increased significantly the concentration of both the aqueous and dilute HOAc-extractable Cu in all the irradiated soils compared to the non-sterilised sludge/soil mixtures, but the increase was more pronounced in the dilute acid-extractable Cu, indicating thatthe Cu rendered extractable in water and dilute acetic acid by γ-irradiation existed in the both soil liquidand solid phases. The additional increase in extractable Cu following the biocidal treatment is likely to bedue to release of Cu from the same fraction of soil microbial biomass.     

用熏蒸提取法校正酸性红壤的KEC值

Commonly used K_EC value (0.45) of the fumigation-extraction (FE) method was obtained on the basis of temperate neutral soils. To ascertain its applicability to acidic red soils widespread in southern China and other subtropical regions, the K_EC value was investigated based on 8 acidic red soils by in situ labelling of native soil microorganisms using ¹⁴C-labelled glucose. Realistic K_EC value for red soils could be obtained by in situ ¹⁴C-labelling as long as an incubation period of 72 h is adopted after addition of ¹⁴C glucose to soil. The single K_EC values for the eight red soils ranged from 0.27 to 0.35 and averaged 0.31. Lower K_EC value obtained in red soils probably resulted from different soil quality, compared with other types of soil, which causes possible changes in microbial community structure and extractability of cellular component. Microbial biomass C contents of the eight red soils measured using a unique and constant K_EC value of 0.45 decreased by 22.2%~40% in comparison to those using variable K_EC values. The results suggest that microbial biomass C would be significantly underestimated using the present K_EC value and a calibration of the K_EC value is necessary for red soils.     

稻田土壤甲烷排放模型: Ⅰ. 模型的建立

With an understanding of the processes of methane production, oxidation and emission, a semi-empirical model, focused on the contributions of rice plants to the processes and also the influence of environmental factors, was developed to predict methane emission from rice paddy soils. In the present model, the amount of methane transported from the soil to the atmosphere was determined by the rates of CH₄ production and an emitted fraction. The rates of CH₄ production in irrigated rice soils were computed from the availability of methanogenic substrates that are primarily derived from rice plants and added organic matter and the influence of soil texture, soil redox potential and temperature. The fraction of methane emitted was assumed to be modulated by the rice plants and declines with rice growth and development. To make it applicable to a wider area with limited data sets, a simplified version of the model was also derived to predict methane emission in a more practical manner.     

土地利用从水稻种植至蔬菜种植的转换对土壤中磷素赋存形态的影响

Excess phosphorus (P) from agricultural soils contributes to eutrophication in water bodies. Samples (n=60) were taken from sites where rice paddies have been converted to vegetable fields for 0, < 10, 10-20, and > 20 years and analyzed for five inorganic P (P_i) fractions, three organic P (P_o) fractions, and several soil parameters to investigate how land use conversion affects P_i and P_o fractions in a peri-urban area of China with soils characteristic of many agricultural areas of Asia. Significant increases of 33, 281, 293, and 438 mg kg^-1 were found for soluble and loosely bound P_i (SL-P_i), aluminum-bound P_i (Al-P_i), calcium-bound P_i (Ca-P_i), and iron-bound P_i (Fe-P_i), respectively, after conversion from rice paddies to vegetable fields. Most of the increase in P_i was in the form of Fe-P_i, which increased from 8% of total P (TP) on paddy soil to 31% on the soil with > 20-year vegetable cultivation, followed by Al-P_i, which increased from 2% to 19% of TP. For Po fractions, there was no significant change in P concentrations. The conversion of land use from paddy fields to high intensity vegetable fields was causing significant changes in soil P fractions. Management practices were causing a buildup of soil P, primarily in the Fe-P_i fraction, followed by Ca-P_i and Al-P_i fractions. If current trends continue, a 30%-70% increase in TP could be expected in the next 20 years. Farmers in the area should reduce P application and use to maximize P uptake.     

土壤中有效结合态氨的一种测定方法

Dynamics of fixed NH₄⁺ in NH₄⁺-treated soils incubated with glucose at 37±2 ℃ during the course of incubation and factors affecting it were studied. Results showed that content of fixed NH₄⁺ in soil reached a minimum on day 7 after incubation and then increased gradually regardless of the amount of glucose added and the kind of soil tested. However, the amount of fixed NH₄⁺ released from the soil at the given time varied with both the amount of glucose added and the kind of soil examined. In cases glucose was added at a rate of 10.0g C/kg soil, the amount of fixed NH₄⁺ retained in soil after 7 days of incubation was almost identical to that found by Neubauer test. Addition of K⁺ depressed the release of fixed NH₄⁺ significantly. Based on the results obtained a method for determining the content of available fixed NH₄⁺ in soils was proposed and the amount of N as available fixed NH₄⁺ in two soils measured by this method on an area profile-depth basis was presented.     

根迹土壤根诱导的化学变化对植物吸收重金属的影响

It is increasingly recognized that metal bioavailability is a better indicator of the potential for phytoremediation than the total metal concentration in soils; therefore, an understanding of the inffuence of phytoremediation plants on metal dynamics at the soil-root interface is increasingly vital for the successful implementation of this remediation technique. In this study, we investigated the heavy metal and soil solution chemical changes at field moisture, after growth of either Indian mustard (Brassica juncea) or sunffower (Helianthus annuus L.), in long-term contaminated soils and the subsequent metal uptake by the selected plants. In addition, the fractions of free metal ions in soil solution were determined using the Donnan membrane technique. After plant growth soil solution pH increased by 0.2-1.4 units and dissolved organic carbon (DOC) increased by 1-99 mg L^-1 in all soils examined. Soluble Cd and Zn decreased after Indian mustard growth in all soils examined, and this was attributed to increases in soil solution pH (by 0.9 units) after plant growth. Concentrations of soluble Cu and Pb decreased in acidic soils but increased in alkaline soils. This discrepancy was likely due to a competitive effect between plant-induced pH and DOC changes on the magnitude of metal solubility. The fractions of free Cd and Zn ranged from 7.2% to 32% and 6.4% to 73%, respectively, and they generally decreased as pH and DOC increased after plant growth. Metal uptake by plants was dependant on the soil solution metal concentration, which was governed by changes in pH and DOC induced by plant exudates, rather than on the total metal concentrations. Although plant uptake also varied with metal and soil types, overall soluble metal concentrations in the rhizosphere were mainly inffuenced by root-induced changes in pH and DOC which subsequently affected the metal uptake by plants.     

Proximity to a forest leads to higher honey yield: Another reason to conserve

Although tropical forest conservation is a top priority for human and environmental health, deforestation persists, mainly because of food and economic needs. No community will totally give up economic activities for the sake of ecological integrity, unless it is given alternative economic activities from which to draw its livelihood. Beekeeping in the forest buffer zone instead of traditional destructive honey-harvesting from forest trees is one such option at Arabuko Sokoke Forest (ASF) in Kenya. ASF is a dry coastal forest which is home to endangered and threatened fauna and is a hotspot considered a priority for conservation. In order to find out whether honey quantity and quality differed with distance from the forest, we studied honey yield per harvest (kg) and obtained samples from hives placed at varying distances from ASF in two successive years. Honey yield increased with proximity to the forest. Indeed the yield almost doubled in hives placed less than 1 km from the forest compared to those placed more than 3 km from the forest. All the honey samples met internationally required quality standards, although sugar levels were at the lower limit. This study demonstrates that the conservation of tropical forest ecosystems can have real local economic benefits. The documentation of the services provided by nearby natural areas should help make conservation of these areas a priority, even for the local communities.     

A proposed method to determine adequate amount of fertilizers to be applied to crops

To determine the adequate amounts of fertilizers to be applied to crops is one of the most important problems in the field of soil science.     

自动分析曲线线型并可绘图的计算机程序

本程序图文并茂,直观性强。而且,引入常数k的曲线模拟模型可提高精确度百倍以上,使其更适合理化特性或理论曲线的模拟分析。     

巩固退耕还林成果水利项目的实践与成效

退耕还林工程是我国改善生态环境、促进可持续发展的重要工程,是解决水土流失、土地沙化等生态恶化现状而采取的重大战略举措。五寨县属退耕还林工程区,为了保证退耕还林成果不反弹,在退耕项目区又实施了巩固退耕还林水利项目。通过实施,改造基本农田253.33 hm2,配套排洪渠6000 m,建旱井13眼,年新增粮食产量98.5万kg,人均增产745 kg,人均增收700元。     

Adsorption of Orthophosphate to Humic-Fe-Complexes and to Amorphous Fe-Oxide

The adsorption of orthophosphate to humic surfaces was studied in a model experiment. The adsorption maximum of humic substances greatly increased with higher concentrations of organically complexed Fe (III), indicating that orthophosphate was bound to humic surfaces via metal bridges. The molar ratio P_adsorbed/Fe was nearly 1 for Fe freshly complexed to humic substances, whereas the ratio for amorphous Fe-oxide was a tenfold lower. An increase in pH from 5.2 to 6.2 lead to an increase of P-adsorption of about 30% in the case of humic-Fe-surfaces, which could be explained by an increased accessibility of adsorption sites at pH 6.2. The addition of a 0.01 M CaCl₂-matrix increased orthophosphate adsorption at pH 6.2 but not at pH 5.2. This could be explained by electrostatic interactions caused by the Ca⁺⁺ ion.     

农林类开放存取资源的获取

阐述了开放存取概念的内涵、产生背景和实现途径,并重点介绍了实现农林类开放存取的各种主要的网络资源。     

Response to Fertilization Associated to Leaf Mineral Content in Strawberry

Leaf mineral content along the crop cycle may explain differences in response to fertilization among strawberry genotypes. A two year field experiment was conducted using responsive (‘Camarosa’, ‘Ventana’) and nonresponsive (‘Camino Real’, ‘Candonga’) to fertilization genotypes under proportional increases in nutrients supply: from a control dose “C” [120 kg nitrogen (N) ha^?1, 70 kg phosphorus pentoxide (P₂O₅) ha^?1, 220 kg potassium oxide (K₂O) ha^?1, 40 kg calcium oxide (CaO) ha^?1 and 20 kg magnesium oxide (MgO) ha^?1] to “1.33C” and “1.66C” in 2007 and to “1.5C” and “2C” in 2008. Response to fertilization was high (45–120%) at begining of harvesting and low (10-28%) at middle and end of harvesting. Correlation between leaf area and total yields was high (r ≈ 0.73) at begining of harvesting, except on ‘Camino Real’ (late and compact genotype). At begining of flowering and harvesting, responsive genotypes showed higher potassium (K) and lower calcium (Ca) leaf contents than nonresponsive genotypes, accentuated with the fertilization increase.