Iron and manganese transformation in louisiana salt and brackish marsh sediment

Abstract

The kinetics of the release of dissolved iron [Fe(II)], manganese [Mn(II)], and phosphate in salt and brackish marsh sediment and the exchange with the overlying water column were investigated. Sediment was incubated in laboratory microcosms and in sediment water columns in studying these exchanges. The rate constants of the dissolved Fe(II), Mn(II), and phosphate release in sediment suspensions were 2.02–2.28,0.08–0.117, and 4.18–5.38 μmol g^‐1 dry sediment d^‐1, respectively. In sediment‐water column studies, the rate constants (K) of dissolved Fe(II), Mn(II), and phosphate removal from the overlying water into the sediment were 0.755–0.989,0.0695–0.0949, and 0.315–0.448, day^‐1, respectively. The flux of dissolved Fe(II), Mn(II), and phosphates from the salt and brackish marsh sediment to the overlying water in the column studies were 2.56–4.93,1.05–1.689, and 208.6–428.9 mg m^‐2 d^‐1, respectively. The fluxes from salt marsh were slightly greater than those measured in brackish marsh, although these differences were not statistically significant.     

Temperature sensitivity of anaerobic labile soil organic carbon decomposition in brackish marsh

The global warming has a potential for acceleration of labile soil organic carbon decomposition. Arrhenius equation is one of the useful equation for predicting temperature sensitivity of carbon decomposition, with the activation energy of rate constant being a key factor. The purpose of this study is the evaluation of temperature sensitivity of labile soil organic carbon decomposition under anaerobic condition in wetland soil using the activation energy of rate constant among different vegetation types. The soil samples were incubated at three different temperatures (10, 20, and 30°C) under anaerobic condition and carbon decomposition rates (sum of CO₂ and CH₄ production) were measured by gas chromatography. The first-order kinetic model with Arrhenius equation was used for approximate of anaerobic carbon decomposition. For determination of activation energy of rate constant, non-linear least-squares method was conducted between observed carbon decomposition rate and predicted carbon decomposition rate which calculated by Arrhenius equation. The activation energy of rate constant of anaerobic labile soil organic carbon decomposition was different among vegetation types. We successfully determined the activation energy of rate constant of CO2 or CH4 production from Phragites, Juncus, and Miscanthus+Cirsium-dominated vegetation soil with Arrhenius equation. Hence, this study suggests that Arrhenius equation was useful for evaluation of temperature sensitivity of labile soil organic carbon decomposition not only aerobic condition, but also anaerobic condition among several vegetation types in the wetland ecosystem. Moreover, gaseous carbon production from soil under Juncus yocoscensis dominated soil appeared higher activation energy and temperature sensitivity than that from soil under other vegetation types.     

Soil management for raising crop water productivity in rainfed production systems in Lao PDR

This study investigated the impacts of organic- and clay-based soil amendments, and their combinations on crop water productivity (CWP) using maize as a test crop. On-station field trials were established over two consecutive years at the Naphok and Veunkham sites in Laos. At each site, 10 treatments were applied in a randomized complete block design with three replications. The treatments were control, rice husk biochar (10 t ha^?1), bentonite clay (10 t ha^?1), compost (4 t ha^?1), clay-manure compost (10 t ha^?1), rice husk biochar compost (10 t ha^?1), bentonite clay + biochar, bentonite-clay + compost, biochar + compost, and bentonite clay + biochar + compost. All treatments were applied in 2011. Significant (p < 0.05) treatment effects in CWP and growing period evapotranspiration were determined. At Naphok, differences between the amended and control plots in CWP varied between 0.1 and 0.6 kg m^?3 in 2011 and from 0.1 to 0.4 kg m^?3 in 2012, whereas differences at Veunkham varied between 0.3 and 1.0 kg m^?3 in 2011 and from 0.05 to 0.29 kg m^?3 in 2012. At both sites, CWP in 2012 was significantly lower than 2011. Our results illustrate that organic- and clay-based soil amendments improve CWP, indicating that soil-based interventions could be suitable options for improving agricultural productivity.     

石膏改良苏打盐碱土研究

采用盆栽与田间试验相结合的方法（试验共设６个处理：即石膏用量０、０．５、１．０、１．５、２．０、２．５ｋｇ／ｍ２）研究了石膏的改良盐碱土作用．结果表明：施用石膏后增加了玉米的保苗数，促进了水稻分蘖及玉米、水稻的生长发育，土壤ｐＨ明显降低，水旱田土壤硬度明显降低，旱田玉米土壤三相比普遍改善，根系干重明显增加，土壤中的二价离子增多，一价离子减少，ＥＳＰ普遍降低，土壤化学性质明显改善．秋收测产表明：玉米单产增加１２．５８～４４．３１％，水稻单产增加６．８３～２９．８６％．     

微咸水灌溉对斥水土壤水盐运移的影响

土壤斥水性影响着作物的产量,为了研究微咸水灌溉对斥水土壤水盐运移的影响,进行了室内土柱微咸水入渗试验。对比了不同矿化度和斥水程度对两种土质水盐运移的影响,探讨了微咸水入渗后土壤斥水性的变化特征。结果表明,不斥水土壤的入渗能力随矿化度的增加而增加。亲水和斥水土壤的入渗率均可采用Kostiakov公式简单模拟。斥水土壤入渗能力在矿化度为1?g/L时达到最大,超过1?g/L后则随矿化度的增大而减小。微咸水入渗的累积入渗量与湿润锋推进距离呈良好的线性关系,斥水性土壤中的相同剖面水盐的含量比不斥水的减小。微咸水入渗后土壤产生了一定的斥水性。该研究表明微咸水灌溉对盐渍化土壤的水盐分布和斥水性均有一定程度的影响。     

Preparation and characteristics of rumen-bypass microcapsules for improvement of productivity in ruminants

Rumen-bypass microcapsules were prepared by a spray-dry method for protection against microbial hydrogenation in the rumen (neutral pH). Porous starch was used as the core material, and the microcapsules were prepared by a triple coating of Eudragit E100, AS-HF, and shellac. Capsules were generated with yield of about 48% and a mean particle diameter of 20-30 microm. The microcapsules had high stability in a neutral solution that mimicked a ruminal pH (pH 6.5). Moreover, when microcapsules were incubated in the presence of ruminal microorganisms, about 65% of the microcapsules were resistant to digestion in ruminal fluids, and protection of the inclusion substance was observed. In addition, the efficiency of release of these microcapsules was about 85% within only 30 min in the abomasal environment (pH 3.0).     

Quantifying the interactions of land management practices and agricultural productivity using a soil quality index

It is desirable to develop an objective Soil Quality Index (SQI) to guide sustainable agronomic intensification, thereby promoting socio‐economic well‐being. This study pioneers the use of Ward's cluster and principal component regression methods to evaluate soil homogeneity and construct a SQI (expressed as %). Field data were acquired from five different sites within Ohio, USA, that were under no‐till (NT), conventional till (CT) management and natural vegetation (NV) land use. Soil pH, carbon/nitrogen (C/N) ratio, nitrate and soil organic carbon (SOC) concentrations were identified as primary drivers of soil quality. Based on Ward's cluster method, the soil properties of croplands were not significantly different from those under NV land use. However, SQI ranked surface soils under CT management as higher in quality than NV and NT managed soils, respectively. The coefficient of determination (R²) between SQI and corn (Zea mays L.) and soya bean [Glycine max (L.) Merr.] yields was 0.7 and 0.9, respectively, implying this SQI effectively relates soil properties, a function of anthropogenic land management practices, with crop yields. In future, time series analyses will be used to assess SQI versus crop yield dynamics, with key socio‐economic and climate variables.     

Estimation of fine root biomass using a minirhizotron technique among three vegetation types in a cool-temperate brackish marsh

The minirhizotron technique is a non-destructive method to evaluate fine roots, which converts two-dimensional image data to three- dimensional root biomass data. Recently, conversion factors in soils at 10-cm depth intervals successfully estimated fine root biomass using image data from the minirhizotron method. However, this technique was conducted only at one forest site and did not consider different vegetation types. Therefore, the objective of this study was to verify a method for calibration of minirhizotron data with the core sampling values obtained by direct measurement of root biomass in wetland ecosystems among three vegetation types. Evaluations by minirhizotron technique and soil-core sampling were made at 30-cm soil depth in a cool-temperate brackish marsh in northern Japan. Linear regression was examined between root volume and weight of fine roots in soil core samples, and the fine root biomass on minirhizotron tubes was calculated from their length and diameter. The technique was well adapted for vegetation types dominated by Phragmites australis, Juncus yokoscensis, and Miscanthus sinensis and Cirsium inundatum. Compared with the fine root biomass estimated by the core sampling method, fine root biomass estimated by the minirhizotron method was overestimated in the 0–10-cm layer. Further, we determined conversion factors based on the ratio of the fine root biomass by the core sampling method to that by the minirhizotron tubes. Estimation of the fine root biomass using the conversion factors for each 10-cm soil depth was well adapted in P. australis vegetation and J. yokoscensis vegetation types as a forest ecosystem; meanwhile, M. sinensis and C. inundatum vegetation types were not well adapted. This study suggests that the minirhizotron technique is available to estimate fine root biomass of single-species dominated vegetation in the brackish marsh using conversion factors for each 10-cm depth.     

去电子处理微咸水矿化度对土壤水盐运移特征的影响

为探究去电子处理微咸水对土壤水盐运移的影响,该文通过室内土柱试验,分析了不同矿化度微咸水(0.14、2、3、4、5 g/L)经去电子处理后土壤水分入渗及盐分分布规律。结果表明:不同矿化度去电子微咸水土壤入渗速率及湿润锋运移速率明显大于未处理微咸水,入渗时间为200 min时,累积入渗量和湿润锋运移深度在矿化度为4 g/L时增加幅度最大。相同矿化度去电子微咸水与未处理微咸水相比,Philip入渗公式吸渗率、Green-Ampt入渗公式饱和导水率及湿润锋处吸力均显著增加。去电子微咸水能够显著提高土壤的持水效率和上层土壤盐分的淋洗效果,矿化度为4 g/L时,相对淋盐率和Na+相对淋洗率最大。该研究表明去电子化处理能够改善土壤水盐运移特性,有利于微咸水安全利用。     

添加黑色粒子降低太阳能苦咸水淡化系统中水体通光性能

针对太阳能苦咸水淡化系统中太阳能集热系统在高温段时(≥100℃)效率低,而苦咸水淡化系统在低温段时效率低的结构性不匹配问题,提出了聚光直接加热式太阳能苦咸水淡化系统,为了提高苦咸水的吸光能力,将黑色粒子投入到透明玻璃蒸发器内的苦咸水中,实现了苦咸水的功能化,从光学角度对功能化苦咸水的通光性能展开研究,给出沸腾状功能化水体的通光性能变化规律,并对非沸腾状苦咸水的通光率进行了理论计算。结果表明,功能化苦咸水的通光率随粒子丰度增大在特定点前快速减小而后减小缓慢,其中在测试范围内,含有粒径为0.63 mm粒子的功能化水体的通光率最小,水体通光率最大可减小60.09%;且理论计算变化曲线与试验测量变化曲线趋势一样,理论计算结果与试验测试结果吻合较好,2个测试水体的决定系数R2分别为0.98694和0.96641。该文为提高苦咸水吸光能力的研究提供了有价值的参考。     

Effect of tillage and farming management on Collembola in marsh soils

The Sanjiang Plain, the second largest marsh in China, has experienced intensive cultivation over the past 50 years. Most of the marshlands were converted to soybean and rice fields. However, little is known about the effects of tillage on the soil fauna. 9 treatments, including original marshland soil, rice and soybean cultivation with and without fertilizer and herbicide applications, were imitated with 135 buckets under greenhouse conditions. The soil characteristics and Collembola in these treatments were investigated for one plant growth season.The soil environment was deteriorated (as indicated by the decreased soil oxidizable organic matter, total nitrogen and soil water content and increased soil compaction) by soybean and rice cultivation treatments. The densities and species richness of Collembola significantly decreased in the rice cultivation treatments but not in the soybean cultivation treatments. For the soybean cultivation treatments, density and species richness of the soil Collembola significantly increased in the fertilizer, herbicide and fertilizer + herbicide application treatments. It probably caused by increasing root and shoot biomass in these treatments.It is concluded that the tillage treatments in a wetland soil had both qualitative and quantitative adverse effects on the soil collembolans, and these effects might further alter the soil ecological processes.     

运用土壤水盐运移模型优化棉花微咸水膜下滴灌制度

为优化设计棉花微咸水膜下滴灌灌溉制度,利用HYDRUS建立含根系吸水项的土壤水盐运移数值模拟模型,并用田间试验资料进行参数识别和模型验证。用验证认可的数值模型优化设计棉花微咸水膜下滴灌和非生育期洗盐灌溉制度,并预测棉花生育期水盐运移规律和长期效应。结果表明:模型仿真度较高、运行速度较快;T检验说明土壤含水率和电导率模拟值与实测值均无显著差异;模型参数中形状系数α、n对含水率影响较大,纵向弥散度DL对电导率影响较大;当地膜下滴灌适合生育期一膜双管、低额高频灌溉,并结合非生育期1年1次或2年1次大水漫灌洗盐,20a的模拟结果显示此灌溉制度下不会引起土壤次生盐渍化。     

聚光蒸发式太阳能苦咸水淡化系统水体光热性能分析

针对太阳能苦咸水淡化系统中太阳能集热系统在高温段时效率低,而苦咸水淡化系统在低温段时效率低的结构性不匹配问题,提出了聚光蒸发式太阳能苦咸水淡化系统。为了提高苦咸水对入射太阳光的吸收作用,对太阳能集热系统中的苦咸水进行功能化处理,并对功能化苦咸水的透射率进行了光学性能分析,在实际天气条件下,对功能化苦咸水的热能利用效率进行了试验研究。结果表明,功能化苦咸水的透射率随粒子丰度增加而减小,随粒径减小而降低;粒子丰度由6.25增加为50.0 mg/L时,含有粒径为0.72 mm粒子的功能化水体的热能利用效率增加了41.3%;功能化苦咸水热利用效率计算结果与光学性能测试结果变化趋势一致。该研究为提高太阳能苦咸水淡化系统热利用效率提供了参考。     

三江平原沼泽与降水、地表水、地下水的关系

简介了三江平原沼泽资源现状,分析了沼泽形成与大气降水、地表水、地下水间的关系,沼泽开发对“三水”减少的影响以及沼泽在“三水”循环转化过程中的功能与作用,并提出保护沼泽的对策。     

微咸水对冬小麦萌发及苗期生长发育的影响

华北地区冬春干旱日益频繁, 而环渤海区微咸水资源丰富。探讨微咸水在冬小麦造墒或冬灌中应用的可行性, 对充分利用该区域的微咸水资源具有重要意义。本研究以华北地区不同生态型冬小麦品种(水旱兼用型“石家庄8号”、旱作型“晋麦47”和抗盐型“小偃81”)为试验材料, 采用盆栽方式, 分析了微咸水对冬小麦萌发和苗期生长发育及水分利用效率的影响。结果表明: 微咸水对“石家庄8号”和“小偃81”的萌发无影响, 使“晋麦47”的发芽势和发芽率显著降低, 而3个品种冬小麦的胚芽鲜重对微咸水处理无响应。微咸水处理抑制冬小麦根系的生长, 而促进了地上部的生长, 使“石家庄8号”、“小偃81”和“晋麦47”的根冠比分别降低51.6%、32.3%和36.8%, 使叶绿素含量分别提高38.5%、26.0%和12.9%。微咸水促进冬小麦的地上部生长, 提高冬小麦的水分利用效率, 但是对冬小麦苗期的根系生长有抑制作用。微咸水处理提高3个品种冬小麦的水分利用效率, 主要是由于降低了冬小麦的单株耗水量。     

Agronomic evaluation of rice cultivation systems for water and grain productivity

Field experiments were conducted during summer (March–July) and kharif (June–September), 2008 at the wetland farm, Tamil Nadu Agricultural University, Coimbatore, India, to study the performance of different rice cultivation methods on productivity and water usage using the hybrid CORH-3 as a test crop. Treatments consisted of different rice cultivation methods, namely, transplanted rice (conventional), direct sown rice (wet seeded), alternate wetting and drying method (AWD), system of rice intensification (SRI) and aerobic rice cultivation. Results revealed that maximum number of tillers m^?2, higher shoot and root length at maturity were recorded under SRI followed by transplanted rice, while aerobic rice produced lower growth parameters in both the seasons. Chlorophyll content at flowering was higher under SRI in two seasons studied (42.74 and 39.48 SPAD value, respectively) and transplanted rice compared to aerobic rice and AWD. In both summer and kharif seasons, SRI produced higher grain yield (6014 and 6682 kg ha^?1), followed by transplanted rice (5732 and 6262 kg ha^?1), while the lowest grain yield (3582 and 3933 kg ha^?1) was recorded under aerobic rice cultivation. Under SRI, 5 and 6.7% increase in grain yield and 12.6 and 14.8% water saving were noticed compared to transplanted rice, respectively, during summer and kharif seasons. In respect to water productivity, the SRI method of rice cultivation registered the highest water productivity (0.43and 0.47 kg m^?3), followed by AWD and aerobic rice cultivation. The conventional rice cultivation and direct sown rice produced lower grain yield per unit quantity of water used.     

Simulating the impact of irrigation management on the water and salt balance in drained marsh soils (Marismas, Spain)

Abstract. Using the simulation model MACRO, this paper investigates the likely consequences of reduced irrigation inputs on the water and salt balance and crop growth in a drained, saline clay in a Mediterranean climate (Marismas, SW Spain). The model was first successfully validated against field measurements of the soil water and chloride balance, water table depths and drain outflows in the 1989 growing season. Three-year simulations were then performed assuming two different irrigation applications (60 and 75% reductions from the 1989 amount) and two different frequencies (12 or 6 irrigations per growing season). The model predictions suggested that reduced irrigation may lead to up to a 15%) increase in the chloride content of the soil profile after 3 years. Also, despite overall reductions in water discharge, slight increases in chloride leaching via field drains ( c. 4 to 8%) were predicted. The model demonstrated that encroachment of salt into the soil profile may he exacerbated by the non-equilibrium nature of water flow and solute transport ('by-passing flow') in structured clays. With reduced water supply for irrigation, more frequent applications may give marginally better crop yields for the same quantity of irrigation but at the expense of slightly increasing salt concentration in the root zone.     

Reducing water erosion in a gypsic soil by combined use of organic amendment and shrub revegetation

Degraded gypsic soils in the centre of Spain can be rehabilitated with organic amendment and shrub revegetation. Erosion has been measured on plots of 2×0·5 m² under simulated rainfall of 70 mm h⁻¹ and a kinetic energy of 18 J mm⁻¹ m⁻². Samples of water runoff and sediments were studied in the summer of the years 2002 and 2003. The presence of shrub Atriplex halimus (Chenonodiaceae) significantly reduces runoff from 16·9 to 6·7 ml m⁻² min⁻¹ and sediments from 0·16 to 0·02 g m⁻² min⁻¹. When sewage sludge is applied the differences among plots with and without bushes disappear. Although both treatments independently applied are efficient as erosion control measures, the combined use of revegetation and organic amendment allows a reduced dose of sewage sludge with the same effect on erosion. A low dose of sludge is desirable in view of the accumulation of toxic chemicals. Copyright © 2005 John Wiley & Sons, Ltd.     

不同灌溉量膜下微咸水滴灌土壤盐分分布与积累特征

于2010年在新疆石河子大学节水灌溉实验站进行膜下微咸水滴灌试验。灌溉水矿化度为3.32 g L-1,三个灌溉定额处理(Q36:3 150 m3 hm-2、Q48:4 200 m3 hm-2、Q60:5 250 m3 hm-2),并分析了土壤盐分分布及其积累特征。在灌溉周期内土壤盐分运移特征为:根区土壤盐分基本表现趋势为湿润体形成阶段降低,再分布阶段聚集;根底土壤盐分表现趋势为湿润体形成阶段增加,再分布阶段降低。秋后土壤盐分剖面与盐量平衡结果显示:Q36、Q48处理中灌溉输入土壤的盐分基本上存于120 cm土壤以内,Q60处理在120 cm以下土壤盐分显著增加。灌前灌后土壤水分入渗剖面显示,三个处理滴灌后36 h土壤水分湿润深度分别达到80、90、120 cm。滴头部位水分携带盐分向深层迁移,在滴灌中起着深层淋溶作用,这对于减缓上层土壤盐分积累具有积极意义。     

Energy and water balance measurements for water productivity analysis in irrigated mango trees, Northeast Brazil

Crop water parameters, including actual evapotranspiration, transpiration, soil evaporation, crop coefficients, evaporative fractions, aerodynamic resistances, surface resistances and percolation fluxes were estimated in a commercial mango orchard during two growing seasons in Northeast Brazil. The actual evapotranspiration (E_a) was obtained by the eddy covariance (EC) technique, while for the reference evapotranspiration (E₀); the FAO Penman–Monteith equation was applied. The energy balance closure showed a gap of 12%. For water productivity analysis the E_a was then computed with the Bowen ratio determined from the eddy covariance fluxes. The mean accumulated E_a for the two seasons was 1419 mm year⁻¹, which corresponded to a daily average rate of 3.7 mm day⁻¹. The mean values of the crop coefficients based on evapotranspiration (K_c) and based on transpiration (K_cb) were 0.91 and 0.73, respectively. The single layer K_c was fitted with a degree days function. Twenty percent of evapotranspiration originated from direct soil evaporation. The evaporative fraction was 0.83 on average. The average relative water supply was 1.1, revealing that, in general, irrigation water supply was in good harmony with the crop water requirements. The resulting evapotranspiration deficit was 73–95 mm per season only. The mean aerodynamic resistance (r_a) was 37 s m⁻¹ and the bulk surface resistance (r_s) was 135 s m⁻¹. The mean unit yield was 45 tonne ha⁻¹ being equivalent to a crop water productivity of 3.2 kg m⁻³ when based on E_a with an economic counterpart of US$ 3.27 m⁻³. The drawback of this highly productive use of water resources is an unavoidable percolation flux of approximately 300 mm per growing season that is detrimental to the downstream environment and water users.