沙粒对碱土饱和导水率和盐分淋洗的影响

为探求碱土饱和导水率与出流液电导率及pH之间的关系,采用室内模拟实验对含沙粒碱土的饱和导水率、出流液电导率及pH进行测定,分析了沙粒添加量和粒径对碱土饱和导水率、出流液电导率及pH的影响.结果表明:随沙粒添加量逐渐增加,碱土饱和导水率不断升高,两者呈极显著指数关系;碱土饱和导水率随沙粒粒径增加呈无规律的变化趋势;出流液电导率和pH值随沙粒添加量增加而降低,电导率和沙粒添加量问存在指数函数关系,但pH与沙粒添加量间无函数关系;出流液电导率和pH值随沙粒粒径增加均呈无规律变化趋势;出流液电导率和pH值均随饱和导水率的升高而降低,二者与饱和导水率间均呈对数关系.     

初始含水量对盐碱土饱和导水能力和盐分淋洗的影响

为了探究初始含水量对盐碱土饱和导水能力和盐分淋洗的影响,采用室内模拟试验,进行了6个不同初始含水量的定水头饱和导水能力试验。结果表明,盐碱土饱和导水率随初始含水量的增加而减小,二者呈显著的线性负相关;随初始含水量的增加,淋洗液pH值降低,电导率升高;随盐碱土饱和导水率的增大,淋洗液pH值升高,电导率降低,二者均与饱和导水率间呈对数关系。长期淹水状态下,盐碱土饱和导水能力平稳降低,盐分淋洗效果也变差。     

苏打碱土盐分淋洗与饱和导水率的关系

土壤饱和导水率是土壤重要的物理性质之一,反映了土壤入渗和渗漏性质,是计算土壤剖面水通量和排水工程设计的一个重要土壤水力参数[1]。准确地估测农田饱和导水率,对于制定正确的水分和盐分、水分和养分的管理措施及有效地防止污染物对环境的影响,都有十分重要的意义。已有研究表明,饱和导水率受土壤质地、结构、盐分含量与组成、容重或孔隙度、土壤水分特征等诸多因素影响[2-7]。就碱土而言,饱和导水率低是其标志性特征之一[8-10],提高饱和导水率是有效淋洗碱土盐分的基本前提[11]。松嫩平原是国内仅次于黄淮海平原的第二大平原,其西部是中国五大盐渍土分布区域之一[12]。土壤盐分以NaHCO3和NaCO3为主[     

不同淋洗模式下干旱区盐渍土改良效果分析

通过开展室外土柱模拟淋洗试验,选择间歇淋洗与连续淋洗两种淋洗模式,分析不同灌水总量和不同灌水频次相互组合条件下盐渍土的改良效果。结果表明:(1)灌水量相同情况下,间歇淋洗滤出液的电导率高于连续淋洗,间歇淋洗的淋洗效果好于连续淋洗;(2)灌水量不同条件下,滤出液体积随灌水量的增加而增多,灌水量越大盐分淋洗效果越好;(3)淋洗结束后,土壤pH值较淋洗前均有下降,与土壤盐分有相同的变化趋势;灌水量越大,脱碱效果越好。在本试验条件下,盐分淋洗效果以15L分3次给水的间歇淋洗方式最优,淋洗效率为11.58g/L,土壤pH值均由8.42下降到8.07。可供制定维持农田水盐平衡的节水灌溉制度以及盐碱地改良参考。     

植被群落演替对土壤饱和导水率的影响

土壤饱和导水率是表征土壤入渗能力的重要参数,对不同土地利用类型反应敏感。为了揭示植被演替对土壤剖面上饱和导水率的影响规律,采用恒定水头法测定了天童林区155 a植物群落演替序列60 cm深土壤剖面上的饱和导水率。结果表明,不同演替阶段饱和导水率均随土壤深度增加迅速降低,在0～20 cm土层内,各演替阶段饱和导水率均存在极显著差异,0～60 cm土层内饱和导水率的平均值从裸地、石栎+檵木灌丛、马尾松林、木荷+马尾松林、木荷林到栲树林升高极为显著,植物群落演替到灌丛阶段,平均饱和导水率已与裸地存在显著差异,演     

不同淋洗对于碱土的影响

当用水淋洗碱土时,其水浸提液中的钙量恆少于普通土壤中者。水土比例增大时,淋洗出的钙量增多,惟增加量不很大。水土比例增大时,普通土壤各次滤液的pH 值并不增大,且易于达到蒸馏水的pH 值,反之,碱土的pH 值很慢的降低至pH 7.5。浸提液中CO_3~=量逐渐减少,和pH 值的降低相一致,重碳酸盐量开始时逐渐增多,以后又降低。反覆用水淋洗时pH 值亦逐渐降低。     

宁南山区草地植被恢复方式对土壤饱和导水率的影响

为评价宁南山区草地植被不同恢复方式对土壤入渗性能的影响,以不同植被群落的饱和导水率为研究对象,采用逐步回归研究退耕农地、禁牧荒地、封育草地导水率的变化及影响因子,并探讨了其作用机制。结果表明：3种植被恢复方式均有利于0-40 cm土壤饱和导水性能提高;各土层土壤饱和导水率均随植被恢复而不断提高,0-5 cm土层改善作用最为明显;农地退耕序列和荒地禁牧序列5-40 cm土层、封育草地序列0-40 cm土层土壤饱和导水率随土层深度下降而降低;影响土壤饱和导水率的因子为土壤有机质因子和土壤结构因子;3种植被恢复方式土壤有机质质量分数与Ks均呈显著的线性相关关系,在该区域有机质质量分数越高,Ks增加越快;土壤有机质积累是土壤饱和导水率提高的根本动力。因此,草地封育更利于提高使该地区土壤导水性能提高,促进生态恢复。     

黄土丘陵区典型植被土壤物理性质差异及其对导水特性影响

选取黄土丘陵区12种典型植被样地,通过测定各样地不同土层植物残体生物量、土壤容重、毛管孔隙度、非毛管孔隙度及饱和导水率,研究各指标随土层深度和植被类型的变化规律及其对土壤饱和导水率的影响。结果表明:(1)除容重随土层深度增加外,植物残体、毛管孔隙度、非毛管孔隙度和饱和导水率均随土层深度减少,其中植物残体大多集中于表层土壤(0—10 cm),占总残体生物量的51.4%～85.7%。(2)不同植被类型其植物残体及土壤物理性质存在显著差异,乔木林地植物残体、农耕地土壤容重、灌木林地非毛管孔隙度及饱和导水率均最大,而毛管孔隙度与不同土地利用类型间无显著差异。(3)饱和导水率随植物残体生物量密度(0—10 cm)和土壤容重呈幂函数减小,随毛管孔隙度和非毛管孔隙度呈幂函数增大;土壤容重(BD)和非毛管孔隙度(NCP)是影响土壤饱和导水率(K_s)的主要因素,且土壤饱和导水率可表示为两者的综合非线性方程(K_s=0.6BD~(-4.717)NCP~(0.203),P0.01,R~2=0.63,NSE=0.50)。此外,沙棘灌木林地平均饱和导水率最大,有利于降雨过程中土壤水分入渗,具有较强的水土保持功能。本研究结果可为黄土高原植被恢复生态水文效益评价提供理论依据。     

重庆市四面山不同土地利用类型饱和导水率

[目的]探讨不同土地利用类型和土壤理化性质对饱对导水率的影响。[方法]采用定水头法测定四面山不同土地利用类型的饱和导水率,并运用回归分析,相关分析和主成分分析法分析其与土壤物理因子和有机质的关系,以及影响饱和导水率的主导因子。[结果]各土地利用类型的平均饱和导水率均高于荒地,其顺序为:林地农地草地,林地中天然林饱和导水率大于人工林;饱和导水率随土层深度的增加呈负指数递减规律;饱和导水率与容重呈幂函数关系,与孔隙度呈正相关,与黏粒含量呈负相关;有机质含量的提高对饱和导水率有积极的促进作用。[结论]影响饱和导水率的主导因子是容重、有机质、非毛管孔隙度和毛管孔隙度,其次,土壤机械组成对其也有一定影响。     

有机肥质量分数对土壤导水率稳定性的影响

饱和导水率是水循环和土壤侵蚀模型中的重要参数,也是土壤结构改善的重要指标.通过室内土柱模拟实验研究有机肥添加量对风沙土和壤土导水率的影响.土壤添加有机肥的比例设置为0％、5％、10％、15％、20％、25％、30％7个水平,土壤密度设3个水平,各处理5个重复.结果表明：1）土壤饱和导水率随有机肥质量分数的增加呈降低趋势,风沙土的饱和导水率随有机肥质量分数的增加呈直线下降趋势,而壤土饱和导水率的降低趋势随有机肥质量分数的增加减缓;2）有机肥质量分数的增加对土壤密度的降低作用可以抵消有机肥增加导致的饱和导水率的降低;3）低土壤密度下土壤导水率随时间变化不稳定,土壤密度增大后随时间变化稳定.随着有机肥质量分数的增加,土壤导水率的测定过程趋于稳定,但是测定时间延长.     

Mineral composition of peanut tissue as influenced by irrigation water quality and irrigation method

Abstract

Peanut (Arachis hypogaea L.), is produced in the Virginia and North Carolina coastal plain where sodic deep well water sources are more readily available than high quality shallow well sources. The objective of this work was to determine the effect of irrigation water quality and irrigation method on the mineral composition of peanut tissue. Virginia‐type peanuts were grown on a Kenansville loamy sand (loamy, siliceous, thermic Arenic Hapludult) in Suffolk, VA from 1985 to 1987. Peanuts were irrigated with either overhead sprinklers or deep buried trickle lines using sodic deep‐well (142 m) and nonsodic shallow‐well (10 m) water. Trickle lines were buried 350 to 410 mm below each row. Sodic water had 220 mg Na/L, a pH of 8.5, and a sodium adsorption ratio (SAR) of 103. Non‐sodic water had 4.8 mg Na/L, a pH of 4.8, and an SAR of 3.1. Sodic water did not affect soil levels of Ca and Mg. Soil Na and pH were both higher to a depth of 900 mm in soil irrigated with sodic water. Sodic water appeared to reduce the concentration of Mg and increase the concentration of K in plant tissue. Plants from plots irrigated with sodic water concentrated Na in the stems and roots. Only in 1987, which was the driest year of the study, did seed concentration of plants irrigated with sodic water differ significantly from non‐sodic irrigated and non‐irrigated concentrations. Trickle irrigation reduced the amount of Na in the plants and may be the best way to use sodic irrigation water for peanut production.     

气相阻力与土壤容重对一维垂直入渗影响的定量分析

分析了土壤容重和气阻对一维垂直积水入渗的入渗率、累积入渗量以及湿润锋的影响,并对入渗过程中土壤平均含水率增量进行了研究。容重和气阻均对入渗率、累积入渗量和湿润锋有明显的影响:容重增加导致累积入渗量减少的减渗率在入渗过程中为一常数,相对于容重为1.3g/cm3土壤的累积入渗量,容重为1.4g/cm3和1.5g/cm3土壤的减渗率分别为31.79%和52.03%。容重增加导致湿润锋减少的减渗率在入渗过程中并非一常数,受到了入渗时间的影响;气阻导致累积入渗量和湿润锋减少的减渗率随基准入渗量的增加而变大,受到了入渗时间的影响。对应于1.3,1.4,1.5g/cm3等3个容重土壤的积水入渗,入渗过程中土壤剖面平均含水率增量Δθ分别为0.377,0.3411,0.3137。     

咸淡水交替灌溉下土壤盐分再分布规律的室内实验研究

咸水灌溉是解决目前淡水资源短缺的重要途径。为寻求合理的咸水农田灌溉方法，进行了不同矿化度和不同灌水模式的室内土柱咸淡水交替灌溉模拟试验，分析了咸淡水交替灌溉条件下土壤溶液电导率(EC)值和钠吸附比(SAR)的变化规律。结果表明：两种灌水模式下，灌水结束时土壤溶液EC值在22.5 cm处达到最高，且4 g/L>2 g/L，且与试验初期相比，土壤溶液EC值明显提高，土柱整体积盐明显。灌水模式对土壤溶液EC值的影响大于矿化度；两种灌水模式不同矿化度处理的SAR值变化规律基本一致。     

Changes in soil hydraulic conductivity, runoff, and soil loss due to irrigation with different types of saline–sodic water

Irrigation with saline–sodic water causes sodic conditions in the soil which reduces soil productivity. We evaluated the changes in a number of important indices related to soil structural stability when treated wastewater (TWW), albeit with higher loads of organic matter and suspended solids, was used instead of more saline–sodic irrigation water, under different degrees of aggregate slaking. We studied soil saturated hydraulic conductivity (HC) using disturbed samples packed in columns, and soil infiltration rate, runoff and erosion under simulated rainfall. Aggregate slaking was manipulated by wetting the samples prior to all tests at either a slow (1–2 mm h^− 1) or a fast (50 mm h^− 1) rate. Samples of a calcareous silty clay (Typic Calciorthids) from the Bet She'an Valley, Israel, were taken from plots irrigated for three years with either TWW, saline–sodic Jordan River water (JRW), or moderately saline–sodic spring water (SPW), and also from a non-cultivated area (control). With little or no aggregate slaking (use of slow wetting), higher HC values and lower amounts of total runoff and soil loss were measured compared to when more severe aggregate slaking was induced (use of fast wetting). The HC values for the TWW treatment were similar to, or lower than, those for the control and significantly higher than those for the JRW treatment. For the runoff and soil loss data, differences among the water quality treatments were, generally, more pronounced when aggregate slaking was substantially reduced, and were related to soil sodicity. Under the latter condition, runoff and soil loss from the TWW treatment were comparable with those from the control and significantly lower than those from the JRW treatment. Our results suggested that replacing saline–sodic irrigation water with TWW could have favorable effects on soil structural stability, especially under conditions where aggregate slaking can be reduced (e.g., in regions with low to moderate rain intensities; and/or use of low intensity irrigation systems).     

Some relationships between quality of irrigation waters and chemical characteristics of irrigated soils of the Nagaur district,Rajasthan

Studies were conducted on the effects of waters of different quality on the chemical characteristics of 74 surface and subsurface soils of the Nagaur district, Rajasthan. The electrical conductivity (EC) of the saturation extract of these sandy and loamy sand soils were found to be less than that of the irrigation water. Correlations were observed between EC and the constituent ions (Na⁺, Ca²⁺ and Mg²⁺ of the irrigation water and of the saturation extract of the soil samples. The pH values of the irrigation water and soil suspensions also showed a positive correlation. The carbonate and bicarbonate ion concentrations in both the irrigation water and the saturation extract of the soils correlated with their respective pH values. EC of both the irrigation water and the saturation extract from surface and subsurface soil layers correlated with total cations. Correlations between the chemical characteristics of the irrigation water and the saturation extract of the soils are of limited value for prediction purposes, due to other factors operating under field conditions.     

华北地区微咸水应用对土壤水力传导性能的影响

由于淡水资源短缺,中国华北地区微咸地下水灌溉面积逐年增多。该文通过室内土柱淋洗试验,研究了灌溉水盐分浓度和钠吸附比(SAR)对华北地区非碱土(可交换钠百分比ESP0)和碱土(ESP30)饱和水力传导性能的影响。灌溉水盐浓度分别为2.5、10和25mmolc/L,SAR分别为0、10和30(mmolc/L)0.5。去离子(盐浓度0)作为对照处理。试验包括2个土壤碱度、9个灌溉水质组合和1个去离子水处理,共20个试验处理。试验结果显示,非碱土和碱土对微咸水应用的反应机理以及反应程度不同。当黏粒弥散程度较弱时,上部土壤的饱和水力传导度显著大于下层土壤;反之,则各层土壤的水力传导度均较小。在试验水质条件下,非碱土的平均饱和水力传导度的变化范围为0.75～13.25cm/h,而碱土的变化范围为0.06～6.50cm/h。碱土的稳定饱和水力传导度随着灌溉水盐浓度的增加或/和SAR的减小而增大,但在非碱土中稳定饱和水力传导度的变化规律与此基本相反。试验结果对合理应用微咸水灌溉非碱土和碱土具有指导意义。     

Acidity Changes of Foreign Acidic Soils Introduced into Calcareous Soil Environment

Abstract

Many tropical plant species originated in areas with acidic soils and do not grow well in calcareous (high pH) soils. It is impossible to acidify soils that have high contents of calcium carbonate in south Florida. Replacing calcareous soils with acidic soils obtained from distant regions is an alternative. Unfortunately, such introduced acidic soils may eventually be neutralized by irrigation and ground water that is saturated with calcium carbonate. The objective of this investigation was to examine the acidity changes and buffering capacities of three types of acidic soils (silica sand soil, red loamy sand soil, and a mixed soil) used to establish tropical plants in a rainforest exhibition at Fairchild Tropical Garden, Miami, FL. The three areas were excavated to remove native calcareous soil, limestone bedrock, and filled with acidic soils. Various rainforest plants were planted. Soil samples were collected in contiguous 10 cm‐deep segments from the soil surface to the bedrock shortly after deposition of the soils and one year later. Soil pH, EC, particle distribution, buffering capacity were determined. Results showed that both silica sand and mixed soils had been neutralized and the soil pH values had risen over 7 in all soil depths after one year. However, less than 10 cm of the surface and bottom soil layers of red loamy sand had been neutralized and the soil pH in the middle of soil profile remained unchanged due to its higher buffering capacity. A column leaching study showed that the acidity in the red loamy sand soil would be neutralized by irrigation water and by capillary movement of groundwater with a high concentration of calcium bicarbonate. Buffering curves indicate that it is easier to maintain acidity in sandy soil than of loamy sand and mixed soils with acidified irrigation water. Indeed it is difficult to acidify the mixed soils with high organic matter content after these soils have been neutralized.     

Tillage Effects on Crop Yield and Physicochemical Properties of Sodic Soils

Tillage modifies soil structure and has been suggested as a practice to improve physical, hydrological and chemical properties of compacted soils. But little is known about effect of long‐term tillage on physicochemical soil properties and crop yield on sodic soils in India. Our objective was to investigate the effect of different tillage regimes on crop yield (wheat and paddy rice) and physicochemical properties of sodic soils. Two sodic sites under conventional tillage for 5 (5‐YT; 5‐year tillage) and 9 (9‐YT; 9‐year tillage) years were selected for this study. Changes in crop yield and physicochemical soil properties were compared with a control, sodic land without any till history, that is, 0‐year tillage/untilled (0‐YT). Five replicated samples at 0‐ to 10‐cm and 10‐ to 20‐cm soils depths were analysed from each site. In the top, 0‐ to 10‐cm soil depth 5‐YT and 9‐YT sites had higher particle density (Pd), porosity, water holding capacity, hydraulic conductivity, organic carbon, total nitrogen (N_t), available nitrogen (N_avail), phosphorus (P_avail) and exchangeable calcium (Exch. Ca⁺⁺) than 0‐YT, whereas bulk density (Bd), C : N ratio and CaCO₃ were significantly lower. Bd, pH, EC and CaCO₃ increased significantly with depth in all the lands, whereas Pd, porosity, water holding capacity, hydraulic conductivity, organic carbon, N_t, N_avail, P_avail and Exch. Ca⁺⁺ decreased. We conclude that continuous tillage and cropping can be useful for physical and chemical restoration of sodic soils. Copyright © 2014 John Wiley & Sons, Ltd.     

自控变频调速式灌溉水注肥装置的研究

为现代农业节水灌溉与精准施肥所需的配套注肥装置的开发，研究采用输液泵将肥料原液和酸碱调节液强行注入灌溉管网，并与灌溉水按比例混合获得一定浓度和酸碱度(EC & pH)的灌溉液。灌溉液浓度和酸碱度通过EC传感器和pH传感器检测并反馈PLC控制系统，通过变频调速进行EC值与pH值动态调节，实现节水灌溉系统的精准施肥灌溉。采用自控变频调速技术的灌溉水注肥装置经过实际运行，完全满足设计要求，可实现灌溉液的正常输送和EC值与pH的动态调节。特别是射流自吸泵变频调速技术的实现，不仅有效实现了灌溉液浓度（EC值）的动态调节，同时降低了设备成本，完全可用于节水灌溉注肥装置的开发。     

水稻秸秆用量对淹水培养土壤表层溶液理化性质的影响

采用模拟培养的方法,研究水稻秸秆用量对淹水培养土壤表层溶液理化性质的影响。试验根据秸秆还田量设0g·盆-1、100g·盆-1、200g·盆-1和300g·盆-14个处理,每盆装土15kg,施尿素2.8g以调节系统碳氮比,分别测定培养液的电导率、pH、全氮、全磷、全钾等指标。研究结果表明,各处理表层溶液电导率在培养初期呈上升趋势,第36d达到最大值,分别为960μs·cm-1、1150μs·cm-1、1467μs·cm-1和1620μs·cm-1,随后略有降低,到培养结束时分别为683μs·cm-1、910μs·cm-1、1083μs·cm-1和1277μs·cm-1。pH值在培养的前3d呈缓慢下降趋势,与秸秆用量呈负相关;从第4d开始pH迅速升高,16d后达到相对稳定状态,到培养结束时变化不大。施加的尿素导致各处理培养液中全氮在20d内保持较高浓度,随后全氮浓度迅速下降,到第76d,下降趋势减缓;施加秸秆对全氮浓度影响较小,施加秸秆能够提高全磷含量。秸秆中钾释放迅速,培养1d后,溶液全钾含量达到较高浓度,分别为6.87mg·L-1、36.10mg·L-1、60.27mg·L-1、114.23mg·L-1,在整个培养期全钾浓度变化不大。淹水培养条件下施加秸秆能够增加培养液中电导率、全磷及全钾浓度,与秸秆用量呈正比,但对pH、全氮影响较小。从养分流失角度考虑,控制田面养分流失主要时期为水稻秸秆还田后30d内。