围垦年限和土壤容重对海涂土壤水分运动参数的影响

为探讨围垦年限和土壤容重双因素对海涂土壤水分运动参数的影响,在室内试验的基础上结合理论计算,对海涂4个年限围垦区土壤2个不同容重下土壤导水率、水分特征曲线和扩散率的变化进行了研究。结果表明:围垦年限对土壤颗粒组成、结构及钠盐含量等影响显著,土壤饱和导水率随围垦年限的增长而减小;持水能力、土壤水分扩散率随围垦年限的增长而增大。土壤饱和导水率、吸渗率、土壤水分扩散率及相同土壤吸力下的含水率均随容重的增大而减小,随着围垦年限的增长,土壤容重对水分运动参数的影响更明显。     

Reclaiming a saline-sodic,sandy loam soil under rice production

A field-plot reclamation experiment was conducted on a virgin saline-sodic, sandy loam, permeable soil while growing rice with pre- and post-planting leaching under conditions of continuous and intermittent submergence. The soil studied contained very high amounts of soluble salts and exchangeable sodium throughout the profile. The chief salts were Cl^? and SO^2?₄ of Na⁺, Ca²⁺ and Mg²⁺. The data obtained showed that post-transplanting leaching under intermittent submergence alone progressively decreased salinity and sodicity throughout the top 100 cm of the soil to levels safe for cultivation of relatively deep-rooted crops. The surface few centimetres of soil were essentially reclaimed within a few hours after leaching so that young rice seedlings established and survived to give good yield. It was concluded, therefore, that reclamation of these types of soil in arid and semi-arid regions, where good quality water is not available for leaching prior to transplanting rice, would not require any such pre-planting leaching. The results further indicated that there is no need to apply an amendment such as gypsum, mainly because Ca²⁺ and Mg²⁺ present in such soils are adequate to replace the initially high exchangeable sodium during leaching. Leaching efficiency was high under conditions of intermittent submergence. It was shown that leaching curves could be useful in determining the amount of leaching water required for a given mode of application in order to decrease harmful levels of salinity and sodicity to safer levels for a particular crop.     

Vegetative bioremediation of calcareous sodic soils: history, mechanisms, and evaluation

Chemical amendments have been used throughout the world for almost 100 years to reclaim saline-sodic and sodic soils. Some amendments supply calcium (Ca²⁺) directly to the soil, which then replaces excess exchangeable sodium (Na⁺), while others help solubilize calcite (CaCO₃) in calcareous soils. Chemical reclamation has become costly for subsistence farmers in developing countries. Amendment costs have increased because of greater usage by industry and reductions in government subsidies to farmers. Laboratory and field research, as well as farmers' experiences, have shown that calcareous sodic soils can also be reclaimed without the application of amendments through the cultivation of certain salt-tolerant crops. This vegetative reclamation strategy is generally known as bioremediation, phytoremediation, or biological reclamation. The principal contributing mechanisms include: (1) enhanced CO₂ partial pressure in the root zone because of root and microbial respiration, which increases the solubility of calcite, and (2) improved soil physical properties due to root growth. Vegetative bioremediation can provide financial benefits from the crops grown which help to support farming operations; to some extent bioremediation is a "pay-as-you-go" option.     

刮板式水稻育苗平盘播土装置的设计与试验

分析了常用的一些水稻毯状秧苗工厂化育秧播土装置的特点，根据Mohr-Coulomb的土壤抗剪强度定律，设计出刮板式播土装置。并对生产上常用的砖红壤、水田土等床土进行了播土试验。试验表明，该播土装置能够适用于不同特性床土在不同播土量要求下的播土作业，播土均匀性较高，变异系数均小于10％，盘土厚度相差不大，符合农艺生产要求。     

Water flow and salt transport in cracking clay soils of the Imperial Valley, California

The principles of irrigation and drainage in cracking soils differ markedly from non-cracking soils, and are not thoroughly understood. This paper presents a conceptual model to simulate water and salt flows in cracking soils of the Imperial Valley, CA, in the presence of ground water that contributes partially to ET demand of crops. A salt reactivity function is introduced in the model to account for mineral precipitation (salt deposition) and mineral dissolution (salt pick up). The conceptual water flow model assumes that surface irrigation water moves into the cracks, infiltrates horizontally to wet the soil profile and a fraction bypasses below the root zone into the shallow ground water and is retained for later crop extraction via upflow. Then, water drains vertically through the soil profile step by step, and root water extractions are calculated. When ET exceeds available water upflow of ground water is calculated. Provision for reclamation leaching before the next crop is also made. The associated conceptual salt transport model involves complete mixing of invading and resident soil water. Salt concentration from ET is subjected to a salt reactivity function to obtain salt deposition of calcite and gypsum to obtain salt concentration after precipitation. This reactivity function is also used in the inverse when two or more waters mix to transform salt after precipitation to salt concentration after ET. The flow of salts follows the water transport algorithum. The model has been applied to a point in the Imperial Valley and observed data from Bali et al. (2001) was used for calibration. Simulated point data from four successive years of alfalfa, reclamation leaching, wheat and lettuce are evaluated in this paper.     

Salt leaching and the effect of gypsum application in a saline-sodic soil

Field leaching studies in representative mixed Hyperthermic Salic Calciorthids showed that for 80% reduction in profile salinity, 0.4 cm leaching water/cm soil depth was required to be passed through the soil. This corresponded to 1.14 pore volume displacement. From four different predictive models, Burns' model, which is theoretically based and requires knowledge of simple parameters, was found to be highly predictive. Dieleman's empirical relationship also adequately described field leaching data. Desalinization of the profile was accompanied by simultaneous reduction in the SAR of the soil solution. When leached in the presence of gypsum, the SAR was reduced to a greater extent in lower depths which would otherwise have been achieved by passing additional quantities of water. Results have been discussed in view of the possible need or otherwise of amendments during reclamation of soils having excess neutral salts and a high SAR of soil solution (saline-sodic soils).     

不同盐渍土中生物炭对玉米生理生长的影响

为研究适宜于不同滨海盐渍土的生物炭改良方案,以江苏滨海垦区2种典型盐渍土(粉砂壤土、砂壤土)和玉米为研究对象,设置0,25,50,75,100 g/kg生物炭水平,探讨了生物炭对不同滨海盐渍土的改良效果及玉米生理生长的影响.结果表明:生物炭添加后,土壤电导率、Na⁺质量浓度降低,Ca²⁺,Mg²⁺,K⁺质量浓度升高,0~20 cm土壤容重减小,孔隙度增大,有机质质量比升高.适量生物炭促进了玉米光合作用,叶片净光合速率、气孔导度、叶绿素质量分数有所增长.同时,生物炭降低了盐渍土对玉米的盐分胁迫,叶片脱落酸物质的量浓度及ω_Na⁺/ω_K⁺比减小,并缓解了氧化应激反应,过氧化氢、丙二醛物质的量浓度明显降低.生物炭改良效果因土壤质地而异,粉砂壤土中,生物炭不宜过多,生理生产指标在50 g/kg时达到峰值,增至75,100 g/kg时,反而导致孔隙堵塞并发生盐分累积,光合受阻,盐分胁迫、氧化损伤加剧,抑制玉米生长生产;砂壤土中,25 g/kg生物炭对土壤及玉米的影响较小,增至50 g/kg及以上时效果显著,但在75,100 g/kg间无明显差异.研究表明,粉砂壤和砂壤质地的盐渍土改良所适宜的生物炭施用量分别是50和75 g/kg.     

Residual alkalinity as tracer to estimate the changes induced by forage cultivation in a non-saline irrigated sodic soil

Soil alkalinisation generally constitutes a major threat to irrigated agriculture in the semi-arid regions of west Africa. The improvement of sodic soils is generally difficult and expensive. However, a recent study in the Niger valley in Niger, reveals that a natural de-alkalinisation is possible under natural conditions in a semi-arid climate. Transformation of non-saline sodic soil into brown steppe soil type was recorded. On the same site, the cultivation of a Sahelian fodder grass, locally known as ‘Burgu’ was used on the sodic soil/brown steppe soil transition zone to accelerate this natural de-alkalinisation and characterise its mechanisms. The geochemical properties of both soil types were monitored before cultivation and 1 year after continuous crop cultivation. After cultivation and regular irrigation, the chemical properties of the former sodic soils were close to those of the surrounding brown steppe soils, which are better suited for agriculture. This modification of the sodic soil properties can be attributed to (i) the large amount of water supplied during cultivation that induced salt leaching. This is the main phenomenon responsible for the changes observed; (ii) the root activity that modified the acid–base equilibrium and consumes alkalinity.

The residual alkalinity (RA) concept was used to select chemical tracers of the concentration/dilution of the soil solution. Here, sodium amount and calcite+fluorite residual alkalinity (RA_{calcite+fluorite}) were the most adequate ones. These two tracers decreased proportionally under the influence of leaching, but the exchanges between cations and protons changed the RA_{calcite+fluorite}, without modifying the sodium amount. Their combined use allowed us to separate and quantify the uptake of the plant from the leaching in the de-alkalinisation process. This study highlighted that reclamation of this type of sodic soils is feasible. The use of the RA concept is advisable to design a sustainable management system for irrigated sodic or saline soils.     

广东山坑渍害低产田的治理

广东省有稻田2000多万亩,其中山坑渍害低产田500多万亩。文章从两个方面,即自然条件和人为因素,分析了广东省渍害田低产成因;根据土壤特征,对山坑渍害低产田进行了分类,找出了低产的原因。就山坑渍害低产田的特点,提出了治理措施。     

四湖地区渍害低产田排水改良研究

江汉平原的四湖地区有耕地面积580万亩,渍害低产田占34.5％,成为发展农业生产的一大障碍。本文在研究渍害田分布,特征和成因的基础上,着重研究了:稻田治渍排水标准,提出适宜的垂直渗漏量是稻田治渍的重要指标;渍害稻田麦作期的地下水位控制;以及田间工程要求和田面水分管理的措施。为平原湖区渍害低产田防治提供了科学依据。     

开采沉陷区不同复垦技术下复垦土壤压实的空间变化

土壤的压实往往造成土壤结构的破坏和土壤的退化。试验对开采沉陷区采用不同复垦技术的复垦土壤进行土壤压实的测定,分析结果表明,在垂直方向上土壤的压实呈现一定的变化规律。泥浆泵复垦的田块在土壤深度5~10 cm处,平均压实度最大,在30 cm处,压实度最小,是由于含水的饱和状态泥浆难以排泄水分引起。铲运机复垦的田块和未复垦的田块,压实度随着深度的增加,压实度逐渐增加。总体上,铲运机复垦田块的平均压实度最大,其次为未复垦田块,泥浆泵复垦田块最小,通过横向对比,铲运机与未复垦田块的变化类似,压实度均呈一定范围的剧烈波动,而泥浆泵复垦田块压实度变化平缓,这与泥浆有一定的流动性有关。因此,泥浆泵复垦对土壤的破坏影响更为严重,技术存在一定的缺陷,有待进一步改进。     

Alternative cropping strategies for assured and efficient crop production in upland rainfed rice areas of eastern India based on rainfall analysis

The productivity of rice in rainfed upland soils of eastern India is very low (<1 t/ha) and unstable because of erratic monsoon, moisture deficit during dry spells, light textured with less fertile soils and several biological constraints (weeds, pests and diseases). Keeping the urgent need of augmenting the productivity of vast rainfed upland rice ecosystem of eastern India (4.3 million ha), crop diversification technology was generated through on-farm research trials in representative upland rice soils of eastern India after analyzing agro-climatic (rainfall variability, probability and onset of effective monsoon) and edaphic (soil water retention properties) constraints and prospects. Based on rainfall analysis, direct seeded, low water requiring, rice substituted alternative upland crops namely maize, groundnut, pigeonpea, greengram and blackgram (sole or intercropping) was sown in light textured upland rice soils on 24th meteorological weeks (11–17 June) in 3 years 2000–2002 with two to three summer ploughings during pre-monsoon shower (May). Study revealed that in deficit rainfall years (2000 and 2002), when rice yield was affected adversely in light textured upland, higher rice equivalent yield and rain water use efficiency were obtained from groundnut+pigeonpea intercropping followed by sole groundnut and sole pigeonpea. Study also revealed that productivity of rice substituted crops in the same upland did not fluctuate much between rainfall excess (2001) and rainfall deficit years (2002 and 2000). Double cropping in rainfed upland rice soils was also explored through maize–horsegram/sesamum rotation with increased productivity and rainwater use efficiency. The crop diversification technology was found to be very effective for drought mitigation.     

Reclamation of saline organic soil

Summary Reclamation of saline, organic soils in the Sacramento-San Joaquin Delta of California was accomplished by both sprinkling and continuously ponding water on the soil surface. The reclamation data support the generalized guideline established for saline, organic soil.A 70% reduction in the average root zone salinity required 3 months under ponding, compared to 4 months under sprinkling. Although accurate measures of water application on the ponded trials were not possible, the limited data indicate that the amount of water required is about the same per unit depth of soil reclaimed for both ponding and sprinkling. Reclamation proceeded more quickly under the second ponding trial than for sprinkling or the first ponding trial because of improved subsurface drainage. With sprinklers, 70% of the salt was removed from the soil profile to a depth of 1.2 m after 850 mm of leaching water entered the profile. Reclamation by ponding required about the same quantity of water but the water required for leaching could be reduced significantly by improved drainage.     

暗管排水改良滨海盐土及其效果分析

试区位于渤海之滨、黄河右岸的山东打渔张灌区,其潜水动态类型属灌溉、降雨——蒸发型,为半湿润季风性气候,暗管排水的工程布局为窄深式、窄浅式、宽深式。由试验分析得出了粉砂壤土地区防治盐碱化,改良后利用阶段的水盐控制标准,以及具体的适宜条件。对暗管排水改良盐土的效果进行了分析,说明了暗管排水改良盐土的机理,为类似地区盐土改良提供了科学依据。     

宁、陕大型灌区地面灌溉存在问题与对策

讨论了陕西与宁夏二省 (区 )大型灌区骨干工程、田间配套工程情况 ;土壤盐渍化发展与治理措施效果 ;井渠结合灌溉、管理体制改革经验等。分析了灌溉定额偏大及土壤盐渍化等问题的成因与危害。针对各灌区存在的实际问题 ,提出了解决的对策与措施     

A methodology for up-scaling irrigation losses

This paper presents a methodology for up-scaling field irrigation losses and quantifying relative losses at the irrigation area level for potential water savings. Two levels of analysis were considered: First, the field level where irrigation is applied. Second, the irrigation area level, where the field level losses are aggregated, or up-scaled, using average loss functions. In this up-scaling approach, detailed crop-soil-water modelling can capture the variability of physical parameters (such as soils, crops, water table depth, and management practices) at the field level which are then used to derive loss functions for aggregating losses at higher scales (irrigation area level). This allows potential field-level adaptations and water management changes made by individual farmers to be assessed for impact at the larger irrigation area level. The APSIM farming systems model was used for simulation of crops (wheat, rice, and soybean) and their interaction with the wider system processes at the field level. Given the climate, soil, and management information (sowing, fertilisation, irrigation, and residue management), the model simulates infiltration, the soil moisture profile, plant water uptake, soil evaporation, and deep drainage on a daily basis. Then, by placing the field level analysis in the context of the wider irrigation system or catchment, it is possible to correlate field level interventions (e.g. water savings measures) with water requirements at these higher levels. Application of this method in the Coleambally Irrigation Area in NSW, Australia, demonstrated that an exponential function can describe the relationship between deep drainage losses and the water table depth for different soil, crop, and water table depth combinations. The rate of loss increase (slope of the curve) with the water table depth is higher on lighter (higher intake rates) soils than on heavy soils and is more pronounced in areas under rice cultivation. We also demonstrate that this analysis technique can assist in identifying spatial distribution of losses in irrigation areas, considering water table depth as an additional factor, leading to targeted areas for water-saving measures.     

Average concentration of soluble salts in leached soils inferred from the convective–dispersive equation

The convective–dispersive, or advective–dispersive, equation (CDE) has long been the model of choice for solute transport in soils. Using the average concentration of soluble salts in soil profile to evaluate changes in salinity due to irrigation can be beneficial when spatial variability of soil salinity at selected depths is larger than spatial variability of soil salinity in the layer encompassing these depths, and when soil salinity is evaluated with electric conductivity measurements that give layer-average rather than depth-specific salinity values. The objective of this work was to present analytical solutions of the CDE that express the average soluble salt content in soil profile as the function of time, water flux, and solute dispersion parameter. The solutions were developed for both semiinfinite and finite domain and implemented in a computer code. Examples are presented of using these solutions to develop a nomogram for the dispersion coefficient estimation and to evaluate the applicability of the semiinfinite domain solution to soil monolith leaching experiments. In cases when the CDE application is justified, the analysis of the salt leaching based on the average salt concentrations in soil profile provides estimates of the effective salt dispersion parameter useful in land evaluation and soil reclamation.     

基于实测数据及遥感图片的土壤采样方法

如何结合土壤特性和先进手段,制定具有代表性,同时又经济的土壤采样方案一直是土壤分析的难题。该文根据陕西省卤泊滩盐碱地改良区土壤含盐量的实测资料和相应的遥感图片数据,并结合土壤属性空间分布特性,提出一种新的土壤水盐含量采集方案。结果表明,用33个已知点的实测数据可以估算出101个未测点的含量并最终构成插值343个点的空间分布图,且水分与盐分含量预测结果相关的确定系数分别为0.869和0.817。在此基础上进而对工程改良措施下的卤泊滩盐渍土表层水盐空间变异性进行研究。分析结果表明,研究区土壤水盐含量具有中等较强的空间自相关性和较弱的变异性。通过对该地区水盐空间变异性的研究可以及时了解盐渍地试验区的改良效果及水资源管理情况。     

In situ water transmission characteristics of a tropical soil under rice-based cropping systems

In soils under rice-based cropping systems in Asia water movement and distribution in the root zone of rice and dryland crops are important for efficient water management. Saturated hydraulic conductivities in the wetland soil profile were evaluated from measurements of hydraulic gradients and percolation rates in the field. The subsoil layer (15–60 cm) restricted percolation rate to a greater degree than the puddled top soil.Unsaturated hydraulic conductivities and soil water diffusivities in the soil profile under dryland conditions were obtained from simultaneous measurements of soil water content using the neutron moderation technique and the soil matric potential by tensiometers over time and soil depth. Soil matric potential versus hydraulic conductivity and soil water content versus soil water diffusivity relations of various soil depths were established. At equivalent soil matric potentials, the hydraulic conductivity of surface soil was greater than that of the subsoil layers. Soil water diffusivity at different depths responded similarly. The study describes a simple in situ technique to measure percolation rates in wetland rice fields and evaluation of water transmission properties of field soil profiles.     

Assessing the response of chickpea (Cicer aeritinum L.) yield to irrigation water on two soils in Punjab (India): A simulation analysis using the CROPMAN model

Shrinking water resources in northwest India calls for diversification from a rice–wheat cropping system to low-water-requiring crops and development of water-efficient technologies in Punjab state. Chickpea, because of its lower water demand (evapotranspiration) and irrigation requirement has been identified as a suitable alternate crop to wheat. Simulations, averaged over 18 years, using the CROPMAN model indicated that the yield of chickpea on coarse- to medium-textured soils was higher in a rice–chickpea cropping system compared with maize–chickpea and mung–chickpea systems because of increased availability of water. Yield response of chickpea to irrigation depended upon soil texture, the timings and number of irrigations. The optimum yield (2 t ha⁻¹) on coarse- to medium-textured soils after rice can be obtained with one heavy pre-plant and two post-plant irrigations, i.e., one in mid-February and one in mid-March synchronizing irrigations with flowering and grain development stages. Grain yield with irrigation water followed a quadratic function and linear with evapotranspiration. Water use efficiency and evapotranspiration was curvilinear. Grain yield was significantly sensitive to water stress during the pod setting to grain development period irrespective of soil texture.