Changes in soil properties at different levels of soil structural arrangement under the impact of irrigation

Processes taking place at different levels of the soil structural arrangement in irrigated and rainfed soils of the Lower Volga region are analyzed. Interactions between these processes and the dependence of their rates on the duration of irrigation are discussed. It is shown that irrigation-induced changes are more pronounced and proceed faster in soils of poorly drained landscapes in comparison with well-drained landscapes. Interaction of the processes taking place at different hierarchical levels of soil arrangement is observed. At the ionic-molecular level, migration and transformation of the composition of soil humus and soluble salts and various exchange reactions take place; at the level of elementary soil particles, the processes of disintegration, peptization, transformation, and the destruction of minerals; at the aggregate level, changes in the water stability of soil aggregates and the degree of soil micro- and macroaggregation; at the level of particular morphological elements, horizons, and pedons, reorganization of soil material (changes in the thickness and bulk density of soil horizons, synthesis and destruction of various neoformations, etc.); finally, at the level of the soil cover pattern, irrigation leads to a higher complexity of the soil cover; the degree of contrast in the soil cover pattern increases, and the soil development at different sites proceeds with different velocities.     

Studies on the gley formation of soils I

Generally, by the stoppage of flood irrigation after the rice growing season, the excess water in paddy field soils is gradually drained off as the ground water level sinks, and soils of plowed layer are generally kept under the oxidised condition due to the introduction of oxygen from the surface of soils during the unirrigated period.     

Environmental Mobility of Radiocaesium in the Pripyat Catchment,Ukraine/Belarus

Evidence from research in the Pripyat catchment, reviewed here, indicates that under the ecological conditions prevalent in this area, radiocaesium (137Cs) is highly mobile in both river water and poorly drained organic soils. Data collected at three different spatial and temporal scales demonstrate the effects of hydrological events on 137Cs mobility. During the period 1988–1994, 137Cs contamination in some poorly drained organic soils in the Pripyat catchment and in the milk from cows grazing on these soils are generally declining much faster than the radioactive half life. However, sharp increases in levels of 137Cs in both floodplain soils and milk to 2–3 times that observed immediately after the initial deposition have been measured immediately after summer floods. The processes causing these observed changes have not yet been fully explained but the sites where enhanced 137Cs mobility has been detected are clearly associated with the spatial patterns of organic soils and river flooding.     

Degradation of soils as a result of human-induced transformation of their water regime and soil-protective practice

The adverse human-induced changes in the water regime of soils leading to their degradation are considered. Factors of the human activity related to the water industry, agriculture, and silviculture are shown to play the most active role in the soil degradation. Among them are the large-scale hydraulic works on rivers, drainage and irrigation of soils, ameliorative and agricultural impacts, road construction, and uncontrolled impacts of industry and silviculture on the environment. The reasons for each case of soil degradation related to changes in the soil water regime are considered, and preventive measures are proposed. The role of secondary soil degradation processes is shown.     

Advances in the prognosis of soil sodicity under dryland irrigated conditions

Salt-affected soils, both saline and sodic, may develop under both dryland and irrigated conditions, affecting the physical and chemical soil properties, with negative consequences in the environment, in crop production and in animal and human health. Among the development processes of salt-affected soils, the processes of sodification have generally received less attention and are less understood than the development of saline soils. Although in both, hydrological processes are involved in their development, in the case of sodic soils we have to consider some additional chemical and physicochemical reactions, making more difficult their modeling and prediction. This is especially true where we have to consider the effects of the groundwater level and composition. In this contribution there are presented three case studies: one related to the development of sodic soils in the lowlands of the Argentina Pampas, under dry-land conditions with sub-humid temperate climate and pastures for cattle production; the second deals with the development of sodic soils in the Colombia Cauca Valley, under irrigated conditions and tropical sub-humid climate, in lands used for sugarcane cropping dedicated to sugar and ethanol production; and the last one related to the sodification of soils in the Western Plains of Venezuela, under irrigated conditions, sub-humid tropical climate and continuous cropping of rice under flooding. The development of sodicity in the surface soil is partially related to the composition and level of the ground-water, mainly affected in the Argentina case by drainage conditions, in the case of Colombia to the inefficient irrigation and inadequate drainage, and in the case of Venezuela to the soil management and irrigation system. There is shown how the model SALSODIMAR, developed by the author, based on the balance of water and soluble components of both irrigation water and ground-water, under different water and land management conditions, may be successfully adapted for the diagnosis and prediction of the different processes and problems, and for selection of alternatives for their prevention and amelioration.     

Preferential flow in a well drained and a poorly drained soil under different overhead irrigation regimes

Abstract. There is environmental concern about the increasing land application of dairy shed effluent in New Zealand. To minimize groundwater contamination by applied nutrients and pathogens it is desirable to avoid preferential flow through topsoils. Our objective was to determine an irrigation rate that retained applied effluent in the topsoil of two commonly irrigated New Zealand soils. In a field experiment, well drained Horotiu soils and poorly drained Te Kowhai soils were irrigated with a pyranine dye/KBr tracer solution at four rates (5, 10, 15, 20 mm/h) using a drip-type rainfall simulator. Twenty minutes after irrigation ceased the soil was excavated horizontally at 25 or 50 mm intervals, and photographed under UV light until no further fluorescence was vishle. Each layer was also analysed for bromide content, without subsampling. The wetting pattern was uneven in both soils as leachate moved preferentially through worm channels and structural cracks. Preferential flow was greatest in the Te Kowhai soil and increased at faster application rates. Dye fluorescence was curvilinearly related to bromide concentration. At both study sites, maintaining the irrigation rate at 10 mm/h minimized leachate movement into the subsoil. Pulsed irrigation at faster rates was not retained in the topsoil.     

Ecological-hydrological and genetic features of the soils of the Tambov Plain

Specific features of the genesis of chernozem-like, solonetzic chernozem-like soils, and hydromorphic chernozem-like solonetzes were investigated on the southern Tambov Plain. Typical chernozems occupy well drained areas. The yield of cereals is limited by the amount of precipitation. On the flat surface of weakly drained watersheds, deeply gleyed chernozem-like soils are formed under the influence of bicarbonate-calcium ground water and water stagnation on the plow sole. In closed depressions with the 1.5- to 2.0-month long stagnation of surface water on the compact lower horizons, podzolized gleyic chernozem-like soils are formed. They have favorable physical properties, weak eluvial differentiation, and rather high acidity. In humid and moderately humid years, the cereals on these soils are waterlogged; in dry years, their yield increases by 20% as compared to that on the typical chernozem. In the low undrained areas of the watersheds, solonetzic chernozem-like soils and hydromorphic chernozem-like solonetzes are formed under the influence of bicarbonate-sodium water. Despite the unfavorable physical properties of the solonetzic horizons, their better supply with moisture determines the possibility to obtain stable high yields of cereals on the solonetzic chernozem-like soils. The productivity of the gleyic chernozem-like solonetzes is low irrespective of the humidity of the year.     

模拟再生水灌溉下污灌土壤中盐分离子交换运移的试验研究

为研究再生水灌溉下原污灌区土壤中主要盐分离子交换运移规律,采用有污水灌溉背景的两种质地土壤,根据再生水的基本性质及其盐分离子组分,配制4种浓度水平的入渗液,进行土柱模拟试验。结果表明,不同质地土壤在低Na^＋配制液淋洗下的穿透曲线都出现下凹现象,但Na^＋在壤土中富集的表现并不显著,而在粉质砂壤土中部分Na^＋吸附累积时间较长;模拟再生水入渗溶液中不同组分的盐分离子在不同程度上影响污灌土壤中发生的离子化学反应的进行,导致各处理下Na穿透时间发生显著差异;长期再生水灌溉会对HCO3^-含量较高且粉粒比重大的土壤的入渗等性能产生更为不利的影响。     

Water retention of light expanded clay amendment

Abstract

Shallow‐drained horticultural soils utilized in containers, sporting areas, and landscape sites tend to retain excess water and thereby be poorly aerated as a consequence of capillary retention following irrigation or precipitation. This problem is usually corrected by soil physical amendment with coarse‐textured particulates to add large pores which drain and provide adequate aeration. A variety of materials are used for soil physical amendment. This study examined the water retention of one of the newer amendments used for this purpose, light expanded clay amendment (LECA), relative to its use in shallow‐drained soils. Although LECA is a porous material, its contribution to soil physical properties when used as an amendment were found to be similar to non‐porous amendments such as river sand or gravel because the internal water is not readily available for plant use.     

Irrigation of steppe soils in the south of Russia: Problems and solutions (Analysis of Irrigation Practices in 1950–1990)

Experience in irrigation of chernozems in the steppe zone of Russia for a period from 1950 to 1990 is analyzed. By the end of this period and in the subsequent years, the areas under irrigation reduced considerably, and the soil productivity worsened. This was caused by the improper design of irrigation systems, on the one hand, and by the low tolerance of chernozems toward increased moistening upon irrigation, on the other hand. The analysis of the factors and regimes of soil formation under irrigation conditions shows that irrigation-induced changes in the soil hydrology also lead to changes in the soil physicochemical, biochemical, and other properties. In particular, changes in the composition of exchangeable cations lead to the development of solonetzic process. In many areas, irrigation of chernozems was accompanied by the appearance of solonetzic, vertic, saline, and eroded soils. The development of soil degradation processes is described. In general, the deterioration of irrigated chernozems was related to the absence of adequate experience in irrigation of steppe soils, unskilled personnel, improper regime of irrigation, and excessively high rates of watering. In some cases, the poor quality of irrigation water resulted in the development of soil salinization and alkalization. To improve the situation, the training of personnel is necessary; the strategy of continuous irrigation should be replaced by the strategy of supplementary irrigation in the critical periods of crop development.     

Salinity and sodicity induced changes in dispersible clay and saturated hydraulic conductivity in sulfatic soils

Abstract

Irrigation is becoming a more commonly used practice on glacially derived soils of the Northern Great Plains. Threshold salinity and sodicity water quality criteria for soil‐water compatibility in these sulfatic soils are not well defined. This study was conducted to relate soil salinity and sodicity to clay dispersion and saturated hydraulic conductivity (K_sat) in four representative soils. Soil salinity (EC treatment levels of 0.1 and 0.4 S m^‐1) and sodicity (SAR treatment levels of 3, 9, and 15) levels were established to produce a range of conditions similar to those that might be found under irrigation. The response of each soil to changes in salinity and sodicity was unique. In general, as sodicity increased clay dispersion also increase, but the magnitude of the increase varied among the soils. In two of the soils, clay dispersion across a range of sodicity levels was lower under the 0.4 S m^‐1 treatment than under the 0.1 S m^‐1 treatment and in the other two soils, clay dispersion across a range of sodicity levels was similar between the two salinity treatments. Changes in K_sat were greatest in the finer textured soil (decreasing an order of magnitude across the range of sodicity levels), but was unchanged in the coarse textured soils. Results suggest that these sulfatic soils are more susceptible to sodicity induced deterioration than chloridic soils. These results and earlier field observations suggest that sustainable irrigation may be limited to sites with a water source having a SAR <5 and an EC not exceeding 0.3 S m^‐1 for these sulfatic glacially derived soils.     

不同土壤水分供给下水稻叶水势的变化规律

用中9B和金早47在温室及网室条件下,设置4个水分处理,对不同生育期的叶水势进行测定.结果表明,不同水分处理下,主要生育期的叶水势日变化表现为早晨和傍晚较大,而在中午前后较小,呈现反抛物线的曲线走向,中午前后是叶水势曲线拐点.水稻叶水势随着土壤水分含量的下降而降低,土壤保持湿润处理和淹水处理的水稻叶水势差异不明显,而水...     

灌溉排水耦合调控稻田水分转化关系

该文利用装配有地下水位自动控制系统的蒸渗仪,分析节水灌溉与旱地控制排水技术耦合调控对于稻田水分转化关系的影响。结果表明,灌排耦合调控在小幅减少水稻产量的同时,显著减少了稻田灌溉水量、地下排水量及水稻蒸发蒸腾量,最终显著增加了水稻水分生产效率。与常规灌排稻田相比,灌排耦合调控稻田水稻产量减少1.9%,灌溉水量、地下排水量及水稻蒸发蒸腾量分别显著减少41.7%、49.9%及24.9%,水分生产效率增加30.5%。随着控灌稻田排水控制限的提高,稻田灌溉水量、地下排水量及水稻蒸发蒸腾量减少,水稻产量保持稳定,使得水稻水分生产效率进一步增加。提高控灌稻田的排水控制限,减缓了稻田土壤水分的衰退速度,并增加稻田地下水位低于排水控制限的比例,稻田灌溉次数与发生地下排水的时段均减少,使得控灌稻田灌溉水量与地下排水量下降,两者综合作用下控灌稻田水稻蒸发蒸腾量减少。在采用控制灌溉模式的基础上,适当提高稻田排水控制限,可以较好地实现水稻生产中水分的高效利用,研究结果可为优化稻田水管理模式提供依据。     

Changes in the probability distributions of particle size fractions in chestnut soils of the Kulunda Steppe under the effect of natural and anthropogenic factors

The stability of soil is considered as an ability to retain its properties and structural organization within the range of natural variation. Changes in the probability distribution and statistical entropy of properties, which are considered as regular properties of open systems, were used as criteria for assessing soil stability in natural and anthropogenic processes. It was theoretically shown that the steady states of geosystems, including that of particle size composition, are characterized by minimum changes in statistical entropy. The probability distribution and statistical entropy of particle size distributions in the Kulunda Steppe chestnut soils and their changes under anthropogenic impacts were studied. Heavy deflation in the 1950s–1960s resulted in the reorganization of the probability distribution of the physical sand fraction, without significant changes in the probability distribution of physical clay; the statistical entropy of all fractions increased by 6%. The long-term plowing entailed a small shift in the probability distribution of physical clay; the statistical entropy of these fractions decreased by 12%, and that of physical sand decreased by 6%. Irrigation with low-saline water entailed a significant shift in the probability distributions of fine sand and silt; the statistical entropy changed by 50–70%. Hence, the particle size distribution showed stability during deflation and long-term use of plowland and did not show it under irrigation.     

Effects of prolonged irrigation on the humus of steppe soils in southwest Siberia

Changes in humus resulting from up to 20 years' irrigation with slightly saline water were studied in dry steppe soils in southwest Siberia. The amounts of brown humic acids and of the Pg fraction increased with the period of irrigation, and their maximum amounts occurred at greater depths in the profile. Other fractions of humus and humic acids fluctuated within the limits typical of dry steppe soils. The humus therefore remained essentially stable under irrigation for up to 20 years.     

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.     

福建典型烟区土壤、灌溉水和肥料中重金属含量调查

农作物体内的重金属主要来自土壤、施肥、大气沉降以及降雨或灌溉.本文采集了福建省主要的烟草肥料和全国清香型烤烟的代表之一福建省龙岩市永定县土壤和烟田灌溉水体样品,分析了其中的重金属含量,并与国家相应标准中的限量进行了对比.结果表明:①烟田土壤中As含量为限量标准的12.3％ ～ 65.0％,Cd为66.7％ ～ 100.0％,Cr为4.0％ ～ 47.3％,Hg为0～ 66.7％,Pb为0.3％ ～ 63.3％,目前尚均属安全级别,但个别烟田的土壤As、Cd、Hg、Pb含量偏高;②烟草肥料中As含量为限量标准的0.7％ ～ 24.0％,Cd为0.5％～2.1％,Cr为0～ 21.4％,Hg为0～ 4.8％,Pb为7.7％ ～ 50.6％,目前尚均属安全级别,但一种钙镁磷肥中的Pb含量略高;③灌溉水体中As含量为限量标准的0～0.5％,Cd为0.1％～5.8％,Cr为0.3％～ 1.6％,Hg为8.6％ ～ 55.4％,Pb为0～ 2.6％,绝大部分灌溉水体中重金属含量远低于限量标准,均属安全级别.     

地下水埋深和灌水频率对土壤溶质(Br-)运移的影响

通过室内均质土柱试验,以Br-为示踪剂,研究了90 mm/15 d和30 mm/5 d两种灌水频率下,1.7,1.2,0.8 m地下水埋深土壤中溶质(Br-)的运移规律。结果表明:不同地下水埋深或同一地下水埋深条件下,高、低灌水频率土壤中溶质运移快慢的趋势是变化的。地下水埋深由深变浅,高灌水频率土壤中溶质(Br-)运移由慢于低灌水频率逐渐转变为快于低灌水频率;高灌水频率土壤中Br-较集中地向下运移,低灌水频率土壤中地下水埋深越大,Br-分布越均匀分散;高灌水频率不利于土壤溶质(Br-)积聚于土表。     

Pore size distribution measurements in swell-shrink soils

A method for the determination of pore size distribution in swell-shrink soils was described. Undisturbed core samples, saturated and drained at 1.5 MPa suction, were filled with a non-polar liquid (xylol), and its retention at suctions lower than 1.5 MPa was measured. Oven dry samples were analyzed in the same way. Derived pore size distributions were compared with those obtained by water desorption. Pore size distributions and their relative changes as a function of water content were related to some soil constituents and properties. Stability factor and sum of montmorillonite and vermiculite significantly influenced the pore size distribution by water release, A higher stability factor resulted in lower relative changes (ratios) in the pore size classes <10 μm and 0.2–10 μm when the samples were drained from saturation to 1.5 MPa suction, however, at extreme dryness, the relative changes were positively correlated to the sum of montmorillonite and vermiculite.     

初始含水率对土壤垂直线源入渗特征的影响

为解决现有渗灌系统在深根系植物应用中存在的问题,该文设计了一种垂直线源灌水器,并通过室内土箱试验研究了不同初始含水率条件下砂黄土和塿土的垂直线源入渗特征。结果表明：Philip入渗公式的形式能够较好地描述2种土壤的三维入渗过程;入渗时间一定时,砂黄土和塿土的累积入渗量均与初始含水率之间呈二次函数递减关系;2种土壤入渗的最大径向距离、最大垂向距离、宽深比均与初始含水率之间呈二次函数抛物线关系;2种土壤相比,偏砂性的砂黄土累积入渗量在低初始含水率下较塿土大,但随着初始含水率的增加其减小速度较塿土快,偏黏重的塿土入渗临界初始含水率较砂黄土大,但其入渗范围较砂黄土小。这些结果可为不同土壤条件下的垂直线源灌水技术发展提供参考。