Water-Saving and High-Yielding Irrigation for Lowland Rice by Controlling Limiting Values of Soil Water Potential

The present study investigated whether an irrigation system could be established to save water and increase grain yield to enhance water productivity by proper water management at the field level in irrigated lowland rice （Oryza sativa L.）. Using two field-grown rice cultivars, two irrigation systems; conventional irrigation and water-saving irrigation, were conducted. In the water-saving irrigation system, limiting values of soil water potential related to specific growth stages were proposed as irrigation indices. Compared with conventional irrigation where drainage was in mid-season and flooded at other times, the water-saving irrigation increased grain yield by 7.4% to 11.3%, reduced irrigation water by 24.5% to 29.2%, and increased water productivity （grain yield per cubic meter of irrigation water） by 43.1% to 50.3%. The water-saving irrigation significantly increased harvest index, improved milling and appearance qualities, elevated zeatin-I-zeaUn riboside concentrations in root bleedings and enhanced activities of sucrose synthase, adenosine diphosphate glucose pyrophosphorylase, starch synthase and starch branching enzyme in grains. Our results indicate that water-saving irrigation by controlling limiting values of soil water potential related to specific growth stages can enhance physiological activities of roots and grains, reduce water input, and increase grain yield.     

Water-Saving and High-Yielding Irrigation for Lowland Rice by Controlling Limiting Values of Soil Water Potential

The present study investigated whether an irrigation system could be established to save water and increase grain yield to enhance water productivity by proper water management at the field level in irrigated lowland rice (Oryza sativa L.). Using two field-grown rice cultivars, two irrigation systems; conventional irrigation and water-saving irrigation, were conducted.In the water-saving irrigation system, limiting values of soil water potential related to specific growth stages were proposed as irrigation indices. Compared with conventional irrigation where drainage was in mid-season and flooded at other times,the water-saving irrigation increased grain yield by 7.4% to 11.3%, reduced irrigation water by 24.5% to 29.2%, and increased water productivity (grain yield per cubic meter of irrigation water) by 43.1% to 50.3%. The water-saving irrigation significantly increased harvest index, improved milling and appearance qualities, elevated zeatin +zeatin riboside concentrations in root bleedings and enhanced activities of sucrose synthase, adenosine diphosphate glucose pyrophosphorylase, starch synthase and starch branching enzyme in grains. Our results indicate that water-saving irrigation by controlling limiting values of soil water potential related to specific growth stages can enhance physiological activities of roots and grains,reduce water input, and increase grain yield.     

Wheat root growth and seasonal water use as affected by irrigation under shallow water table conditions

Summary Irrigation experiments with wheat (Triticum aestivum L.) in clay loam, silty clay loam and the silty clay loam. Contrary to this, irrigation at late jointing, and late jointing and milk stages produced deepest root system in the loam. Roots followed the receding water table. was greatest in the loam. Avoiding irrigation at late jointing stage caused shifting of the zone of peak root density downwards and concentration of roots near water table both in the clay loam and the silty clay loam. Contrary to this, irrigation at late jointing, and late jointing and milk stages produced deepest root system in the loam. Roots followed the receding water table. Seasonal evapotranspiration (E) was affected by number of irrigations and water table depths. Water table contribution ranged from 61.6–64.5% of the total E in clay loam, from 39.0–46.8% of the total E in silty clay loam and from 4.0–8.1% of the total E in loam. Irrigations after late jointing contributed largely to the drainage. Yield was significantly higher in the treatments with scheduled irrigations at crown root initiation and late jointing stages in the clay loam and silty clay loam and at crown root initiation, late jointing and milk stages in the loam. This research has been financed in part by a grant made by USDA, ARS, authorized by Public Law-480     

Balinese "Water Temples" and the Management of Irrigation

Bali has figured prominently in debates on the question of whether irrigation centralizes state power. New evidence shows that irrigation is actually organized by networks of "water temples" that constitute an institutional system separate from the state. Earlier attempts to identify a discrete system of irrigation management misconceived the problem. For most crops, irrigation simply provides water for the plant's roots. But in a Balinese rice terrace, water is used to construct a complex, pulsed artificial ecosystem. Water temples manipulate the states of the system, at ascending levels in regional hierarchies. The permanence of water temple networks contrasts sharply with the instability of the traditional Balinese states. Since the water temples are real, perhaps it is the Balinese "state" that is chimerical.     

Plant Pathogens in Irrigation Water: Challenges and Opportunities

Plant pathogens in irrigation water were recognized early in the last century as a significant crop health issue. This issue has increased greatly in scope and degree of impact since that time and it will continue to be a problem as agriculture increasingly depends on the use of recycled water. Plant pathogens detected from water resources include 17 species of Phytophthora, 26 of Pythium, 27 genera of fungi, 8 species of bacteria, 10 viruses, and 13 species of plant parasitic nematodes. There is substantial evidence demonstrating that contaminated irrigation water is a primary, if not the sole, source of inoculum for Phytophthora diseases of numerous nursery, fruit, and vegetable crops. These findings pose great challenges and opportunities to the plant pathology community. A variety of water treatment methods are available but few have been assessed for agricultural purposes under commercial conditions. Investigations into their technical feasibility and economics are urgently needed. Aquatic ecology of plant pathogens is an emerging field of research that holds great promise for developing ecologically based water decontamination and other strategies of pathogen mitigation. Pathogen detection and monitoring as well as biological and economic thresholds are much-needed IPM tools and should be priorities of future research. Teaming with hydrologists, agricultural engineers, ecologists, geneticists, economists, statisticians, and farmers is essential to effectively attack such a complex issue of growing global importance. Research should proceed in conjunction with nutrient and pesticide management studies in a coordinated and comprehensive approach as they are interrelated components of water resource conservation and protection.     

农田灌溉对气候的影响研究综述

过去200年全球灌溉农田面积迅速扩张,灌溉对气候的影响逐渐受到世界各国研究者的关注。回顾了过去有关灌溉对气候的影响研究,归纳了前人的研究手段,指出了目前研究中存在的问题和困难,并提出了未来灌溉对气候的影响研究应该注重如下几个方面:1)同时利用观测数据分析方法和模型模拟研究方法进行灌溉对区域气候的影响,并将两者的结果进行对比分析,以求做到互相验证;2)对于缺乏地面观测数据或者地面数据受其他因素(比如:城市化)影响大的区域,建议利用遥感观测数据进行灌溉对地表参数的影响研究;3)注意对灌溉四大属性(灌溉位置、灌水量、灌溉方式和灌溉时间)的精确模拟,可以考虑耦合气候模型和作物模型进行模拟研究,并注意区分灌溉旱地和灌溉水田。4)提倡利用多模式集合的方式研究灌溉对区域气候的影响,以减少灌溉对气候影响(强度和方向)模拟结果的不确定性;5)未来也应该考虑模拟灌溉和气候变化间的互馈影响。     

Stomatal Infiltration in Irrigation Experiments on Cotton, Grain Sorghum, Groundnuts, Kenaf, Sesame and Wheat

Stomatal infiltration was observed in irrigation experimentson field crops of cotton, groundnuts, grain sorghum, kenaf,sesame and wheat in the Sudan. On days of peak scores afterrain or irrigation scores of all crops except groundnuts wereusually positive by sunrise. Rates of increase in score wereusually constant or decreasing through the 2 h period of themorning observations. During the midday hour there was usuallyno systematic trend and mean values of all crops except wheatwere generally about the same as at the end of the morning andbeginning of the afternoon periods of observation. Afternoonscores usually decreased linearly or approached zero at a slightlyincreasing rate but sometimes the decrease was very rapid. Peakscores were apparently not affected by fluctuations of totalirradiance of 300–1000 W m^–2 The problem of relatingscores to irradiance in the field is discussed. Scores fromall crops except kenaf tended to be smaller towards the endof the season. Flooding of the soil was followed by a largedecrease in sesame scores. Scores during the morning period increased less in unirrigatedthan in irrigated treatments in the absence of rain. The greatestdifferences between wet and dry treatments were usually duringmidday and afternoon periods. Regressions relating scores asa percentage of maximum to ‘operational’ soil watercontent were calculated. In terms of water content (0–60cm) as a percentage of oven d. wt, maximum scores were at 31–36percent; at 23–24 per cent scores of kenaf were 20 percent and of other crops 50 per cent of the maximum. The mean score indicating the level of the plateau attainedis likely to be more useful for scheduling irrigation than thetime of first positive score or the slope to it. The calculationby available statistical methods of a sample mean or differencebetween means at which irrigation should be scheduled, whencriteria for watering and withholding water at given absolutescores or differences from peak scores have been specified interms of probabilities, is described.     

Fishes, their biology and fisheries management in Lake Peipsi

The management of aquatic weeds in an irrigation scheme is constrained by the agro-economic system in relation to scheme layout, the nature and ecology of the aquatic weeds, agricultural practice, irrigation and drainage requirements, and the available resources for maintenance. The way in which the ecology, engineering and economics of irrigation and drainage channels interact to produce a pattern of management is investigated for the Mwea Irrigation Settlement Scheme, Central Province, Kenya. This is used to develop a simple model which enables the economic implications of varying the aquatic weed management practice to be identified. The model brings the selection of a weed control programme within the principles of engineering economy.     

Estimation of Infiltration Parameters and the Irrigation Coefficients with the Surface Irrigation Advance Distance

A theory based on Manning roughness equation, Philip equation and water balance equation was developed which only employed the advance distance in the calculation of the infiltration parameters and irrigation coefficients in both the border irrigation and the surge irrigation. The improved procedure was validated with both the border irrigation and surge irrigation experiments. The main results are shown as follows. Infiltration parameters of the Philip equation could be calculated accurately only using water advance distance in the irrigation process comparing to the experimental data. With the calculated parameters and the water balance equation, the irrigation coefficients were also estimated. The water advance velocity should be measured at about 0.5 m to 1.0 m far from the water advance in the experimental corn fields.     

排水沟蓄水条件下农田与排水沟水盐监测

为了查明盐碱地排水沟蓄水条件下农田与排水沟之间的水盐交换,基于两年现场观测试验数据,分析了农田与排水沟的水位响应以及电导率变化规律。结果发现:研究区排水沟蓄水条件下,相邻排水沟水位与农田地下水位变化基本一致,作物生长期较为强烈的蒸发蒸腾作用进一步降低了田间地下水位;排水沟水位变化可以直接或间接地影响周围农田的地下水位和水质状况,在无外界来水干扰的情况下,农田地下水和排水沟水样的电导率变化趋势一致,当排水沟受到外来淡水补给时,沟内浓缩的盐分得到稀释,电导率明显低于农田地下水。研究结果可为类似地区盐碱地治理和生态环境保护提供参考依据。     

Successfully Governing the Commons: Principles of Social Organization in an Andean Irrigation System

Throughout the world it is unusual to find irrigation systems that work well, distributing water efficiently and with minimal conflict, especially in situations where the resource is scarce. This paper describes one such system in the Peruvian Andes, a peasant village where irrigation and water management are handled in an unusual way. It analyzes the village principles of social organization, showing that these create a situation of equity and transparency which provides people with a strong incentive to obey the rules and conserve water. By doing so, they are directly maximizing the frequency of irrigation, a benefit that is the same for everyone using a given source of water. The system is argued to be a highly effective and sustainable way of dealing with a scarce and fluctuating resource.     

The Effect of Nitrogen Fertilization and Irrigation Frequency on Photosynthesis of Potatoes (Solanum tuberosum)

Gas exchange parameters for the potato (Solanum tuberosum L.,cv. ‘Desiree’) crop were measured under field conditions.Nitrogen nutrition was found to have a positive effect on photosynthesisthroughout the growing season. The gas exchange data and thechlorophyll content in the leaves indicated that this effectwas essentially in the mesophyll. Stomatal resistance increasedas photosynthetic rate decreased, but substomatal CO₂ concentration(Ci) was not affected by nitrogen treatments. Long term effects of water deficit on photosynthetic capacitywere also mostly mesophyllic in origin. A reduction in photosyntheticrate was observed after a period of moisture stress and alsoafter relief of drought by irrigation, indicating a limitedcapacity for recovery. A short term afternoon increase in stomatalresistance, associated with lower Ci values, occurred afterlong periods without irrigation. Leaf water potential was affectedby irrigation frequency, but less strongly than the gas exchangeparameters. Mesophyll activity and stomatal behaviour were bothaffected by water stress and by nitrogen deficiency, whereasCi values were not affected in most cases. Solanum tuberosum L, photosynthesis, mesophyll, stomata, irrigation frequency, nitrogen deficiency, chlorophyll, leaf water potential     

The Response of Groundnut (Arachis hypogaea L.) to Timing of Irrigation

A timing-of-irrigation experiment was conducted in controlled-environmentglasshouses, in which a finite quantity of water was appliedto four stands of groundnut (Arachis hypogaea L.) at differentstages of the growing season. Irrigation schedules were broadlydivided into two periods; sowing to pod initiation and pod initiationto final harvest. Within these periods two levels of soil moisturedeficit were imposed by withholding or applying limited amountsof irrigation at regular intervals. Shoot dry matter yields were hardly affected but pod yieldswere more than 4-fold lower in early- than in late-irrigatedstands. Thermal time was used to separate the effects of temperatureand water stress on developmental processes. The degree-dayrequirement for peg initiation was similar in all treatmentsbut late-irrigation delayed pod development by about 200 °Cd.The effect of timing of irrigation on pod yield operated mainlythrough its influence on the duration of pod production, whichwas closely linked to the rate and duration of canopy expansionlate in the season. The insensitivity of pod yield to earlymoisture deficits reflected the extreme plasticity of growthand development in groundnut, since most processes resumed ratessimilar to the pre-stress levels in early-irrigated stands oncestress was released. Key words: Groundnut, irrigation, growth, development     

Irrigation development in the Sahelian Countries: The Kirene District in Senegal

Sahelian decision-makers must discern whether wider adoption of irrigation techniques would relieve the existing food production crisis. This case study of the Kirene District illustrates, how, despite the capital intensive investment, the prevailing design fails to adequately adjust or reform existing institutions so as to provide incentives to farmers. Consequently, the full economic potential of irrigation remains untapped. Vested interests in the status quo to perpetuate the monopoly of the State further compromise the potential benefits that irrigation could provide.     

Trigonelline Concentration in Field-Grown Soybean in Response to Irrigation

Trigonelline (TRG) is a conjugate of nicotinic acid, and is postulated to function as a compatible solute in response to salinity- and water deficit-stresses. TRG concentrations and several agronomic characteristics were measured under irrigated field and non-irrigated field conditions within 18 soybean (Glycine max) genotypes using leaves taken from different growth stages (vegetative, flowering and pod development). Under irrigation, relative water content (RWC) ranged from 90.0 to 99.6 %. Under non-irrigation, RWC ranged from 86.3 to 97.5 %. TRG concentration ranged from 364 to 555 μg g⁻¹(d.m.) under irrigation, and from 404 to 570 μg g⁻¹(d.m.) under non-irrigation. TRG concentrations increased in the majority of genotypes (15 of 18) under non-irrigation even though RWC did not significantly differ in many genotypes between treatments. TRG decreased as plants progressed to pod development and seed filling. Mean seed yield under non-irrigated conditions declined 55 % relative to the irrigated controls. TRG concentrations among all genotypes were significantly correlated with seed yield. This revised version was published online in July 2006 with corrections to the Cover Date.     

Much Improved Irrigation Use Efficiency in an Intensive Wheat-Maize Double Cropping System in the North China Plain

Crop yield and water use efficiency （WUE） in a wheat-maize double cropping system are influenced by short and uneven rainfalls in the North China Plain （NCP）, A 2-year experiment was conducted to investigate the effects of irrigation on soil water balance, crop yield and WUE to improve irrigation use efficiency in the cropping system, Soil water depletion （~SWS） by crop generally decreased with the increase of irrigation and rainfall, while ASWS for the whole rotation was relatively stable among these irrigation treatments, High irrigations in wheat season increased initial soil moisture and ASWS for subsequent maize especially in the drought season, Initial soil water influenced mainly by the irrigation and rainfall in the previous crop season, is essential to high yield in such cropping systems, Grain yield decreased prior to evapotranspiraUon （ET） when ET reached about 300mm for wheat, while maize showed various WUEs with similar seasonal ET, For whole rotation, WUE declined when ET exceeded about 650 mm, These results indicate great potential for improving irrigation use efficiency in such wheat-maize cropping system in the NCP, Based on the present results, reasonable irrigation schedules according to different annual rainfall conditions are presented for such a cropping system.     

Much Improved Irrigation Use Efficiency in an Intensive Wheat-Maize Double Cropping System in the North China Plain

Crop yield and water use efficiency (WUE) in a wheat-maize double cropping system are influenced by short and uneven rainfalls in the North China Plain (NCP). A 2-year experiment was conducted to investigate the effects of irrigation on soil water balance, crop yield and WUE to improve irrigation use efficiency in the cropping system. Soil water depletion (△SWS)by crop generally decreased with the increase of irrigation and rainfall, while △SWS for the whole rotation was relatively stable among these irrigation treatments. High irrigations in wheat season increased initial soil moisture and △SWS for subsequent maize especially in the drought season. Initial soil water influenced mainly by the irrigation and rainfall in the previous crop season, is essential to high yield in such cropping systems. Grain yield decreased prior to evapotranspiration(ET) when ET reached about 300 mm for wheat, while maize showed various WUEs with similar seasonal ET. For whole rotation, WUE declined when ET exceeded about 650 mm. These results indicate great potential for improving irrigation use efficiency in such wheat-maize cropping system in the NCP. Based on the present results, reasonable irrigation schedules according to different annual rainfall conditions are presented for such a cropping system.     

Deficit Irrigation as a Strategy to Save Water： Physiology and Potential Application to Horticulture

Water is an increasingly scarce resource worldwide and irrigated agriculture remains one of the largest and most inefficient users of this resource. Low water use efficiency （WUE） together with an increased competition for water resources with other sectors （e.g. tourism or industry） are forcing growers to adopt new irrigation and cultivation practices that use water more judiciously. In areas with dry and hot climates, drip irrigation and protected cultivation have improved WUE mainly by reducing runoff and evapotranspiration losses. However, complementary approaches are still needed to increase WUE in irrigated agriculture. Deficit irrigation strategies like regulated deficit irrigation or partial root drying have emerged as potential ways to increase water savings in agriculture by allowing crops to withstand mild water stress with no or only marginal decreases of yield and quality. Grapevine and several fruit tree crops seem to be well adapted to deficit irrigation, but other crops like vegetables tend not to cope so well due to losses in yield and quality. This paper aims at providing an overview of the physiological basis of deficit irrigation strategies and their potential for horticulture by describing the major consequences of their use to vegetative growth, yield and quality of different crops （fruits, vegetables and ornamentals）.     

Irrigated agriculture and freshwater wetlands: A struggle for coexistence in the western United States

This paper is a review of the major environmental problems associated with irrigated agriculture in the western United States. Freshwater wetlands are being contaminated by subsurface agricultural irrigation drainage in many locations. Historic freshwater inflows have been diverted for agricultural use, and remaining freshwater supplies are not sufficient to maintain these important natural areas once they are degraded by irrigation drainage. Migratory birds have been poisoned by drainwater contaminants on at least six national wildlife refuges; waterfowl populations are threatened in the Pacific and Central flyways. Revised water allocation policies and regulatory actions are probably necessary to correct existing damage and prevent future problems. The benefits of maintaining healthy wetlands should be used as a rationale for negotiating increases in freshwater supplies. Cost analyses that show the importance of wetlands in dollar values are critical to the success of these negotiations. The next few years will provide unique opportunities for wetland managers to use cost analyses to make changes in water allocation policies. Federally subsidized water has supported and expanded agriculture at the expense of native wetlands for over 100 years in the western United States. This trend must be reversed if these wetlands and their fish and wildlife populations are to survive.