Every-other-furrow irrigation with different irrigation intervals for grain sorghum

The water stress effects caused by every-other-furrow irrigation on yield may be alleviated by more frequent irrigation intervals. This research was conducted to determine yield and water use efficiency of grain sorghum under fixed and variable every-other-furrow and every furrow irrigations at different irrigation intervals and shallow and deep water table conditions. Water needs of grain sorghum grown on a fine-texture soil may not be met by using Every-Other Furrow Irrigation (EOFI) especially under 15 and 20 day irrigation intervals. The water stress decreased the grain yield mainly through decreasing the number of grains per cluster and in a lesser degree by decrease in 1000-seed weight. The clay soil with a layer of high clay content at depth of 70-100 cm and shallow water table may restrict the root growth and consequently the longer irrigation intervals with greater soil water stress can cause lower grain yield in these conditions. However, more frequent EOFI using 10 day intervals has produced very similar results with only a marginal reduction in crop yield. Furthermore, there was no statistically significant difference in grain yield between fixed and variable every-other -furrow irrigations. In general, at given applied water, the relative grain yield with respect to the maximum grain yield of sorghum at EOFI was higher than those at EFI. At relative applied water of 85% (mild deficit irrigation), EOFI may be recommended to obtain the same grain yield as that of EFI with full irrigation. Furthermore, it may result in 23% more grain yield than that obtained by EFI with the same amount of applied water as deficit irrigation.     

Issues of scale in water productivity in the Zhanghe irrigation system: implications for irrigation in the basin context

In the context of increased competition for water, growing more rice with less water will be one of the major challenges of the 21st century. This paper examines water savings and issues of scale in water productivity. The main objective is to understand if and how field-scale interventions scale up to subbasin-scale water savings in the Zhanghe Irrigation District (ZID) in Hubei Province, central China. Our results confirmed that on-farm water-saving practices result in higher water productivity per unit of irrigation water at the field scale due to lower irrigation water input. However, the question is, if these field-scale practices have led to real water savings; savings which can be transferred to other agricultural and non-agricultural uses without lowering existing production levels. To investigate this question, we examined water use and productivity at four different scales: field scale, meso scale, main canal command scale, and subbasin scale using the water accounting methodology. The study clearly demonstrates the high dependence on the scale of water use and productivity parameters. Depleted fraction and water productivity per unit of gross inflow and irrigation water varied dramatically across scale. Thus, it is not possible to conclude from field-scale observations that basin level water savings will or will not take place. The major reasons for these scale effects are the lateral flow of water across boundaries, differing land use patterns across scales, and changing water management patterns across scales. In the ZID, going from field and meso scale to even larger scales, water productivity per unit of irrigation increases to even higher levels than at the field scale. Here it becomes clear that the ZID, with its possibilities of reuse of drainage return flows and capturing rainfall and runoff in all the reservoirs within the system, is very effective in capturing and using water productively. Factors that influence water productivity and depleted fraction are on-farm water savings as well as the reuse of drainage water, effective capturing and utilization of rain, and canal water management. The scope for additional real water savings in the Zhanghe Irrigation District is limited. Only 13% of the combined rainfall and Zhanghe reservoir irrigation water releases flow out of the basin. A further reduction in drainage surface outflow from the ZID may have negative downstream effects on other water uses, including environmental uses. The main lessons learned are that (1) employing a combination of factors—on-farm practices, reuse, and canal operations—can be an effective means of conserving water resources within irrigation systems, (2) the scope for savings must be considered by an analysis at larger scales (i.e. irrigation system or basin scale), and may be less than thought because of the interactions of these factors. The results clearly indicate that scale effects are important for understanding and planning for water savings and water productivity.     

New performance indicators for rice-based irrigation systems

Various indicators are used for evaluating the performance of different aspects of an irrigation system. This study proposes rice relative water supply (RRWS) and cumulative rice relative water supply (CRRWS) indicators to characterize the irrigation water delivery performance as the season advances in rice irrigation systems. These indicators were determined from field tests and evaluated. Traditionally, some standing water depth is kept in the field throughout the irrigation season. Some water is continuously delivered to maintain the standing water depth in the field due to the difference between the maximum standing water depth (WSmax _j ) and the present standing water depth (WS _j ). The widely used relative water supply (RWS) concept is found to incorrectly characterize an oversupply condition on irrigation deliveries for not considering the additional water supply to maintain standing water. Consequently, the cumulative relative water supply (CRWS) gives a wrong scenario in characterizing irrigation delivery performance throughout the season. The RRWS, on the other hand, distinctly characterizes the oversupply and undersupply condition on irrigation delivery as the season advances. A value of 1.0 for RRWS indicates an irrigation delivery that perfectly matches with the field water demand. Both in the main and off-season, RWS remains higher than RRWS during depletion periods (WS _j −WS _j ). On the other hand, the values of RWS and CRWS were higher than RRWS and CRRWS during 3rd to 6th weeks in the main season; and 3rd to 7th weeks in the off-season. The proposed indicators were found to be useful to enhance the decision-making and operational strategy for delivering the right amount of water to the fields for the upcoming period.     

Transferring water from irrigation to higher valued uses: a case study of the Zhanghe irrigation system in China

The Zhanghe irrigation system (ZIS) is located in the Yangtze River Basin approximately 200 km west of Wuhan in Hubei Province. The reservoir was designed for multiple uses—irrigation, flood control, domestic water supply, industrial use, aquaculture, and hydropower. Over a period of more than 30 years a steadily increasing amount of water has been transferred from irrigation to other uses. Activities on the part of government, irrigation system managers, and farmers made this transfer possible with only modest decline in rice production. Most important factor was the steady increase in rice yields. The water pricing system provided an incentive for ZIS to reduce irrigation releases. With the steady decline in releases, farmers were forced to find ways to save water. Farmers improved existing ponds and built new ones to store water (improved infrastructure). Access to pond water on demand facilitated the adoption of alternate wetting and drying (technology) particularly in dry years. The establishment of volumetric pricing (price policy) and water user associations (institutions) may also have provided incentives for adoption of AWD, but more research is needed to establish their impact. These activities taken together can be seen as potentially complementary measures. Farmers received no direct compensation for the transfer of water, but recently farm taxes have been reduced or altogether abolished. Further reduction in water releases from the ZIS reservoir could adversely affect rice production in normal or dry years.     

山区茶园喷灌技术

本文针对山区特点,探索总结山区茶园节水喷灌技术,该技术利用山区自然水源,具有节水,投资少,省工省力,增产增效的优点,适宜在山区大力推广应用。     

Evaluation of irrigation water requirements and crop yields with different irrigation schedules for paddy fields in ChiaNan irrigated area,Taiwan

Recent water shortages in reservoirs have caused such problems as insufficient water and fallow rice fields in Southern Taiwan; therefore, comparing irrigation water requirements and crop production of paddy fields using a technique that differs from the conventional flood irrigation method is important. Field experiments for the second paddy field with four irrigation schedules and two repeated treatments were conducted at the HsuehChia Experiment Station, ChiaNan Irrigation Association, Taiwan. Experimental results demonstrate that irrigation water requirements for the comparison method, and 7-, 10- and 15-day irrigation schedules were 1248, 993, 848, and 718 mm, respectively. Compared to the conventional method of flooding fields at a 7-day interval, the 10- and 15-day irrigation schedules reduced water requirements by 14.6 and 27.3 %, respectively; however, crop yields decreased by 7 and 15 %, respectively. Based on the results, it was recommended that the ChaiNan Irrigation Association could adopt 10 days irrigation schedule and plant drought-enduring paddy to save irrigation water requirements for the water resource scarcity in southern Taiwan. The CROPWAT model was utilized to simulate the on-farm water balance with a 10-day irrigation schedule for the second paddy field. A comparison of net irrigation water requirements with the 10-day irrigation schedule from model and field experiment were 818 and 848 mm, respectively, and the error was 3.54 %.     

Economic assessment of water-saving irrigation management techniques and continuous flooded irrigation in different rice production systems

Paddy and Water Environment - Globally, increasing water scarcity and higher production costs are the challenges in the cultivation of conventional transplanted rice (TPR). Under such conditions,...     

A GIS-based framework of regional irrigation water demand assessment

Although a lot of research has been performed on estimating irrigation water demand at the on-farm level, far less has been done on irrigation water demand for a region-wide basis, such as for a river basin or an area covering multiple river basins. The capture and management of the spatial variations in related data such as soil, climate, crops, and canal networks is the key to effective and efficient regional irrigation water demand estimations. The Geographic Information System (GIS), with its powerful spatial data management and analysis capabilities is used in this study to extend the scope of on-farm irrigation water estimation into a regional estimation. A command area covering several river basins in southern Taiwan was used to build a model prototype. The model framework shows the capability of the system to estimate regional irrigation water demand with most of the spatial variations preserved. The model also shows the capability for quickly reflecting changes in irrigation water demand in response to changes in cropping patterns, a feature that may be a necessary for regional water resource planning.     

The reasonable scale of water reuse system in irrigation area: a case study of Chitong irrigation district in Taiwan

The aim of this study is to assess the potential of the irrigation return-flow in a water reuse system, for the supply of other local water users. Both field survey and water-budget analysis were conducted, and the Chitong irrigation district in Taiwan was selected as the case study area. The results indicate that through the regulation of a pond with the effective capacity of 20,000 m³, a stable supply of 10,000 CMD of reuse water can be generated if the return-flow from the irrigation area of 200 hectares, which is about the size of a rotation plot, is intercepted. However, as the irrigation and effective rainfall are low from December to March, which are considered high risk for water supply, the irrigation return-flow decreases accordingly, and a series of responding measures are also suggested.     

汉沽管理区农田水利发展状况

揭示出汉沽管理区地理位置和自然旱灾引起的海水倒灌，地上水盐分超标，以及地下水开采超量等原因所造成的水少、水暴、水脏三大问题，启示人们应从全局和战略高度提高认识，加强农田水利基本建设。并总结了近年来管理区农田水利发展的经验，提出了今后的发展规划。     

Characteristics of paddy irrigation in Taiwan

Paddy and water environment are closely related to each other in Asia. Developing agriculture by way of construction of farmland irrigation works has long been the principal objective of policies in Taiwan. Owing to significant temporal and spatial difference in rainfalls, natural river runoff has hardly corresponded with irrigation requirements. The cultivation of rice paddies and upland crops are practiced according to the state of the water sources, and cultivation patterns and irrigation systems are framed by placing the same importance on the role of irrigation and drainage management. In this article, the characteristics of paddy irrigation in Taiwan, distinguishable from the western arid farming, have been categorized and will be reviewed in terms of irrigation development, agricultural water utilization, equitable distribution management, farmland consolidation, and the Irrigation Association with its role as that of a public juridical body.Dr. Tsai is the Chief of Irrigation and Engineering Division, Council of Agriculture (COA), Executive Yuan, Taiwan, R.O.C, and also serves as the president of the Chinese Society of Agricultural Engineers (CSAE), the Vice-President of the International Society of Paddy and Water Environment Engineering, the vice-president of International Commission on Irrigation and Drainage (ICID) Chinese Taipei Committee, Managing Supervisor of Chinese Water Resources Management Society. He has an M.Sc. diploma in agricultural engineering from the National Taiwan University and in 1990 he received his Ph.D. degree in natural science and technology from Okayama University, Japan.     

汉沽管理区农田水利发展状况

揭示出汉沽管理区地理位置和自然旱灾引起的海水倒灌、地上水盐分超标,以及地下水开采超量等原因所造成的水少、水暴、水脏三大问题,启示人们应从全局和战略高度提高认识,加强农田水利基本建设。并总结了近年来管理区农田水利发展的经验,提出了今后的发展规划。     

Infiltration properties of paddy fields under intermittent irrigation

Puddling and recurring intermittent irrigation, common praxis in wet rice cultivation, modify the soil structure and therewith cause a temporal variation of the infiltration properties. This study attempts to evaluate the temporal variation of the infiltration rates of plough pan (vertical infiltration) and paddy fields’ surrounding bunds (bund infiltration) by analyzing (i) the infiltration rate as a function of time, (ii) the relationship between ponding water depth and infiltration rate, and (iii) the influence of cultivation age on vertical water loss and cross-flow through bunds. Two experimental fields with respective cultivation ages of 30 (A) and 7 (B) years were investigated. The results revealed that the time series of vertical infiltration rate (IR _v) was with time consistency and the persistency of the bund infiltration was uncertain. The mean infiltration rate into the plough pan of A and B was 3.34 and 1.01 cm d^?1, respectively. A total water depth of 230 and 85 cm would be, respectively, lost in A and B through the plough pan during rice growing season. The correlation coefficient between ponding water depth and IR _v was ?0.48 and ?0.81 in A and B, respectively, demonstrating that the dynamic IR _v in the old paddy field was less affected by the drying and wetting cycles. It is concluded that rice paddies which have been taken into cultivation since only a few decades may contribute to water losses. Maintenance of equilibrium condition between ponding and drying stages and careful preparation of bunds may reduce water loss.     

Longwave radiation environment of an irrigation reservoir surrounded by mountains

In areas where irrigation facilities are not available or in mountainous areas, reservoirs are used for paddy rice culture in Japan. Water temperature must be adequately maintained because it affects water quality and has a significant impact on the growth and yield of the rice crop. Stratification of water in a reservoir occurs due to heat storage on the water surface by solar radiation, and destratification results from vertical mixing by wind-induced flow and heat convection. This study used a simple topography model to estimate numerically the spatial distribution of longwave radiation on the water surface of an agriculture reservoir surrounded by mountains. A radiation thermometer was used to estimate global longwave radiation. The spatial and temporal variations of longwave radiation on the water surface were calculated using view factors of objects surrounding the reservoir. The simulation showed that longwave radiation absorbed by the water surface increased with distance from the center of the reservoir. The proposed procedure can be used to estimate the longwave radiation environment and heat balance on a water body such as a reservoir and a stream.     

Individual lift irrigation: a case study in the Cau Son irrigation and drainage area, Red River Basin, Vietnam

The irrigation trend in Asia has been characterised as a shift from gravity to lift irrigation, but the importance of individual lift irrigation using surface water remains to be documented. Surveys on field water application by farmers using lift were undertaken in three sites and across the 44,600 ha Cau Son irrigation and drainage area in the spring crop season. Lift irrigation was found to be practised by 82 % of households. The main lift technology was mechanical pump (petrol and electric), followed by traditional swing and long-handle baskets. The main source for lifting was on-farm canals. Although gravity irrigation was the dominant field application method, the area solely irrigated by individual lift ranged from 25 to 52 % of the irrigated areas. Scaling up from the sites, individual lift accounted for 29 % by irrigation area and volume, with 17 and 12 % attributed to mechanical and manual lift. The application of mechanical pumps was a response to locally high-field elevations and significantly increased with the distance of water delivery from the main canal. The impact of mechanical pumping on flexibility and reliability was significant and positive. Petrol driven pumps had relatively high operational and investment costs, but farmers gained higher flexibility and reliability and compensated by applying less water. Farmers using electric pumps applied significantly more water and thereby wasted electric energy as a compensation for uncertain electric power supply. The importance of individual lift irrigation suggests that it should be explicitly considered in irrigation management policies and performance assessments.     

Dissolved nitrogen model for paddy field ponded water during irrigation period

Based on an experimental field study in Japan, a model was developed to simulate dissolved nitrogen in water ponded in a paddy field. As input data, the model uses meteorological data, water balance in the field, nitrogen concentration in inlet water, and the nitrogen contribution of applied fertilizer. Five model parameters need calibration. A practical application of the model is the simulation of NH₄-N and NO₂₊₃-N concentrations in water ponded in a paddy field. The model improves our understanding of the interactions between forms of dissolved nitrogen in ponded water and can explain the complex changes in dissolved nitrogen concentrations in water ponded on a paddy field.     

Increasing water productivity for paddy irrigation in China

This paper introduces the research on practices to increase water productivity for paddy irrigation in China and summarizes the experience on implementation of the alternate wetting and drying (AWD) irrigation technique. The widespread adoption of the AWD practice on 40% of the rice growing area provides an opportunity for China to produce more food in the water-surplus south where it is wet and the traditional based paddy field agriculture is dominant. Physical and institutional measures leading to increasing water and land productivity in rice-based systems are discussed. Research studies show that AWD practice does not reduce rice yield, but does increase the productivity of water. Water use and thus water charges can be reduced. However, experience shows that demonstrations and training are needed to encourage farmer adoption. Furthermore, there are a range of complementary policies and practices, such as volumetric pricing or farm pond development, which provide incentives for adoption of AWD. Finally, there remain many scientific issues to be addressed. Application of the AWD technique in some regions is still very difficult because of both bio-physical and socio-economic problems. In conclusion, the widespread adoption of AWD is only a first step in the continuing effort to find practices that will increase water productivity for paddy irrigation in China.Dr. Yuanhua Li was a Professor and Dean in Wuhan University of Hydraulic and Electric Engineering from 1996 to 2000. After that, he has been a Professor and Deputy Director General of the National Centre for Irrigation and Drainage Development, Ministry of Water Resources, China. He has been doing research on irrigation principally for paddy since 1982.Dr. Randolph Barker is an agricultural economist and Professor Emeritus Cornell University. From 1966 to 1978 he served as head of the Economics Department, International Rice Research Institute, Los Banos, Philippines and from 1995 to 2004 was principal researcher, International Water Management Institute, Colombo, Sri Lanka.     

Cost sharing and sustainability of Pongsak Muang Fai irrigation system

The centuries-old, self-organizing Muang Fai community irrigation institution in northern Thailand has high potential in illustrating exemplary practices in irrigation cost sharing. This paper examines the cost sharing structure of the Pongsak Muang Fai Irrigation System in Mae Hong Son Province and its relationship with the system water management and sustainability. Results show that this primitive and high cost system accepts costs of the weir, the entire length of main ditch, not only the individually related ditch sections, and the management as common costs that should be equally shared so that it can gather sizeable membership to support the system. The capacity of this small scale run-of-the-river irrigation system with no river flow limitation is a simple summation of all determined farm intake capacities. The maintenance cost of the system every year depends on how much water should be diverted and conveyed, hence the use of “relative” scale of each farm intake capacity as the basis for sharing cost in the wet season paddy farming. Such structure is directly related to the water management under which every intake shall be served with continuous supply without permitting mid-canal water check-up and the members prefer to take collective action to keep enough water supply without leaving any room for suspicion of unfair water distribution. The direct relationship makes the members understand the purpose of payment and be willing to share the costs which are transparently estimated in easily understood terms and clearly de-aggregated into categories.     

Effect of saline irrigation and water deficit on tuber quality

Summary The effect of salinity and water dificit on the quality of tubers for processing was investigated. Total tuber yield was not affected by the treatments, while the percentage of non-marketable tubers was significantly reduced by high salinity (EC_i=6dS m⁻¹) and by water reduction. Accumulation of dry matter in the tubers was increased by all the treatments, that of proline by salinity only and the content of reducing sugars was increased only by water deficit. The colour of the french fries was similar in tubers from the various treatments.