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.     

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.     

Frequent low-volume sprinkler irrigation of potatoes

Potatoes, cv. Netted Gem, irrigated at intervals of approximately one week or daily to replace daily evapotranspiration, were cooled by lowvolume sprinkling when air temperature exceeded 26.7 C (80 F). During 3 years when average temperatures for the hottest 2 months of the growing season, were within 1.5 C (2.7 F) of the 69-year average (17.5 C or 63.5 F), yields of potatoes irrigated by frequent low-volume sprinkling were not significantly greater than those of potatoes irrigated weekly. Salt deposits on leaves of plants that were irrigated daily and cooled had no effect on yield. It was concluded that frequent low-volume sprinkling would not be superior to conventional irrigation scheduling for potatoes in southern Alberta.     

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.     

Water-nutrient-herbicide management of potatoes with trickle irrigation

A study was designed to test the effectiveness of nitrogen and herbicide applications through soil moisture-controlled, trickle-irrigation systems, and to test the effectiveness of automatic irrigation via soil moisture control to minimize the water requirement and N-losses for high-frequency, trickle-irrigation systems. Results indicated that single or multiple applications of herbicide at recommended rates can be used effectively with trickle irrigation to control weeds in the potato row where cultivation is not possible. Nitrogen can be efficiently applied through a trickle system that features automatic soil moisture control through the use of a high-frequency irrigation schedule.     

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。     

Potential rainwater storage capacity of irrigation ponds

From antiquity to the present, Japan has irrigated many paddy fields from irrigation ponds. There are some 64,000 such irrigation ponds with a benefit area of over 2 ha each. These irrigation ponds not only function as a water-source for the stable production of food, but also are thought to reduce flooding in lower regions through temporary storage of rainwater and catchment runoff because they are located upstream of paddy fields, upland fields and residential land. Centering our research on Kagawa and Osaka Prefectures, we assessed the potential of rainwater storage capacity created by free space in irrigation ponds resulting from irrigation at a macro level as an indicator of flood mitigation. In these prefectures, potential rainwater storage capacity of irrigation ponds in early September was 2.1 and 1.4 times that of the potential storage capacity of associated paddy fields in an ordinary year.     

Effect of irrigation applied at different growth stages and length of irrigation period on quality characters of potato tubers

Summary Potatoes were irrigated at three growth stages: (1) planting-stolon initiation. (2) stolon initiation-tuber bulking, and (3) tuber bulking, when available soil water dropped to 25%, 50% and 75%, bringing it up to field capacity; and irrigation ceased 0, 10 and 20 days before maturity. Significant increases in specific gravity, dry matter, starch content, chip yield and significant decreases in protein content and oil absorption rate of chips were observed due to the frequent irrigation at growth stages 1 and 2. No significant effect on chip colour was attributed to irrigation during the early growth stages. Frequent irrigations at the final growth stage were found to have deleterious effects on specific gravity, dry matter, starch content and chip yield especially when irrigation continued until maturity.     

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.     

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.     

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.     

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.     

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.