Recent irrigation practices in the Upper East Bank of the Chao Phraya Delta

This study aims to investigate recent practices on water allocation and cultivation in the Upper East Bank of the Chao Phraya Delta in Thailand, by using data collected by RID local offices, questionnaires, and analyses of satellite images. As a result, we have identified the advantage that upstream areas of irrigation canals have enjoyed, namely the preferential water allocation over the downstream areas. This advantage was strongly associated with the intensive cropping patterns of rice: the upstream areas were estimated to conduct almost continuous rice cultivation throughout a year. In addition, the intensive rice cultivation would partly be supported by water from private shallow wells, which were mostly concentrated in the upstream areas of main canals. Those shallow wells would be used at the beginning of the dry season and in drought years, when farmers could not expect water supply from irrigation canals. The result indicated that the conjunctive use of surface and ground water would be practiced in this region.     

The projected changes in water status of the Mae Klong Basin,Thailand, using WEAP model

River basin management has become more dynamic and challenging due to increased competition among different water use sectors. Mae Klong Basin is rich in term of water availability, but increasing water demands in future due to inter-basin-based water management policy addressed by the national government may strongly influence the changes in water status. WEAP model was implemented to assess the current water supply and demand situations for this basin. Six different scenarios were established to evaluate the response of the basin to increasing demands under two SRES scenarios A2 and B2. The simulated results have shown that currently the water resources in the basin are sufficient to meet the existing needs in the wet season, but water shortage has occurred in the dry periods of 2014 and 2015 due to less rainfall in these years. The results have also shown that more water shortages have occurred under A2 scenario as compared to B2 scenario. Water shortages have occurred in all the developed scenarios indicating that the basin will face water scarcity particularly in the scenario five where transferring water to the adjoining area is difficult to possibly be implemented. The scenario six where a new hydropower project is proposed is considered feasible under both A2 and B2 scenarios and can help in meeting hydropower demands in the basin. It is pertinent to shape more effective policies and regulations in the basin for effective water resources management in reducing water shortage as well as achieving downstream water needs and power benefit in future.     

Delay of heading date as an index of water stress in rainfed rice in mini-watersheds in Northeast Thailand

Drought is recognized as a primary constraint for rainfed rice production. In this study, the spatial distribution of heading date of rainfed rice and its relation to field water conditions were investigated for 2 years in mini-watersheds called Nong in Northeast Thailand, in order to clarify the toposequential variation in the degree of water stress of rice. Although the difference in the relative field elevation in the mini-watersheds was only a few meters, the water availability in terms of standing water and soil moisture markedly decreased with ascending elevation. Rice cultivars, KDML 105 and RD 6, the two dominant genotypes in Northeast Thailand, reached the heading stage at nearly the same day in the absence of water stress, independent of transplanting or seeding date under customary management. As the water availability decreased with ascending field elevation, the heading date of rice was markedly delayed. The delay seemed to be related to the cumulative water stress before heading of rice. The rice harvest index and yield at farmers’ fields decreased linearly with the delay of heading. The observed toposequential distribution of heading date indicated that quite severe water stress was imposed in the uppermost fields of the mini-watersheds, while practically no water stress occurred in the lower fields, at least in the lower half of the mini-watersheds. These results suggest that the delay of heading is a good index for rice water stress in rice in Northeast Thailand and can be applicable to field classification with respect to drought risk.     

Factors determining adoption of integrated pest management by vegetable growers in Nakhon Ratchasima Province,Thailand

Widespread use of highly toxic pesticides primarily for agricultural purpose has generated increasing concerns about the negative impact of pesticides on human health and the environment. Integrated pest management (IPM) usually seeks to minimize the use of pesticides and can be utilized to solve pest problems while minimizing risks to people and the environment. A total of 220 vegetable farmers in Nakhon Ratchasima Province of Thailand was interviewed with the objective of investigating the factors determining their adoption or non-adoption of IPM practices. The findings demonstrated that farmers had different uncompromising reasons for determining the use of IPM for their insect pest management. Higher costs of insecticides (91%), adverse effects of insecticides on human health and the environment (80%), and a greater risk of insect pests developing resistance to insecticides (28%) were the primary reasons for the adoption of IPM by vegetable growers in the study area. The reasons for the rejection of IPM practice were unsuitability of IPM for a large farm (52%), implementation difficulties (80%) and a greater belief in synthetic insecticides and their efficacy for target pest control (39%). A comparison between the IPM and the non-IPM farmers showed a significant difference (P < 0.01) in farmers' knowledge of pest management, which influenced IPM adoption or non-adoption. The IPM farmers had greater knowledge about identifying natural enemies and their beneficial role in controlling insect pests, about plant extracts and their efficacy in controlling insect pests and about sticky traps and their efficacy in monitoring natural enemies and controlling insect pests. For example, 24% of IPM farmers had knowledge of natural enemies whereas it was only 4% for the non-IPM farmers. A logistic regression model was fitted which showed that lower cost of pest management, better knowledge on IPM after training and availability of extension services were the factors which influenced farmers' adoption of IPM practice. The non-IPM farmers rejected adoption of IPM due to the common belief that natural enemies would not be effective in controlling insect pests and yields of vegetables would not be increased by practicing IPM.     

辽河三角洲水稻病虫草害综合生态防控体系的构建

简单论述了构建辽河三角洲水稻病虫草害综合生态防控体系的必要性,重点提出建立以科学的预测预报、抗性育种、完善的生态系统、合理的人为调控和稻田紧急处理系统五位一体的综合生态防控体系,实现辽河三角洲水稻生产的可持续发展和稻区生态系统的可持续利用。     

Participatory system for water management in the Toyogawa Irrigation Project, Japan

In principle, participatory irrigation management (PIM) means the involvement of irrigation users in all aspects at all levels of irrigation management. In practice, all over the world efforts are being made to realize the principles. However, in the execution of PIM, role sharing between farmers and government is a serious problem, and thus a clear method and ideas are needed to improve PIM. In particular, a broad discussion of role sharing is demanded. This article illustrates how the Japanese way of role sharing in PIM is realized based on the case of the Toyogawa Irrigation Project. Organizationally, the project is jointly managed by five entities, including both the public sector and the farmers’ organizations. These entities have clearly divided their functional roles, with the ultimate decision power in all aspects of irrigation management given to organized farmers. The power is realized either directly or through the land improvement districts’ representative system depending on the levels of the irrigation system. The public entity provides coordination support to create a transparent forum of discussion together with scientific information for farmers’ understanding and decision making. The participatory institutional line-up of this project enables the upland areas that suffered periodically from water deficits.     

Quantitative analysis of reusing agricultural water to compensate for water supply deficiencies in the Nile Delta irrigation network

The main problem facing farmers in the Nile Delta is water shortages at the ends of irrigation networks and canals. These problems have worsened as water demands have increased. Egypt’s Ministry of Water Resources and Irrigation is currently trying to avoid water deficits by returning agricultural drainage water to the irrigation canals. In the Kafr El-Sheikh Governorate, some canals have an oversupply in some months and deficits in others. Ministry officials started a project by constructing culverts connected canal ends with the main drain (Bhr Nashrat) to provide supplemental agricultural drainage backflows (SADB) channeled through these culverts. However, this return is not controlled, and flows are based only on differences in the hydraulic head. In this study, we evaluated the effectiveness of SADB to counteract water shortages when the water supply from head regulators (WSHR) is insufficient. Our analysis considered the adequacy of the water supply and indicators of dependability and equity of supply. We tested two water supply conditions: (1) WSHR only and (2) WSHR plus SADB. During the summer (May–September) of 2008, SADB significantly improved the system’s ability to meet the irrigation water requirements (IWR) in some months. Adequacy and dependability, therefore, improved from “fair” to “good.” During the following winter (October–April), SADB improved adequacy and equity only in March and April, since water availability was generally sufficient under WSHR.     

黄河三角洲地区棉花牧草两熟机械化种植模式及配套技术集成

棉花牧草两熟栽培模式能最大限度利用气候和土壤资源,不仅经济效益提高,而且还凸显了生态效益和社会效益。本文通过对黄河三角洲地区棉花牧草两熟模式的研究,探讨了发展棉花牧草两熟种值模式需要关注的问题,研究总结了黄河三角洲地区棉花牧草两熟配套技术,对于稳定棉花生产,发展生态农业、机械化农业有着积极的促进作用。     

冀中南棉花无膜栽培技术

为了治理冀中南棉田地膜污染,河北省农林科学院高效复种课题组经过多年研究与实践,总结出一套适合冀中南棉花无膜栽培的技术方案。本文从棉田备播、栽培技术要点等方面介绍了该技术,概述了其在当地的良好示范表现,为当地棉花绿色高效生产提供参考。     

Integrated management of major wheat diseases in Brazil: an example for the Southern Cone region of Latin America

Wheat is an important crop in the Southern Cone region of Latin America. Some of the common wheat diseases in this region are Xanthomonas streak, spot blotch, tan spot, and leaf blotch and the rusts. Rice blast on wheat could also be a problem in certain years. Disease management through varietal resistance, cultural practices including appropriate fungicidal spraying schedule, levels of tolerance for field and seed infections and seed treatment criteria, have been integrated and used for several years in Brazil. Emphasis in integrated disease management (IDM) is on reduction in use of fungicides and consequently in the cost of production. Wheat productivity in Brazil has almost doubled during the past 10 years, owing mainly to the IDM approach. The IDM practices used in Brazil for each of the major diseases can also be adopted in other Latin-American countries with similar agroecosystems.     

Crisis management of water shortage in an irrigation area with a pipeline network system

Problems caused by water shortage in a paddy-field district with a pipeline network system are different from those in a district with an open channel system. Abnormally low rainfall in Japan caused a very serious water shortage in 1994. A survey was carried out in the Hokuriku region, about 300 km in the north of Tokyo, and a typical paddy cultivation area, to determine problems in irrigation practices caused by water shortage and to find countermeasures for the problems. The following results were obtained. A tank model was proposed to estimate water requirements at the field level. The results showed that the amount of rainfall during the irrigation period in 1994 was only 27.1% of an average year and the rate of water sufficiency at the field level was 70.6%. Then, a simulation method was proposed to estimate hydraulic phenomena in a pipeline network system. The result showed that the pipeline network system distributed water to each hydrant unequally during water shortage. Based on simulations, the methods to equalize water supply to each hydrant and to set up reuse system of water were proposed.     

Equal water sharing in scarcity conditions: the case of the Chaisombat Muang Fai Irrigation System in Thailand

With increasing water conflicts arising from competing demands and global climate changes, it has become paramount to understand how the available water resources can be judiciously utilized for sustaining life. This article extends the previous studies on equal water sharing in water-abundant conditions to water-scarce conditions. On the basis of a case study of the self-managed Chaisombat Muang Fai irrigation group in Chiang Rai Province of northern Thailand, the article analyzes the factors that helped the group in successfully sharing water equally when they faced dry-season water scarcity caused by the competing demands of upstream irrigation systems. Interview data on Muang Fai development and management obtained from all levels of Muang Fai managers and field observations reveal three major success factors. First, Muang Fai managers across all levels recognized that water scarcity is a common problem and that, in their capacity as delegates accountable to all members, they must decide how intense competition for water and extensive crop failure can be prevented. Second, the Muang Fai organization provided a large number of farmers of diverse backgrounds with two-way communication and resilient implementation mechanisms for reaching a mutual agreement and synchronically adapting to a new water environment. Third, the group was ready to constantly update and employ socio-technical information to maximize the total benefit, so that all members obtain a proportionately larger share. These results reveal that in addition to social organization and traditional practices related to the normal condition, in the scarcity condition, it is essential to understand the “common” nature of the problem and acquire skills in extracting, updating, communicating, and using socio-technical information for decision making on equal water sharing. Therefore, these capacities should be built, or knowledge on building them should at least be developed, before the water scarcity problem worsens.     

Integrated management of Striga hermonthica, stemborers,and declining soil fertility in western Kenya

Striga hermonthica (Delile) Benth., stemborers, and declining soil fertility are serious threats to sustainable food production in the Lake Victoria zone of Kenya. To address these constraints, promising integrated crop management technologies were evaluated, using a multi-locational design in four sub-locations in Siaya and Vihiga district (western Kenya) for six cropping seasons. Technologies evaluated consisted of the traditional maize (Zea mays L.) – bean (Phaseolus vulgaris L.) intercrop, maize – Desmodium (Desmodium uncinatum (Jacq.) DC.) push–pull intercrop, Crotalaria (Crotalaria ochroleuca G. Don) – maize rotation, and soybean (Glycine max (L.) Merr) – maize rotation. Within each of these systems, imazapyr-coated herbicide-resistant maize (IR-maize) and fertilizer were super-imposed as sub-plot factors. The push–pull system was observed to significantly reduce Striga emergence and stemborer damage from the second season onwards. IR-maize reduced and delayed Striga emergence from the first cropping season. Differences in Striga emergence and stemborer damage between the other systems were not significantly different. After five cropping seasons, the Striga seedbank was significantly higher in the maize-bean intercrop system than in the push–pull system under both maize varieties while the rotational systems had intermediate values not different from the day zero values. Under IR-maize, the Striga seedbank was significantly lower than under local maize for all cropping systems. Maize yields varied between seasons, districts, and cropping systems. Yields in the push–pull system were higher than in the maize-bean intercrop after two seasons and in the absence of mid-season drought stress. Both maize and soybean responded significantly to fertilizer application for both districts and for most seasons. The various interventions did not substantially affect various soil fertility-related parameters after five seasons. In the short term, IR-maize integrated in a push–pull system is the most promising option to reduce Striga while the rotational systems may need a longer timeframe to reduce the Striga seedbank. Finally, farmer-led evaluation of the various technologies will determine which of those is really most acceptable under the prevailing farming conditions.     

Simulated long-term effects of different soil management regimes on the water balance in the Loess Plateau, China

A soil management regime that improves water use efficiency (WUE) is urgently required to increase the sustainability of the winter wheat-summer fallow system in the Loess Plateau, China. However, the long-term partitioning of the water balance must be understood in order to evaluate the viability of possible soil management regimes. Therefore, an ecosystem model (CoupModel) was used to explore the effects on components of the water balance of five types of soil management regimes: conventional practice, wheat straw mulching, incorporation of high organic matter contents, compaction, and use of a harvested fallow crop. Three variants of the fallow crop approach were also considered, in which the crop was harvested 15, 30 and 45 days before sowing the wheat (designated Fallow-15d, Fallow-30d and Fallow-45d, respectively). Simulations were used to identify the relative magnitude of soil evaporation, wheat transpiration and deep percolation and to elucidate the temporal variability in these components for a selected location using climate records spanning 45 years. However, the soil management regime significantly influenced the magnitude of every component of the water balance (in terms of minimum, maximum and mean values) over the long periods considered. Consequently, wheat yield and WUE differed significantly among the simulated treatments. Mulching led to significantly lower soil evaporation, higher transpiration, and more frequent and extensive deep percolation than other regimes, thereby improving fallow efficiency (percentage of rainfall stored in the soil during the fallow period at the end of the fallow period), wheat yields and WUE. In contrast, soil compaction gave the opposite results, leading to the most unfavourable partitioning of the water balance reflected in the lowest wheat yield and WUE values of all the regimes. In 90% of the years no deep percolation occurred in the soil compaction simulations. Use of a fallow crop with optimal harvest timing (Fallow-30d) improved partitioning of the water balance (decreased soil evaporation) and did not significantly reduce wheat yield compared with conventional practice. High organic matter contents in the soil also had a positive influence on the water balance and improved wheat yield and WUE relative to conventional practice. Therefore, mulching appears to be the best management practice for the winter wheat-summer fallow system in the Loess Plateau, according to the simulations. Increasing soil organic matter may be the best option if mulching cannot be implemented. The ideal time for harvesting a fallow crop for use as green manure or fodder appears to be ca. 30 days before sowing the winter wheat.     

我国香蕉园土壤肥力现状的整合分析

了解我国蕉园土壤肥力现状对明确土壤障碍因子,制定有效的消障措施和合理的养分管理方案具有重要指导意义。收集已公开发表有关蕉园土壤肥力的文献数据及结合实地调研测定的数据,建立土壤养分数据库,包括土壤pH、有机质、碱解氮、有效磷、速效钾、交换性钙、交换性镁、有效铁、有效锰、有效铜、有效锌和有效硼含量。参考第二次全国土壤普查养分分级指标,明确我国蕉园土壤养分现状,并分析海南、广东、广西、云南和福建香蕉种植区域土壤养分分布特征。我国蕉园土壤pH平均为5.3、有机质含量平均为14.9 g/kg、碱解氮含量平均为77.3 mg/kg、有效磷含量平均为96.0 mg/kg、速效钾含量平均为227 mg/kg、交换性钙含量平均为1039 mg/kg、交换性镁含量平均为102 mg/kg、有效铁含量平均为169 mg/kg、有效锰含量平均为41.8 mg/kg、有效铜含量平均为2.84 mg/kg、有效锌含量平均为4.82 mg/kg、有效硼含量平均为1.16 mg/kg。86.3%的蕉园土壤有机质处于潜在缺乏及以下水平,97.1%的蕉园土壤碱解氮处于中等以下水平,60.8%的蕉园土壤交换性镁处于潜在缺乏及以下水平,50%以上的蕉园土壤速效磷、有效钾和微量元素含量处于极高水平。不同省份蕉园土壤养分含量及有机质、大中量元素、有效锰和硼处于中等以下水平的蕉园存在差异。我国蕉园土壤综合肥力指数平均为0.71,福建蕉园土壤肥力综合指数为0.78,显著高于其他省份;广东（0.71）和云南（0.69）蕉园土壤综合肥力指数显著高于海南（0.62）和广西（0.61）,不同省份13.3%~37.1%蕉园土壤综合肥力指数在中等以下水平。我国蕉园土壤有效磷、速效钾、交换性钙、微量元素（除有效硼外）处于中等偏上水平,土壤pH偏低,有机质、交换性镁和有效硼处于中等或缺乏水平,成为蕉园土壤肥力潜在限制因子。因此,我国香蕉生产中,应重视有机肥、镁肥和硼肥的施用,不同香蕉种植省份要因地制宜,制定有效障碍因子消减措施,提升蕉园土壤肥力,促进香蕉提质增效和产业绿色发展。     

Influence of overplanting paddy rice on irrigation water delivery performance: a case study in the Dakalt branch canal,Nile Delta of Egypt

In the North Nile Delta of Egypt, the impacts of overplanting paddy rice on water delivery performance have not been discussed quantitatively. Further, the amount of water that could have been saved if farmers would follow the planned area is unknown. In this study, water delivery performance was assessed by comparison of actual paddy rice planting and the government’s planned conditions. For both conditions, performance indicators relating to adequacy, equity, and dependability were analyzed across six locations in conjunction with the branch canal water level in 2013 and 2014. Based on the difference between the actual water supply and planned water demand, the amount of water that could have been saved for downstream uses was calculated. The average adequacy for the investigation period was good at one location, fair at 2 locations, and poor at 3 locations in both years. Further, adequacy under both actual and planned conditions was poor in late July at all locations. The planned adequacy and dependability downstream and equity among locations improved compared to the actual condition in both years. Under the condition that paddy rice area is the upper limit planned by the government, about 12.3% and 9.6% of water could be potentially saved in each year. The difference between actual and planned water delivery performance is caused by the branch canal’s low water level. Control of overplanting paddy rice and coordination of water distribution among water user associations would improve stable water level in the canal and, eventually, water delivery performance.

     

Operation of the Ba Lai irrigation system in the Mekong Delta, Vietnam

Ba Lai Irrigation Project is located at coastal area in the Mekong Delta. In dry season when the flow rate decreases and the strong east wind blows into the delta, the salinity intrusion increases and seriously affects agricultural and domestic water use. Intakes of Ba Lai system have to be closed for 1–3 months depending on their locations, and no water supply during this period often causes water pollution in the project area. In order to solve such problems, this study aims to seek gate operation procedures for salinity control and water environment improvement. A numerical model is developed to simulate water movement, salinity concentration and duration of remaining water (water age) within the system under three scenarios: (1) without control structures, (2) with available control structures, (3) with the full control structures. Through the numerical simulations, control structures are confirmed to be an effective measure for the salinity control and suitable gate operation schedules are proposed to improve the water environment in the project.     

辽河三角洲盐渍土区水土资源利用技术及发展方向

辽河三角洲盐渍土是在三角洲沉积与滨海沉积的母质上发育而成的。区内盐渍土的主要类型有潮滩盐土等六类。在开田筑渠、引淡排咸的条件下,以种植水稻为主体,形成了水土资源综合利用的模式;同时构建了田间工程纵向布置、暗管排水等完善的综合技术体系。在新的历史阶段及资源条件下,发展盐土经济与加强次生盐渍化防治是区域内生产与经济发展的主要方向。