Causes of animal extinction in small irrigation reservoirs in Japan and requirements for future re-establishment

In the past, small irrigation reservoirs were constructed only for rice paddy irrigation in Japan. Many of the watersheds for these irrigation reservoirs were forests. These watersheds have been gradually developed into farmland or housing areas. After World War II, the use of chemical fertilizers, such as ammonium sulphate, became popular in upland fields in Japan. As a result, there are high concentrations of nitrates in groundwater and spring water under upland fields. Hence, irrigation reservoirs that collect water from these watersheds have been polluted by nitrates. High nitrates concentrations in irrigation reservoirs have been found where the watershed is located close to tea yards. However, there has been minimal research into these reservoirs in the fields of limnology and agricultural engineering. We have therefore tried to verify the water‐quality characteristics in irrigation reservoirs from the point of view of water‐quality conservation. In the process of the investigation, we encountered a quite significant reservoir called the Tanno Reservoir that has not seen any forms of life. We examined the causes of this lack of life, as well as measures that could be taken for the remediation of such a reservoir. This paper discusses and clarifies the results of these studies.     

辽河下游平原区淹灌条件下水稻的需水规律研究

下辽河平原的台安地区,水田灌溉用水量,约占农业灌溉用水总量的80%左右。在灌溉用水量中,只有水稻的叶面蒸腾量才是灌溉的有效水量,只有这部分水量被水稻所吸收,其余水量都是损失量。因此水稻叶面蒸腾量的确定对水稻的节水灌溉、对实现水稻生产的可持续发展和农业水资源的可持续利用具有重要的意义,节水灌溉的社会效益、经济效益和环境效益都十分巨大。     

Improving Water Reuse in Paddy Field Districts with Cascaded On-farm Ponds using Hydrologic Model Simulations

On-Farm Ponds (OFPs) are an important irrigation facility in rice-based irrigation systems. An OFP water reuse system in paddy field districts is composed of upstream commanded paddy fields, irrigation and drainage ditches, cascaded OFPs and downstream irrigated paddy fields. This study assesses the performance of an OFP water reuse system and explores potential water management strategies to enhance return flow reuse for rice production. A cascaded model including a modified two-tank module and a pond water balance module is developed to describe hydrologic characteristics of the water reuse system. Model calibration and validation show that the measured and simulated data are in a good agreement and the proposed model can be used to hydrologic analyses of OFP water reuse systems. The water reuse system has high water reuse efficiency as the return flow regulated by OFPs was reused several times from the upstream to downstream of the paddy fields. Return flow and actual reuse water increase with the maximum ponded depth of paddy fields. As the water level in a drainage ditch decreases, the available return flow increases and local water shortage can be alleviated. The supply-and-demand gap between seasons becomes more harmonized when the regulated water level in pond increases, resulting in a decrease in water shortage. The reuse of return flow is a quick-response water supply solution to meet the rice water demand during peak demand periods.     

南方地区水稻节水灌溉的综合效应研究进展

水稻节水灌溉技术的应用对于提高水肥利用效率、减少面源污染和温室气体排放、维持生物多样性和保障粮食安全具有重要意义。近年来,水稻节水灌溉的生态环境效应日益凸显,并逐渐受到重视。阐述了南方地区水稻节水灌溉模式的应用现状,分析了主要节水灌溉模式的特点及其节水、经济、环境、生态效应,指出在田间节水灌溉的综合效应、节水灌溉对温室气体排放的综合影响机理、对杂草和动物多样性调控机制的研究和节水灌溉模式的多准则评价方面的不足,从开展节水灌溉与节水、增产、环境、生态之间的互馈机制、节水灌溉条件下温室气体排放的协同和微生物驱动机制、水管理措施下稻田杂草群落之间的竞争和群落调控机制的研究以及利用考虑多重效应的综合评价指标体系进行灌溉模式优选等方面提出下一步的研究方向。     

鄱阳湖流域典型稻田水量平衡分析

为探索稻田田间水量平衡要素之间关系及其影响因素,通过在鄱阳湖流域赣抚平原灌区选取典型田块,结合江西省灌溉试验中心站系列灌溉试验资料,开展了稻田田埂渗流试验和田间水量平衡试验。田埂渗流试验表明,田埂侧向渗流速度为3.97 mm/d,侧向渗流占稻田蒸渗量49.2%,这一部分水将在下田块或下游区域得以重复利用;上框和双套环水位呈直线下降趋势,在田面低水层情况下(田面覆水30 mm),田面覆水深度对田间渗漏影响较小,田间渗漏(垂直入渗和侧向渗流)保持一个相对平稳状态。田间水量平衡试验表明,典型地块的灌水量和排水量明显小于有底测坑;在一季稻全生育期内,典型田块的侧向渗流在当地稻田渗漏量中占相当大比例,占全生育期耗水量的10.9%。     

气候变化和灌溉方式对稻田需水量的影响

气候变化改变了水稻的耗水过程和灌溉需水。基于高邮灌区历史气象资料(1955—2013年),利用稻田水量平衡和MK检验方法,分析了不同灌溉模式下稻田耗水与灌溉需水量的变化。结果表明:高邮灌区水稻全生育期积温随时间序列显著增加,而降雨量略有减少,但趋势不明显;不同灌溉模式下水稻需水量ET_c和渗漏量均随时间序列缓慢增加;节水灌溉模式能有效降低稻田耗水量;节水灌溉稻田灌溉需水量随时间序列缓慢降低,而常规灌溉稻田呈增加趋势,但趋势均不明显;节水灌溉模式能够有效降低稻田灌溉需水量,提高降雨利用率。因此,节水灌溉能够有效缓解气候变化给水稻种植带来的不利影响,是变化环境下灌区可持续发展的重要技术措施。     

Using precise data sets on farming and pesticide properties to verify a diffuse pollution hydrological model for predicting pesticide concentration.

Verification of a diffuse pollution model involves comparing results actually observed with those predicted by precise model inputs. Acquisition of precise model inputs is, however, problematic. In particular, when the target catchment is large and substantial estimation uncertainty exists, not only model verification but also prediction is difficult. Therefore, in this study, rice-farming data were collected for all paddy fields from all farmers in a catchment and pesticide adsorption and degradation rates in paddy field soil samples were measured to obtain precise model inputs. The model inputs successfully verified the model's capability to predict pesticide concentrations in river water. Sensitivity analyses of the model inputs elucidated the processes significantly affecting pesticide runoff from rice farms. Pesticide adsorption and degradation rates of the soil did not significantly affect pesticide concentrations, although pesticide discharge to river water accounted for less than 50% of the total quantity of pesticide applied to fields, possibly owing to pesticide adsorption and degradation. The timing of increases in pesticide concentrations in river water was affected mostly by the farming schedule, including the time of pesticide application and irrigation, and secondarily by rainfall events.     

基于ORYZA 2000模型的鄂北地区水稻水分生产函数构建

湖北省北部地区水资源短缺,有限降水难以满足水稻需水量,需要实施灌溉以补充水分。为此,根据长渠灌溉试验站水稻灌溉试验成果,基于ORYZA 2000模型构建了鄂北地区水稻生长模型。根据不同受旱阶段及受旱水平设置了多种受旱方案,利用构建的模型模拟分析了不同受旱方案水稻需水量和产量的变化规律。结果表明随受旱程度的增加,水稻需水量与产量呈现降低的变化趋势。在模拟成果分析基础上,根据最小二乘法原理,计算分析得到了Jensen模型中不同生育阶段敏感系数,构建了鄂北地区水稻水分生产函数,对指导当地水稻灌溉具有重要意义。     

Microbiological quality of reclaimed water used for golf courses' irrigation.

Microbial quality of reclaimed water used for irrigation in two golf courses located in the southern Iberian Peninsula (Spain and Portugal) was evaluated. Bacterial indicators for faecal pollution (total and faecal coliforms, Escherichia coli and enterococci) were tested by membrane filtration using appropriate selective media. In addition, somatic E. coli bacteriophages, enteric viruses (entero-, hepatitis A and rota-) and Legionella pneumophila were also analysed. The results obtained showed that all wastewater treatment processes reduced adequately the number of indicator microorganisms although a significant correlation between pathogenic and indicator microorganisms tested was not found. L. pneumophila was detected by PCR but not confirmed by culture. Survival experiments of pathogenic microorganisms in aerosols and irrigated turf are conducted to determine the health hazards for the golf practice and to propose a microbial standard for wastewater used for irrigation of golf courses.     

Groundwater contamination risks with manure-borne microorganisms under different land-application options

There is a huge potential for recycling animal manure in agricultural farms, but fecal microorganisms from land-applied animal manure can join shallow groundwater through leaching especially in alluvial formations. Thus, this study investigated the leaching rate of total viable count (TVC) below a 1.1-m soil depth in a field lysimeter planted with rice–maize–rice rotation, where the rotation received different treatments, i.e., chemical fertilizer, dry manure, fresh manure, alternate wetting and drying (AWD) irrigation, and traditional irrigation. Leachate samples of six major irrigation/rainfall events were collected and analyzed for TVC concentration. In the Aman rice season, manure application had a significantly higher TVC leaching (5.5 × 10⁶ colony forming units (CFU) per milliliter) than the no-manure treatment (8.2 × 10⁴ CFU/mL). In the maize season, manure application increased more than one log-scale of TVC leaching concentration. A higher concentration of TVC leaching (3 × 10⁵ CFU/mL) was observed even after 93 d of fresh manure application. The fresh manure had a higher TVC load, and it possibly helped microorganisms survive longer by providing a more manure-like environment in the soil. In the Boro rice season, manure application increased the TVC leaching up to 3–4 log-scale compared with the control treatment. The AWD irrigation increased TVC leaching compared with the continuous irrigation because the desiccation fractures developed in the AWD irrigation helped TVC bypass the organic-rich topsoil. The Boro rice fields had higher TVC leaching than the maize fields with higher manure doses. The study suggests that there is scope to improve manure management to protect the groundwater quality.     

Surface discharge of heavy metals from low farmland.

Runoff heavy metals from farmland were examined using the field data for the summer of 2005. The observation farmland is located on lowland where the irrigation water was contaminated with the drained water from the upstream farmlands. The area of the farmland is 11.2 ha, of which 6.0 ha and 4.5 ha have been used for rice paddy fields and soybean cultivation, respectively. During the observation, heavy metal concentrations at the downstream end were usually found to be higher than those in the irrigation water. That is, the heavy metal concentrations increased due to the passage of the water through the farmland. This increase in the heavy metal concentrations is not equal to the discharge of the heavy metal because the evaporation on the surface of the paddy field and the absorption by plants makes the surface water volume small. The discharged load from the farmland generally indicates the gross surface load from the farmland. When the effects of circulation irrigation on the heavy metal concentrations are estimated, the discharged load from the farmland should be calculated as the net surface load. When the runoff heavy metals from the circulation irrigation farmland are estimated, it is important to consider the inflowing heavy metals with irrigation water. All the heavy metal types observed in this study were discharged from the farmland. The net surface loads of Cr, Fe, Cd, and Pb were 371 microg m(-2) day(-1), 14.9 mg m(-2) day(-1), 0.26 microg m(-2) day(-1), and 3.3 microm( -2) day(-1), respectively.     

推广稻田综合节水技术提高节水效率--以辽宁省节水灌溉为例

稻田综合节水技术是近年来辽宁省在节水灌溉方面形成的一种新的灌溉模式.本文阐述了灌溉节水技术在综合使用中应采取的措施及方法,同时提出了节水灌溉的新思路、新观点.     

寒地水稻控制灌溉技术试验研究

采用田间对比实验方法,实验结果表明,根层土壤含水量作为控制指标的水稻节水控制灌溉技术,在寒地气候条件下,其产量水平相近外,节水幅度、水的生产效率均明显高于浅湿灌溉和常规灌溉处理。通过连续两年的实验结果综合分析,认为不同频率水文年型中比较适宜寒地水稻的节水、低耗、高效的灌溉新技术,对于提水灌溉的水稻作用尤为适宜。     

Farmers’ perceptions of irrigation and constraints on rice production in Benin: a stakeholder-consultation approach

ABSTRACT

This article examines rice farmers’ perceptions of irrigation and constraints on rice production in the municipality of Malanville, Benin. Farmers’ positive perceptions of irrigation include the use of irrigation for insurance against drought, crop yield improvement, higher income, food security and poverty reduction. Analysis of constraints reveals that farmers face major constraints such as lack of agricultural credit, poor access to production inputs, inadequate knowledge of water resources management, poor access to agricultural information and markets, and flooding of fields. Specific constraints in the irrigation scheme of Malanville include the high cost of irrigation and unavailability of water.     

Estimation of pesticide runoff from paddy fields to rural rivers.

The runoff characteristics of pesticides from paddy fields to rural rivers were investigated over a period of three years in Hokkaido Prefecture, Japan. High pesticide concentrations were usually observed in rivers during pesticide application periods. In one year, the growth of rice seedlings slowed down after transplantation owing to low temperatures and lack of sunshine, and many farmers delayed herbicide application. In that year, high-concentration runoff of herbicides in rivers was observed 1-3 weeks later than in average years. The pesticide runoff rates ranged from 0.3% for fenthion to 42% for benfuresate. The runoff rates of pesticides applied post-flood were large. Furthermore, the larger the water solubility of the pesticide, the larger the runoff rate. The highest concentrations of herbicides in paddy water were observed on the day of application or 1-2 days later, and the concentrations decreased exponentially afterwards. The half-lives of the herbicides ranged from 1.2 days for pretilachlor and esprocarb to 5 days for simetryn; the concentrations of the herbicides in paddy water had decreased to 1/10 of their initial concentrations by about 7 days after application. Therefore, the runoff amounts of pesticides from paddy fields could be decreased by improving irrigation-water management.     

Evaluation of anaerobic biodegradability of forage rice straw fertilized with livestock waste

Fertilizing livestock waste for forage rice production can remove nitrogen and reduce the need for chemical fertilizers. Furthermore, rice straw can be used for biogas production. Here, the growth characteristics of different forage rice varieties in Japanese paddy fields fertilized with liquid cattle waste were investigated. Six experimental plots were established in a paddy field planted with three varieties of forage rice developed for livestock feed. Methane production potential assays were then conducted to investigate the anaerobic digestion characteristics of the stems and leaves of these three varieties. The total methane production potential of the Leafstar variety was higher than that of other varieties, while its lag phase was significantly shorter. Co-digestion of ethanol fermentation residue with Leafstar straw revealed that the NH(4)(+)-N concentration decreased as the C/N ratio increased. Additionally, the methane production potential of the mixed substrate was higher than that of ethanol fermentation residue or forage rice straw applied alone. Hence, Leafstar forage rice is a promising variety for establishment of agricultural resource recycling systems in which higher straw biomass can be achieved by applying liquid cattle waste and more biogas can be produced due to the potential for increased methane production.     

HSPF-Paddy simulation of water flow and quality for the Saemangeum watershed in Korea.

The Hydrological Simulation Program-FORTRAN (HSPF) is a comprehensive model that was developed to simulate many processes related to water flow and quality in watersheds of almost any size and complexity. Paddy rice fields often dominate extensive portions of the landscape in the Asian monsoon region. The hydrological and environmental conditions of paddy fields differ somewhat from those of other land uses, and HSPF may not adequately simulate watersheds in paddy farming regions. HSPF was previously modified to HSPF-Paddy; here, we examined the applicability of the modified model. The model was applied to simulate the water flow and quality of the Saemangeum watershed (2523 km2) in Korea, where paddy rice fields comprise about one-third of the total watershed area. Long-term monitoring data (5 years for water flow, 10 years for water quality) were used in the calibration and verification processes. Model performance was in the range of "very good" and "good" based on model efficiency (R2) and percent difference. The accuracy of the daily simulation was lower than that of monthly simulation for water flow. The water-quality simulation results were encouraging for this sizable watershed with mixed land uses; HSPF-Paddy proved adequate, and its application is recommended to simulate watershed processes in paddy farming regions.     

考虑随机降雨时稻田高效节水灌溉制度

在分析水稻生育阶段水分生产函数中敏感指数变化规律的基础上，导出了敏感指数累积函数模型及分旬敏感指数值。以此为基础，将降雨视为随机变量，结合高效节水灌溉条件下稻田水量平衡的特点，充分考虑水稻实际腾发、稻田渗漏和稻田水分实际消退过程，建立了随机降雨情况下，求解稻田高效节水优化灌溉制度的随机动态规划模型。实例研究表明，模型及求解方法合理可行。     

灌溉水温对高寒地区水稻的影响及增温措施

水温是高寒地区制约水稻生产的主要因素之一。通过对水稻生长与水温的关系 ,灌溉水温对水稻生长和产量的影响以及各种提高灌溉水温的措施进行试验研究 ,取得了明显的增温、节水、增产效果     

基于缺水率模型的蓄水型水田灌区旱情预报

频发的干旱灾害制约着我国社会经济的发展,其中农业干旱灾害的危害尤为明显。以江西省莲花县楼梯蹬水库灌区、罗卜冲水库灌区、河江水库灌区这3个以蓄水型水源为主的水田灌区为研究对象,在考虑水利工程对农业干旱影响的基础上,通过实地调查走访、理论联系实践的方式建立了各灌区的缺水率模型,以预报其农业旱情。结果表明,分析得出的水利用系数与实地调查结果基本吻合;且经对比计算,缺水率模型比连续无雨日数更适合评估水田灌区干旱程度,说明该模型可运用于以蓄水水源为主的水田灌区农业旱情的预测。