Effects of water-saving irrigation on weed infestation and diversity in paddy fields in East China

The purpose of the article is to investigate the effects of water-saving irrigation on weed infestation and diversity in paddy fields; a two-year field experiment was conducted in Gaoyou Irrigation District, China. The responses of two irrigation treatments, controlled irrigation (CI) and traditional irrigation (TI), were observed and compared. The irrigation water use, yield, weed density, coverage ratio, height, species richness, density, dominant species, Shannon–Wiener index, and Pielou index were examined to analyze the water productivity, weed infestation, and diversity in paddy fields under the two treatments. The results showed that the water conditions were similar before the late tillering stage, and thereafter the CI fields were alternatively dry and wet with shallow standing water and low soil water content, while the TI fields were mostly continuously flooded by deep standing water and high soil water content. Irrigation water use for CI was 46.8% lower than TI. The CI treatment reduced weed density by 38.0%, decreased coverage ratio by 13.8%, and resulted in a 39.0% increase in weed height. Fewer species were found in CI fields than TI fields. The Shannon–Wiener index decreased by 11.5%, and the Pielou index increased by 3.2%. The changed water regime under CI not only impeded the growth of dominant species but also placed the whole weed community at a relatively stable level with reduced weed density. Meanwhile, aquatic weeds were well controlled; however, semi-aquatic weeds became the dominant species. In general, CI effectively reduced the risk of weed outbreaks, and weed diversity also decreased when it reduced irrigation water use.     

Performance diagnosis of Mae Lao Irrigation Scheme in Thailand (I) Development of Unsteady Irrigation Water Distribution and Consumption model

The Mae Lao Irrigation Scheme is one of the largest irrigation projects in Northern Thailand. According to the field reconnaissance, water shortage usually occurs during the dry season. And it is very difficult to equally distribute available water to the paddy fields from the upstream to the downstream parts of the system. To understand and identify the causes of the problems, the measurement of water level and flow rate along all canals may be effective. However, it is not easy to achieve this in such a large-scale irrigation system. Thus, the numerical simulation becomes the second option. The objective of this study is to identify and quantify the real water shortage causes by developing an Unsteady Irrigation Water Distribution and Consumption model which can simulate the water movement and consumption in the whole irrigation system. The beneficial area of the right main canal is modeled based on the physical aspect of the system. The components of the model consist of canal networks, control structures, and paddy fields. A canal is divided into several portions called reach. The Saint-Venant equations are applied to describe the unsteady water movement in each reach. Flow movement at the control structure is expressed by the boundary condition. The paddy fields are modeled to make paddy block and connected to each reach. The water consumption in each paddy block is estimated by Paddy Tank model. The numerical model is successfully developed showing the ability to simulate the water movement and consumption properties in this irrigation system.     

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 %.     

Effect of water management on soil respiration and <Emphasis Type="Italic">NEE</Emphasis> of paddy fields in Southeast China

Water management is an important factor in regulating soil respiration and the net ecosystem exchange of CO₂ (NEE) between croplands and atmosphere. However, how water management affects soil respiration and the NEE of paddy fields remains unexplored. Thus, a 2-year field experiment was carried out to study the effects of controlled irrigation (CI) during the rice season on the variation of soil respiration and NEE, with flooding irrigation (FI) as the control. A decrease of irrigation water input by 46.39% did not significantly affect rice yield but significantly increased irrigation water use efficiency by 0.99 kg m^?3. The soil respiration rate of CI paddy fields was larger than that of FI paddy fields except during the ripening stage. Natural drying management during the ripening stage resulted in a significant increase of the soil respiration rate of the FI paddy fields. Variations of NEE with different water managements were opposite to soil respiration rates during the whole rice growth stages. Total CO₂ emission of CI paddy fields through soil respiration (total R _soil) increased by 11.66% compared with FI paddy fields. The increase of total R _soil resulted in the significant decrease of total net CO₂ absorption of CI paddy fields by 11.57% compared with FI paddy fields (p < 0.05). There were inter-annual differences of soil respiration and the NEE of paddy fields. Frequent alternate wetting and drying processes in the CI paddy fields were the main factors influencing soil respiration and NEE. CI management slightly enhanced the rice dry matter amount but accelerated the consumption and decomposition of soil organic carbon and significantly increased soil respiration, which led to the decrease of net CO₂ absorption. CI management and organic carbon input technologies should be combined in applications to achieve sustainable use of water and soil resources in paddy fields.     

Strategies and engineering adaptions to disseminate SRI methods in large-scale irrigation systems in Eastern Indonesia

The system of rice intensification (SRI) developed in Madagascar has been controversial in part because there have been no large-scale, long-term evaluations of the impact of its alternative methods. This paper summarizes experience with the dissemination of SRI practices across eight provinces in Eastern Indonesia over nine seasons from 2002 to 2006 under a major irrigation project. The Decentralized Irrigation System Improvement Project (DISIMP) was financed by the Japanese Government with project management by a Nippon Koei consultant team. SRI has been introduced in Indonesia via several organizations and in different parts of the country starting in 2000. The evaluation reported here, made by the DISIMP technical assistance team, is based on data from 12,133 on-farm comparison trials that covered a total area of 9,429 ha. Under SRI management, average paddy yield increase was 3.3 t/ha (78%). This was achieved with about 40% reduction in water use, 50% reduction in chemical fertilizer applications, and 20% lower costs of production. The farmers whom DISIMP was assisting to take up SRI were usually cultivating their paddy fields individually within irrigation systems where it was difficult to reduce water applications as recommended for SRI. Accordingly, innovations had to be made in soil and water management to create relatively aerobic soil conditions so that farmers could get the more productive rice phenotypes expected from SRI practice. This article describes the modifications made to adapt SRI concepts, pointing to the value of introducing in-field ditches, which was confirmed through paddy tract surveys. This experience and analysis showed how SRI methods could be utilized within irrigation systems where water management was not (yet) tailored to SRI production practices. Subsequently, modifications in irrigation system management are being made to be more supportive of SRI cultivation.     

Effects of tillage and irrigation on the occurrence and establishment of native wetland plant species in fallow paddy fields

Traditional weed management, such as tillage and irrigation, has led to an enhanced maintenance of wetland plant species in fallow paddy fields. Recent herbicide usage and improvements in irrigation and drainage systems however have caused habitat loss of these species, especially in fields on open lowlands. We conducted experiments in three fallow paddy fields situated on the alluvial Echigo Plain in central Japan with an aim to restore the habitat of native wetland plant species. The three experimental fields were managed under different irrigation regimes, (1) perennially flooded with water, (2) intermittent irrigation, and (3) temporary irrigation. Half the area of each experimental field was tilled before irrigation. Detrended correspondence analysis revealed obvious floristic differences between experimental and control fields with no irrigation. The proportion of wetland plant species in the experimental fields increased corresponding to the irrigation period, ranging 60–86%, and was relatively greater than that in control fields. In the experimental fields, differences in both tillage and irrigation affected the occurrence of plant species. Tillage restricted the occurrence of many non-wetland plant species, and had a positive effect on the establishment of several annual wetland plant species. In addition, a longer duration of irrigation is not necessarily suitable for the occurrence of all wetland plant species. We concluded that fallow paddy fields provide a possible habitat for the restoration of native wetland plant species through appropriate tillage and irrigation.     

Spatial-uniform application method of methane fermentation digested slurry with irrigation water in the rice paddy field

Promoting biomass utilization, the objectives of this study were to clarify the spatial distribution of nitrogen, one of the most important fertilizer components in the methane fermentation digested slurry (i.e., the digested slurry), and to establish an effective method to apply spatial-uniformly digested slurry with irrigation water in the rice paddy field. A numerical model describing the unsteady two-dimensional flow and solution transport of paddy irrigation water was introduced. The accuracy of this model was verified with a field observation. The tendencies of the TN simulated in inlet and outlet portions had good agreement with the measured data and the accuracy of the numerical model could be verified. Using the numerical model, scenario analyses were conducted to determine the method for spatial-uniform application of the digested slurry with irrigation water. The simulated results indicated that drainage of the surface water and trenches at the soil surface were effective for spatial-uniform application of the digested slurry with irrigation water in the rice paddy fields. The effect of the trenches was maximized when the surface water of the rice paddy field was drained adequately.     

Assessment and water saving issues for Ningxia paddies,upper Yellow River Basin

In the Hetao Irrigation Districts of the Ningxia autonomous region, Upper Yellow River Basin, the continuous deep flooding irrigation method is used for the rice paddies. The field irrigation water use during the rice-growing season is two to three times higher than in other regions of North China where water-saving practices have been introduced. This paper, based on the data measured in experimental rice fields and sub-branch canal systems, presents main results concerning crop evapotranspiration, percolation and irrigation requirements for deep and shallow water irrigation. Causes for water waste relate to both the lack of regulation in supply and distribution canals and to the poor management of paddy fields. The potential for water saving is discussed using water balance data. Improved irrigation techniques and water management strategies, including the shallow water irrigation method, are suggested considering the expected impacts and benefits. Replacing the current continuous deep flooding with the shallow-ponded water irrigation method may reduce the growing season irrigation water use from 1,405 to 820 mm in average, with a likely increase in yields of 450 kg/ha. Water productivity would then increase from 0.49 to 1.03 kg/m³. Adopting improved canal management and modernization of regulation and control structures may lead to decreasing the gross irrigation demand from the present 3,100 mm to about 1,280 mm, which would highly benefit the environmental conditions in the area.     

Irrigation and soil temperature effects on Russet Burbank quality

Potato growers in the Pacific Northwest suffer large economic losses in seasons with above normal temperatures, due to excess reducing sugars in tubers, which cause dark-end French fries. Our objective was to study irrigation management effects on potato quality, particularly the factors causing dark-end French fries or sugar-end syndrome. Solid-set sprinkler irrigated plots were established on potatoes at Kimberly, Idaho during the 1987, 1988 and 1989 irrigation seasons, and at Parma, Idaho in 1987 and 1988. Irrigation treatments were high and low frequency (3/week and I/week) and two or three water application amounts referenced to estimated evapotranspiration (ET, ET+20%, and ET-20%). Neither frequency nor amount significantly affected yields. Irrigation frequency had more influence on potato quality than application amount. More frequent irrigation produced slightly higher quality tubers and lower incidence of dark-ends when fried. Soil temperature was inversely related to tuber grade quality and directly related to percentage of sugar-end tubers. Soil temperature was about 0.5 C lower under the high frequency than under the low frequency irrigation regime. On these silt loam soils, allowing available soil water to decline to 50 percent had no adverse affect on yield or quality.     

The influence of seepage from canals and paddy fields on the groundwater level of neighboring rotation cropping fields: a case study from the lower Ili River Basin,Kazakhstan

In the large-scale irrigation schemes of the lower Ili River Basin of Kazakhstan, crop rotation combines paddy rice and non-rice crops. Continuous irrigation is practiced in paddy fields, whereas other crops are sustained from groundwater after only limited early irrigation. The water table in non-rice crops is raised by seepage from canals and the flooded paddy fields. We investigated the areal extent to which the groundwater level of non-irrigated fields is influenced by seepage from canals and paddy fields by examining the relationship between distance (from canal and paddy field) and groundwater level in upland fields. The groundwater level was influenced for up to 300 and 400 m from the canals and paddy fields, respectively. Geographic information system analysis of crop and canal patterns in the 11 selected years showed that if the zone of influence is 300 and 400 m from the canals and paddy fields, respectively, the groundwater level of most of the area of upland fields was raised by seepage. We conclude that the water supply to cropping fields by seepage from irrigation canals and paddy fields is adequate, but the spatial distribution of the paddy fields may be an important factor that needs more attention to help improve water use efficiency in this irrigation district.     

Pesticide discharge and water management in a paddy catchment in Japan

Concentrations of several pesticides were monitored in a paddy block and in the Kose river, which drains a paddy catchment in Fukuoka prefecture, Japan. Detailed water management in the block was also monitored to evaluate its effect on the pesticide contamination. The concentrations of applied pesticides in both block irrigation channel and drainage canal increased to tens of μg/L shortly after their applications. The increase in pesticide concentrations was well correlated with the open of irrigation and drainage gates in the pesticide-applied paddy plots only 1–3 days after pesticide application. High concentration of other pesticides, mainly herbicides, was also observed in the inflow irrigation and drainage waters, confirming the popularity of early irrigation and drainage after pesticide application in the area. The requirement of holding water after pesticide application (as a best management practice) issued by the authority was thus not properly followed. In a larger scale of the paddy catchment, the concentration of pesticides also increased significantly to several μg/L in the water of the Kose river shortly after the start of the pesticide application period either in downstream or mid–upstream areas, confirming the effect of current water management to the water quality. More extension and enforcement on water management should be done in order to control pesticide pollution from rice cultivation in Japan.     

Irrigation management transfer (IMT) and system of rice intensification (SRI) practice in the Philippines

SRI practices can usually increase the yield of paddy without using special varieties of rice or chemicals. High yield of paddy can be simply achieved through the combination of transplanting single seedlings about 8–10 days old with just two leaves on 40 cm × 40 cm spacing, providing organic fertilizer, and intermittent irrigation. No pesticides are applied. Historically, integrated management of water and crop (particularly rice) in the Philippines, had its beginning with the Spaniards, but more formal events were recorded in the 1950s by Margate (1954) in “Rice: 100 Cavans (50 kg/cavan) per Hectare.” This was followed by the Water Management Manual released in the 1970s by the Asian Development Bank (ADB) and National Irrigation Administration (NIA). Recently, the Southern Philippines Irrigation Sector Project (SPISP), a joint ADB–NIA effort, has commenced trials with the system of rice intensification (SRI) practice. One of the most specific features of SRI is the intermittent irrigation system which requires assured water supply at necessary timing. It is easier to attain assured water supply on timely manner through irrigation management transfer (IMT) which encourages the empowerment of fair water distribution. This article analyzes the merit of IMT for SRI.     

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.     

Evaluation of water intake rate using the diffusive tank model in the low-lying paddy area

The subject of this study is water management in low-lying paddy fields. The objective of this study is to quantify the water requirement, and estimate an appropriate volume and facilitate management of irrigation water in areas where it is difficult to estimate the flow rate continuously. A field observation was conducted at a 14-ha study site located in the Kuwabara area, Fukuoka City, southwest of Japan, to evaluate water management conditions in the command area of the reservoir. This site near the reservoir was selected, because it was impossible to understand the water supply situation in the entire command area. The farmers in this region have been unable to retain sufficient irrigation water. The observation results indicate that the water depth fluctuates widely in every irrigation canal. The canals are frequently empty because rotational irrigation is conducted by water managers; this makes quantifying the flow rate in the irrigation canal very difficult. To quantify the water requirement, an improved tank model was introduced. The accuracy of the model was examined by comparing the observed and calculated ponding depths at a paddy field. The simulation results agreed with the observed data. Using this model, water management for the reduction of water managers’ labor was simulated. Simulation results indicated that rotational irrigation effectively reduces labor and saves irrigation water.     

Modeling irrigation return flow for the return flow reuse system in paddy fields

This research is to construct a water balance model to estimate the amount of return flow in an irrigation system. A simple computation framework for the model was established to include various irrigation applications in cropping seasons. The model was able to estimate evapotranspiration, deep percolation into groundwater aquifer, and return flow. Return flow can be split into two parts, which are surface and subsurface return flows. The water balance model was then applied at the irrigation system (rotational block No. 11-2 of five paddy field units) which is operated by the Taoyuan Irrigation Association in Taiwan as an example. Two study cases were simulated, in which one was for using return flow and the other one was for using no return flow. The study period for the model simulations is the first rice cropping term in 2010 which was from February 16 to July 10. As a result, return flows calculated by the model were 27, 27, 34, and 39% of outflows for sandy loam, sandy clay, clay loam, and light clay soil, respectively. Irrigation water at the downstream field unit with use of return flow was supplemented by the upstream field units, and the amount is 5?C8% of irrigation water for using no return flow. Furthermore, it can be seen from the simulations that increases in irrigation water provide increases of return flow. Increases of irrigation water result in slight increases of subsurface return flow, while increases of irrigation water cause nearly none of change in deep percolation.     

增氧处理对稻田土壤微生物量碳、氮和酶活性的影响

【目的】探讨增氧方式对稻田土壤微生物量碳、氮和土壤酶活性的影响。【方法】以中旱221(旱稻)、中浙优8号(水稻)和IR45765-3B(深水稻)为材料,研究微纳米气泡水增氧灌溉、干湿交替灌溉、淹水灌溉对稻田土壤微生物量碳、氮,土壤氮代谢作用强度和土壤氮素转化相关酶活性的影响。【结果】微纳米气泡水增氧灌溉和干湿交替灌溉可以显著提高稻田土壤微生物生物量碳、氮,中旱221、中浙优8号和IR45765-3B的增氧处理较淹水灌溉处理微生物生物量碳、氮分别增加了30.0%~46.1%和7.1%~92.1%,并且增氧处理降低了3个水稻品种的微生物量碳氮比;与淹水灌溉相比,微纳米气泡水增氧灌溉和干湿交替灌溉有助于提高稻田土壤脲酶、蔗糖酶、过氧化氢酶、蛋白酶、羟胺还原酶活性,降低硝酸还原酶活性和亚硝酸还原酶活性。【结论】微纳米气泡水增氧灌溉和干湿交替灌溉改善稻田土壤的氧化特性,提高土壤酶活性、微生物量碳、氮和硝化强度,有助于改善土壤环境和肥力状况,协调了C、N代谢的平衡。     

A combined technique of floodplain storage and reservoir irrigation for paddy rice cultivation

This paper introduces an irrigation system developed in the floodplain of a lake and studies the water management technique of the irrigation system by estimating the total water balance of the whole system. The system is characterized by a reservoir combined with a dike system in the floodplain of the Tonle Sap Great Lake and an irrigation system. Two main models are used for calculating the total water balance. The first model is the water balance of the reservoir. The inputs to the model are water level of the reservoir, precipitation, lake evaporation, infiltration, and area–volume curve of the reservoir. The outputs are inflow and outflow of the reservoir. The supply from the reservoir to paddy fields is computed from the outflow. The second model is the water balance of paddy fields, based on which the water requirement in paddy fields is derived. The reference evapotranspiration needed to calculate the water requirement is simulated for monthly time series using the FAO Penman–Monteith model. Since there is no drainage network in the irrigation system, surface drainage and runoff are not included in the calculation of the water balance, and seepage is considered negligible in the flat floodplain area. The evapotranspiration, rice variety, soil type and irrigated area are used to simulate water consumption in paddy fields. Finally, the two models are connected to produce the total water balance from the reservoir to paddy fields. The total outflow from the reservoir is estimated and the total water consumption for dry season cultivation is also determined. Finally, the efficiency of the whole system is examined.     

Assessment of the camellia seed meal impact on loaches in paddy fields

In Taiwan, Camellia seed meal is often sprayed on rice paddies during rice transplantation season to stop the growth of Pomacea canaliculata. However, the application of camellia seed meal endangers muciferous mollusks and fishes in paddy fields. Though researchers have examined the effects of the saponin in the camellia seed meal on Pomacea canaliculata, previous studies ignore the effects of saponin on fish. Loaches often inhabit the rivers, lakes, ponds, paddy fields, and canals of low elevation where there have muddy layer with plant chips. This study uses vanillin-sulfuric acid method and field tests on loaches in paddy fields to determine the duration of camellia seed meal’s effect on loaches (Misgurnue Angullicaudatus). Results indicated that the best application to stop the growth of Pomacea canaliculata is to seal the rice field immediately after transplantation, apply the camellia seed meal, and then irrigate the field 2?days after camellia seed meal application for the summer transplantation, and 3?days for the spring transplantation. Water should not be drained from the paddy field after the application of camellia seed meal to reduce the chance of endangering loaches in irrigation canals. Field Tests show that high water temperature during summer also has a negative effect on loaches in paddy fields and irrigation canals.     

Relationship between increment of groundwater level at the beginning of irrigation period and paddy filed area in the Tedori River Alluvial Fan Area, Japan

There are many paddy fields and large amounts of groundwater in the Tedori River Alluvial Fan in Ishikawa Prefecture, Japan. Water infiltration from paddy fields during irrigation may significantly contribute to groundwater recharge. Groundwater recharge is known to be one outcome of paddy farming, and in general is usually related to land use. However, a decreased area of paddy fields because of socioeconomic factors such as urbanization and increasing area of fallow fields has possibly affected the groundwater environment. Evaluation of the quantitative effect of paddy fields on groundwater is necessary for groundwater conservation. This study examined the relationship between differences in the depth of groundwater from just before the irrigation period to just after the first irrigation of paddy fields (increments of groundwater levels) in observation wells and the area of paddy fields around each well. The paddy areas within circular buffer zones, which were delineated at 0.2 km intervals between 0.2 and 2.0 km centered on each observation well, were calculated. A positive relationship was found between the rise in groundwater and the area of paddy field within different buffer zones at most wells. In addition, in the middle or upper part of the fan, the effect of changes in the area of paddy fields surrounding the well on the groundwater level rise was greater than that on the lower part of the fan.