Irrigated Paddy Fields Research Articles

Effects of topography on status and changes in land-cover patterns, Chongqing City, China

Chongqing Municipality, located on the upper reaches of the Yangtze River, is one of China’s four largest megacities, comparable with Shanghai, Beijing, and Tianjin. In recent years, Chongqing and its surroundings have been experiencing severe environmental problems, such as urbanization, pollution, and deforestation, due to the rapid economic development of China’s inland region. Understanding the current land-cover status over a wide scale, as well as changes in land-cover over time, are necessary for improving the urban environment and implementing conservation measures in the Chongqing region. In this study, remote-sensing data from 1993 and 2001 were used to analyze land-cover changes. Due to the distinctive mountainous topography of Chongqing, digital topography data shuttle radar topography mission (SRTM)-3 were also used. The results of the analysis showed that urban area increased from 109.91 km2 (5.7%) in 1993 to 166.84 km2 (8.7%) in 2001. This increase came at the expense of agricultural and vegetated areas. Although irrigated paddy field and dry farm land decreased due to the development, these two land-cover categories still covered the largest agricultural area. Correlating the land-cover changes with different topography types, the results showed that forest covered a larger area and enjoyed a higher frequency of distribution at higher elevations and on steeper slopes. The increase in urban area, in contrast, was apparently associated with lower elevations and milder slopes. These results indicate that incorporating terrain characteristics into remote-sensing analysis can be a useful tool in developing conservation measures for vegetated and agricultural areas.

Arsenic Dynamics in Porewater of an Intermittently Irrigated Paddy Field in Bangladesh

In Bangladesh, irrigation of dry season rice (boro) with arsenic-contaminated groundwater is leading to increased As levels in soils and rice, and to concerns about As-induced yield reduction. Arsenic concentrations and speciation in soil porewater are strongly influenced by redox conditions, and thus by water management during rice growth. We studied the dynamics of As, Fe, P, Si, and other elements in porewater of a paddy field near Sreenagar (Munshiganj), irrigated according to local practice, in which flooding was intermittent. During early rice growth, As porewater concentrations reached up to 500 μg L(-1) and were dominated by As(III), but As release was constrained to the lower portion of the soil above the plow pan. In the later part of the season, soil conditions were oxic throughout the depth range relevant to rice roots and porewater concentrations only intermittently increased to ∼150 μg L(-1) As(V) following irrigation events. Our findings suggest that intermittent irrigation, currently advocated in Bangladesh for water-saving purposes, may be a promising means of reducing As input to paddy soils and rice plant exposure to As.

Mitigating methane emissions from irrigated paddy fields by application of aerobically composted livestock manures in eastern China

AbstractLivestock manure heaps and wetland rice fields are major sources of CH4 emissions. A field experiment with an associated composting study were undertaken to investigate CH4 emissions during manure composting and subsequent land application on paddy. Over a 24‐day period in the composting experiment, CH4 emissions from stored manure was 17 times higher than that from composting manure, indicating that composting as an aerobic process was effective in mitigating CH4 emissions compared with manure storage, which is normally under an anaerobic environment. Stored and composted manures were subsequently applied as organic fertilizers in the field experiment. Compared with the non‐fertilized control treatment, stored and composted manures increased grain yields by 30% and 21%, respectively. During the full rice‐growing season, the cumulative CH4 emission was 15.8 g CH4/m2 with the application of composted manure, only one‐third of that from stored manure. CH4 emission per unit of grain yield was significantly decreased by composted manure, with a reduction of 56% from the control and 73% from stored manure. The results indicate that composted livestock manure in rice cultivation is a triple‐win option through sustaining rice yield, mitigating CH4 emissions and re‐utilizing livestock waste.

On the pharyngeal tooth remains of crucian and common carp from the neolithic Tianluoshan site, Zhejiang Province, China, with remarks on the relationship between freshwater fishing and rice cultivation in the Neolithic Age

ABSTRACTThe pharyngeal tooth remains of crucian and common carp from the Tinaluoshan site of the Hemudu Cultural Stage, Zhejiang Province, China, were analysed. The body‐lengths (BLs) of the fish were estimated from tooth size and plotted as bar diagrams. Based on these, we infer that Neolithic dwellers used gill nets to efficiently catch fish of a specific size during the breeding season. The BL distribution of common carp there is similar to those from Jomon sites in Japan, and we therefore infer that the technology for controlling water for rice cultivation in paddy fields had not yet been developed. The abundance of tooth remains of crucian carp unearthed at the Tianluoshan site is reminiscent of similar finds in Western Japan, and we thus infer that the culture trait of utilizing crucian carp as a major protein resource was distributed from the Yangtze River basin to Western Japan. Analysis of pharyngeal tooth remains of carp at various Japanese archaeological sites shows that freshwater fishing was conducted quite differently before and after the establishment of paddy fields. With this fact in mind, one of the present authors tried to model the development of freshwater fishing, with reference to the relation of fishing to rice cultivation (Nakajima, 2010). In Phase I, artisanal fishing became an active and technically developed endeavour, and people began to cultivate rice at fishing site. In Phase II, people began to cultivate rice purposefully in irrigated paddy fields while also fishing there. Comparing the present results of the pharyngeal tooth remains from the Tianluoshan site with those from the Jomon Period, we see that the Tianluoshan site was in the same stage as the end of Phase I in Japan, which rice cultivation was done as a supplementary activity at fishing site. Copyright © 2010 John Wiley & Sons, Ltd.

Temporal variations in arsenic uptake by rice plants in Bangladesh: The role of iron plaque in paddy fields irrigated with groundwater

The transfer of arsenic to rice grains is a human health issue of growing relevance in regions of southern Asia where shallow groundwater used for irrigation of paddy fields is elevated in As. In the present study, As and Fe concentrations in soil water and in the roots of rice plants, primarily the Fe plaque surrounding the roots, were monitored during the 4-month growing season at two sites irrigated with groundwater containing ∼ 130 μg l − 1 As and two control sites irrigated with water containing < 15 μg l − 1 As. At both sites irrigated with contaminated water, As concentrations in soil water increased from < 10 μg l − 1 to > 1000 μg l − 1 during the first five weeks of the growth season and then gradually declined to < 10 μg l − 1 during the last five weeks. At the two control sites, concentrations of As in soil water never exceeded 40 µg l − 1 . At both contaminated sites, the As content of roots and Fe plaque rose to 1000–1500 mg kg − 1 towards the middle of the growth season. It then declined to ∼ 300 mg kg − 1 towards the end, a level still well above As concentration of ∼ 100 mg kg − 1 in roots and plaque measured throughout the growing season at the two control sites. These time series, combined with simple mass balance considerations, demonstrate that the formation of Fe plaque on the roots of rice plants by micro-aeration significantly limits the uptake of As by rice plants grown in paddy fields. Large variations in the As and Fe content of plant stems at two of the sites irrigated with contaminated water and one of the control sites were also recorded. The origin of these variations, particularly during the last month of the growth season, needs to be better understood because they are likely to influence the uptake of As in rice grains.

Scenario analysis for reduction of pollutant load discharged from a watershed by recycling of treated water for irrigation

A model in which a river model was layered on a distributed model (double-layered model) was developed to analyse the transport of water and pollutants (nitrogen, phosphorus, and BOD as organic matter) in watersheds and rivers. The model was applied to the watershed of Abragafuchi Lake, Japan, where serious water pollution has occurred over three decades, and the applicability of the model was demonstrated. Scenarios of recycling of sewage treated-water into agriculture to reduce pollutant load discharged into the lake were analysed. The results showed that irrigating paddy fields with the sewage-treated water could contribute to conserving water and reducing pollutant load, with reduction rate in BOD, nitrogen, and phosphorus ranging from 6%–36%, 16%–46%, and 18%–51%, respectively. Particularly, the results indicated that, irrigating paddy fields with the treated water during non-cropping periods and the accompanying reduction in withdrawn water from the river were more effective in reducing pollutant loads discharged into the lake. Further study is required on the effect of recycled water on crop cultivation and soil conditions for safe implementation.

Water-saving irrigation of paddy field to reduce nutrient runoff

The purpose of this work is to study the effect of a type of water-saving irrigation (WSI) on nutrient runoff of paddy field. The volume of surface drainage was maintained low by WSI. In particular, WSI effectively reduced surface drainage in rain events. Model simulation indicated that net runoff load of total nitrogen (TN) from the paddy field was increased by WSI. Meanwhile, net runoff loads of total phosphorus (TP) and total organic carbon (TOC) from the paddy field was decreased by WSI. Because ponding waters of the study fields were enriched with TP and TOC, WSI reduced runoff of these nutrients by controlling the volume of surface drainage. WSI could be considered an effcient method for reducing runoff loads and could conserve water quality in an agricultural watershed.

Quantitative risk assessment for reclaimed wastewater irrigation on paddy rice field in Korea

Water shortage has become an important issue for Korean agriculture. Korea suffers from a limited agricultural water supply, and wastewater reuse has been recommended as an alternative solution. This study examined the concentrations of toxic heavy metals and Escherichia coli in a paddy rice field irrigated with reclaimed wastewater to evaluate the risk to farmers. Most epidemiological studies have been based on upland fields, and therefore may not be directly applicable to paddy fields. In this study, a Beta-Poisson model was used to estimate the microbial risk of pathogen ingestion. The risk value increased significantly after irrigation and precipitation. The results of the microbial risk assessment showed that risk values of groundwater and reclaimed wastewater irrigation were lower than the values of effluent directly from wastewater treatment plants. The monitoring results of heavy metals for each irrigated paddy fields did not show specific tendency. A risk assessment for toxic heavy metals was performed according to various exposure pathways; however, the results of the carcinogenic and noncarcinogenic risk estimation showed that the risk from reclaimed wastewater-irrigated paddy fields was the lowest.

Heat-Induced Floret Sterility of Hybrid Rice (Oryza sativa L.) Cultivars under Humid and Low Wind Conditionsin the Field of Jianghan Basin, China

Projected global warming is expected to increase the occurrence of heat-induced floret sterility (HIFS) in rice. However, there are few field-scale studies that could aid in predicting the potential risks to rice yield and developing countermeasures against yield losses. The aim of this study was to elucidate the factors that induce floret sterility under high temperature conditions during the flowering season in the field condition in China. Studies were conducted in irrigated paddy fields with the regional hybrid-rice cultivars grown in Jianghan Basin where air temperature is not so high during the flowering season but HIFS frequently occurs. The microclimate, panicle temperature, floret sterility, pollination, and size of dehiscence formed at the base of anthers were investigated. Significant losses in seed set were observed under the high temperature condition. Although the maximum atmospheric temperature was approximately 35ºC, the relative humidity was very high (around 70% at the time of maximum temperature), with low wind speeds, occasionally below 1 m s1. Under such conditions sunlit panicle temperature exceeded atmospheric temperature by as much as 4ºC. Moreover, the anthers of some cultivars exhibited short basal dehiscence, and the dehiscence length was positively correlated with the percentage of sufficiently pollinated florets (r=0.859, P<0.05, n=7) and with seed set (r=0.827, P<0.05, n=7) across the cultivars. The results suggest that the combination of hot, humid, and windless climatic conditions with short basal dehiscence of anthers induces HIFS in hybrid rice grown in this region.

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (II)

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (II)

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (V)

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (V)

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (IV)

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (IV)

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (III)

Technical Cooperation for Paddy Field Irrigation Engineering in Malaysia (III)

Water management — A tool for methane mitigation from irrigated paddy fields

Water drainage is considered to be one of the important practices that reduce the CH 4 efflux from paddy fields. In this study, four different drainage systems (continuous flooding, tillering stage drainage, mid-season drainage and multiple drainage) were compared to find out the best one, for attenuation of CH 4 emission from rice fields. Except for continuous flooding, from all the other three drainage systems, irrigation water from the paddy fields was drained out at the different stages of the crop cycle. Highest efflux of the methane was recorded from continuously flooded plots (346.6 mg/m 2/day), followed by 9% less CH 4 efflux from tillering stage drainage (315.1 mg/m 2/day), 36.7% less efflux from mid-season drainage (219.3 mg/m 2/day) and the least 41% CH 4 efflux from multiple drainage plots (204.7 mg/m 2/day). Among all the four different drainage systems applied, mid-season drainage and multiple drainage were found to be highly effective in mitigating methane efflux. Redox potential of the soil of the drainage system was found to be inversely proportional to the methane efflux from all the treatments.

Climate change effects on paddy field thermal environment and evapotranspiration

The effect of air temperature increase from meteorological data on thermal microenvironment of irrigated paddy field is simulated using energy balance model. Statistical test was used to determine the existence of the trend in temperature change of data from meteorological stations in Indonesia. The temperature was tested to have positive trend, and it was used to generate future and past increase of temperature for the simulation. According to the simulation, the change in energy balance occurs following additional heat contributed by the increase of air temperature. The results show that irrigated paddy field seems to have function of decreasing effect of temperature increase whereas, evapotranspiration increases. However, increasing air temperature also increases temperature in paddy system, but seems to be more moderate than in nonpaddy field.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Identifying Two-Dimensional Characteristics of Surface Water Hydraulics in an Irrigated Paddy Field

To efficiently manage the water supply for paddy rice and to reduce the inundation damage from floods, it is necessary to enhance our understanding of the characteristics of the surface water hydra...

Estimation of methane and nitrous oxide emissions from paddy fields in Taiwan

To investigate the greenhouse gases emissions from paddy fields, methane and nitrous oxide emissions were estimated with the local measurement and the IPCC method during 1990–2006 in Taiwan. Annual methane emission ranged from 9001 to 14,980 ton in the first crop season for 135,314–242,298 ha of paddy fields, and it was between 16,412 and 35,208 ton for 101,710–211,968 ha in the second crop season with the local measurement for intermittent irrigation. The value ranged from 31,122 to 55,729 ton of methane emission in the first crop season, and it was between 29,493 and 61,471 ton in the second crop season with the IPCC guideline for continuous flooding. Annual nitrous oxide emission from paddy fields was between 371 and 728 ton in the first crop season, and the value ranged from 163 to 365 ton in the second crop season with the local measurement. Methane emission from paddy fields in Taiwan for intermittent irrigation was only 26.72–28.92%, 55.65–57.32% and 41.19–43.10% with the IPCC guidelines for continuous flooding and mean temperature of transplanting stage in the first crop, the second crop and total paddy fields, respectively. The values were 53.44–57.84%, 111.29–114.55% and 82.38–86.20% with the IPCC guidelines for single aeration and mean temperature of transplanting stage, respectively; and the values were 133.60–144.61%, 282.56–286.62% and 205.96–215.49% with the IPCC guidelines for multiple aeration and mean temperature of transplanting stage, respectively. Intermittent irrigation in paddy fields reduces methane emission significantly; appropriate application of nitrogen fertilizer and irrigation in paddy fields also decreases nitrous oxide emission.

Estimation of irrigation return flow from paddy fields considering the soil moisture

The objective of this study was to estimate irrigation return flow in irrigated paddy fields considering the soil moisture. The proposed model was applied to examine its feasibility with regard to the growing period of rice. Simulation results showed a good agreement between the observed and simulated values: root mean square error (RMSE) of 6.05–7.27 mm day −1, coefficient of determination ( R 2) of 0.72–0.73, and coefficient of efficiency ( E) of 0.54–0.55. The estimated average annual irrigation return flow during the period from 1998 to 2001 was 306.2 mm, which was approximately 25.7% of the annual irrigation amounts. Of this annual irrigation return flow, 14.1% was attributable to quick and 11.6% to delayed return flow. These results indicate that considerable amounts of irrigation water in the paddy fields were returned to streams and canals by surface runoff and groundwater discharge. The modeling assessment method proposed in this study can be used to manage agriculture water and estimate irrigation return flow under different hydrological and water management conditions.

Investigation of death due to fever in patrasayer block in the district of Bankura, West Bengal

Sir, Communicable diseases contribute to a significant disease burden and are a major cause of morbidity, mortality, and long-term, severe mental and physical disabilities.(1) Disease surveillance is needed to recognize cases or a cluster of cases, to identify a high-risk group or geographic areas, with a view to initiate an effective response in a timely manner, to prevent transmission of disease or to reduce morbidity and mortality.(2) In the case of the death due to fever of unknown origin of two persons in the Patrasayer block of Bankura District, West Bengal, an investigation was conducted on the request of the District Health Officials, to investigate the deaths to find a suggestive cause of death and to suggest the control measures to mitigate the situation and to prevent future occurrence of such incidents. The team visited Birsingha and Champabani villages in the Patrasayer Block on 2 April, 2008, and the sequence of events that occurred in the lives of the deceased persons up to their death were collected from close relatives, by verbal autopsy. Bed head tickets, other records, and reports related to these deceased persons were reviewed. Information was collected from Medical Officers (MOs), Public Health Nurses (PHNs), Auxiliary Nurse Midwives (ANMs), and Medical Technologists. The index case was a 22-year-old male, a daily laborer of Birsingha village of Patrasayer Block. He and his 20-year-old wife visited his in law's house at Chapaboni village of same Block. He had a low-grade fever with malaise for three days. His wife was pregnant, in the third trimester, with jaundice. Unexpectedly, both of them developed high intermittent fever with rigor and intense headache, and after three days both had altered sensorium, followed by unconsciousness, without any history of convulsion. They were initially managed conservatively at Sonamukhi Rural Hospital and recorded to have nuchal rigidity. The attending doctor reached a clinical diagnosis of meningo-encephalitis, not confirmed by laboratory investigation. Blood slides, 276, from the same two villages were taken from the inhabitants surrounding the household of the two deceased persons and examined. They were found to be negative for malaria parasite. Ten percent of the slides were randomly taken by the investigating team and cross-checked at B.S. Medical College, Bankura, and found to be negative for malaria parasite. No case of Plasmodium falciparum was reported in the last three years at these localities. On query, it was evident that death due to similar clinical presentation of intermittent high rise in temperature for three to five days, with headache and malaise, followed by unconsciousness, had taken place earlier in both villages. In the Chapaboni village, with a population of 438, deaths of two male persons aged between 20 and 25 years were reported in the last two years. In Birsingha village with a population of 5490, a couple within the age group of 30 - 40 years had expired within the last eight months, as a consequence of similar disease manifestations. Causes of these deaths were not confirmed by laboratory test. Patrasayer Block is a bordering area with Burdwan District, endemic for Japanese encephalitis, having similar environmental conditions, such as, vast irrigated paddy fields encircling the human habitats, plenty of water-land attracting several types of migrating birds, rearing pigs, and cattle as common domestic animals living closely with human beings. Two couples died with same type of fever of short duration. So, man to man transmission could not be ruled out. However, no laboratory evidence was available to label it as bacterial meningitis. Ecological background, male predilection, sporadic distribution, and clinical presentation like fever with impaired sensorium and unconsciousness went in favor of vector borne viral encephalitis (JE). Following recommendations were made: Any case of fever and altered sensorium should be suspected to be JE. It should be immediately notified to the higher authorities for further action. Spot mapping of fever cases with loss of sensorium, in the block along with adjacent blocks (retrospectively for at least for last two years, as well as, prospectively) is recommended, to specify place distribution of the disease. Entomological survey is required to detect the species of the vector. Proper investigation of such cases reported to any health facilities should be ensured, especially analysis of Blood (Pf and PV Ag, Blood slides for malaria parasite) and Cerebrospinal fluid, for confirmation of meningitis and serum for JE.