Prediction of the environmental concentration of pesticide in paddy field and surrounding surface water bodies

Pesticides are very important in European rice production. For appropriate environmental protection, it is useful to predict the potential impact of pesticides after application, in paddy fields, in paddy runoff, and in the surrounding water, by calculating predicted environmental concentrations (PECs). In this paper, a joint simulation is described, coupling a field-scale pesticide fate model (RICEWQ) and a transportation model (RIVWQ) to evaluate the potential for predicting environmental concentrations of pesticides in the paddy field and adjacent surface water bodies and comparing the predicted values with the monitoring data. The results demonstrate that the application of the calibrated field-scale RICEWQ model is a conservative method to predict the PEC at the watershed level, overestimating the observed data; the coupled RICEWQ and RIVWQ models could be adequately used to predict PECs in the surrounding water at watershed level and in the higher tier risk assessment procedure.     

Predicting water surface evaporation in the paddy field by solving energy balance equation beneath the rice canopy

The energy flux on the ground surface depends not only on climatological and biophysical controls in the vegetative canopy, but also on the available energy and energy partitioning beneath the canopy. Quantifying the evaporation and energy partitioning beneath the canopy is very important for improving water and energy utilization, especially in arid areas. In this study, we measured meteorological data, the net radiation and latent heat flux beneath the rice canopy, and then applied the radiation and energy balance equations to get the water surface temperature beneath the rice canopy. To apply the equations, we constructed shortwave and longwave radiation beneath the canopy sub-models and a bulk transfer coefficient sub-model. A plant inclination factor was parameterized with plant area index for the shortwave and longwave radiation sub-models. Bulk transfer coefficient was parameterized by plant area index and soil heat flux was predicted by the force restore model. With calculated water surface temperature and constructed sub-models, we reproduced net radiation and latent heat flux beneath the rice canopy. As a result, the reproduced water surface temperature, net radiation, and latent heat flux beneath the rice canopy were very close to the measured values and no significant differences were found according to 2-tail t test statistical analysis. Therefore, we conclude that these constructed sub-models could successfully represent water surface temperature, net radiation, and latent heat flux beneath the rice canopy.     

Effect of swine liquid manure application in paddy field on water quality,soil fertility and crop yields

Paddy and Water Environment - Land application of animal manure has been accepted as an effective method and disposal option, which has economic, environmental and social benefits, while also...     

Characteristics of water balance in a rainfed paddy field in Northeast Thailand

Rice productivity in rainfed paddy fields varies with seasonal changes of water availability in which the conditions of flooding are affected by the water balance. Hydrometeorological measurements were performed in a rainfed paddy field in Northeast Thailand from July 2004 to December 2006 to analyze the water balance. As a result of our measurements, climatologically conditions were classified as semi-humid with an annual precipitation of 1,100 mm/year and annual potential evaporation of 1,660 mm/year in both the year. The surface layer of the paddy soil was clayey and the hydraulic conductivity was very low, so groundwater levels remained below the soil surface even under flooded conditions during the rainy season. Seasonal changes in the amount of soil water were very small, comprising only less than 16% of the total precipitation during the rainy season. Consequently, an effective precipitation of less than 180 mm was enough to establish standing water in the rainfed paddy field. Shinkichi Goto, Tsuneo Kuwagata and Pisarn Konghakote contributed equally to the paper.     

Numerical simulation on effect of irrigation conditions on water temperature distribution in a paddy field

Water management methods regulate water temperature in paddy fields, which affects rice growth and the environment. To understand the effect of irrigation conditions on water temperature in a paddy field, water temperature distribution under 42 different irrigation models including the use of ICT water management, which enables remote and automatic irrigation, was simulated using a physical model of heat balance. The following results were obtained: (1) Irrigation water temperature had a more significant effect on paddy water temperature close to the inlet. As the distance from the inlet increased, the water temperature converged to an equilibrium, which was determined by meteorological conditions and changes in water depth. (2) Increasing the irrigation rate with higher irrigation water amount increased the extent and magnitude of the effects of the irrigation water temperature. (3) When total irrigation water amount was the same, increasing the irrigation rate decreased the time-averaged temperature gradient effect over time across the paddy field. (4) Irrigation during the lowest and highest paddy water temperatures effectively decreased and increased the equilibrium water temperature, respectively. The results indicate that irrigation management can be used to alter and control water temperature in paddy fields, and showed the potential of ICT water management in enhancing the effect of water management in paddy fields. Our results demonstrated that a numerical simulation using a physical model for water temperature distribution is useful for revealing effective water management techniques under various irrigation methods and meteorological conditions.

     

Pyrethroids levels in paddy field water under Mediterranean conditions: measurements and distribution modelling

The cultivation of rice (Oriza sativa L.) under Mediterranean conditions regularly requires the use of treated wastewater due to shortage of freshwater. As a consequence, the intensification of rice production to supply the uprising demand of grain could break the stability between agriculture and environment. In this work, we studied the occurrence and distribution of pyrethroids in surface water and groundwater collected during two periods (flooding and dry soil conditions) in paddy fields located in the Spanish Mediterranean coast. Pyrethroids were detected at concentrations ranging from 14 to 1450 ng L^?1 in surface water and from 6 to 833 ng L^?1 in groundwater. The results obtained were evaluated statistically using principal component analysis, and differences between both sampling campaigns were found, with lower concentrations of the target compounds during the flooding sampling event. Moreover, a geographic information system program was used to represent a model distribution of the obtained results, showing wastewater treatment plants as the main sources of contamination and the decrease of pyrethroids during flooding condition when water flows over the paddy fields. The impact of these compounds on water quality was discussed.     

稻田排水晒田对土壤饱和含水量的影响和在机械作业上的应用

水稻田间作业的主要机械 ,如收割机、插秧机等均要求稻田土壤有一定的硬度才能正常行走作业。而稻田土壤硬度与其含水量密切相关 ,含水量越低 ,硬度越高。降低稻田饱和含水量 (土壤全部孔隙为水份充满时的含水量 ) ,可使稻田含水量在排水后较快地降至适应机械作业的水平。有利水稻机械及时下田作业 ,争取农时。本试验的目的在于研究稻田的排水晒田措施对其饱和含水量的影响 ,为稻作生产机械化提供相应的农艺管理措施。1　研究方法试验在福建省农科院稻麦所农场进行 ,试验地土壤质地为壤土 ,将试验地按正常耕作要求用拖拉机耕耙平整 ,沉实一…     

Effect of N-fertilizer application on return flow water quality from a terraced paddy field in Northern Taiwan

Intensive use of chemical fertilizer for crops may be responsible for nitrogen and phosphate accumulation in both groundwater and surface waters. The return flow polluted by nutrients not only results in the limitation of water reuse goals but also creates many environmental problems, including algal blooms and eutrophication in neighboring water bodies, posing potential hazards to human health. This study is to evaluate the N-fertilizer application of terraced paddy fields impacting return flow water quality. Water quality monitoring continued for two crop-periods around subject to different water bodies, including the irrigation water, drainage water at the outlet of experimental terraced paddy field, and shallow groundwater were conducted in an experimental paddy field located at Hsin-chu County, Northern Taiwan. The analyzed results indicate that obviously increasing of ammonium-N (NH₄ ⁺-N) and nitrate-N (NO₃ ^?-N) concentrations in the surface drainage water and ground water just occurred during the stage of basal fertilizer application, and then reduced to relatively low concentrations (<0.1 mg/l and <3 mg/l, respectively) in the remaining period of cultivation. The experimental results demonstrate the potential pollution load of nitrogen can be reduced by proper drainage water control and fertilizer application practices.     

The effect of adding surface water to herbage on its digestion by ruminants

In two experiments the effects of adding surface water to herbage on its digestion by ruminants were examined. In experiment 1, with sheep, adding water to silage reduced DM intake and the diet DM digestibility. Offering a high DM alternative forage, hay, increased DM digestibility with the wetted silage, but tended to decrease it with the dry silage. More hay was eaten with the wetted than dry silage. In experiment 2, with steers, adding water to fresh herbage reduced DM intake but had no effect on rumen pH or ammonia levels. Adding water to the herbage reduced the rate of DM disappearance from nylon bags placed in the rumen and the proportion of rumen liquor particles of low specific gravity. The proportion of very short and very long particles in the rumen liquor was also reduced by adding water to the herbage.     

Effect of slope on surface drainage in converted rice paddy

Due to the recent regulation of rice production in Japan, it has become necessary to convert rice paddy to other field crops production. To achieve this, drainage conditions, especially for surface drainage, must be improved. We propose the introduction of a slight slope to improve surface drainage, but the optimal slope must be determined in order to prevent soil erosion caused by excessive slope, as well as increased cost. In Japan, a 0.1% slope has recently come into widespread use and, therefore, the impact on surface drainage must be quantified. In this report, observations were carried out to quantify the impact of a 0.1% slope for converted rice paddy and the following results were obtained: (1) An approximate 0.1% slope enables improvement of 46% of the soil surface saturation area as compared to flat conditions about 10 h after inundation; and (2) Inundated water remains on a flat field, while it moves downward toward the end on a sloped field. These results give a basis for determining a slope on a rice paddy in terms of surface drainage improvement. However, the optimal slope should be decided from various perspectives including engineering, agronomy, and economics etc.     

水田除草剂药害产生原因、症状及补救措施

介绍了常用水田除草剂药害产生的原因,指出了苯氧类除草剂、三氮苯类除草剂、酰胺类除草剂等产生的药害症状,同时阐明了产生药害后换水、喷施叶面肥、追施分蘖肥等补救措施。     

长白山人参对小鼠的急性毒性实验

目的 观察人参水煎液对小鼠灌胃给药后急性毒性反应,评价其安全性,为中医临床应用提供参考依据.方法:以人参水煎液最大浓度、最大体积对小鼠进行一次灌胃给药,观察7d内小鼠的毒性反应以及死亡情况.结果 人参水煎液2g/ml,0.4ml/10g进行灌胃给药,与成人日用人参量3～9g相比,相当于成人临床用量的266.67～800倍,却未见药物引起的毒性反应和死亡情况.结论 人参水煎液具有较好的安全性.     

Impact of climate change on paddy field irrigation in southern Taiwan

Climate change can have a serious impact on water resources. The main agricultural product in southern Taiwan is rice, the planting of which consumes far more water than other crops. This makes agriculture in Taiwan especially vulnerable to climate change. In this study, we used the generalized watershed loading functions (GWLF) hydrological model to simulate the discharge of the Kaoping River under climate change scenarios A2 and B2 as released by the Intergovernmental Panel on Climate Change. We discussed the potential impact of climate change on water resources based on the results of GWLF simulations carried out using rainfall and temperature data from five general circulation models (GCMs). The simulation results indicate that river discharge in the wet season increases significantly, and decreases in the dry season. The discharge variations from using the various GCMs as inputs fall within the range of ?26 to +15 % for the dry season and ?10 to +82 % for the wet season. The variation in available water will seriously impact the first period rice farming (the period between the beginning of January and the end of May) in southern Taiwan. Consequently, effective reduction in conveyance loss in the irrigation canal systems and proper fallowing of paddy fields will be the main challenges to Taiwan’s agricultural sector for alleviating the impact of climate change. For further decision making, we show the effects of adapting to climate change by various degrees of the following two methods: fallowing paddy fields to various degrees and reducing conveyance loss in irrigation canal systems.     

Fertilization management of paddy fields in Piedmont (NW Italy) and its effects on the soil and water quality

The fertilization management of the rice crop in Piedmont was analyzed at a regional scale, and the agronomic and environmental sustainability of the actual fertilization strategy of rice was evaluated through the analysis of its effect on the soils and waters quality. On average, a total amount of 127 kg ha⁻¹ of N, 67 kg ha⁻¹ of P₂O₅ and 161 kg ha⁻¹ of K₂O were supplied to the rice crop. In most cases N and P fertilization was rather well balanced with crop removal. The N balance was in the range ±50 kg for 77% of the surface. The low concentration of N in the groundwater reflected the small N surplus. P fertilization resulted to be smaller than removal for 53% of the surface. Nevertheless, the soil extractable P was very high, probably because of former higher P inputs. This resulted in a high concentration in water courses and aquifers. The K fertilization was excessive (surplus >100 kg ha⁻¹) for 53% of the surface, but most soils showed a low K content. K is probably contributing to nutrient leaching to a great extent. The average soil organic matter (SOM) content of paddy fields was higher than that of normally-cultivated soils in Piedmont, and the C/N was higher, owing to the low mineralization rate in waterlogged conditions. The SOM content was in relation with the management of the crop residues, as the tradition of burning straw after harvest was still widespread on 65% of the paddy surface.     

栽培措施对南方水田花生产量及效益的影响

采用五因素二次通用旋转组合设计试验方法,研究了基本苗及氮、磷、钾、钙施用量五项主要栽培措施对南方水田春花生产量及效益的影响。通过产量及效益数学模型的优化与解析,以明确影响南方水田春花生产量及效益的关键因子和实现高产高效优化栽培的综合农艺措施。结果表明,在5个因素中,对花生产量的影响为:基本苗CaOP2O5K2ON;要获得300kg/667m2以上产量和1500元/667m2以上的经济效益,其最佳栽培措施组合是:保持基本苗1.75～1.83万/667m2,施纯N:9.93～10.21kg/667m2,P2O5:5.91～6.18kg/667m2,K2O:11.80～12.07kg/667m2,CaO:3.73～4.13kg/667m2。     

Nitrogen transformation and carbon sequestration in wetland paddy field of Bangladesh

Paddy and Water Environment - Rice-based cropping systems in Bangladesh have received little consideration of changing nitrogen (N) and carbon (C) in soil. Therefore, this study was conducted at...     

铁岭地区稻田土壤养分肥力状况调查报告

为掌握铁岭地区稻田土壤肥力变化情况,提高水稻产量及品质,特采集土样进行检测。结果表明,铁岭地区稻田土壤中有效磷、有效钾含量丰富;碱解氮、有机质和全氮含量处于中等水平;有效硅、交换性钙和交换性镁含量很丰富;有效铜、有效锌和有效锰含量很丰富;有效铁含量丰富;有效硼含量处于中等水平;土壤酸碱度差异很大。     

湖南稻田耕作制度改革的形势与对策

总结了湖南从1999年以来实施稻田耕作制度改革所取得的主要成效，阐明了这一轮稻田耕作制度改革的新特点，分析了存在的主要问题．并有针对性地提出了稳步推进我省稻田耕作制度改革的对策措施。     

Evaluation of spatial variability of the integral energy of plant available water and its influential properties in paddy soil

Paddy and Water Environment - Plant Available Water is the main concept for describing the existing water content in a soil profile. Along with this concept, Integral Energy shows the energy...