PADDY model

Tejada AW, Varca LM, Calumpang SMP, et al. 1997. Fate of pesticides in a model rice paddy ecosystem. In Environ Behav Crop Prot Chem Proc Int Symp Use Nucl Relat Tech Stud Environ Behav Crop Prot Chem 1996, Int Atom Energy Agency Vienna, Austria pp. 265-278. 

In this article, sampling methods for sediments of both paddy field and adjacent water bodies, and also for water from paddy surface and drainage sources, streams, and other bodies, are described. Proper sample processing, residue analysis, and mathematical models of dissipation patterns are also overviewed. 

Figure 1 Structure of a lysimeter for a model paddy study...

Data on weather conditions, especially temperature and rainfall (temporal distribution and intensity) in the study area are essential for the evaluation of the dissipation data. It is very important to understand the water balance in the paddy field as accurately as possible when calculating the rate of outflow. Records of changes in water temperature and sediment temperature are also helpful for modeling the behavior of a chemical in the rice paddy field. 

Only a few models applicable to paddy field conditions have been developed. RICEWQ by Williams, PADDY by Inao and Kitamura," and PCPF-1 by Watanabe and Takagi are useful for paddy fields. EXAMS2 by the United States Environmental Protection Agency (USEPA), a surface water model, can also be used to simulate paddy fields with an appropriate model scenario and has been used for the prediction of sulfonylurea herbicide behavior in paddy fields. The prediction accuracy of PADDY and PCPF-1 is high, although these models require less parameter... 

RICEWQ was the first model developed for agrochemical runoff from paddy fields, incorporating aircraft application, dissipation by drift, adhesion on leaf surfaces, and dissipation from the leaf surface in addition to the processes affecting degradation and transport in sediment and paddy water. An important parameter, desorption from sediment to paddy water, is not considered, although this is not as important as other parameters in paddy fields such as sedimentation rate, behavior of SS, etc. 

Nouchi I, Hosono T, Aoki K, Minami K. Seasonal variation in methane flux from rice paddies associated with methane concentration in soil water, rice biomass and temperature, and its modeling. Plant Soil. 1994 161 195-208. 

A.W. Tejada, L.M. Varca, S.M.F. Calumpang, C.M. Bajet, M.J.B. Medina, Fate of Pesticides in a Model Rice Paddy Ecosystem, in Proceedings of a Symposium Environmental Behavior of Crop Protection Chemicals, IAEA-SM-343/33, Viena, Austria, 1997, pp. 265-278. 

Cai Z. and Yan A. (1999) Kinetic model for methane oxidation by paddy soil as affected by temperature, moisture and N addition. Soil Biol. Biochem. 31, 715—729. 

Probabilistic risk assessment through pesticide fate modeling for evaluating management practices to prevent pesticide runoff from paddy fields (S. H. Vu, Tokyo Univ. of Agric. Tech., Japan)... 

Compound 9 (Figure 4), which was selected for commercialization, showed a broad spectrum of activity against weeds as well as safety to the rice plant under paddy conditions. The compound had other favorable characteristics unrelated to the QSAR modeling, such as mobility in the soil, so that it could reach the stumps and tubers of perennial weeds. Bromobutide has been marketed in Japan since 1987. 

Laohavanich. (., Wongpichet, S., 2008. Thin layer drying model for gas-fired infiared drying of paddy. Sor danakarin J. Sd. Technol. 30(3) 343-348. 

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