Title: Studies on the Dynamics of Pesticide Residues and Application Frequency at the Middle-late Stage of Rice
Abstract: 【Objective】As rice pests often cause serious damage, the dosage and application frequency of pesticides have being increased sharply in last decades and the food safety of rice have attracted more and more attention. The dynamics between time and frequency of pesticides application and pesticide residues in rice grain were studied, which would be helpful for finding out the bestpesticide and optimum time and frequency of pesticides application. It could provide a scientific basis for the application of pesticides. 【Method】The experiments were carried out in Mabei Village, Jinsha Town, Tongzhou County, Nantong City from August to October in 2006. The rice cultivar in experiment was Wuyujing 3 and the experimental plots were 666.7 m2. The pesticides used in experiments were dichlorovos, triazophos, acephate, methamidophos, chlorpyrifos and imidacloprid. Pesticides were used in the rice developmental period before and after heading and the application frequency was one, two and three times during growth of rice. After harvest and threshed, the pesticide residues in rice grain, rice hull and straw were detected, respectively. 【Result】The results showed that the pesticide residues in rice grain were high with application pesticides and there was a positive correlation between pesticide residues and the dosage and application frequency of pesticides. The pesticide residues used in experiments were all detected in rice grain except dichlorovos and followed the order of triazophosacephatemethamidophoschlorpyrifos imidacloprid. Pesticide residues used in the period before heading was significantly lower than that in the period after heading. The residues of chlorpyrifos (40 g/666.7 m2 once or twice before heading), triazophos (40 g/666.7 m2, once before heading) and acephate (30 g/666.7 m2, once before heading) were lower (≤0.1 mg·kg-1). Residues of imidacloprid (3 g/666.7 m2, all treatments) were less than 0.1 mg·kg-1. It was less than the national standard of maximum residue limit in food and could be regarded as green and non-pollution rice in China. There was a close relationship between residues and storage period of rice. For example, as acephate (60 g/666.7 m2) and triazophos (80 g/666.7 m2) were applied three times in the period of after heading, their residues were 0.39, 0.24 mg·kg-1 (acephate) and 0.25, 0.07 mg·kg-1 (triazophos) on 30 and 90 d of grain storage period, respectively. The residues in grain were lower than allowed limit for food. The percent of residues in straw, rice hull and grain was 46.0%, 36.6%, and 17.4%, respectively. Straw and rice hull were important feedstuff in China and their pollution should be paid more attention. 【Conclusion】 The variety of pesticide, the date and the dosage and frequency of employing pesticides were connected with the security of rice grain. Among the pesticides for experiments, besides dichlorovos, others were all detected in the rice grain and the pesticide residues of triazophos were the most, that of acephate and methamidophos was next and that of chlorpyrifos was the least. When pesticides were employed two times in the period before heading, the pesticide residues of methamidophos and triazophos were beyond the national standard of maximum residue limit in food and when three times, that of chlorpyrifos was equivalent to the national standard and that of acephate didn’t meet the national standard. The dosage of above-mentioned pesticides doubled with a residues increase of 30%-50% and besides chlorpyrifos, others were all beyond the national standard after they were employed two times. When pesticides were employed in the period after heading, the pesticide residues rose remarkably. The residues of methamidophos, triazophos and chlorpyrifos were beyond the national standard exept acephate when they were employed two times at the normal dosage and all of them were beyond the national standard when the dosage doubled. The residues of imidacloprid, one kind of neonicotinoid pesticide, were all below the maximum residue limit in food whenever it was employed in the period before or after heading. The pesticide residues in rice grain were connected with the storage life. The rice which had been stored for 90 days all met the national standard. The authors considered that it was very important in the production of innocuous rice to reduce the using frequency and dosage of pesticides and employ high-effective, safety and less-residual pesticides.
Publication Year: 2008
Publication Date: 2008-01-01
Language: en
Type: article
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Cited By Count: 4
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