Effects of nitrogen fertiliser and pesticide management on floodwater ecology in a wetland ricefield |
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Authors: | Ian C Simpson Pierre A Roger Roberto Oficial Ian F Grant |
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Institution: | (1) Natural Resources Institute, Central Avenue, ME4 4TB Chatham Maritime, Kent, UK;(2) Institute Français de Recherche Scientifique pour le Developpement en Cooperation, 213, rue la Fayette, F-75480 Paris Cedex 10, France;(3) International Rice Research Institute, P.O. Box 933, Manila, Philippines |
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Abstract: | We investigated the effects of N fertiliser and pesticide applications on the population dynamics of benthic molluscs in a tropical wetland rice field. Populations were monitored for two consecutive dry seasons in selected treatments during a study on the effects of agricultural practices on the floodwater ecology of tropical rice fields. The most abundant species recorded in the ricefields were the snailsMelanoides tuberculata andMelanoides granifera. Population densities and biomass values in planted plots ranged between 0 and 1530 individuals m-2 and 0 and 1060 kg ha-1, respectively. Snails were more abundant in unplanted than planted plots (1991: 170–2040 versus 0–1040 individuals m-2, respectively). Populations in planted plots declined as the crop season progressed. Snail populations were significantly reduced by the broadcast application of mineral N fertiliser at 110 kg N ha-1. There was little evidence that snails were affected by carbofuran or butachlor applications. |
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Keywords: | Benthic molluscs Snails Melanoides spp Wetland rice Nitrogen fertiliser Pesticide Carbofuran Butachlor |
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