Characterization of rice cropping practices and multiple pest systems in the Philippines
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A body of descriptors of the rice crop system was collected in a sample of farmers' fields in Central Luzon, Philippines, and these data were used to characterize cropping practices and pest constraints. The analysis was conducted in four steps: (1) the time-dependent, quantitative information pertaining to pests (diseases, insects, and weeds) was integrated over crop development to account for injuries to the crop; (2) classes reflecting the various distribution frequencies were developed, and the quantitative information was categorized accordingly; (3) seven patterns of cropping practices (PR) and seven types of pest profiles (PE) were characterized from two independent cluster analyses using a chi-square distance; (4) two contingency tables, yield by cropping practices (Y x PR) and yield by pest profile (Y x PE), were built and jointly submitted to correspondence analysis. Two first axes accounted for 52.2% and 25.5% of total inertia, and were used to interpret the relationships among PR, PE, and yield. A path of increasing yield levels was associated with increasingly favourable production situations, and was opposed to the accumulation of pest injuries. Cropping season, date of establishment, fertilizer input, and weed control practices were identified among the components that drive production levels. Correspondences of specific key pests, or key pest combinations, with particular production levels and patterns of cropping practices were identified. The analysis suggested that weeds and stemborers may contribute much to yield reduction. Sheath blight was closely associated with the highest yields, suggesting that (1) the disease did not contribute to any yield reduction, and/or (2) it is particularly enhanced in potentially high-yielding crops. In the latter case, control of sheath blight might result in even higher yields.
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