Influence of hosts plants and management practices on the populations of arthropod pests and their natural enemies on soybeans (Glycine max L.) in corn-based agroecosystems in Cagayan Valley [Philippines]
2001
Gaspar, M.G. (Philippine Rice Research Inst., San Mateo, Isabela (Philippines))
Field studies showed that arthropod species richness and abundance were affected by two variables: fertilizer source and insect pest control. A third variable, the cropping system, significantly affected species richness of the herbivores and soil arthropods. Interaction among factors was generally not significant except of the abundance of herbivores at flowering and silking stage for dry and wet seasons, respectively. The population level and the damage by Helicoverpa armigera, being the focus of investigation, was varyingly affected by cropping system, fertilizer source, and insect pest control.The interaction among the three variables had no significant effect on the abundance of H. armigera and the damage on soybean and corn. The population level and damage were very low at 1 individual. The level of herbivory (feeding) by arthropods was also affected by cropping system, fertilizer source, and insect pest control through their damage. However, this was not consistently related with the yield. The most important factor that affected yield was nutrient level, particularly nitrogen, which was accumulated in plant tissues. Nutrient level was also significantly related to above-ground arthropod abundance. In the case of below-ground arthropods, organic matter level in the soil was the most important factor than nutrient level affecting abundance, since it is their food and habitat. Conventionally produced soybeans had comparable yields with non-conventionally produced soybeans. Results also showed that conventionally produced corn was more productive and profitable than the non-conventionally produced corn. The increase in yield was 37-48% when corn was synthetically fertilized and 10-12% increase in yield when applied with the recommended insect control method. This indicates that Cagayan Valley [Philippines] corn farmers need synthetic fertilizers and pesticides to increase their yield and profit
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