Effects of nitrogen fertilization on the rice arthropod community
1992
Medina, C.
The application of nitrogen fertilizer in rice increased the abundance of the phytophagous and entomophagous population. The increase in their abundance was a function of an increase in the number of species as well as an increase in population size. A few species, however, increased disproportionately in number relative to the other species consequently reducing the equitability of the population. These varying responses of the arthropods to nitrogen fertilization were highly correlated to fertilizer-induced changes in the height, number of tillers and total nitrogen content of the rice plants. The efficacy of chemical control varied with the level of nitrogen fertilizer. Spraying monocrotophos at 1.0 kg ai/ha at 15 and 40 DAT did not reduce the phytophagous population in unfertilized plots and in plots receiving the highest fertilizer rate. It seemed that the tolerance of the population to insecticide treatment was affected by nitrogen fertilization. The study was able to demonstrate the interrelationship of the effects of nitrogen fertilization on the different components of the rice arthropod community. It also indicated that excessive amounts of nitrogen fertilizer could diminish the efficacy of insecticide spraying.
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