Effects of fertilizer, irrigation level and spider presence on abundance of herbivore and carnivore in rice cultivation in Yogyakarta

Cultivation techniques that are usually followed in rice cultivation is believed to greatly affect the interaction between arthropods in form of bottom-up and top-down ways, which in turn, affects their diversity and abundance. Beside of that, the spider is generalist predator that has a great potential as a biological pest control agent. This research aimed to determine the effects of spider presence, fertilizer and irrigation level on abundance of herbivore and carnivore in rice cultivation in Yogyakarta,Indonesia (Wates –Kulon Progo). It was done in factorial design using three factors: fertilizers (organic, inorganic, and without fertilizer), irrigation levels (less water = 2 cm, conventional >10 cm), and spider presence (with and without spider). Eachcombination treatment had three replications. The results showed that the interaction between fertilizer and irrigation level affected soil PH and total N of rice plant but not to total N of soil. Organic fertilizer with less irrigation decreased the abundance of carnivore but it did not affect the abundance of herbivore. Meanwhile, interaction between spider presence and irrigation level affected carnivore abundance, but not to herbivore generally. The spider presence decreased Delphacidae abundance but did not affect the abundance of Alydidae dan Staphylinidae.