Effects Of The Fertilization Application On The Arthropod Community In Rice Field

Over-application of chemical fertilizers is one of the key reasons for insect pest outbreaks. Our understanding of the effect of the nutrition management (fertilizer application) on the arthropod community in rice fields and its underlying ecological mechanism is still rudimentary. To reveal them, an investigation was carried out in eight rice fields in which fertilizers at different levels were applied in Wuyishan, Fujian province from June to October 2004. The structure of the arthropod community in rice fields, the effects of fertilizer application on the arthropod community, and its ecological mechanism were studied. The results are as follows:1 Structure of the arthropod community in the rice fields in WuyishanA total or 307 species (or taxa) of arthropods, including 82 species (or taxa) of predators, 107 species (or taxa) of parasitoids, 40 species (or taxa) of neutral insects and 78 species (or taxa) of insect pests were collected and identified from the rice fields. The species number of natural enemies accounts for 61.56% of the total species number of arthropods in the rice fields. This indicates that rice fields are rich in natural enemies, with great potential for the ecologically-based management of pests.Based on the calculation of the dominance index (Berger-Parker), it was found that Lycosa sp. and Microvelia horvathi were dominant in the guild of predators; Anagrus sp., Paracentrabia andoi and Oligosita sp. in the guild of parasitoids; planthopper nymphs, white-backed planthopper (Sogatella furcifera) and leafhopper nymphs in the guild of insect pests; springtail (Chironomidae) and Chironomus sp. (Collembola) in the guild of neutral insects.The fluctuations of arthropod community and dominant species of different guilds were analyzed. The results showed that natural enemies had an obvious control effect on rice pests. Microvelia horvathi played a significant role in controlling planthoppers in the early growing stage of rice, while spiders played a major role in controlling planthoppers and leafhoppers in the late growing stage of rice.Comparison on the structure of arthropod communities in the rice fields under different levels of fertilizer application showed that nitrogen (N), phosphor (P) and potassium (K) all had some...