author(s)
Amanda Ignacia Calista and Binari Manurung

abstract
Arthropod diversity and abundance, particularly spiders and insects are key markers of agricultural ecosystem health because they serve as biological control agents, pollinators, and trophic chain components. Agricultural intensification through the use of synthetic inputs frequently diminishes biodiversity, necessitating an evaluation of the merits of organic farming practices in sustaining agroecosystem stability. This research examine the diversity and richness of spiders and insects in organic and inorganic rice fields in Sumber Rejo Village, Percut Sei Tuan Subdistrict, Deli Serdang Regency, North Sumatra. The study was carried out over three months, from May to July 2025, using Yellow Sticky Trap (YST) and sweep net technologies that were strategically put in both types of rice fields. The obtained data were evaluated using the Shannon-Wiener index (H?) for diversity, the Shannon-Wiener for abundance, the Evenness index (E) for evenness, and the Dominance index (C) to assess community structure. Differences between systems were examined using the t-test. The results demonstrated that organic rice fields are more diverse and abundant than inorganic rice fields. The spider diversity index in organic rice fields was 1.77, whereas in inorganic rice fields it was just 1.36, both in the moderate range. Similarly, the insect diversity index in organic rice fields was 2.37, greater than in inorganic rice fields (2.00). Spider and insect abundance values are also greater in organic rice fields (1.21 and 2.26) than in inorganic rice fields (0.87% and 1.57%). Meanwhile, spiders and insects have a relatively balanced distribution in both systems, with organic rice fields being slightly more stable, and the dominance index in both environments is low, indicating that neither species dominates significantly. Overall, these data show that organic farming practices promote biodiversity and ecosystem resilience, whereas synthetic inputs in inorganic farming reduce natural ecological processes and increase sensitivity to pest disturbances.