Diversity and Community Composition of Soil Macro-Arthropods under Contrasting Irrigation Regimes in Tomato Fields of Okara, Pakistan

Abstract

Soil macro-arthropods are important components of agroecosystems and may respond to changes in irrigation-associated soil conditions. This study compared the abundance, community composition and diversity of soil macro-arthropods in tube-well-irrigated and wastewater-irrigated tomato fields in Okara, Punjab, Pakistan. Sampling was conducted from February to May at fortnightly intervals, with seven sampling events under each irrigation condition. Macro-arthropods were collected using quadrat sampling, hand sorting, forceps and Berlese funnel extraction and were identified using morphological characteristics and standard taxonomic keys. A total of 1,031 individuals were recorded, including 351 (34.04%) from the tube-well-irrigated field and 680 (65.96%) from the wastewater-irrigated field. The tube-well-irrigated field supported 63 species belonging to 53 genera, 33 families and 10 orders, whereas the wastewater-irrigated field contained 42 species belonging to 33 genera, 24 families and 7 orders. Isopoda was the dominant order under wastewater irrigation, accounting for 75.59% of individuals, with Porcellio scaber alone representing 53.09% of the total wastewater-irrigated community. Shannon diversity (H′ = 3.6514), Pielou evenness (J = 0.8813) and Margalef richness (R = 10.5788) were higher in the tube-well-irrigated field, while Simpson dominance was higher under wastewater irrigation (D = 0.3149). These findings indicate that wastewater irrigation was associated with greater total abundance but stronger dominance by a limited number of taxa, whereas tube-well irrigation supported a richer and more evenly distributed soil macro-arthropod community.