Soil Fertility Management and Insect Pest Dynamics in Organic Vegetable Systems of Peshawar: An Integrated Approach

Abstract

Organic vegetable production faces the dual challenges of managing soil fertility in low-input systems and suppressing insect pests without the use of synthetic pesticides. This study investigated the integrated relationship between soil fertility management and insect pest dynamics in organic vegetable cropping systems in Peshawar, Pakistan. Field experiments were conducted at four organic farms during 2025-2026 across three seasons (Spring, Summer, Monsoon), with treatments including four levels of organic matter management (control, 5 t/ha, 10 t/ha, and 15 t/ha compost annually) integrated with biological pest control and conservation agriculture practices. Composite soil samples were analyzed for pH, electrical conductivity, organic matter, total nitrogen, available phosphorus, potassium, zinc, and Fe. Insect pest populations (aphids, diamondback moths, and whiteflies) and beneficial arthropods (ladybird beetles, lacewings, and parasitic wasps) were monitored weekly using visual inspections, sticky traps, and sweep netting. Vegetable yield and quality parameters were assessed during harvest. The results demonstrated that farms receiving 15 t/ha of annual compost exhibited 65% lower aphid populations, 58% lower whitefly infestations, and 47% lower diamondback moth larvae than the control plots. The soil organic matter increased from 0.87% to 2.34% with the highest compost application. Strong negative correlations were observed between soil organic matter and major pest densities (aphids: r = -0.78, P < 0.01; whiteflies: r = -0.65, P < 0.05). Beneficial arthropod abundance increased significantly with soil organic matter enrichment, with ladybird beetles showing a 340% increase in high-fertility plots. Crop yields increased by 48-67% in high-fertility treatments compared to controls, while quality parameters, including vitamin C content and shelf life, improved significantly. Statistical models identified soil organic matter and Zn as the primary predictors of pest suppression. The integrated approach combining soil fertility management with biological control proved to be more effective than either strategy alone. This study establishes soil fertility as a foundational component of integrated pest management in organic systems, with direct implications for sustainable vegetable production under the alkaline soil conditions of Peshawar.