The influence of cropping system and soil amendment on the diversity and abundance of arthropods in cultivated cabbage and onion

Abstract

Cabbage and onion are good sources of vitamins and minerals for humans and income to farmers and marketers. The current study sought to investigate the abundance of arthropods associated with cabbage, onion, and their intercrop under field conditions. These two crops were planted as sole and intercrop with different organic soil amendments during the major and minor rainy seasons of 2014 in the vertisols of the Accra Plains of Ghana. Insects on the two crops were counted weekly, in the sole crops and intercrop, and other arthropods were sampled from the topsoil around the crops, as well as catches from pitfall and yellow sticky traps placed in the vicinity of the crops. The highest abundance and diversity of arthropods occurred in the major than in the minor rainy season. Unexpectedly, the diversity indices revealed more diverse arthropods with high abundance occurring in sole onion than intercrop and sole cabbage. However, the intercrop had fewer incidence of pests (diamondback moth, whiteflies and cabbage webworm), and a high abundance of natural enemies. Organic soil amendment resulted in significantly higher diversity and abundance of soil arthropods, than unamended soil.