Effects of organic amendments on crop production and soil fauna community in contrasting Zambian soils

The use of organic materials has been widely promoted to improve soil health. Surface-active soil macrofauna serves as a key biological indicator of soil health as it supports agricultural productivity. However, the effects of organic amendments on soil fauna and their relationships with crop production are still unknown in C-limited soil conditions. A field experiment was conducted under different fertilizer management in two soils with contrasting C content (14.2/5.1 g C kg⁻¹ at the Lusaka/Kabwe site) in Zambia. Our results show a contrast in soil fauna abundance in two soils. During the experimental period, we collected a total of 926 individual soil fauna in all plots at the Lusaka site, while only 145 individual soil fauna were collected at the Kabwe site. Soil fauna was predominantly composed of Araneae, Coleoptera, Dermaptera, Diplopoda, and Orthoptera. Organic amendments significantly increased soil fauna abundance only at the Lusaka site, and the abundance of Coleoptera and Diplopoda was highly related to the crop yield. At the Kabwe site, the effect of organic amendment on soil fauna abundance was minimal, although significantly higher crop yields were observed in soils with organic amendment. These contrasting results may be due to soil nutrient and water status between different sites. Our findings suggest that site-specific strategies are required to protect and enhance soil fauna communities in C-depleted soils.