Synergistic effects of integrated nutrient management on growth and yield performance of Amaranthus sp. and Cleome gynandra under subtropical conditions

Amaranthus sp. and Cleome gynandra are nutrient rich African indigenous leafy vegetables with strong potential to improve food and nutrition security under climate change, but sustainable fertility guidelines for their production are lacking. This study evaluated the effects of integrating cattle manure (M) and mineral nitrogen (N) on the growth and yield of both species over three cropping seasons under subtropical conditions in Zimbabwe. Six treatments, control (0 N), manure (M) at 10 t ha − 1 , 30 kg N ha − 1 (30 N), 60 kg N ha − 1 (60 N), M + 30 N and M + 60 N, were tested in a randomised complete block design replicated three times. Combining manure with mineral N (M + 30 N and M + 60 N) consistently produced the greatest growth, fresh biomass and seed yield of both species, with benefits strengthening over successive seasons. M + 30 N achieved yields statistically comparable to M + 60 N while using half the mineral N, giving 87.7% higher agronomic efficiency. Integrating cattle manure with a moderate mineral N rate is an economically and environmentally sustainable fertility strategy. This is the first multi season evidence of integrated soil fertility management performance in Amaranthus sp. and Cleome gynandra , offering smallholder farmers a practical, resource efficient nutrient management option that supports food security in the face of climate change.