Impact of fertilizer applications on grain and vegetable crops in smallholder Mixed Crop-Livestock (MCL) systems in West Africa

Abstract

Mixed crop-livestock (MCL) systems can enhance crop yield, and improve nutrient cycling while reducing chemical fertilizer use. However, only a limited number of studies that reported this assumption were conducted under real-world conditions of small-scale farmers or followed an integrated approach. A survey was conducted in the 2021/2022 and 2022/2023 cropping seasons in Ghana and Burkina Faso, respectively, to determine the impact of fertilizer application practices on the yield of grain and vegetable crops in real-world MCL systems. Detailed information on fertilizer management practice and yield was collected from 317 MCL system farms distributed across three (3) districts/provinces in the Upper East region of Ghana and over the Plateau central of Burkina Faso, respectively summarising data on their grain and vegetable yields under (1) major fertilizer sources; organic, chemical, and combined (organic + chemical), (2) N fertilizer rate (crop x country specific N kg ha⁻¹ recommendation), (3) application timing of fertilizer sources (recommended crop x country specific time of application), and (4) fertilizer placement methods (broadcast versus side placement versus furrow). Results show that the use of different fertilizer source increased (P < 0.05) yields of all grain crops (in Burkina Faso) and maize, rice, sorghum, millet, cowpea and all vegetable crops (in Ghana). The application of crop and country specific recommended N rates significantly influenced (P < 0.05) yields of sorghum, cowpea and green beans in Burkina Faso and rice, sorghum, millet, cowpea and pepper in Ghana compared to low N application rates. The contribution of manure application and appropriate timing on yield mostly differed between countries, such that high tendencies of increased yields were recorded when manure was applied for 0–3 weeks before planting (WBP) in Burkina Faso, while in Ghana, the highest yield improvements were observed when application periods exceeded 3 WBP. Not broadcasting chemical fertilizer only increased (P < 0.05) yields of millet and green beans (in Burkina Faso) and vegetable crops in both countries. These results help improve our understanding of fertilizer practices in mixed crop-livestock systems of Burkina Faso and Ghana, and may help guide recommended fertilizer management in MCL systems of these countries and similar ecologies in West Africa.