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Enhancing crop productivity through fertiliser applications to neglected and under-utilised crops in sub-Saharan African countries: A meta-analysis

¹UNISS - University of Sassari, Agricultural Science - Desertification Research Center, Italy
²CIHEAM BARI - Mediterranean Agronomic Institute of Bari, Sustainable Water & Land Managament in Agricultural Ecosystems, Italy

Abstract

Land degradation, soil nutrient depletion and loss of biodiversity have intensified over the years with sub-Saharan Africa. In response, neglected and underutilised crop species (NUS) are garnering attention within African farming systems due to their adaptability and valuable nutritional content. To assess their potential impact, we conducted a meta-analysis focusing on the effects of both organic and inorganic fertiliser applications across several NUS crops, including groundnut, millet, teff, lablab, fonio and anchote.
Our study involved fourteen selected research papers, from an initial pool of 106 publications. The selection process followed a systematic approach, defining inclusion criteria and outlining rigorous methods for literature search, data extraction, meta-analysis, and synthesis.
A three-level random effects model was applied using the metafor package in R. The data were categorized into organic (OF), inorganic (IF), and combination treatments (OF-IF). Forest plots were generated for all the Treatments vs Control and OF, and OF-IF vs IF, in both cases classified by two different moderators. i.e. crop and climate class. Linear models (lm) were fit to assess the significance of the relationships between total nitrogen (Tot N) and Log Response Ratio (LRR) across different crops, fertilisation treatments and climate class on R environment.
When comparing treatments to control, Millet under OF-IF showed a significant yield increase of 77%. Additionally, Teff under IF also demonstrated a notable yield increase of 74%, Under semi-humid climates, the OF-IF and IF showed a yield increase of 101% and 77% respectively. On the other hand, when comparing treatments to inorganic, Teff exhibited 109% and 119% of yield improvements under both OF-IF and OF respectively. In Humid climates, the OF-IF resulted in 118% yield increase.
Full OF showed a strong positive relationship between yield increase and Tot N, with R² of 0.74 and P value of 0.013. Similarly, Teff under OF exhibited a strong relationship between yield increase and Tot N, with R² of 0.67 and P value of 0.025, indicating significant impacts of Tot N on yield. These findings underscore the importance of integrating organic and inorganic fertilisation to enhance NUS productivity, offering valuable insights for the sustainability of African cropping systems.

Keywords: Crop yield, fertilisation systems, multilevel analysis, NUS

Contact Address: Rodolphe Aziz, UNISS - University of Sassari, Agricultural Science - Desertification Research Center, Viale Italia 39A, 07100 Sassari, Italy, e-mail: razizuniss.it