Seasonal Consistency and Agronomic-Economic Trade-offs of Arbuscular Mycorrhizal Fungi, Organic Manure and NPK Nutrient Management for Maize in Semi-Arid Taveta, Kenya
Peter Murungi
Department of Agricultural Sciences, School of Agriculture, Earth and Environmental Sciences, Taita Taveta University, P.O. Box 635-80300, Voi, Kenya.
James Gacheru Wanjiku *
Department of Agricultural Sciences, School of Agriculture, Earth and Environmental Sciences, Taita Taveta University, P.O. Box 635-80300, Voi, Kenya.
Mwamburi Mcharo
Department of Agricultural Sciences, School of Agriculture, Earth and Environmental Sciences, Taita Taveta University, P.O. Box 635-80300, Voi, Kenya.
Benard Mwololo
Department of Agricultural Sciences, School of Agriculture, Earth and Environmental Sciences, Taita Taveta University, P.O. Box 635-80300, Voi, Kenya.
Anne Kelly Kambura
Department of Agricultural Sciences, School of Agriculture, Earth and Environmental Sciences, Taita Taveta University, P.O. Box 635-80300, Voi, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Sustainable maize production in semi-arid environments requires nutrient-management strategies that account for seasonal variability in crop responses to biological, organic and mineral inputs. This study evaluated the agronomic and economic responses of maize to arbuscular mycorrhizal fungi (AMF), organic manure (OM), NPK fertiliser and their pairwise combinations in Taveta, Kenya. A two-season randomised complete block experiment comprised seven treatments replicated three times per season. Maize (Zea mays L.) cv. DK 777 received AMF, OM, NPK 17:17:17, AMF+OM, AMF+NPK, OM+NPK or no amendment. Plot-level analyses tested treatment, season and treatment × season effects, with Tukey HSD used for mean separation. Treatment significantly affected grain yield and biomass (P < .001), whereas treatment × season interactions were not significant (P = .772 and .408, respectively). Pooled grain yield was highest under NPK (148.23 g plant⁻¹), OM+NPK (147.77 g plant⁻¹) and AMF+NPK (146.17 g plant⁻¹), compared with 92.03 g plant⁻¹ in the control. Root length showed a significant treatment × season interaction (P = .011), indicating greater seasonal sensitivity of below-ground responses. Week-6 plant height, leaf area and stem diameter were strongly associated with grain yield in both seasons. NPK generated the highest two-season mean net benefit (KSh 1,401.08) and benefit-cost ratio (4.00). Overall, NPK and NPK-containing pairwise treatments produced strong productivity responses, although pairwise combinations did not significantly outperform NPK alone for pooled grain yield. These findings support context-specific nutrient management that integrates agronomic performance, seasonal variability and short-term economic returns.
Keywords: Arbuscular mycorrhizal fungi, maize, nutrient management, organic manure, semi-arid agriculture