Impact of organic amendment on the agronomic performance of selected improved sorghum (Sorghum bicolor L. Moench) varieties in the humid tropics

Sorghum's inherent resilience predisposes it for organic cultivation, despite minimal evidence of its performance under organic cultivation practices. This research evaluated the agronomic productivity of three improved sorghum varieties (SAMSORG 44, SAMSORG 47, and SAMSORG 48) under poultry manure application (0, 2.5, and 5.0 t ha⁻¹) at the Certified Organic Research Plots, Institute of Food Security, Environmental Resources and Agricultural Research (IFSERAR), FUNAAB (June – December, 2023) and the Organic Agriculture Professionals in Tertiary Institutions in Nigeria (OAPTIN), FUNAAB (September – November, 2024). Experiments were conducted in randomized complete block design with three replications. Analysis indicated that application of manure had no significant (p < 0.05) influence on days to 50% flowering, 100% flowering, and maturity in both the years though there was a significant (p < 0.05) variety impact on them. SAMSORG 44 also had the earliest date for flowering and minimum interval to maturity. Dry matter accumulation, plant height, panicle weight, seed weight per plot, threshing percentage, biomass and seed yields were significantly (p < 0.05) enhanced by the application of manure. Significant (p < 0.05) interaction of variety × manure showed shortest maturation period and maximum seed yield of 2748.4 kg ha ^− 1 and 2599.1 kg ha ^− 1 , both years respectively at application of manure 5.0 t ha ^− 1 particularly by SAMSORG 44 which is significantly higher than African (924.8 kg ha ^− 1 ) and world (2534.2 kg ha ^− 1 ) average values. Therefore, application of 5.0 t ha⁻¹ poultry manure in SAMSORG 44 is advised for prospective resource-constrained organic sorghum farmers in the humid tropics.