Agronomic responses of selected improved sorghum (Sorghum bicolor L. Moench) varieties to organic soil amendment with poultry manure in the humid tropics

Sorghum's intrinsic resilience makes it ideal for organic farming, although there is little research on its performance in organic production systems. This study investigated the agronomic performance of three improved sorghum varieties (SAMSORG 44, SAMSORG 47, and SAMSORG 48) in response to poultry manure application (0, 2.5, and 5.0 t ha⁻¹) at the Certified Organic Research Plots of the 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). The experiments were laid out in randomized complete block design with three replications. Results revealed that manure application had no significant (p < 0.05) effect on days to 50% flowering, 100% flowering, and maturity in both years although there was significant (p < 0.05) varietal effect on them. SAMSORG 44 exhibited the earliest flowering and the shortest time to maturity. Plant height, dry matter accumulation, panicle weight, seed weight per plot, threshing percentage, biomass and seed yields were significantly (p<0.05) increased with manure application. Significant (p < 0.05) interactions between manure and variety indicated shortest time to maturity and highest seed yields of 2748.4 kg/ha and 2599.1 kg/ha, both years respectively at 5.0 t ha−1 manure application particularly for SAMSORG 44 which are significantly higher than the average yield values in Africa (924.8 kg/ha) and the world (2534.2 kg/ha). Hence, application of 5.0 t ha⁻¹ poultry manure on SAMSORG 44 is recommended for potential resource-constrained organic sorghum farmers in the humid tropics.