Growth and Yield Response of Sorghum (Sorghum Bicolor (L.) Moench) Varieties to Applied Rates of NPSZn Fertilizer at Omorate, Southern Ethiopia

Sorghum ( Sorghum bicolor (L.) Moench) is a key cereal crop in the arid and semi-arid lowlands of Ethiopia, where it contributes significantly to food security, livestock feed, and household income. However, its productivity remains low due to declining soil fertility, limited use of improved varieties, and inadequate fertilizer management. A field experiment was conducted during the 2023/24 main cropping season in Dassenech district, Southern Ethiopia, to evaluate the growth and yield performance of sorghum varieties under different rates of NPSZn blended fertilizer and to determine the optimum fertilizer rate for the study area. The experiment consisted of five sorghum varieties (Dhekeba, ESH-4, ESH-5, Melkam, and a local check) and four NPSZn fertilizer rates (0, 50, 100, and 150 kg ha⁻ 1 ) arranged in a factorial combination using a randomized complete block design with three replications. Data on phenology, growth, yield, and yield components were analyzed using SAS software. The results indicated that both main and interaction effects of variety and fertilizer rate significantly (P < 0.05) influenced most measured parameters, including days to flowering, maturity, plant height, panicle length, grain yield, straw yield, and biomass yield. The Melkam variety consistently outperformed other varieties, producing the highest grain yield (4.28 t ha⁻ 1 ), while the local check yielded the least (2.74 t ha⁻ 1 ). Grain yield increased with increasing fertilizer rates, with the highest mean yield recorded at 150 kg NPSZn ha⁻ 1 , although yields at 100 and 150 kg ha⁻ 1 were statistically comparable. The highest combined yield (4.97 t ha⁻ 1 ) was obtained from Melkam fertilized with 150 kg NPSZn ha⁻ 1 . Based on agronomic performance and economic considerations, Melkam variety with 100 kg NPSZn ha⁻ 1 is recommended for sorghum production in the study area. Further multi-location and multi-season studies are recommended to confirm the findings.