Response of Tef (Eragrostis tef [Zucc.] Trotter) to Rates of Nitrogen from Urea and Urea Stabil on Vertisols in the Central Highlands of Ethiopia

Abstract

Nitrogen loss through leaching, volatilization, and denitrification poses significant challenges with highly soluble fertilizers like urea, leading to decreased crop yields and nitrogen use efficiency. To address this issue, field experiments were conducted from 2017 to 2019 at Becho district of the southwest Shewa zone in Oromia Region with the objectives of evaluating the efficiency of Urea ^Stabil as a slow-release nitrogen source; and determining optimum rate of nitrogen application for tef production on Vertisols in the central highlands of Ethiopia. The experimental design used was a randomized complete block design with three replications. Four levels of Urea ^Stabil fertilizer, applied once at sowing and in two splits, were compared to conventional urea at recommended and one-third more than recommended rates, resulting in a total of nine treatments. Nine treatments, including four levels of Urea ^Stabil and conventional urea at recommended and higher rates, were compared across six farmers' fields. Results revealed significant effects of nitrogen levels on various tef growth parameters. While the highest biomass and grain yields were obtained with 92 kg ha^-1 N from Urea ^Stabil applied in two splits, comparable yields were achieved when the same nitrogen rates were applied from Urea ^Stabil once at sowing or from urea in splits. The timing and source of nitrogen did not significantly affect tef yields, certain similar nitrogen rates. Moreover, increasing nitrogen levels beyond existing recommendations improved both biomass and grain yields, indicating the insufficiency of current recommendations for optimizing tef yield in the study area. Generally, applying 92 kg ha⁻¹ N in splits using Urea Stabil enhanced tef productivity more effectively than the previously recommended nitrogen rates.