Seeding and NP Fertilizer Rates’ Effect on Irrigated Wheat Yield and Water Use Efficiency in Midland Tropical Environment

A field experiment was conducted under irrigation condition to investigate the interactive effects of seeding, and nitrogen (N) and phosphorus (P) fertilizer (NP fertilizer) rates on yield attributes, yield, and water use efficiency (WUE) of wheat in the midland tropical environment. The treatments consisted of four seeding rates (50, 100, 150, and 200 kg ha−1) and three NP fertilizer levels (73–30, 110–45, and 146–60 kg N–P ha−1) under irrigation condition. The experiment was laid out in split plot design with fertilizer and seeding rates as main and sub-plot treatments, respectively, and replicated thrice. The seeding and NP fertilizer rates significantly influenced the yield attributes, yield, and WUE of wheat under irrigation condition. Irrigated wheat sown at a seeding rate of 200 kg ha−1 along with 110–45 kg N–P ha−1 provided maximum grain yield (5318 ± 480 kg ha−1), biomass yield (11,137 ± 944 kg ha−1), and WUE (22.3 ± 2 kg ha−1 mm−1), along with 189% economic benefit. The highest economic benefit of US$9.29 for every US$1.0 investment on seed and NP fertilizers with equivalent grain yield (4898 ± 116 kg ha−1) to the treatment that provided maximum yield and WUE was obtained from a seeding rate of 150 kg ha−1 together with 73–30 kg N–P ha−1. Thus, farmers can enhance yield, optimize water use, and maximize economic benefit by seeding wheat at a rate of 150 kg ha−1 coupled with 73–30 kg N–P ha−1 for irrigation-based production system in the midlands of Ethiopia and other similar agroecologies in the tropics.