Growth, yield and economic performance of lettuce (Lactuca sativa L.) in response to nitrogen and phosphorus fertilization under irrigation in Bahir Dar, Ethiopia

Abstract

Abstract Lettuce is a popular salad crop and an important cash leafy vegetable, with growing demand in urban and peri-urban areas of Ethiopia. Despite this, research on soil fertility management for lettuce is limited, and productivity remains low. This experiment evaluated the effects of nitrogen and phosphorus fertilizer rates on lettuce growth and yield under irrigation in 2025 at Bahir Dar, Ethiopia. The experiment comprised five nitrogen rates (0, 46, 92, 138, and 184 kg ha −1 N) and four phosphorus rates (0, 23, 46, and 92 kg ha −1 P 2 O 5 ), arranged in a Randomized Complete Block Design with three replications. Data were analyzed using R software. Results revealed that the main effects of nitrogen and phosphorus rates significantly ( P ≤ 0.001) influenced plant height, number of leaves per plant, and leaf width of lettuce, while leaf length was not affected by phosphorus rates. The interaction of nitrogen and phosphorus significantly ( P ≤ 0.001) influenced days to maturity, fresh weight of leaf per plant, marketable fresh leaf yield, and total fresh leaf yield. Partial budget analysis revealed that the highest net benefit (241,070 ETB ha −1 ) with a marginal rate of return of 190.51% was achieved from the application of 138 kg ha −1 N with 92 kg ha −1 P 2 O 5 . This combination was identified as economically optimal and can be recommended for lettuce production in the study area and similar agro-ecological zones. However, the experiment was conducted at a single location and over one season, which may limit generalizability. Varietal differences and environmental impacts were also not assessed; hence, future research should include multi-location, multi-season trials and evaluate varietal differences and environmental impacts.