Evaluation of Nutrient Requirements of Sweet Lupine in Bread Wheat-Sweet Lupine under Additive Design Intercropping System in Northwest Ethiopia

The application of optimal fertilizer rates for component crops improves productivity, land use efficiency, and profitability in an intercropping system. Two field experiments during the 2019 and 2020 cropping seasons were conducted in Adet and Debre Tabor districts with the objective of evaluating the nutrient requirements of sweet lupine in bread wheat-sweet lupine under additive design intercropping systems. Sweet lupine grown in bread wheat-sweet lupine intercropping was fertilized with seven fertilizer levels (0%, 25%, 50%, 75%, 100%, 125%, and 150% of the blanket-recommended NP fertilizer rate of sole lupine) and laid out in a randomized complete block design with three replications. The findings revealed that the highest grain yield of sweet lupine in wheat-sweet lupine intercropping system at Adet was achieved at 125% NP (0.51 t·ha−1) and 150% NP (0.52 t·ha−1), followed by 100% NP (0.43 t·ha−1) and 50% NP (0.35 t·ha−1) fertilizer levels of sweet lupine. Similarly, the highest grain yield of sweet lupine in Debre Tabor was recorded by the application of 125% NP (2.07 t ha−1) fertilizer level of sweet lupine followed by 150% NP (1.89 t·ha−1), 100% NP (1.71 t·ha−1), and 50% NP (1.70 t·ha−1) fertilizer levels. For every invested Ethiopian Birr in the treatments of 50% and 125% NP fertilizer levels of sweet lupine averaged additional profits of ETB 7.667 and ETB 4.537, respectively, can be obtained from sweet lupine that grew under bread wheat-sweet lupine intercropping system. Based on the averaged MRR across the different cost price ratio, application of 50% NP fertilizer level of sweet lupine can be recommended for profitable production of sweet lupine in bread wheat-sweet lupine under additive design intercropping system in Adet and Debre Tabor and areas with similar agroecology as it recorded the highest net return with acceptable marginal rate of return.