Food production on continuously declining agricultural land to feed the ever-increasing population is a severe issue in Ethiopia. The present study was therefore initiated to evaluate inter and intra-row spacing on yield performance, land-use efficiency and competition in bread wheat-sweet lupine additive series intercropping system. Field experiments were conducted for 2 years in Adet and Debre Tabor experimental sites. The treatments consisted of three inter-rows spacing and 3 intra-rows spacing of sweet lupine. Moreover, the sole crop of wheat and lupine were also included as controls. The experiments were laid out in a factorial randomized complete block design with three replications. The results showed that the combination of 20 cm inter-row spacing with 10 cm intra-row spacing of sweet lupine in bread wheat-sweet lupine intercropping system gave the highest total yield of 4.36 t ha-1 and 4.75 t ha-1 at Adet and Debre Tabor respectively; the land equivalent ratio of 1.43 and 1.57 at Adet and Debre Tabor respectively. System productivity index of 4.96 and 5.88 at Adet and Debre Tabor respectively. Gross monetary value of 2511.26 and 2752.19 USD ha-1 at Adet and Debre Tabor experimental sites respectively. Gross monetary value was generally higher for intercrops than sole cropping systems in both locations; it is linked to intercropping yield and economic benefits compared to sole cropping. Farmers in the study area and areas with similar agroecology are recommended to intercrop sweet lupine with bread wheat at 20 cm inter-row spacing with 10 cm intra-row spacing of sweet lupine.

Food production on ever-dwindling agricultural land is a severe problem in Ethiopia, necessitating the adoption of more efficient and sustainable land-use strategies to feed the country's growing population. The benefits of intercropping are known to be limited by a variety of factors such as companion crop sowing date and variety. The present study was therefore initiated to evaluate the effect of varieties and planting dates of lupines in bread wheat-lupine under an additive design intercropping system in Northwest Ethiopia. Field experiments were conducted for two years in Adet and Debre Tabor experimental sites. The treatments consisted of four planting dates of lupines and two varieties of lupine. Moreover, the sole crop of bread wheat (Triticum aestivume L.), local lupine (Lupinus albus L.) and sweet lupine (Lupinus angustiflolius L.) were also included. The experiments were laid out in factorial randomized complete block design (RCBD) with three replications. The results showed that at the Adet experimental site, the highest land equivalent ratio (LER) was recorded in the simultaneous planting of sweet lupine and bread wheat (1.3), followed by the planting of sweet lupine two weeks after bread wheat (1.23). While at Debre Tabor experimental site, the highest LER was recorded in planting sweet lupine two weeks after bread wheat (1.67). A greater area time equivalent ratio (ATER) was reported in the simultaneous planting of sweet lupine and bread wheat (1.29), followed by the planting of sweet lupine after bread wheat (1.22) at the Adet experimental site. A greater ATER was also recorded in the planting of sweet lupine after bread wheat (1.53) had the highest ATER in Debre Tabor, followed by simultaneous planting of sweet lupine after bread wheat (1.39) intercropping. This revealed that sole cropping would necessitate 29 and 53% more area, respectively, to attain the same yield as intercropping. In Adet, the simultaneous planting of sweet lupine and bread wheat intercropping, while in Debre Tabor, planting of sweet lupine two weeks after bread wheat boosted productivity, and production efficiency and is a viable option for increasing household food security.

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.