Maize-Blue Lupin Intercropping Response to Applied Nitrogen and Phosphorus in Northwestern Ethiopia.

Maize (Zea mays L.) - legume intercropping is important for staple crop production by small scale farmers of northwestern Ethiopia. Sweet blue lupin (Lupinus angustifolius) is a potential substitute of commercial concentrates for livestock feeding. Intercrop response to applied N and P was determined with N levels of 0, 64, 128 and 192 kg ha-1 and with P levels of 0, 20, 40 and 60 kg ha-1 arranged in complete factorial RCB design with three replications. Trials were conducted at Achefer and Merawie areas of northwestern Ethiopia in 2013. Sole crops of maize and lupin were additional treatments. Nitrogen use efficiency by maize was determined. The basis for determining the most economical N and P rates with varying costs and commodity prices was developed for the intercrop, with and without financial constraint. Grain yield and yield components of maize responded significantly to applied N, P and their interactions. The highest maize grain yield and land equivalent ratio (LER) were obtained at 178/55 and 202/57 kg ha-1 N/P for Achefer and Merawie, respectively. [CW1]Maize-lupin intercropping was more productive than sole maize with LER of 1.6 and 2.18 in Achefer and Merawie, respectively. Profit per hectare under maize-lupin intercropping was maximized, when one ton of grain buys 170 of N or 85 of P, with 150/46 and 136/42 N/P kg ha-1 at Achefer and Merawie, respectively. In case of low availability and/or finance constrained fertilizer use, 128/20 or 64/20 kg ha-1 N/P were recommended. Intercropping improved N use efficiency of maize, and generally N use efficiency declined as N rate increased. A mathematical model was developed to determine N and P rates that maximize maize yield and profit under maize-lupin intercropping at the two locations of northwestern Ethiopia. [CW1]Lets use values determined from the response functions.