Maize (Zea mays) is a major staple crop in North-Western Ethiopia. Narrow leaf lupine (Lupinus angustifolius) grain is a commercial concentrates for livestock feed. Maize-lupine intercropping is a sustainable and emerging crop production approach for the resource poor smallholder farmers of North-Western Ethiopia; however, there is no recommended fertilizer rate for the intercrop. Therefore, field experiment was undertaken to determine maize-lupine intercrop yield response to applied N and P; to determine N use efficiency of maize; and to establish the basis for determining the most economical N and P rates with varying costs and commodity prices for the intercrop. The experiment was conducted at South Achefer and Mecha areas of North-Western Ethiopia in 2013 crop season. Four levels of each N (0, 64, 128 and 192 kg N ha-1) and P (0, 20, 40 and 60 kg P ha-1) were arranged in factorial combination. Sole crop maize and lupine were included as check treatments. The treatments were laid out in a randomized complete block design with three replications. The results indicated that maize growth parameters and yield components, maize grain yield, and total maize-lupine intercrop yield increased significantly with applied N, P, and N x P interactions. The highest total intercrop yields were obtained on 162/45 kg N/P ha-1 at South Achefer and 205/61 kg N/P ha-1 at Mecha with yield advantage of 4.14 and 7.05 t ha-1 over unfertilized, respectively. The economic optimum rates for maize-narrow leaf lupine intercrop were 130/39 kg N/P ha-1 at South Achefer and 177/53 kg N/P ha-1 at Mecha with cost price ratio of N cost kg-1/maize grain price kg-1 equal to 6 and P cost kg-1/maize grain price kg-1 equal to 11. The economic optimum rates decreased as cost price ratio increased, therefore, seasonal price information is vital to adjust the economic optimum rates. Maize N use efficiency declined as N rates increased in the maize-lupine intercrop.
Key words: Intercropping, lupine, maize, optimum rate, yield response.
AEN, agronomic efficiency of applied Nitrogen; AONR, agronomic optimum Nitrogen Rate, AOPR, agronomic optimum phosphorus rate; CPR, cost price ratio; EONR, economic optimum nitrogen rate; EOPR, economic optimum phosphorus rate; EYM, equivalent Yield of Maize; LAI, leaf area index; PEN, physiological efficiency of applied nitrogen; PFPN, partial factor productivity of applied Nitrogen; REN, recovery efficiency of applied Nitrogen; TKW, thousand kernel weight.
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