LAUSR

Abstract The impact of increasing rates of typically used mineral fertilizer on Rain water use efficiency (WUE) and Radiation use efficiency (RUE) of maize grain yield and stover biomass productivity was estimated across the Agro-Ecological Zones (AEZs) of Ethiopia using the crop model LINTUL5 embedded into a general modeling framework, SIMPLACE (Scientific Impact Assessment and Modeling Platform for Advanced Crop and Ecosystem Management) with the hypothesis that WUE and RUE would increase with higher application rates of mineral fertilizer and vary for maize grain yield and stover biomass across the AEZs. The simulations were run using a long maturing cycle maize variety (BH660) and a medium maturing cycle maize variety (BH540) with historical weather data (2004–2010).There were strong effects of the application rate of mineral fertilizer on WUE and RUE of maize yield and stover biomass across the AEZs. The highest WUE of 11.5 kg mm−1 and 9.4 kg mm−1 in maize grain yield and stover biomass respectively was estimated with the application of 315 kg N ha−1 + 105 kg P ha−1 in AEZ 3 having the lowest amount of rainfall during the crop growth period as compared with AEZ 1 and 2.The findings of the current study indicate that WUE in grain and stover production can be increased to by 172% to 363%, and 230% to 352% respectively depending upon the AEZs, based on management intervention in terms of increased fertilizer application rates as compared with the WUE under unfertilized conditions. On the other hand, the highest RUE of 3.0 kg MJ−1 and 2.1 kg MJ−1 in maize grain yield and stover biomass respectively was estimated in AEZ 2 with the application of 315 kg N ha−1 + 105 kg P ha−1. RUE in grain yield and stover biomass can be increased to the tune of 177% to 362%, and 216% to 351% respectively depending upon the AEZs with the increased application of N and P compared with the RUE under unfertilized conditions. The economic analysis indicates optimal fertilizer application levels of 225 N + 75P kg ha−1 for maize production under average national conditions and prices and a slightly lower rate of 180 N + 60P kg ha−1 in regions where water availability tends to constrain grain yields in addition to the nutrient deficit.