Exploring optimal farm resources management strategy forQuncho-teff (Eragrostis tef (Zucc.) Trotter) using AquaCrop model

Teff is a major staple food crop in Ethiopia. Moisture and soil fertility are the two major factors limitingteff yield. Studies were conducted across three sites in Ethiopa [Mekelle (MK) in 2012 and 2016, Ilala(IL) in 2012 and Debrezeit (DZ) in 2009 and 2010]. The objectives of these studies were (1) to assessthe response of Quncho-teff to different fertilizer and irrigation levels; 2) to quantify irrigation waterproductivity (IWP), and (3) to collect data to calibrate and validate AquaCrop model for simulating yieldand evaluate optimal irrigation and sowing date strategy for Quncho-teff at different locations in Ethiopia.The different fertilizer levels were: 1) 64 kg N and 46 kg P/ha (N2P2); 2); 32 kg N and 23 kg P/ha (N1P1); 3)0 kg N and 0 kg P/ha (N0P0) and 4) 52 kg N and 46 kg P/ha (N3P3). The four irrigation treatments were: zero(rainfed), two, four and full irrigation applications. Findings showed that full irrigation in combinationwith high fertilizer (N2P2) could give better yield. However, during abnormal rainfall, spreading theavailable fertilizer at a rate of 32 kg N and 23 kg P/ha may be preferable to applying 64 kg N and 46 kgP/ha. This study also indicated that the regional fertilizer recommendations for teff need to be revisedtaking in to account the soil characteristics, climate and irrigation water availability. The AquaCrop modelwas able to simulate the observed canopy cover, soil water, biomass and yield of teff satisfactorily. Canopycover was simulated with normalized root mean square error (NRMSE), index of agreement (I) and R2of7%, 0.5 and 0.8, respectively. Soil moisture during the season was simulated with NRMSE of 11.4–15.7%,I of 0.99 and R2of 0.85–0.9. Simulated final aboveground biomass values were in close agreement withthe measured (NRMSE, 7.8%, I, 0.89 and R2, 0.66). There was also good agreement between simulatedand measured grain yield with NRMSE, I and R2values of 10.9%, 0.93, 0.80, respectively. Scenario analysisindicated that early sowing was the best option to maximize teff yield with the least amount of irrigation.Scenario analysis also showed that one irrigation during flowering stage could substantially improveirrigation water productivity (IWP) of teff and minimize the yield loses which could occur due to shiftingof sowing date from early to normal. Two irrigation applications also substantially improved the yieldand IWP of late sown teff. However, to get high yield, a late sown teff should receive at least four irrigationapplications during the mid-growth stage of the crop. These results suggest that AquaCrop model can beused to identify optimal farm resource management strategies for teff production.