Title: How Much Sugarcane and Soybean Production is Possible in Brazil on existing farmland? Authors: Fábio R. Marin, Geraldo Martha Jr, Kenneth G. Cassman, Patricio Grassini Brazil is the major world sugarcane and soybean producer with an annual production of 3,815 and 371 Mt, respectively. Future increases in the yields of these two crops will affect global and national trajectories of food and fuel prices, and crop land expansion. The objective of this paper was to quantify yield potential, yield gaps, and potential production for sugarcane and soybean in Brazil. Target areas for estimation of yield potential and gaps (hereafter called reference weather stations; RWS) were selected based on specific-crop harvested area, agro-ecological zones, and location of weather stations with 20+ years of weather data. A total of 20 and 21 RWS were selected for sugarcane and soybean, respectively. Yield potential was estimated using crop simulation models (CANEGRO and CROPGRO for sugarcane and soybean, respectively) based on RWS-specific actual weather, soil, and management practices. Yield gaps were estimated as the simulated yield potential minus average farmers’ yield derived from sub-national statistics. Results from the analysis will be added to this abstract before the final deadline in August.National average sugarcane Yw in Brazil is 118 t/ha (stalk fresh weight), while actual yields (Ya) averaged 82 t/ha, which is 70% of potential yield Average yield gap is 35 t/ha, with range of 29 to 66 t/ha depending upon climate zones. Largest gaps were found in the Mato Grosso area while the smallest gaps were found in the southern sugarcane production area.