Determination of favorable sowing date of sweet sorghum in the State of So Paulo, Brazil by crop modeling

Sweet sorghum is a biofuel source for alternating with sugarcane in the State of Sao Paulo due to its short cycle, good sugar quantity and the possibility of using the same machinery that has been used for cane harvesting. The interest in the use of this crop is increasing because it keeps the sugar mills with material supply from all areas throughout the year. Thus we used an agrometeorological model to determine the best sowing dates for sweet sorghum, taking into account an early Brazilian cultivar (BRS 700), medium (BRS 601) and late (BRS 506). This model mainly relates solar irradiation, air temperature and water availability to crop yield. The simulations were done in important sugarcane regions in the State as north (Barretos), central-north (Jaboticabal), west (Tupa) and south (Itapetininga). After calibration, the model was used to estimate the potential yield, actual yield, climatic risk and the relative yield loss for 36 sowing dates per year with available data (1971-2012). The cultivars had the highest average yield in Itapetininga due to the increase of the cycles followed by Tupa, Barretos and Jaboticabal. The cultivar BRS 700 had the greatest climatic risk (84.19%) at Tupa and BRS 506 the lowest (63.17%) at Itapetininga. On average the best planting dates for cultivars were the second 10-day period (TDP) of September (2TDP-Sept) up to 2TDP-Jan to the Barretos, Jaboticabal and Tupa regions, and 2TDP-Jul up to 2TDP-Nov to Itapetininga.   Key words: Climate risk, yield estimation, planting season, Food and Agriculture Organization (FAO), agrometeorology.