Estimating the genetic coefficients of irrigated lowland rice varieties through the decision support system for agrotechnology transfer (DSSAT) to simulate crop growth and potential yield

Genetic coefficients are sets of quantitative parameters needed to simulate rice crop growth and potential yield. These are inputs for the application of crop growth simulation models in simulating potential yield or the highest genotypic yield under optimum crop management and favorable weather condition. The genetic coefficients can be determined by measuring specific traits in controlled environmental chamber experiments. However, it is time-consuming, very expensive and conditions differ from experimental and farmer's fields. The Genetic Coefficient Calculator tool (GenCalc) is part of the DSSAT model. This study assessed the ability of DSSAT to estimate the genetic coefficients of irrigated lowland rice varieties using crop and soil management and weather data during the 2012 dry and wet seasons. The GenCalc tool identified the best fit of genetic coefficients of PSB Rc82, NSIC Rc160 and Mestiso 20 through several runs. Each cultivar's values for the growing degree days during vegetative phase (P1), the beginning of grain filling to physiological maturity (P5), the critical day length for flowering in hours (P20), the photoperiod sensitivity coefficient (P2R), potential spikelet number coefficient (G1), single grain weight in grams (G2), tillering coefficient relative to variety IR64 (G3), and temperature tolerance coefficient (G4) were calculated in the program. These coefficients will be used to simulate potential yield in a given crop management and weather conditions. Once validated by comparing the observed and simulated growth and yield values, the model will be used to predict the potential impact of climate change on rice crop yield.