Title: Determination of genetic coefficients of some rice cultivars for application in the crop simulation model
Author: Shahram Nazari
Abstract: Rice (Oryza sativa L.) is one of the most important cereal products and half of the world’s population depends on rice as a staple food. Rice production systems are affected by environmental factors. Researchers are trying to develop a sustainable system that can be dealt with many challenges of crop systems. The rice modeling technique is very useful in agriculture because these techniques estimate the effect of factors on the system. An Important challenge to crop model simulation, especially for future crop performance projections varied conditions, is the unavailability of reliable genetic coefficients for model calibrations. In order to determine the genetic coefficients of some rice cultivars for use in simulation models, an experiment was done on rice crops in the research farm of the Rice Research Institute (Rasht) in 2020 based on randomized complete blocks design with three replications. The experimental treatment was six rice cultivars (Rash, Anam, Gohar, SA1, SA6, and M7). The results showed that the highest growth rate was observed in the vegetative phase, photo-sensitive phase, and panicle formation phase in Anam and SA1 cultivars. Furthermore, the highest grain filling period was obtained in Gohar, Anam, and SA1 cultivars, respectively. The minimum and more than the last time required to time to incipient emergence with 3 and 6 days were observed in Anam and Gohar cultivars, respectively. Also, the highest days to flowering and physiological maturity were 71 and 103 days in the Gohar cultivar, and the lowest days to flowering and physiological maturity were 54 and 86 days in the Anam cultivar. The highest flowering period with 19 and 20 days was obtained in late-maturing Rash and Gohar cultivars, respectively. Also, the shortest flowering period with 13 days was related to the SA6 cultivar. The highest harvest index with 50.91 and 49.13% was obtained in Gohar and Rash cultivars, respectively. The results also showed that the highest growing degree days (GDD) from the time period from the beginning of grain filling stage to maturity with 401, 394, and 396 GDD were related to M7, SA6, and Anam cultivars, respectively, and the lowest GDD was observed in Gohar and Rash cultivars with 300 and 350, respectively. Comparison of the cumulative temperature time of growth day for pre-flowering growth period showed that the highest quantity with 1208 and 1187 degrees of growth belonged to Gohar and Rash cultivars, respectively, and the lowest cumulative temperature pre-flowering with 804, 853, and 919 degrees of growth day were related to Anam, SA1 and SA6 cultivars, respectively. The highest and lowest potential spikelet number coefficient with 58 and 50 were related to Gohar and Anam cultivars, respectively. The results also showed that the highest potential weight of a single grain with 0.030 gr was observed in Gohar and M7 cultivars. The results showed that the highest plant height belonged to cultivar M7 with 150 cm. The results show that the genetic coefficients calculated in different models differ between cultivars and in general, the coefficients vary in the range defined in the model for different groups of maturity.
Keywords: Anam cultivar, APSIM-ORYZA model, Degree of growth day, Harvest index, Plant height