Rice yield potential as a function of sowing date in southern Brazil

Most studies about yield potential (Yp) of modern rice (Oryza sativa L.) varieties have been grown under tropical conditions of Asia, and little is known about the rice Yp in the subtropics of Brazil, the biggest rice producer outside Asia. Playing a key role in the global rice production, it is necessary to estimate the amount of rice that Brazil can potentially produce. The objective of this study is to provide estimations of Yp in southern Brazil by using the SimulArroz v1.1 and ORYZA v3 models. Models were calibrated and evaluated with data collected from five growing seasons across Rio Grande do Sul (RS) state in Brazil, where the cultivar IRGA 424 RI was sown from September to December. Both models presented similar performance in simulating phenology, with root mean square error (RMSE) of 9 d for ORYZA and 11 d for SimulArroz. For grain yield, the RMSE was 1.0 and 0.9 t ha(-1) for ORYZA and SimulArroz, respectively. Using the SimulArroz model, yield potential maps were drawn, which ranged from 14 t ha(-1), according to the region and sowing date. The penalty in Yp caused by the delay in sowing date is 0.03 t ha day(-1) from 1 September to 13 October, 0.08 t ha day(-1) from 14 October to 21 December, and 0.29 t ha day(-1) after 21 December. SimulArroz model is a suitable model for studies on rice Yp in the Brazilian subtropics.

Automated summary

This study estimated the yield potential of rice in southern Brazil using the SimulArroz v1.1 and ORYZA v3 models. The results showed that the SimulArroz model is suitable for studying rice yield potential in the subtropics of Brazil.