Feasibility of early sowing of irrigated rice based on the choice of cultivar

The early sowing of irrigated rice at the end of winter reduces plant growth and yield due to low water and air temperatures. This work aimed to assess the response of different rice cultivars to the early sowing time in the southern region of Brazil, and to determine the viability of this management practice. The experiment was set in a randomized block design, arranged in split plots at a latitude of approximately 29°11′ S and an altitude below 50 m. Two sowing dates were tested in the main plots: September 01 (early sowing date) and October 15 (preferential sowing date). Four cultivars were evaluated in the subplots: IRGA 424 RI, SCS116 Satoru, SCS 121CL and SCS122 Miura. The experiments were conducted over two growing seasons (2020/21 and 2021/22), using the pre-germinated system. Plant stand, grain yield, and yield components were determined. The early sowing date reduced plant stands at both growing seasons. Grain yield ranged from 7856 to 10213 kg/ha in 2020/21 and 9320 to 11114 kg/ha in 2021/22 season. Considering the average of cultivars, differences in yield obtained in the early sowing date, when compared with the preferential sowing date, were 11 kg/ha and 324 kg/ha, in the first and second growing season, respectively. SCS 116 Satoru was the only cultivar that did not show a reduction in grain yield when sown in September compared with October. The correct choice of cultivar is a management practice that can enable the early sowing of rice at the end of winter in the South of Brazil.