Study and Modelling the Emergence of Five Hungarian Rice Cultivars
In Hungary rice (Oryza sativa L.) is cultivated under flooded conditions. Direct seeding into the soil is applied usually. The optimal sowing date is a key factor necessary to the success of this annual crop because of the relatively short growing season. The main objective of this research was to: (1) analyse duration of period from sowing to emergence at different temperature values, (2) determine base temperature of this phenophase and (3) establish a thermal time model for rice emergence. To do this, growth chamber experiments with 5 Hungarian cultivars were conducted to determine the time to median emergence (E50) at constant temperature of 14 to 34 °C in 2 °C steps. The sowing depth was 2 cm, and moisture was not a limiting factor. It was found that the critical thermal zone, which is of highest practical importance, is between 14 and 16 °C. At these values the E50 is 23.9 and 13.4 days, respectively, showing a border between unfavourable and acceptable conditions. In the temperature interval between 26 and 34 °C the time needed for emergence was only 3.3 to 4.4 days. Variety differences were also detected. Base temperature was found between 9.8 and 10.9 °C. The thermal time requirements of 4 cultivars varied between 69 and 73 °C day. Data of field experiment with 9 sowing dates and a pot experiment with 3 sowings confirmed that our thermal time model can successfully simulate the emergence of rice.
Keywordsrice emergence thermal time base temperature linear model
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