Impact of temperature and relative humidity on sowing date and commercial grain yield of wheat in southern Sonora, Mexico

This work aimed to analyze the variation in temperature (T) and relative humidity (RH) in wheat seasons 2004-05 to 2023-24, and its impact with sowing dates on grain yield in southern Sonora, Mexico. The T and HR were recorded in hourly format from the meteorological stations in the region during November to April. Commercial fields were selected based on territorial distribution in the Yaqui (YV) and Mayo (MV) Valleys, covering sowing dates from November 1 to January 15, and grain yield was determined based on a 1 m 2 sample with six replications in each field. The daytime T in both valleys had a positive trend, in the YV it increased between 1.4 and 2.9 °C, while in the MV between 1.8 and 3.5 °C. The night T had mostly a negative trend in both valleys, the MV had a tendency with 1.6 °C less and the YV with 1 °C. RH during the day showed a decreasing tendency throughout most of the season in both valleys, in the YV the decrease ranged from -2.6 to 0.9 %, and from -4.9 to -2.5 % in the MV. Nighttime humidity had an increase tendency in the YV with a range of 1.1 to 8.0 %, whereas in the MV, it showed a tendency to decrease in November, January, February, and March. The night temperature was negatively correlated with grain yield in both valleys, while relative humidity was not. The grain yields (above 9.5 t ha -1 ) were obtained in wheat seasons characterized with more than 670 cold units, and grain yield over 6.5 t ha-1 was obtained highest in sowing dates from November 21 to December 20.