- Up to 35% increase or decrease, acceleration of flowering is the key for stable production -
The National Agriculture and Food Research Organization (NARO) and the Tokyo University of Agriculture have revealed that weather in the five-day period including the flowering day and two days before and after the flowering day has greatly influenced the wheat yield in major Hokkaido production areas with "Kitahonami" as the main cultivar in recent years. It was estimated that the yield would be reduced in case of cloudy or rainy weather, with a difference of up to 35% when compared to that of clear weather. This research outcome will be useful for developing stabilization technology of wheat yield.
Hokkaido is a major production area, accounting for two-thirds of the domestic wheat production. Especially the eastern part of Hokkaido including the Tokachi and Okhotsk regions are the main production areas of wheat. The yield per unit area of wheat in the regions has been increasing year by year on average due to the change of major cultivars and improved cultivation techniques associated with breed improvement. However, the annual yield has been so fluctuating that the yield in a year could drop to 30-50% of that in the previous year. Therefore, it has been required to elucidate the causes of such big yield fluctuation in the production sites.
To date, the research group of NARO and other institutes have clarified that high temperature and cloudy weather in June-July are the greatest meteorological factors for the yield decrease in major production areas in Hokkaido. However, there have been years in which we could not identify the cause of the yield reduction even taking into account the above-mentioned meteorological factors. Therefore, we focused on the short-term weather conditions for a few days to investigate the relationship between weather and wheat yield.
Wheat yield gap (simulated potential yield minus actual on-farm yield) was analyzed in the major production areas in Hokkaido in the 1984-2020 period with the general-purpose crop growth analysis model to investigate the relationship between the yield gap and the six different meteorological conditions in the short-term of a few days. The results showed that weather in the five days including the flowering period and 2 days before and after the flowering day had the greatest impact on the yield in the years after 2011. In case of the cloudy or rainy weather during the flowering period, wheat yield decreased up to 35% in comparison with the case of clear weather. This relationship is characteristic for the current major cultivar "Kitahonami" and there was a different trend before 2011 when "Chihoku-komugi" or "Hokushin" were the major cultivars.
From the above-mentioned results, it was found that, it is most important to reach the flowering period in fine weather and to pollinate reliably, in order to achieve high yield of the current major cultivar "Kitahonami". Winter wheat in Hokkaido often flowers in mid-June when it is prone to have a long spell of rain. The Risk of flowering during the rainy season increases as much as the delay in flowering. It has been suggested that accelerating the flowering with growth-promoting techniques such as sowing at appropriate times or spraying snowmelt material to the field may lead to stabilization of the yield.
Budget: Grant for Operational Expenditure, Grant for Scientific Research, Fundamental Research A [19H00963]
Shimoda Seiji, Terasawa Youhei, Nishio Zenta, 2022, Improving wheat productivity reveals an emerging yield gap associated with short-term change in atmospheric humidity. Agricultural and Forest Meteorology, 312, 108710