Abstract
We analyzed the correlation of wheat yields with climate conditions in Northern Kyushu from 2000 to 2014. The yield of wheat seeded at the standard date (November 20) was 1) negatively correlated with precipitation in mid-December (beginning of tillering stage), 2) positively correlated with temperature in early-January (early tillering stage), 3) negatively correlated with temperature in late-February (terminal spikelet formation stage), and 4) negatively correlated with temperature in mid-May (late maturing stage). Precipitation in mid-December and temperature in mid-May showed a stronger negative correlation with the yield in lower yield areas, indicating that a combination of wet damage at the early growing stage and heat damage at the late maturing stage results in a significant yield reduction. Higher temperatures in early January increased spike number and hastened the time of spike formation stage which extended the duration to heading and increased the yield. Thus, we considered that wheat yield in Northern Kyushu as 1) effective field drainage before planting, 2) seeding after November 5 to 10 to avoid frost damage and to accelerate spike formations, 3) effective field drainage and topdressing in all growing stages to sustain plant activity. Further yield increase should be achieved by improvement of frost tolerance other than winter habit, utilization of wheat Vrs1 gene that increases grain number, and the improvement of dual tolerance to wet and heat damage in addition to the tolerance to pre-harvest sprouting and grain discoloration by rain.
