汉中盆地位于北纬32.5～33.5度之间,具有亚热带北缘气候特点。年大于10℃以上活动积温4498.5℃,其中水稻生长的4月10日至9月30日为3922.41℃,占全年的87.2%。气候适宜于杂交水稻生产和制种,常年水稻种植10万ｈｍ2,制种0.13万ｈｍ2。水稻制种关键技术之一是确定最佳出穗期,从而 Hanzhong Basin is located between latitudes 32.5 ~ 33.5 degrees, with the northern subtropical climate characteristics. The annual accumulated temperature above 44 ℃ was 4498.5 ℃, of which rice was grown from April 10 to September 30 at 3922.41 ℃, accounting for 87.2% of the whole year. Climate suitable for hybrid rice production and seed production, perennial rice planting 100,000 hm2, seed production of 13 300 hm2. One of the key technologies of rice seed production is to determine the best heading date