凤县从1980年起,先后在杨家山、庙沟、鹿母寺、安河寺等10个播区进行了飞播造林试验,造林而积达1.9万公顷。几年的造林试验发现,播前有透雨,播后遇连阴雨或有充足的雨量,种子出苗效果就好,反之就差。据此对最佳播期进行了选择。从降水情况看,风县全年降水量夏秋两季所占比重较大,分别为306.4mm、172.3mm,且春夏两季降水量逐月上升,直止9月达最大,为108.4mm。春季降水量为126.9mm,冬季只有5.7mm。如只考虑降水因子,凤县飞播应选在7月。但7月连阴雨较多,不利于飞机高空作业。8、9两月降水条件虽好,但气温高,水分蒸发快,不利于种子 Since 1980, Fengxian County has carried out aerial seeding afforestation experiments in ten broadcast areas such as Yangjiashan, Miaogou, Luma Temple, and Anhe Temple, with a total area of ​​19,000 hectares. A few years of afforestation test found that there is a see-through before sowing, after sowing rainy or have adequate rainfall, seed germination effect is good, and vice versa. Accordingly, the best sowing date has been chosen. In terms of precipitation, the annual precipitation in Fengxian takes a larger proportion in summer and autumn, at 306.4mm and 172.3mm, respectively. The precipitation in spring and summer increases month by month, reaching the maximum in September at 108.4mm. Spring precipitation is 126.9mm, only 5.7mm in winter. If only consider the precipitation factor, Fengxian aerial broadcasting should be selected in July. However, more rainy in July, is not conducive to the aircraft at high altitude. 8,9 February precipitation conditions are good, but the high temperatures, water evaporation is fast, is not conducive to the seeds