河南玉米制种单产下降原因分析近年来，我省玉米制种总面积在逐年增加，玉米制种重点县仍然不断扩展。据统计资料，９４年以前，全省玉米制种总面积一直是３０万亩左右。全省玉米制种重点县仅有２０个，而到９６年，全省玉米制种面积却猛增到４０万余亩，全省玉米制种重点... In recent years, the total area of ​​corn seed production in our province is increasing year by year, and the key counties of corn seed production are still expanding. According to statistics, 94 years ago, the total area of ​​corn seed production in the province has been about 300,000 mu. The province’s corn seed production key counties only 20, and by 1996, the province’s corn seed area has soared to 400,000 acres, the province’s corn seed focus ...