最佳播期 ,是北方旱地覆膜玉米高产栽培中关键技术措施之一。通过对北方干旱、半干旱生态类型区自然资源的分析 ,提出了综合应用地膜的增温、保墒效应 ,对覆膜玉米适时早播的理论基础和生产实践进行了分析研究 ,进一步明确了适时早播的标准 The best sowing date is one of the key technical measures in high-yield cultivation of plastic film mulching in dry land in northern China. Based on the analysis of the natural resources in northern arid and semi-arid ecotype area, the paper puts forward the theoretical basis and production practice of comprehensively applying plastic film in warming and preserving soil moisture, analyzing and researching timely and early sowing of plastic coated corn, Broadcast standard