Abstract: Grain mechanical harvesting is the developing direction of maize production in China, selecting maize varieties with suitable growth period, high lodging resistance and dehydrating rate, and adopting the corresponding agricultural machinery and cultivation technology is the effective approach for realizing maize grain mechanical harvesting. Field experiments were conducted in the north of Huang-huai summer maize region, Tongzhou District, Beijing, to study the effect of mechanical harvest date on maize grain moisture content and grain mechanical harvesting quality, under 5 grain mechanical harvest date treatments with physiological maturity (PM)(H1), 5 (H2), 10 (H3), 15 (H4), 20 (H5) d after PM. Maize varieties registered by National Crop Variety Approval Committee Jingnongke 728( JNK728), MC812 and MC121 selected by using maize core inbred Jing 2416 which characterized by high density and lodging resistance, early maturity and fast dehydrating rate as the male parent and the two dominant maize varieties Zhengdan 958(ZD958) and Xianyu 335(XY335) were used as the materials. The results showed that: ① Growth period (emergencing to physiological maturity) of JNK728, MC812, MC121, XY335 and ZD958 was 101, 106, 105, 111 and 113 d, respectively. ② Grain moisture content averaged 31.2%, 29.4%, 27.6%, 26.0%, 24.4% under H1, H2, H3, H4, H5 treatments; the grain dehydrating rate after PM differed significantly among varieties with JNK728 [0.039%·(℃·d) ^-1]＞MC812 [0.037%·(℃·d) ^-1]＞MC121 [0.032%·(℃·d) ^-1]＞XY335  [0.031%·(℃·d) ^-1]＞ZD958 [0.026%·(℃·d) ^-1]. ③ Grain broken rate averaged 7.4%, 6.8%, 6.2%, 5.4%, 5.0%, impurity rate averaged 1.2%, 1.0%, 0.8%, 0.6%, 0.6%, and loss rate averaged 3.7%, 3.4%, 3.3%, 3.3%, 3.1% under H1, H2, H3, H4, H5 treatments; mechanical harvesting quality indexes of grain broken rate, impurity rate and loss rated of JNK728, MC812 and MC121 at H4 treatment could reach GB standard, but ZD958 and XY335 were not suitable for grain mechanical harvesting because of higher grain broken rate. ④ Correlation analysis showed that, maize grain moisture content was significantly correlated with grain broken rate, impurity rate and loss rate, grain loss rate was significantly correlated with grain broken rate and impurity rate. Thus, mechanical harvesting date was the major factor influencing maize grain moisture content and mechanical harvesting quality. Selecting maize varieties with earlier maturity, higher dehydrating rate and lower grain moisture content at harvest, and harvesting at suitable period was the key for realizing maize grain mechanical harvesting in the north of Huang-huai summer maize region. JNK728, MC121 and MC812 which characterized by earlier maturity and higher dehydrating rate after PM were suitable for grain mechanical harvesting at 15 d after PM under the sowing condition of June 15th in the north of Huang-huai summer maize region, ZD958 and XY335 which characterized by relatively later maturity and lower dehydrating rate after PM could not realize grain mechanical harvesting in this region.

Key words: harvest date, maize, grain moisture content, mechanical grain harvesting quality

摘要： 籽粒机收是我国玉米生产发展的趋势和方向，选用熟期适宜、抗倒性好、脱水快的玉米品种并农机农艺结合、良种良法配套是实现玉米籽粒机收的技术途径。选用以耐密抗倒伏、早熟脱水快的玉米骨干自交系京2416为父本组配选育并通过国审的3个早熟耐密玉米新品种京农科728、MC812、MC121，以及郑单958、先玉335两大主导品种，在黄淮北部夏播区北京通州开展籽粒机收试验，设置生理成熟期（H1）及生理成熟后5（H2）、10（H3）、15（H4）、20（H5）d共5个机收籽粒收获期处理，研究并明确了收获期对不同玉米品种籽粒含水率及籽粒机收质量的影响，为黄淮北部夏播区机收籽粒玉米品种选择和适期机收提供指导。结果表明：①参试玉米品种京农科728、MC812、MC121、先玉335和郑单958夏播出苗至成熟分别为101、106、105、111、113 d。②H1、H2、H3、H4、H5五个不同收获期条件下，籽粒含水率平均为31.2%、29.4%、27.6%、26.0%、244%；不同品种生理成熟后的籽粒平均脱水速率差异显著，表现为京农科728 [0.039%·(℃·d) ^-1]＞MC812 [0.037%·(℃·d) ^-1]＞MC121 [0.032%·(℃·d) ^-1]＞先玉335 [0.031%·(℃·d) ^-1]＞郑单958 [0.026%·(℃·d) ^-1]。③H1、H2、H3、H4、H5五个收获期，籽粒破碎率平均为7.4%、6.8%、6.2%、5.4%、5.0%，杂质率平均为1.2%、1.0%、0.8%、06%、0.6%，落粒率平均为3.7%、3.4%、3.3%、3.3%、3.1%；在H4收获期，早熟品种京农科728、MC812和MC121的籽粒破碎率、杂质率和落粒率均达到国家机收标准，而郑单958和先玉335因籽粒破碎率高不适宜机收籽粒。④相关性分析表明，籽粒含水率与破碎率、杂质率和落粒率均极显著正相关，落粒率与破损率和杂质率极显著正相关。由此说明，收获期是影响玉米籽粒含水率和籽粒机收质量特别是籽粒破碎率的重要因素，在黄淮北部夏播区选择早熟、脱水快、收获时籽粒含水率低的品种以及适期收获是实现玉米籽粒机收的关键；京农科728、MC812和MC121熟期早、脱水快，在黄淮北部6月15日夏播条件下生理成熟后15 d即可机收籽粒，而郑单958和先玉335熟期偏长且后期脱水相对较慢，在黄淮北部夏播区不宜机收籽粒。

关键词: 收获期, 玉米, 籽粒含水率, 籽粒机收质量