延迟收获对长江中游春玉米农艺性状及机收质量的影响

为探明长江中游玉米籽粒机械直收适宜品种与配套农艺措施，2018—2019年选用不同玉米品种，测定不同机收时间下玉米关键农艺性状、产量及机收质量指标。结果表明，收获时间对春玉米机收产量与机收质量均有显著影响。延迟1周收获后籽粒容重显著增加，机收产量显著提高，2年平均提高9.72%；而延迟2周收获则有降低机收产量的趋势。2年收获时杂质率总体≤3%，而机收籽粒破碎率与损失率均>5%，是该区域春玉米籽粒机收面临的主要问题。籽粒厚度、籽粒含水率和百粒重是影响机收籽粒破碎率的关键性状，三者与机收籽粒破碎率均呈显著的倒二次曲线关系；玉米的倒伏率、穗位高和重心高度是影响机收损失率的关键性状，倒伏率与机收损失率呈显著正相关，而穗位高和重心高度与机收损失率均呈显著的二次曲线关系。延迟收获能显著降低籽粒含水量，从而降低籽粒破碎率，但继续延迟收获有增加倒伏的风险。综上，长江中游春玉米成熟后适时延迟7~10 d收获，可有效降低籽粒含水量与机收籽粒破碎率，提高玉米籽粒机收产量。

Effect of delayed harvest on the agronomic traits and mechanical harvest quality of spring maize in the middle reaches of the Yangtze River

To explore the suitable varieties and supporting agronomic measures of maize mechanical harvesting in the middle reaches of the Yangtze River, different maize varieties were selected and harvested at different times after grain maturity in 2018 and 2019 to analyze the changes in yield and quality of mechanical harvest. The key agronomic traits were further identified influencing the broken rate and loss rate in mechanical harvest. The results showed that the harvest time had significant effects on mechanical harvest yield and quality in spring maize. The delayed harvest by a week significantly increased the grain test weight, thus increased the mechanical harvest yield by 9. 72% averaged across varieties and two years. However, delayed harvest by 2 weeks would reduce the yield of mechanical harvest. In the two experimental years, the impurity rate was less than 3%, while the broken rate and loss rate of mechanical harvest were all higher than 5%, which were the major problem in maize mechanical harvest in this region. Grain thickness, grain moisture and 100-grain weight were the key traits affecting the grain broken rate in mechanical harvest, which showed a significant negatively quadratic curve relationship with the grain broken rate. The lodging rate, ear height and barycenter height were the key traits affecting the loss rate. The lodging rate is positively linearly correlated with the mechanical harvest loss, while the ear height and the barycenter height had a significant quadratic curve relationship with the loss rate. In conclusion, the delayed harvest by one week significantly decreases the grain moisture and thus reduces the grain broken rate. However, continuing to delay the harvest has the risk in increasing lodging rate. It is suggested that spring maize in the middle reaches of Yangtze river could be mechanically harvested 7-10 d after maturity, which could effectively reduce the grain moisture and the grain broken rate, thus increase the mechanical yield.