夏玉米籽粒含水率对机械粒收质量的影响

玉米机械粒收过程中出现的籽粒破碎、果穗遗漏、籽粒散落等影响收获质量的现象是机械粒收推广过程中备受关注的问题。开展机械粒收质量及其影响因素研究,是确定适宜粒收时期、指导品种改良等的基础,对于机械粒收技术的推广普及具有重要意义。本研究于2015年和2017年在中国农业科院新乡综合试验站,以黄淮海夏玉米区生产用品种为试材,采用同一收获机和操作人员分期收获,调查不同收获期籽粒含水率变化以及破碎率、杂质率、落粒率和落穗率等机械粒收质量指标,分析籽粒含水率与粒收质量指标的关系。结果显示,随着收获期推迟,籽粒含水率逐渐降低,籽粒破碎率和落粒率呈先降低后升高趋势,杂质率逐渐降低,落穗率逐渐增加。2年参试样本籽粒含水率分布在9.68%～41.36%之间,破碎率与籽粒含水率的关系符合y=0.068x2–2.743x+31.09 (R2=0.79**, n=140)模型;含水率在15.47%～24.78%之间时,破碎率低于5%;含水率为20.05%时,破碎率最低。杂质率与籽粒含水率的关系符合y=0.0158e0.1111x (R2=0.66**,n=140)模型,杂质率随着含水率降低逐渐降低并趋于稳定。落粒率与籽粒含水率符合y=0.006x2–0.236x+3.479 (R2=0.42**, n=127)模型,含水率为20.37%时,落粒率最低。落穗率与籽粒含水率符合y=2578.7645/x2.2453 (R2=0.35**, n=140)模型,当含水率低于16.15%时,落穗率将超过5%。研究还发现,即使籽粒含水率相近,不同品种的收获质量(特别是籽粒破碎率)也存在显著差异。本研究的结果表明,破碎率是决定机械粒收质量的关键因素,以破碎率5%和落穗率5%为标准,黄淮海夏玉米适宜机械粒收的籽粒含水率范围为16.15%～24.78%,籽粒含水率在20%左右时,收获质量最佳。

Effects of Grain Moisture Content on Mechanical Grain Harvesting Quality of Summer Maize

Broken grains, losing ears and grains always occur when maize is harvested by grain harvester, which is a hot topic. Studying grain mechanical harvesting quality and its affecting factors is of great significance for popularizing this technology, which provides a basis for finding out the best harvesting time and the direction of maize cultivar development. The experiments were conducted in Comprehensive Experiment Station of Chinese Academy of Agricultural Sciences located in Xinxiang city in 2015 and 2017. The dozens of popular cultivars grown in the Yellow-Huaihe-Haihe Rivers Plain summer maize region were harvested in different harvest times by a same grain combine harvester and a same driver. Indicators of grain moisture content, broken rate, impurity rate, grain loss rate and ear loss rate were measured to analyze their mutual relationships. With delaying harvest time, grain moisture content and impurity rate declined gradually, grain broken rate and grain loss rate decreased first and then increased, ear loss rate gradually rose. The grain moisture contents ranged from 9.68% to 41.36% in the two years. Its relationship with broken rate could be fitted by the equation y = 0.068x ²-2.743x+31.09 (R ²= 0.79 ^**, n = 140). Broken rate could be less than 5% when moisture content was 15.47%-24.78%. When moisture content was 20.05%, broken rate was the lowest. The relationship between impurity rate and moisture content could be fitted by the equation y = 0.0158e ^{0.1111 x}(R ²= 0.66 ^**, n = 140). Impurity rate decreased first and then tended to be stable with falling moisture content. Grain loss rate and moisture content could be regressed in the equation y = 0.006x ²-0.236x+3.479 (R ²= 0.42 ^**, n = 127). Grain loss rate was the lowest when moisture content was 20.37%. Ear loss rate and moisture content could be regressed in the equation y = 2578.7645/x ^2.2453 (R ²= 0.35 ^**, n = 140). Ear loss rate was more than 5% when moisture content was below 16.15%. We also found that harvesting qualities, especially broken rate, of different cultivars had significant differences while their grain moisture contents were the same. In conclusion, broken rate is the key factor that determined the quality of grain mechanical harvesting. The optimal grain moisture content interval of mechanical harvesting in Yellow-Huaihe-Haihe Rivers Plain summer maize region is 16.15%-24.78% at the standard of 5% broken rate and 5% ear loss rate. The harvesting quality would be the best when the moisture content is about 20%.