籽粒破碎率高是当前中国玉米机械收获籽粒的重要限制因素，解析破碎率变化原因,建立其简便预测模型是有待解决的重要问题。本文采集了7个玉米品种×3个种植密度组合的果穗，在不同水分梯度条件下开展单穗脱粒试验。种植密度在6～9株/m2范围内对籽粒破碎率没有影响，品种、籽粒的含水率、抗侧压碎力和穿刺强度等的影响均达到统计显著水平；品种对破碎率变化的偏贡献率为12.7%，而且，品种的偏贡献率 < 籽粒含水率的偏贡献率 < 抗侧压碎力的偏贡献率 < 穿刺强度的偏贡献率,而种植密度的偏贡献率接近于零；破碎率的最优预测因子是穿刺强度，预测模型为：破碎率=10.25×0.990穿刺强度，满足破碎率不高于5%约束的穿刺强度值不得低于60 MPa。研究结果为玉米破碎率预测，宜机收玉米新品种培育与鉴定、脱粒机具设计与制造提供了数据支撑和技术参考。
英文摘要:
High broken rates of kernels in maize combine harvesting are one of the most important factors limiting technology transfer, extension and application of mechanical harvesting for maize in China. Broken rates are dependent on both of maize properties itself and shelling machine. This paper aimed at evaluating biophysical factors influencing the broken rates of kernels under mechanical shelling and building single factor models for prediction of broken rates. Ears with an assign set of different moisture levels, from 7 maize cultivars grown at 3 plant densities, were subject to shelling tests using the same machine in order to explore influences on broken rates of such factors as maize cultivars, plant densities, kernel moisture and mechanical strength, as well as to screening optimum predictors and models for prediction of broken rates. Plant densities from 6 to 9 p/m2 didn’t influence broken rates, but all of maize cultivars, kernel moisture, kernel side crushing forces and kernel puncture strength did at statistically significant level. In respect of effect sizes of different factors for broken rates, total contribution, in terms of squared omega, of maize cultivars was smaller than that of kernel moisture to variations in kernel broken rates. Kernel moisture contributed less than both of side crushing forces and puncture strength to broken rate variation, and side crushing forces did less then puncture strength. The contribution of plant densities to broken rate variation was close to zero. Kernel puncture strength was the optimum predictor to estimate broken rates, which are an exponential decreasing function of puncture strength, and read as: kernel broken rate = 10.25×0.990^kernel puncture strength. Value 60 MPa of puncture strength is a lower limit to reach a broken rate no more than 5%. To sum up, the factors ranked as kernel strength and cultivars in descending order by their influence on kernel broken rates, with plant densities negligible. In addition, kernel moisture directly acted on kernel mechanical strength but indirectly act on kernel broken rates. Our findings provide useful information and an approach for broken rate estimation, screening of new maize cultivar suitable to mechanical kernel harvesting, shelling machine design and manufacture.
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