度尾文旦柚辨形疏果最佳FSI阈值研究

Threshold Fruit Shape Index for Optimal Pomelo Thinning on Duweiwendan Trees

【目的】根据裂果率(FCR)与果形指数(FSI)负相关原理,研究FSI辨形疏果的最佳FSI阈值。【方法】由2016-2018年于仙游县度尾文旦柚主产区采集n=8660的果实裂宽(FCW)与FSI数据,对果实FSI及其裂顶与否的分布进行分析,研究FSI辨形疏果的报酬与降低裂果率代价。【结果】FSI=0.90是疏果报酬盈亏拐点,疏果FSI阈值的上限为0.90。经迭代回归模拟Logistic累积曲线,FSI≤0.83区间疏除裂果效率相对较高;当FSI≤0.80时,疏果量约20%,疏果报酬>2.0;若FSI>0.80时,疏果量将陡增,疏果报酬<2.0,反之FSI<0.80裂果疏除效率降低。据试验总体与3年裂果率Logistic累积曲线变率的峰值评估,FSI≤0.80疏果阈值可靠安全,无过度误导疏果可能。【结论】为降低疏果对产量的影响,提高疏果FSI阈值的可靠性,本文推荐最佳疏果阈值为FSI≤0.80,丰产年份可考虑提升疏果阈值为FSI≤0.83。

【Objective】Based on the inverse relation between the fruit cracking rate and fruit shape index(FSI),thresholds to achieve optimal pomelo thinning on Duweiwendan,Citrus grandis(L.)Osbeck.cv.Duweiwendan,was studied for orchard management.【Method】From 2016 to 2018,8660 pomelos on Duweiwendan trees were collected from the major producing areas in Xianyou County,Fujian to determine the fruit crack width(FCW)and FSI at the orchards.Distribution of the data compiled was used to access the cost/benefit to arrive at a recommended threshold for the fruit thinning.【Result】The upper limit of FSI at 0.90 was found to be the inflection point on the iterative regression simulation of logistic cumulative curve of the operation.According to the curve,at FSI≤0.83 a relatively high efficiency of cracked fruit elimination was obtained.At FSI≤0.80,20%of the pomelos were discarded resulting in a definition greater than 2.0.At an FSI>0.80,the amount of thinned fruits increased significantly,while the corresponding gain dropped to below 2.0.Conversely,if the FSI was reduced to less than 0.80,the operational efficiency declined.The peak of the logistic cumulative curve on the 3-year fruit crack rates,as well as the field statistics,indicated that a thinning threshold at FSI≤0.80 was appropriate with little concern of excessive loss on the fruit harvest.【Conclusion】An optimal threshold of FSI≤0.80 to improve the financial gain with a minimized harvest reduction was recommended for the Duweiwendan pomelo orchards.An FSI up to 0.83 could be considered in years when a bumper pomelo harvest is expected.