A canopy height‐to‐row spacing ratio (CHRSR) of 1.0 is expected to be a simple and practical onsite index for soybean growers to determine when further weed control is no longer necessary. This is decided when relative photosynthetic photon flux density (PPFD) reaches 50% under the soybean canopy. To evaluate the validity of this index, a 2‐year field experiment was conducted to compare days after sowing (DAS) to reach a relative PPFD of 50% (defined as PPFD50) and DAS to reach a CHRSR of 1.0 (defined as CHRSR1.0) in 190 accessions with different canopy architectures from a soybean core collection. A total of 104 accessions, for which final relative PPFD reached <10% in 2014, were examined for the differences between CHRSR1.0 and PPFD50. The mean and median values of the difference in 2014 were 0.02 and 2.2, respectively. Similarly, the mean and median values in 2015 were 2.8 and 2.6, respectively. Thus, CHRSR1.0 tended to be achieved slightly later than PPFD50, so a consideration was made that there would be a negligible risk of failure if growers used CHRSR1.0 to determine the termination time for weed control in the most of accessions. Although there were some accessions with a standing type of morphological characteristics or with a smaller or narrower leaf, showing negative differences between CHRSR1.0 and PPFD50 larger than 1 week, a CHRSR of 1.0 could be used to estimate PPFD50 in most of accessions without risk of failure to control weeds.

中文翻译：

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评估大豆冠层高低行间距比作为使用多种大豆品种控制杂草的现场指标的有效性和局限性

冠层高度与行距之比（CHRSR）为1.0有望成为大豆种植者确定何时不再需要进一步除草的简单而实用的现场指标。决定何时在大豆冠层下相对光合作用光子通量密度（PPFD）达到50％。为了评估该指数的有效性，进行了为期2年的田间试验，比较播后（DAS）达到相对PPFD为50％（定义为PPFD50）和DAS达到CHRSR 1.0（定义为CHRSR1）的天数。 0）来自大豆核心品种的190个具有不同冠层结构的材料。审查了2014年最终相对PPFD达到<10％的104种材料的CHRSR1.0和PPFD50之间的差异。2014年差异的平均值和中位数分别为0.02和2.2。同样，2015年的平均值和中位数分别为2.8和2.6。因此，CHRSR1.0的获得往往比PPFD50稍晚一些，因此考虑到，如果大多数种植者使用CHRSR1.0来确定杂草控制的终止时间，则失败的风险可以忽略不计。尽管有些种质具有直立的形态特征或叶片较小或较窄，表明CHRSR1.0和PPFD50之间的负差大于1周，但在大多数种质中，CHRSR 1.0可以用来估计PPFD50，没有风险。无法控制杂草。0可确定大多数种质除草的终止时间。尽管有些种质具有直立的形态特征或叶片较小或较窄，表明CHRSR1.0和PPFD50之间的负差大于1周，但在大多数种质中，CHRSR 1.0可以用来估计PPFD50，没有风险。无法控制杂草。0可确定大多数种质除草的终止时间。尽管有些种质具有直立的形态特征或叶片较小或较窄，表明CHRSR1.0和PPFD50之间的负差大于1周，但在大多数种质中，CHRSR 1.0可以用来估计PPFD50，没有风险。无法控制杂草。