Quantification of border effect on grain yield measurement of hybrid rice

► Border effect for the sides with wide hill spacing was 1.3 times higher than that with narrow hill spacing. ► Higher biomass production, more sink development, and better grain filling were responsible for the border effect. ► An equation was developed to calculate yield overestimation by considering border effect of sides with wide and narrow hill spacing separately. ► For a plot with 667 m2, minimum yield overestimation rate due to a border effect was 2.7%. ► Yield overestimation would be substantially higher for a plot with more rectangular shape and smaller plot size.