Printed sowing improves grain yield with reduced seed rate in machine-transplanted hybrid rice

Machine transplanting is an alternative establishment method to replace manual transplanting that reduces labor inputs in rice production. It is important to reduce the seed rate in mechanical transplanting, especially for hybrid rice with expensive seeds. Printed sowing (PS), i.e. pasting seeds to paper, is a new sowing method for reducing the seed rate. This study was conducted to compare seed rate, grain yield, and yield attributes in machine-transplanted hybrid rice between PS and manual sowing (MS). Field experiments were conducted in the early and late seasons of 2017 and 2018 in Yongan Town, Hunan Province, China. Seed rates under PS were 9.6-19.8 kg h(-1), which were lower by 2.73-5.65 times than under MS. PS produced 11 % higher grain yield compared to MS. The higher grain yields under PS compared to MS were mainly due to higher seedling quality, larger panicle size, higher spikelet filling percentage, higher aboveground biomass, and higher harvest index under PS than under MS. The better performance of yield attributes under PS compared to MS could be explained by improvements in morphological and physiological traits including number of vascular bundles and leaf photosynthetic capacity. Our study suggests that PS is a feasible method to reduce seed rate and increase grain yield in machine-transplanted hybrid rice production.