Mechanical transplanting has been applied to rice cultivation to save labor costs and ease labor shortages in Asian countries, especially in China.  However, little information is available related to the characteristics of agronomic performance when comparing inter-sub-specific hybrid rice (IHR) and inbred japonica rice (IJR) under mechanical transplanting method.  In 2013 and 2014, field experiments were conducted using IHR (Yongyou 2640) and IJR (Wuyunjing 24) under two cultivation patterns, that is, pot seedlings mechanically transplanted (PS) and carpet seedlings mechanically transplanted (CS).  Grain yield, yield components, leaf area index (LAI), leaf area duration (LAD), aboveground biomass, crop growth rate (CGR), nitrogen (N) uptake, and N accumulation were investigated.  When compared with CS, PS displayed significantly increased grain yield for both varieties because the larger sink size allowed higher N accumulation from panicle initiation to maturity.  Moreover, total aboveground biomass under PS increased significantly compared with that under CS; that is, higher photosynthetic productivity resulted from a greater LAI and higher LAD during the grain filling stage.  Higher N absorption capacity in the middle and late growth periods resulted in significantly enhanced total N uptake under PS.  When compared with IJR for both treatments, IHR generated 75.2% more grain yield.  However, the characteristics creating high yield of IHR were different from those of IJR.  Greater aboveground biomass production as well as higher N uptake and accumulation created higher grain yield in IHR than in IJR.  These results suggest higher yield could be achieved using PS with IHR, attributing to exploit both yield superiority and productive potential.

Several studies have demonstrated the effect of planting methods on rice yield, but information on the climate resources is limited.  This study aims to reveal the effects of planting methods on climate resources associated with rice yield in a rice-wheat rotation system in the lower reaches of the Yangtze River, China.  Field experiments were conducted in 2014 and 2015 with two japonica, two indica hybrid, and two japonica-indica hybrid varieties grown under three mechanized planting methods: carpet seedling of mechanical transplanting (CT), mechanical direct seeding (DS), and pot-hole seedling of mechanical transplanting (PT).  The rice yield and total This study was financially supported by grants from the Major Independent Innovation Project in Jiangsu Province, China (CX(15)1002), the Agricultural Science and Technology Innovation Fund in Jiangsu Province, China (CX(12)1003-09), the National Key Research Program of China (2016YFD0300503), the Science and Technology Plan of Jiangsu Province, China (BE2015340), the Research Innovation Program for College Graduates of Jiangsu Province, China (KYLX15_1369), and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China.dry matter under PT were greater than those under CT and DS methods.  Besides, the entire growth duration and daily production showed significant positive relations with rice yield.  Compared with CT and DS, the effective accumulated temperature and cumulative solar radiation of rice under PT were higher in phenological phases.  In addition, the dry matter/effective accumulated temperature and solar energy utilization of rice under CT and DS were higher during vegetative phase and lower during reproductive and grain filling phases in contrast to PT.  The mean daily temperature and mean daily solar radiation in the entire growth duration showed significant positive correlation with rice yield, total dry matter, and harvest index.  This study demonstrated that when the mean daily temperature is <25.1°C in vegetative phase and >20.1°C in grain filling phase, rice yield could be increased by selecting mechanized planting methods.  Most varieties under PT method exhibited high yield and climate resources use efficiency compared with CT and DS.  In conclusion, the PT method could be a better cultivation measure for high rice yield, accompanied with high temperature and solar radiation use efficiency in a rice-wheat rotation system in the lower reaches of the Yangtze River, China.