Enhancing Grain Yield and Operational Feasibility by Transplanting Young Hydroponically Grown Long-Mat Rice Seedlings

Seedling transplanting is one of the predominant rice production systems in China. The production of hydroponically grown long-mat rice seedlings (HLMS) is a novel seedling cultivation method that reduces labor costs and improves efficiency. There is an urgent need to explore the optimum seedling age that maximizes grain yield from HLMS. Experiments were conducted to investigate the effects of seedling age on the seedling quality, field growth characteristics and grain yield of rice grown from HLMS. The grain yield was higher for young seedlings (13 d) than for older seedlings (27 d) as a result of robust seedling quality, increased mechanical transplanting quality, slight transplanting shock, sufficient tillers and increased panicle numbers in both cultivars when grown from HLMS under normal seeding density, and there was no significant difference in grain yield between transplanted 13-and 20-d-old seedlings. Moreover, the decreased yield in Wuyunjing24 might due to the reduced number of spikelets per panicle in old seedlings. In addition, the force of root entwining was significantly enhanced with increasing seedling age for both seedling cultivation methods and cultivars, and it was significantly higher for HLMS than for conventional mat seedlings raised in soil (CMSS). In general, transplanting young seedlings (13-20 d) by the HLMS method under normal seeding density brings better plant performance and higher yield than does transplanting older seedlings; relative to CMSS, HLMS increased the flexibility of seedling age (> 7 d) and operational feasibility, which can be mainly ascribed to the enhanced force of root entwining.