Morphological and physiological traits of roots and their relationships with shoot growth and grain yield in direct-seeded rice in northeastern China

Abstract

Context In recent years, direct-seeded rice (DSR) cultivation methods have been widely adopted in Asia. Aims The objective of this study was to evaluate the grain yield, nitrogen use efficiency and associated plant traits of DSR in northeastern China. Methods A 2-year field experiment was conducted using two varieties under three cultivation methods (1) conventional transplanted rice (CTR); (2) wet direct-seeded rice (WDSR); and (3) dry direct-seeded rice (DDSR). Key results The grain yield of CTR and DSR ranged from 10.16 to 9.39 t ha−1 and from 8.85 to 6.90 t ha−1, respectively, accross varieties and years. The wide difference was attributed to the differences in spikelet number per panicle and biomass. Compared with the CTR, the DSR decreased the spikelet number per panicle, which resulted in lower spikelet number per m2. Meanwhile, a significant positive correlation was observed between spikelet number per m2 and nitrogen uptake. The nitrogen uptake of CTR and DSR ranged from 151 to 153 kg ha−1 and from 96 to 132 kg ha−1, respectively. The root biomass, root length and zeatin + zeatin riboside contents in roots were higher in CTR than DSR, which contributed to the higher nitrogen uptake. Conclusions These results suggest that DSR reduced nitrogen uptake, thereby resulting in decreased number of spikelets per panicle, and hence lower rice grain yield. Implications These findings have highlighted the deficiencies in direct seeded rice system, and further research is required to overcome these deficiencies.