Effects of seedling age and root pruning on root characteristics and dry matter accumulation dynamics in machine-transplanted rice

To investigate the impact of different seedling transplanting times on rice growth, the present study evaluated seedling age and root pruning using treatments consisting of root pruning (RC20, RC30, and RC40) and no root pruning (CK20, CK30, and CK40). Quantitative analysis using curve fitting of the changes in dry matter accumulation (DMA) during the seedling and field stages was performed, and the changes in root parameters during the re-greening stage were observed. The results showed that the seedling stage could be divided into a gradual increase period, a rapid increase period, and a slow increase period. Transplanting at different time periods resulted in different transplanting shock effects. During the field stage, the DMA exhibited a slow-fast-slow "S" shaped curve as the developmental time progressed. However, significant differences were observed in growth parameters among the different treatments. Root injury promoted early maturity in young seedlings but also prolonged the whole growth period in older seedlings. The inhibitory effect of root pruning on rice root growth increased with young seedling age. The present results provide a theoretical basis for the design of seedling needle structure and the optimisation of rice seedling cultivation practices.