Regulating effect of Paclobutrazol and retention agent on rice seedling quality in straw-ash substrate.

The effects of Paclobutrazol and retention agent application on the quality of rice seedlings in straw-ash substrate and traditional nutrient soil substrate were studied.The results showed that,since the effective components of Paclobutrazol in straw-ash had a lot of loss,Paclobutrazol significantly controlled seedling height after the emergence of rice seedlings.With the increase of rice seedling age,the control effect of Paclobutrazol on rice seedling height was weakened significantly.After the emergence of the 3rd leaf in rice seedling,Paclobutrazol basically had no control effect on seedling height.When Paclobutrazol application was combined with retention agent,they could significantly decrease the loss of Paclobutrazol in straw-ash,substantially increase the control efficiency and effective period of Paclobutrazol,greatly decrease the height of rice seedlings in straw-ash substrate,and averagely reduce the 1st,2nd and 3rd leaf height by 30.5%,23.9% and 17.2% respectively.Furthermore,the mixed application of Paclobutrazol and retention agent could increase the leaf age,make the plant-type close,and enhance the stem diameter and rice seedling quality.Therefore,the raised rice seedlings could meet the requirement of transplanting machinery.