Study On Mechanism Of Bast Fiber Seedling Film In Improving Rice Seedling Quality For Mechanical Transplanting

Rice seedling blocks raised for mechanical transplanting were easily cracked in practice and it's very common in China.Bast fiber seedling film is a new type of film material developed to solve this problem.A large number of application practices showed that the bast fiber seedling film laid on the bottom of seedling tray can significantly promote the growth and development of seedling root system and form blanket,and improve the rice yield.However,its mechanism was not clear yet.Based on the existing research,this study comprehensively summarized the effect of bast fiber seedling film on the quality of mechanical transplanting rice seedlings;exploredits mechanism from the aspects of oxygen supply and soil environment in rice root zone;studied the effect of oxygen deficiency at different leaf ages on the growth of rice seedling and enzymes activity of nitrogen metabolism in roots.The main results are as follows:(1)Under submergence,the soil was hypoxia or anoxia because oxygen in seedling soil was consumed in 5-7 hours due to the soil microbial activities.Short-term waterlogging treatment at different leaf ages promoted the growth of rice seedling and reduced the activity of Nitrate Reductase(NR),Glutamine Synthetase(GS)and Glutamate Synthase(GOGAT)in root in a short time.(2)The effects of bast fiber seedling film on the height of rice seedling were variable,but they surely promoted the growth and development of seedling roots,increased the ratio of root to shoot,and increased the soluble sugar content of rice plant.(3)The soluble sugar content in rice seedling explained 73.6%-75.4% variation of rooting ability,and the nitrate nitrogen content explained 7.3%-14.2% variation of rooting ability,which indicated that the soluble sugar content in rice seedling is the key determining its rooting ability.(4)The application of bast fiber seedling film compensated the oxygen consumed by soil microbial respiration and maintain the oxygen concentration in the bottom of seedling soil,so as to achieve the effect similar to aerobic cultivation.The oxygen-increasing effect of the film may be determined by its unique pore structure,which was mainly distributed in 250-300 ? m,accounting for 46.9%.(5)Application of bast fiber seedling film changed the soil enzyme activity,soil microbial community composition and soil nutrients in the root zone of rice seedling.Compared with the control,the nitrate nitrogen,ammonium nitrogen and alkali hydrolyzable nitrogen content in the root zone soil of rice seedling rasied with bast fiber seedling film increased by 25.4%,2.3% and 9.3% respectively after 10 days of application,and increased by 39.3%,14.6% and 11.5% respectively after 20 days of application.The correlation analysis showed that these changes of root zone soil characteristics were closely related to rice seedling quality.In conclusion,the bast fiber seedling film can compensate the oxygen consumed by the soil microorganism respiration in the root zone of rice,maintain the oxygen concentration in the root zone soil,change the soil enzyme activity and the soil microorganism composition in the root zone of the seedling,then affect the soil nutrients,promote the growth and development of the rice seedling,improve the seedling quality,especially the soluble sugar content of the plant,and then the seedlings have higher rooting ability,and can return to green more quickly,tiller earlier,have more effective panicle,and finally have higher rice yield.