Effects of different seedling substrates on physiological characters and grain yield of mechanized-transplanted rice

Abstract: With the expansion area of mechanized-transplanted rice, the demand to high quality of rice seedling becomes more and more important. Traditional seedling raising pattern such as use of nutrient soil is difficult to meet the growing demand of mechanized-transplanted rice seedling. It is predicted that in the future, there will be more seedling substrate to replace nutrient soil for raising rice seedling. Thus the research for physical and chemical properties of seedling substrate, seedling physiological characters from those substrates, mechanized quality, grain yield and relationship among those are very important for selecting a proper substrate for raising rice seedlings. In this study, we used three different types of rice seedling substrate treatments: nutrient soil (CK), light soilless substrate and mixed substrate to determine the relation among physical and chemical properties of seedling substrate, seedling physiological characteristics, mechanized quality and grain yield, and to evaluate their adaptability and applicability. The results showed that volume-weight of light soilless substrate and mixed substrate were 85.19% and 74.07% lower than the control treatment, while the aeration porosity, water-holding porosity and their nutrient content were significantly higher (P＜0.05) than the control. Seedling age and plant height and shoot weight and shoot width showed advantage compared with that of the control treatment. Their seedling roots that can coil into a block and empty cone rate were less than 5%, and both were 4.17% and 4.32% lower than the control, respectively (P＜0.05). With more dry matter accumulation in seedling stage, the seedlings from two substrate treatments regrew quickly and tillers started earlier after transplanted in field, resulting in the advancement of tillering stage and heading stage compared with the control treatment. The initial tiller stage of light soilless substrate treatment was ahead for four days than that of CK, and mixed substrate was two days. In both substrate treatments, rice was two days shorter in their total growth duration compared to that of CK. Light soilless substrate rice accumulated more root and shoot dry matter in seven days after transplanted, but after 14 days, Mixed substrate rice behaved the same in dry accumulation with soilless substrate rice. From both substrates, rice had significantly (P＜0.05) more dry matter accumulation than that of the control treatment in all growing stages. More dry matter accumulation in tiller stage and strong root system in tillering stage helped the tillers to fade slowly, which led to more effective tillers per plant and more numbers of panicle than that of the control treatment. Yield and storage capacity (number of kernels and kernel size per plant) of light soilless substrate treatment and mixed substrate treatment were significant higher than the control treatment. The range of increased storage capacity were 14.01% and 10.67% (P＜0.05), and yield were 5.30% and 6.14% (P＜0.05), respectively. This study indicated that the physical and chemical properties of light soilless substrate and mixed substrate were superior to the control treatment, and their seedlings were suitable for mechanized transplanting technology. This was helpful to the development of industrialized seedling substrate product. Light soilless substrate is made of crops, straw, which is easy to get and can be decomposed completely in soil. Moreover, lighter in weight of light soilless substrate helped to reduce labor intensity and lower in water content helped to prolong the storage life. The yield from light soilless substrate was almost the same with the mixed substrate treatment, but was significant higher than that of control (P＜0.05). With the obvious application advantage above, light soilless substrate was better for the production and application of seedling substrate.