Effect of machine transplanting of potting seedlings with different hole spacing on yield of high-quality indica rice in South China

Rice potting seedling transplanting reduces root damage and recovering period of rice seedling, so it can promote rice growth, improve photosynthetic capacity of rice and increase rice biomass and grain yield．However, research of hole spacing setting of rice potting seedling transplanting on grain yield and population indicators of high-quality rice has rarely been reported in South China．Using hybrid indica rice variety Taifengyou 208 and conventional indica rice variety Nanjingxiangzhan, which have a wide planting area in Southern China, as materials, four hole spacing treatments（A₁ treatment hole spacing 12.4 cm, A₂ treatment hole spacing 14.5 cm, A₃ treatment hole spacing 17.9 cm, and A₄ treatment hole spacing 20.7 cm）were set up to study effects of different planting hole spacing treatments on tiller number, leaf area index, photosynthetic potential, material production, and yield of bowl seedlings．Results showed that tiller number, leaf area index, photosynthetic potential and biomass increased with reduction of hole spacing．Compared with traditional hole spacing of 17.9 cm for farmers（A₃ treatment）, the 12.4 cm of hole spacing treatment（A₁ treatment）increased tiller number by 36.2% to 38.7%、37.3% to 42.4% and 21.5% to 36.9%, leaf area index by 30.8% to 55.9%、16.4% to 41.0% and 37.7% to 53.1%, and biomass by 32.0% to 38.6%、20.1% to 34.2% and 37.1% to 59.0% at middle tillering, beginning of panicle initiation, and heading stages, respectively．Photosynthetic potential increased by 17.9% to 49.2% and 28.1% to 49.2% from mid tillering stage to beginning of panicle differentiation and from beginning of panicle differentiation to heading stage, respectively．Correlation analysis revealed that rice yield was significantly positively correlated with tiller number at heading stage, leaf area index and biomass at beginning of panicle differentiation, photosynthetic potential from mid tillering stage to beginning of panicle differentiation, biomass at maturity stage, and effective panicle number．In conclusion, in the double-season rice system of South China, an appropriate increase in planting density of potting seedling transplanting increased tiller number, leaf area index, photosynthetic potential and biomass in early stage of rice, and maintain advantages of population indexes in late stage of rice, thus increasing rice yield．