Effect of the interaction of nitrogen and transplanting density on the rice population structure and grain yield in low-yield paddy fields Effects of Transplanting Density on Density and Biomass of White Clover Effect of Low Nitrogen Rate Combined with High Plant Density on Yield and Nitrogen Use Efficiency of Machine-transplanted Early-late Season Double Cropping Rice Nitrogen Utilization Efficitncy and Fate of Fertilizer under Different Transplanting Density Effects of Transplanting Density on Contribution and Accumulation of Soluble Sugar on Japonica Rice in Cold Region Effect of Mechanical-Transplanting Density on Lodging Resistance and Yield in Different Types of Rice