Calculation and verification of quantitative parameters of optimal planting density machine-transplant rice

Based on the calculation of transplant rice, taking conventional japonica rice (Ningjing-3) and hybrid japonica rice (Changyou-1) as material, different planting density experiments were conducted to determine the parameters in planting density quantitative equation of machine-transplant rice. Then optimized cultivation program for machine-transplanting rice was designed using the machine-transplanting rice cultivation system and the designed leaf area index at heading, dry matter at maturity, harvest index, yield and yield components were compared with the measured values in the experiments. The results showed that missing tiller number of the machine-transplant conventional japonica rice and hybrid japonica rice was 1.5 and 0.5, respectively. Seedling number per hole significantly affected the adjusting factor in plant density quantitative equation. Highest yield was obtained for conventional japonica rice with 3 seedlings per hole and for hybrid japonica rice with 2 seedlings per hole, respectively. Thus, the adjusting factor was set to be 1.5 for conventional japonica rice and 1.0 for hybrid japonica rice. The tiller emerging rates after transplanting were 0.8 for both conventional and hybrid japonica rice. The comparison showed that the deviation between designed and average measured values was less than 5%, which verified the reliability of parameters in planting density quantitative equation for machine-transplanted rice. This research provides a technology support for accurately determining planting density for machine-transplant rice.