Effect Assessment of Planting Density Control and Simulation of Optimal Planting Density for High Profitability of Long-term Planting of Cherry Tomatoes

To develop a new cultivation system that enhances yield by increasing the amount of photosynthesis while avoiding an increase in temperature and any associated damage, we evaluated the effect of a cultivation system wherein dense planting is only conducted in the summer, which is the initial stage of cultivation, pinching in autumn, and reducing planting density to the same level as conventional cultivation systems in winter. This experiment was conducted on cherry tomatoes. Additionally, we estimated the optimum leaf area index (LAI) and planting density necessary to maximize the amount of photosynthesis. Our study confirmed that a greenhouse environment was effective at lowering temperature and increasing humidity due to the increased transpiration that resulted from dense planting. The yield per plant throughout the entire period remained the same as that in the beginning, suggesting that the yield per area markedly improved. This is believed to be due to the fact that in summer, the amount of photosynthesis increased with increases in LAI and the sink strength of the plant community, as well as a decrease in the number of damaged, mainly cracked, fruits. Additionally, the integrated photosynthesis amount by each LAI was estimated from the amount of solar radiation, relative light intensity on the plant community, and light-photosynthesis curve. The optimum planting density (5.21 plants・m–2 in summer) was estimated from LAI that maximized the amount of photosynthesis.