What is the optimal soil moisture content for the growth of Cymbidium sinense

SinceCymbidium sinenseis a drought-tolerant plant, what then is its optimal soil moisture content? This point is closely related tocultivationmanagement. We plantedCymbidium sinensein orchid pots with different soil moisture contents, expressing soil moisture content as the maximum water-holding capacity of the soil. The test soil at 100% maximum water-holding capacity is equivalent to a soil content (wet weight %) of 51.66%. Every 30 days we measured changes in plant growth rate, fresh weight and dry weight, and also measured the photosynthetic rate. From the measured data it can be seen that in the treatments with 90% and 70% maximum soil water-holding capacity, the growth increase rates of the two were similar, and growth was relatively normal. When soil moisture content dropped to 50% of maximum water-holding capacity, growth became slow, with one third of the seedlings dying at 90 days and half dying at 150 days; when the maximum soil water-holding capacity was 30%, plant growth stopped from the very beginning, one third of the seedlings died at 90 days, and all seedlings died at 150 days. The changes in aboveground fresh weight and dry weight among the different treatments were also the same as the growth rate. At 20 days and 60 days after planting, the photosynthetic rates of the various maximum soil water-holding capacity treatments were measured separately, and it was also seen that the 90% and 70% maximum soil water-holding capacity treatments had the highest photosynthetic rates, and the two were also similar; however, when soil moisture content dropped to 50% of maximum soil water-holding capacity, photosynthesis declined, especially in the 60-day treatment. IfCymbidium sinensegrows under more arid conditions (30% maximum soil water-holding capacity), the photosynthetic rate weakened by 20 days, and by 60 days it had lost photosynthetic capacity. Combining the results of growth rate and photosynthetic rate, we consider that the optimal soil moisture content for the growth of Cymbidium sinense is 70-90% of maximum soil water-holding capacity; below 50%, growth is inhibited and may even lead to death. (Ye Qingsheng, Pan Ruichi)