Effects of Liquid Nutrient Depth on Float Seedlings Cultured in Sand

In order to find the best fit liquid nutrient depth for float seedling cultured in sand and reduce labor cost, different depth trials were conducted. The results showed that:1) the appropriate liquid depth was 1.5-2.5 cm from seeding to 4 true leaves stage, shallower liquid needed more frequent refilling, hence more labor cost, while deeper liquid caused sand leak and lower germination rate and seedling livability resulted; 2) sand body moisture should be alternated between dry and wet states every 4-8 days from the time when seedling germination rate reached 90% to 4 true leaves stage, the moisture content in dry sand body was 4% and in wet sand body was 20%; 3) maintaining oxygen content in sand body at about 5 mg/L would benefit to the aerobic respiration of root system and raised the rates of existence and vigorous seedling, and root volume. Otherwise, blue-green algae and diseases would outbreak seriously and deteriorated the existence rate of seedling.