VERTICAL COLUMN AND SYSTEM OF COLUMNAR SOILLESS CULTURE (SCSC) AND ITS APPLICATION TO CULTIVATION OF LETTUCE (CAPITATA L.)

A culture column was composed of hat named as dripping unit, columnar body which was an axle contacted 12 one-liter volume plastic pots with overflow tube and columnar base. The column was 200 cm tall and was 15 cm indiameter. The columns were arranged by 80 cm×80 cm in rows to establish the columnar cultural unity, which consisted of 636 columns in 540 m 2 cultivable area in glass house and was used for cultivating lettuce. This columnar cultural unity stood on the culture water troughs on the ground, and both the former and the later were connected through the circulating irrigating system of water to form a big stereoscopic culture unity named as the system of columnar soilless culture (SCSC). The culture area of SCSC system was enlarged 3 times more than that of the culture water troughs. Each plastic pot in the column held 5 plants and one column could carry 60 plants. The columnar cultural unity could support 38 160 plants and included 10 314 plants grown on the water troughs, so it could totally support 48 474 plants, which was 4.7 times more than that held by the cultural water troughs on the ground. At the middle-late growth stage of letluce (40 d after planting), in the columnar culture area illumination (E) was 680～860 μE m -2 s -1 , and was 180～360 μE m -2 s -1 higher than that of the saturation point of photosynthesis of lettuce. As a result of a good space between the small culture pots in the pot and water surface in the pot (Fig 7), the young plants grown above the water surface could get enough air, water and nutrition through the rock fibre wrapped plant. The maximum mean air temperature was 20 ℃, the minimum mean temperature was 3.3 ℃ and the humidity (RH) was 57%～71% in the columnar culture area in winter. After 53 d growth, the yield of fresh lettuce by SCSC in a area of 160 m 2 was 5.6 kg/m 2, 3.7 times higher than that of CK. The SCSC was shown as large production model with high yield and benefit. Fig 7, Tab 3, Ref 7