遮阳网性能与夏白菜的覆盖栽培技术研究

连续3个夏季在南京测试了不同覆盖方式和规格型号的遮阳网性能及其对夏白菜产量与品质的影响,结果表明:不同类型遮阳网的遮光率、透射光质、照度均不同。蒸散量减少率与遮光率基本同步。降温效应主要表现为地面最高温度,地上至地下各20cm范围和叶温均显著降低。在夏季最高气温超过35℃的晴热型气候下,地面最高气温上限达56.2C,下限41C,覆盖后平均降温9～13℃,最大降幅达19.9℃,夏白菜覆盖增产63％～435％(1992年);最高气温在30～35℃时,地面最高温度变幅为33.7～44.5℃。在冷夏多阴雨的1991和1993年,黑网覆盖的均减产,仅45％～50％遮光率的灰网大棚覆盖的增产;最高气温在25～30℃时,覆盖降温效应很弱。覆盖栽培的夏白菜外观商品性优于露地产品,但内涵营养品质均下降,硝酸盐积累量上升。如在采收前5天揭网处理,各项营养品质指标均赶上或超过露地的,硝酸盐含量也低于露地产品,故采前揭网是必不可少的栽培措施。

Studies on Shade-net Characters and Covered Cultivation of Summer Pak-choi

Test the shade-net characters and its effect on the yield and quality of summer Pak-choi in continuous three summers. Results show that different shade-nets are different in shading rate, quality of transmissive light and illuminance. Reduced rate of transpiration roughly synchronizes with the shading rate. The character of temperature lowering is proved by the significant drop in the highest surface temperature, the temperature at 20 cm above and under the earth, and the leaf temperature. In the fine and hot summer with the highest air temperature over 35C the maximum surface temperature is 56. 2 C and the minimum is 41C , while the temperature will drop 9~13C after being covered by shade-net. The maximum difference will be 19. 9C, and 63~435% increase of summer Pak-choi production will be resulted (1992). When the highest air temperature is between 30'C and 35 C , the highest surface temperature ranges from 33. 7 C to 44. 5 C. In the cool, overcast and rainy summers (1991 and 1993), black shade-net decreases the yield, while the grey shade-net of 45%-50% shading rate increases the yield. When the air temperature is between 25C and 30 C the shade-net makes little temperature drop. The exterior commercial quality of covered summer Pak-choi is better than that of open-air product, but the interior nutrient quality is worse, and the nitrate accumulation raises. Revealed 5 ~ 7 days before harvest, each nutrient quality is equal to or over that of open-air one, and the nitrate is lower. Therefore, revealing before harvest is a necessary cultivation measure.