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（一）温度条件

(I) temperature conditions

塑料薄膜具有保温性。覆盖薄膜后，大棚内的浊度将随着外界气温的升高而升高，随着外界气温下降而下降。并存在着明显的季节变化和较大的昼夜温差。越是低温期温差越大。一般在寒季大棚内日 增温可达3－6℃，阴天或夜间增温能力仅1－2℃。春暖时节棚内和露地的温差逐渐加大，增温可达6－15℃。外界气温升高时，棚肉增温相对加大，最高可达20℃以上，因此大棚内存在着高温及冰冻危害，需进行人工调整。在高温季节棚内可产生50℃以上的高温。进行全棚通风，棚外覆盖草帘或搭成＂凉棚＂，可比露地气温低1－2℃。冬季晴天时，夜间最低温度可比露地高1－3℃，阴天时几科与露地相同。因此大棚的主要生产季节为春、夏、秋季。通过保温及通风降温可使棚温保持在15－30℃的生长适温。

Plastic film has thermal insulation. When the film is covered, the turbidity in the greenhouse will rise with the increase of the external temperature, and decreases with the decrease of the outside temperature. There are obvious seasonal variations and large diurnal temperature differences. The greater the temperature difference is at the lower temperature. In the cold season, the daily increase of temperature is up to 3-6 degrees C, and the ability to increase the temperature of the cloudy day or at night is only 1-2. The spring season and in the greenhouse temperature gradually increased, increasing temperature can reach 6 to 15 DEG C. When the outside temperature rises, the temperature of greenhouse meat increases relatively more, up to 20 degrees centigrade, so there is high temperature and ice damage in the greenhouse, and it needs to be adjusted artificially. In the season of high temperature shed can generate high temperature above 50 DEG C. The whole roof ventilation, shed covered straws or a "shelter", can be 1 than that of the low temperature of - 2 DEG C. In winter sunny, minimum night temperature can be higher than that of 1 C, almost the same in cloudy days. So the main production season in the greenhouse is spring, summer and autumn. The temperature of the greenhouse temperature can be kept at 15-30 centigrade by heat preservation and ventilation.

（二）光照条件

(two) light conditions

新的塑料薄膜透光率可达80－90％，但在使用期间由于灰尘污染、吸附水滴、薄膜老化等原因、而使透光率减少10－30％。大棚内的光照条件受季节、天气状况、覆盖方式（棚形结构、方位、规模大小等）、薄膜种类及使用新旧程度情况的不同等，而产生很大差异。大棚越高大，棚内垂直方向的辐射照度差异越大，棚内上层及地面的辐照度相差达20－30％。在冬春季节以东西延长的大棚光照条件较好、它比南北延长的大棚光照条件为好，局部光照条件所差无几。但东西延长的大棚南北两侧辐照度可差达10－20％。 不同棚型结构对棚内受光的影响很大，双层薄膜覆盖虽然保温性能较好，但受光条件可比单层薄膜盖的棚减少一半左右。

The new plastic film transmittance up to 80-90%, but during use due to dust pollution, water adsorption, aging and other reasons, the film transmittance decreased 1030%. The illumination conditions in the greenhouse are quite different from seasons, weather conditions, coverage methods, such as canopy structure, orientation, scale, etc., and the type of films and the difference between the old and new ones. In the tall, radiant intensity difference in vertical direction is shed, shed upper and ground irradiance is about 20% - 30%. To what extend in the winter season in a better light conditions, than the north and South extension greenhouse light conditions as well, local illumination conditions are almost the same. But what extension of the north and south sides of greenhouse irradiance was up to 10 - 20%. Different roof structure on the shed by the light of the great influence, double film covering although good insulation properties, but light conditions than the monolayer film cover shed reduced by about half.