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塑料薄膜作为烟草苗床的罩盖物虽然解决了防御低温的问题,但也带来一些新的问题,其中包括:必需建造一个专用的架置塑料薄膜的框架并致使雨水流走;需要在苗床灌溉时搬掉罩盖物;在当苗床内的温度趋向过高时需要进行通风。打有洞孔的塑料薄膜苗床罩盖物被介绍来解决这些问题。试验是在1966年和1967年进行。苗床的构造为平框冷床型,宽1.57米,长9.15米,床框壁用2.5×20.3厘米的木板制成,设置有展铺聚乙烯塑料薄膜罩盖物用的拱形支架。展铺薄膜上的打孔处理及苗期反应的效果如下表:
The plastic film as cover for the tobacco seedbed, while solving the problem of low temperature protection, poses new problems, including the need to create a dedicated frame that holds the plastic film and allow rainwater to flow away, Remove the lid when ventilation temperature is too high in the seedbed. Hole-covered plastic film seedbed cover was introduced to solve these problems. The test was conducted in 1966 and 1967. The seedbed is constructed as a flat-bed cooling bed with a width of 1.57 meters and a length of 9.15 meters. The bed frame is made of 2.5 × 20.3 cm wood board and is provided with arched brackets for spreading polyethylene plastic film covers. The punching process and the effect of seedling reaction on the spreading film are as follows: