摘要：
Crop safety period of plastic film mulching means the appropriate choice of a photo-selective mulch film according to the transplant season, to the ecological conditions of the area under cultivation and, finally, to the type of crop. In the days before the transplant, the plastic mulching film should be basic whole, and it works to warm soil and to decrease soil moisture evaporation. Successively, these functions almost reduce.Soil moisture conditions can basically meet the needs of potato growth and temperature is the most important factor to be considered in intensive agricultural region of North China.This study will give a guide in mulching film management and the choice of appropriate degradable mulch in intensive agricultural region of North China in Qingdao by determining the safety period of plastic film mulching of the local crop. The effects of plastic film mulching on the growth of potato were studied, as well as the soil temperature in the 10cm soil layer and the yield, by removing the film at different times.In this experiment, conducted from March to June in 2016, six treatments were set up: planting potatoes without plastic film(T1); planting potatoes with plastic film and removing film after 30d (T2), 60d (T3), 75d (T4), 90d (T5), respectively, and planting potatoes with plastic film for the entire growth period (T6). The results indicated that the plastic film could promote the emergence of potatoes by 5 days, and the emergence rate was significantly higher than T1. It also showed that removing the plastic film after 60 days could shorten the growth period of potatoes and accelerate its growth. The effect of plastic film on soil temperature in the 10cm soil layer was significant between the sowing and seeding stage of the potatoes. During this period, the daily average temperature under plastic film was 1.1°Chigher than without it, and the accumulated temperature was 66.1°Chigher than without it, respectively. The disappearance time threshold of the film mulching effect was about 70 days after the plastic film. The results of the experiment showed that the soil accumulated temperature in the 10cm soil layer was highest at 60 days, which was ·d higher than non-mulching in the whole growth period, indicating plastic mulching had an significant warming effect. Within the potato growth process, the warming effect of film mulching was weakened. Film mulching can significantly improve the temperature in the 10cm soil layer between 1 and 60 days after mulching. If removing the film after 60 days, there would be no significant difference among T3, T4, T5 and T6, which indicated that the effect of plastic film on soil temperature was weakened after 60 days. It further demonstrated that the yield 96.5°C-1 under non-mulching had the lowest yield (40.3t?ha). The highest and the second highest yield were occurred when film were removed after 60 days (T3) and 75 days (T4), which were 13.4% and 10.4% higher than T1, respectively. Obviously, removing film after 60-75 days would produce the highest yield. Thus, the potato safety period of plastic film mulching is at 60-75 days in intensive agricultural region of Northern China, which should be the deadline for removing plastic film or degradable plastic film duration.%作物地膜覆盖安全期指某一作物在某一区域要求地膜覆盖的最佳天数,也就是地膜覆盖农田土面能保持膜面完整的日数,在此日数之前地膜应该保持基本完整,维持增温保墒等功能,此日数之后,这些功能基本消失.华北集约农区水分条件基本能满足马铃薯生长的需求,因此,生产中主要根据该区域自然条件和作物对温度需求的特点适期揭膜.为确定华北集约农区马铃薯种植的最佳揭膜时间,在青岛市以露地种植为对照(T1),分别设置了播种后覆膜30d(T2)、60d(T3)、75d(T4)、90d(T5)4个中途揭膜和全生育期覆膜不揭(T6)共6个处理,观测田间10cm土层土壤温度以及马铃薯生育期、出苗率及产量等指标.结果发现:与露地(T1)相比,地膜覆盖(T2、T3、T4、T5和T6)可以促使研究区马铃薯提前5d出苗,且出苗率得到提高;全生育期覆膜(T6)通过提高地温从而促进马铃薯的生长发育,在马铃薯播种-出苗期,全生育期覆膜(T6)处理较露地(T1)10cm土层土壤日平均温度提高1.1°C,10cm土层地积温增加66.1°C·d.不同揭膜时间的试验结果显示,在播种后60d揭膜处理中,马铃薯田10cm土层的地积温较高,为1795.6°C·d.此外,在马铃薯播种60d内地膜覆盖可以显著提高马铃薯田10cm土层地温日较差,播种60d后揭膜对10cm土层地温日较差影响不大.研究结果显示马铃薯产量与地膜覆盖和揭膜时间密切相关,对照露地种植(T1)产量最低,为40.3t?hm-2;60d揭膜(T3)最高,为45.7t?hm-2,较露地种植(T1)增产13.4%;75d揭膜(T4)较高,较露地种植(T1)增产10.4%.综合看,在该地区马铃薯生产中覆膜后60~75d进行揭膜最合适,即该地区马铃薯地膜覆盖安全期为60~75d.
