Abstract:

Based on the daily meteorological data, such as precipitation, rain days and sunshine duration during the flowering and fruiting stages (from November to April) of strawberry in greenhouse of Cixi City from 2012 to 2021, both occurrence frequency and intensity of continuous cloudy and rainy days in Northern Zhejiang Province were analyzed. Meanwhile, a comparative experiment was conducted regarding the application effects between silver-black mulch films (the upper layer adopts a silver mulch film while the lower layer adopts a black one) and black mulch film onto strawberry greenhouse. According to the findings, the probability of continuous cloudy and rainy days was 17.7% during the flowering and fruiting stages of greenhouse strawberry in Cixi City from 2012 to 2020, with their occurrence frequency of a slightly declining trend, and their linear trend coefficient was -0.005; the average intensity of continuous cloudy and rainy days was 6.3, with their occurrence intensity of an increasing trend, and their linear trend coefficient was 0.0264. The most frequent continuous cloudy and rainy days took place in November while the least took place in April. November saw the most frequent continuous cloudy and rainy days that lasted for over 7 days, followed by January. In the low-temperature winter and spring, both kinds of mulching modes could effectively raise and maintain the shallow soil temperature at or above 10℃; the shallow soil temperature of the silver-black-film-treated group was lower than that of the black-film-treated group, and the average temperature of the former group was 0.4℃ lower than that of the latter group; the total solar radiation of the silver-black-film-treated group was 9.1 w/m² higher in average than that of the black-film-treated group. In the early producing stage (from December to February), the average yield of strawberries treated with silver and black films was 3629.4 kg/hm² while the average yield of strawberries treated with black film was 2951.1 kg/hm², thus realizing an increase of 20%. Silver-black-film treatment exerted certain promoting effect on the SPAD value of strawberry leaf, the soluble solid and the transverse fruit diameter. Therefore, in the production, covering silver-black mulch films can improve the micro-climatic environment in the greenhouse and achieve the role of increasing production and income of strawberries.

Key words: Northern Zhejiang Province, strawberry, continuous cloudy and rainy days, silver-black mulch films, covering effect, flowering and fruiting season, yield