The effect of temperature and light on strawberry production in a solar greenhouse
Abstract Strawberry production is greatly affected by environmental factors, especially temperature and light. A solar greenhouse with opaque photovoltaic (OPV) modules and a solar combined air source heat pump system was built for strawberry production. The aim of this study was to assess the impact of differences in both temperature and light factors caused by OPV modules and solar heating on strawberry growth and quality in a constructed greenhouse. The 'Jingzangxiang' strawberry was selected and planted in the greenhouse. The indoor temperature with the heating system was 5.3 7.3 degC higher than the ambient temperature at the coldest period in the city of Kunming. At noon, the chlorophyll content of the shaded strawberry plants was 1.3 times higher than that of the unshaded plants in sunny weather, and the average shaded photosynthetically active radiation (PAR) was 230 mmol*m 2*s 1 in the greenhouse, where 25.9% of the roof was covered with OPV modules. Under this shading treatment, the optimum light range of PAR for the 'Jingzangxiang' strawberry was 387 437 mmol*m 2*s 1, and the optimum temperature range during the daytime was 20.5 27.4 degC. The largest single strawberry fruit weighed 33.9 g, and the soluble solids content of the shaded strawberry fruit was 16.4% which was higher than that of the unshaded strawberry samples. Furthermore, the yield of the shaded samples was 1.2 times that of the unshaded samples. In summary, strawberry plants shaded by OPV modules were superior to unshaded strawberry plants in terms of growth, quality and yield. This research provides experimental support and information on the optimal temperature and light ranges for the growth of the 'Jingzangxiang' strawberry in solar greenhouse.