| Artificial light plant factories have significantly increased the output of raw menu area due to multi-layer three-dimensional cultivation,but the high cost of construction,operation and maintenance has inhibited its development.Artificial light sources consume the most energy,accounting for about82%of the total power consumption.In order to solve this problem,the multi-layer three-dimensional lettuce plant was applied in the natural light plant factory by combining natural light with artificial light in order to reduce the energy consumption of supplementary light.The main purpose of this study was to explore different light-supplementing strategies in multi-layer plant factories under natural light conditions,analyze the effects of natural light and artificial light on the yield and quality of lettuce,and calculate the economy of different light-supplementing strategies.The experiment was carried out in a natural light plant factory in Beijing.The lettuce planting experiment was carried out by using two groups of identical three-layer stereo cultivation scaffolds.The main contents and conclusions of this study are as follows:(1)Typical solar terms in the whole year were selected as the study time.The light distribution in natural light plant factories under typical climatic conditions was analyzed.The results showed that the average daily accumulation of light in upper,middle and lower layers in summer was 36.2,12.4,3.7mol/(m~2·d),in winter was 9.7,3,2.4 mol/(m~2·d),and in spring and autumn,the average daily accumulation of light in upper,middle and lower layers was 17.7,8,4.7 mol/(m~2·d)and 17.7,7.7,4.3mol/(m2.d).According to the light requirement of lettuce,the daily accumulation of lettuce should satisfy 6-12 mol/(m~2·d),so taking the season with the largest amount of light supplement in winter as an example,the middle layer needs 3-9 mol/(m~2·d)and the lower layer needs 3.6-9.6 mol/(m~2·d)to satisfy the normal growth of lettuce.(2)Effects of gradient light supplementation on Yield and quality of lettuce in multi-layer Stereoscopic Cultivation in natural light plant factories.In the preliminary study of light supplementation intensity of middle and lower layers lettuce in natural light plant factories,it was found that the yield of lettuce under middle layer light supplementation of 3 mol/(m~2·d)and 6 mol/(m~2·d)was 66.4%and 72.0%higher than that under middle layer natural light,respectively.There was no significant difference between light supplementation treatments.The yield of lettuce under 6 mol/(m~2·d)and 9 mol/(m~2·d)light supplementation in the lower layer was 77.6%and 79.5%higher than that under natural light,respectively.There was no significant difference between light supplementation treatments.Therefore,the recommended light supplement intensity for the middle and lower layers of the cultivation shelf is 3 and 6 mol/(m~2·d)respectively,and the yield per unit area is 3.2 times that of the traditional greenhouse.(3)Effects of different light quality supplements on Yield and quality of purple leaf lettuce under multi-layer stereo cultivation in natural light plant factories.In the experiment of full spectrum and red-blue light supplement for the lower layer of purple leaf lettuce in natural light plant factory,it was found that the purple leaf lettuce treated with R/B=9:1 had the advantages of high soluble sugar content and high anthocyanin content.Therefore,the quality of purple leaf lettuce treated with R/B=9:1 was better.(4)According to the economic benefit analysis of light supplement,the plant factory designed in this study can ensure a higher yield of lettuce,while its output is 3.2 times that of the traditional greenhouse.By controlling the light supplement intensity and using wet curtain system,the operating cost of the plant factory will be reduced to 19.4%of that of the artificial light plant factory,80.6%of the energy is saved,the energy consumption of supplementary light lamp can save 3 kw·h/m~2 per day compared with that of artificial light plant factory.In this study it reflects the huge cost advantage and yield advantage of the plant factory.In conclusion,under the condition of multi-layer three-dimensional cultivation in natural light plant factory in winter,considering the light intensity required for lettuce growth,the best way to supplement light was selected.3 mol/(m~2·d)in the middle layer and 6 mol/(m~2·d)in the lower layer,to cultivate green and purple lettuce under red and blue light.The quality of lettuce could be improved while increasing the yield,especially the quality of purple lettuce flower.And the overall operating cost is 80.6%more energy-saving than that of plant plants,in which the energy consumption of supplementary lamp is 3 kw·h/m~2 less than that of artificial light plant plants. |
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