Influence of Shading Methods and Planting Density on Field Microclimate and Cigar Yield and Quality

This study aimed to investigate the effects of different shading methods and planting densities on the microclimate and tobacco yield and quality in cigar fields. Using cigar tobacco variety Haiyan 101 as the experimental material, six treatments were set up: conventional density without shading (ZM1), conventional density with top shading (ZM2), conventional density with full shading (ZM3), high-density without shading (ZM4), high-density with top shading (ZM5), high-density with full shading (ZM6). The microclimate of the tobacco field throughout the entire growth period, agronomic traits at maturity, physical and chemical indicators of tobacco leaves after air-curing, as well as tobacco yield and output value were measured. The results showed that the soil temperature in tobacco fields treated with shading decreased, the temperature difference between day and night and wind speed decreased, and the air humidity increased. During high temperature periods, the top shading treatment significantly reduced the light intensity by 37.22% to 38.11%, and the full shading treatment significantly reduced it by 42.07% to 42.56%. Shade treatments could improve the agronomic traits of mature tobacco plants, with a significant increase in plant height. Among them, the leaf thickness of ZM6 decreased significantly by 11.32% compared to ZM4; after air-curing, the physical properties of tobacco leaves were improved, with a significant increase in gray value. The yield, output rate, and total output value of wrapper all significantly increased, and the improvement effect of full shading treatment was more significant. Compared to conventional density, the soil moisture content in high-density tobacco fields decreased, and the wind speed slowed down; the growth of tobacco plants was inhibited. The total yield of tobacco leaves increased after air-curing, but the yield and total output value of wrapper decreased. Under the interaction of two factors, under full shading treatment, the leaf length and width of tobacco leaves dried at conventional planting density (ZM3) increased significantly by 12.26% and 8.17% respectively compared to ZM1. The tobacco leaves were thinner and had the best combustibility, with the highest wrapper yield, yield rate, and total output value, which contributed to improving the quality of cigar leaves. In summary, ZM3 is suitable for improving the quality and economic benefits of cigar tobacco leaves in Hainan region.