Effects of air current speeds on the microclimate of plug stand under artificial lighting

摘要

Experiments were performed in a newly developed wind tunnel with lighting system to investigate the effects of air flow speed on the microclimates above and inside a plug seedling stand. The objective was to collect basic data for large-scale plug production under artificial light in a semi-closed ecological system. Maximum air temperature appeared near the top of the plug stand. Differences in relative humidity (DRH) between the inlet of the main air flow conditioner inside and above the plug stand decreased with increasing air speed. DRH inside a stand of plugs was 5-10% lower at an air speed of 0.9 m/s than at 0.3 m/s. DRH inside a stand of plugs was 2.8-6.5% higher at a leaf area index (LAI) of 2.6 than of 0.5. Difference in vapour pressure deficit (DVPD) between the inlet of the main air flow conditioner inside and above the plug stand increased with increase in height above the medium surface. DVPD inside the plug stand was 0.3-0.4 kPa higher at an air speed of 0.9 m/s than that at 0.3 m/s.Results for the effects of air speed on relative humidity and VPD indicated that the microclimates above and inside the plug stand at the rear region in plug trays were slightly unfavourable compared to those in the middle region. Concentration of CO2 near the top of a stand of plugs was 8-12mol/mol lower than that above a stand of plugs. The concentration of CO2 at the rear region was 3-4mol/mol lower than that in the middle region. CO2 enrichment would be effective for the uniform growth of plugseedlings at a controlled air speed under artificial light in a semi-closed ecological system.