Variations in Environmental Parameters inside a Polyhouse during Two Growing Seasons of Hydroponic Basil

Abstract

Hydroponic cultivation under protected structures requires regular monitoring of internal environmental conditions because crop performance is influenced by seasonal changes in the polyhouse microclimate. The present study evaluated variations in temperature, relative humidity and carbon dioxide (CO₂) concentration inside a naturally ventilated polyhouse during hydroponic basil (Ocimum basilicum L.) cultivation at Dr NTR College of Agricultural Engineering, Bapatla, Andhra Pradesh, India. The crop was grown using the Nutrient Film Technique (NFT), and environmental parameters were recorded with a Rotronic CP11 handheld instrument at 1-hour intervals. Observations were made during Season 3 (October-November) and Season 4 (January-February) to compare the environmental behaviour of the polyhouse across two growing periods. The recorded data showed clear seasonal variation in the internal microclimate. During Season 3, temperature ranged from 25.64°C to 34.04°C, relative humidity ranged from 65.05% to 90.56% and CO₂ concentration ranged from 411.91 to 463.66 ppm. During Season 4, temperature ranged from 24.15°C to 32.05°C, relative humidity ranged from 63.96% to 85.23% and CO₂ concentration ranged from 446.42 to 545.17 ppm. Basil yield was higher in Season 3 (38.9 kg) than in Season 4 (36.2 kg). The comparatively lower yield during Season 4 was associated with lower temperature, reduced light intensity, shorter day length and higher relative humidity during winter, which affected photosynthesis, nutrient uptake and vegetative growth. The findings provide a seasonal basis for interpreting microclimatic variation in the studied hydroponic production system. The study indicates that continuous monitoring and regulation of temperature, relative humidity and CO₂ concentration are important for maintaining a favourable microclimate for hydroponic basil production under polyhouse conditions.