Light Condition Based Analysis of Microclimate Parameters for Improvement of Closed-Field Tomato Production in Tropical lowlands

Abstract.

Modern closed-field plant production requires innovative methods for shifting from conventional greenhouses to smart controlled environments that benefit from natural resources for eliminating deleterious external conditions. The ultimate objective in this regard would be achieving high yield and high quality fruits at minimum possible cost. This paper presents a partial report of an interactive database program that is being developed for adaptive management of crop production in tropical lowlands of Malaysia. Two groups of climate data were collected from an open-field and three closed-fields with different covering materials. Custom-designed computer program was developed to process raw data and to perform inferences based on light condition maps. Tomato’s growth responses to temperature, relative humidity, and vapor pressure deficit (VPD) were simulated for each light condition according to peer-reviewed published literatures. Preliminary results showed that inverse relationship exist between radiation and VPD of air. It was also observed that the lowest VPD values belong to night hours at which temperature and relative humidity are at their minimum and maximum levels respectively. Further analysis indicated that for the open-field case study, at early growth stage, averaged growth response to temperature were significantly higher (between 0.8 to 1) at night condition, while at vegetative to mature fruiting growth stage, the average growth response to temperature was higher in sun condition. No significant difference was observed between night and cloud condition hours at these stages. For growth response to relative humidity at the early growth stage, night condition provided the highest values, almost equal to 1 in the entire days of experiment. Results of hypotheses testing that growth response values have equal means under different light conditions depended on growth stage and specific environments. The outcome of this study and the proposed simulation methods can contribute to energy efficient and cost reduction techniques for improvement of closed-field production systems through cultural practices and management strategies that benefit from optimum light conditions.