Air and nutrient solution temperatures influence growth, development, mineral nutrients, and storage of five culinary herbs

Culinary herbs are specialty crops commonly grown in controlled environment agriculture (CEA) using glass-glazed greenhouses. Greenhouses extend seasons and enhance environmental control but energy costs are prohibitive. Air temperature regulation during cold and hot seasons is particularly energy expensive. Air temperature effects on culinary herb growth, development, and tissue mineral concentrations are well-explored; however, rootzone temperature effects and interactions with air temperature are comparatively less characterized. Characterizing air and rootzone temperatures’ interactions could assist hydroponic producers they could regulate rootzone temperature and reduce air temperature control to increase efficiency and potentially improve yield and quality. Therefore, the research objective was to [1] quantify the effects of, and interactions between, air and nutrient solution temperatures on growth, development, shoot tissue mineral concentrations, and postharvest storage of four culinary herb species. To achieve those objectives, we grew basil (Ocimum basilicum) ‘Nufar’ and ‘Red Rubin’, cilantro (Coriandrum sativum) ‘Santo’, common sage (Salvia officinalis), and parsley (Petroselenium crispum) ‘Giant of Italy’ in deep-water-culture tanks with 15, 20, 25, 30, or 35 ° [degrees] C nutrient solution temperatures with 20 or 30 °C air temperature. At harvest, we quantified plant yield, development, and mineral concentrations, and stored fresh tissue in coolers held at 4 and 10 °C for 12 days. Basil ‘Nufar’ and ‘Red Rubin’ yielded the greatest fresh mass, dry mass, nodes and longest stems in 25-30 °C nutrient solution temperature with 30 °C air temperature. Basil grown in high air and nutrient solution temperatures greater than or equal to 30 °C lost water at a reduced rate compared to those grown in lower temperatures. Cilantro ‘Santo’ fresh mass, dry mass, and leaf number were not significantly influenced by air temperature, but quadratically increased as nutrient solution temperature increased from 15 to 25 °C. Common sage and parsley ‘Giant of Italy’ fresh mass, height, and leaf and node numbers were greatest in 25 °C nutrient solution. Producers may regulate nutrient solutions to achieve temperatures of 25 to 30 °C for adequate shelf life and biomass yield.