Biomass and volatile profile responses of hydroponically grown Basil (Ocimum basilicum L.) to different nutrient solution regimes

Abstract

Hydroponics is a soilless cultivation technique that has gained increasing interest in its capacity to address specific constraints of conventional agriculture, notably through the precise management of mineral nutrition and growing conditions. This study evaluated the effects of different nutrient solution regimes defined by nitrogen (N) and phosphorus (P) concentrations and covarying potassium (K) concentrations on basil (Ocimum basilicum L.) cultivated in a hydroponic nutrient film technique (NFT) system. Agronomic parameters and volatile organic compounds (VOCs) were analyzed at final harvest, while response surface methodology (RSM) was applied to identify model-predicted candidate nutrient combinations associated with the production of linalool, eugenol, and eucalyptol. Nine nutrient treatments varying in N and P concentrations were evaluated, while K was considered a dependent nutrient, with Hoagland nutrient solution (HNS) serving as the reference treatment. High N treatment produced the highest fresh aerial weights, reaching 430 g, 408 g, and 365 g, values close to those obtained with the HNS (471 g). Intermediate N treatments showed fresh weight values of 154 g, 254 g, and 210 g, whereas low N treatments resulted in fresh aerial weights below 100 g. Aerial dry weight, leaf number, leaf area, and plant height followed the same trend. In contrast, root parameters remained generally similar among treatments. An exploratory principal component analysis (PCA) suggested three compositional groupings: high N associated with eugenol, intermediate N with eucalyptol, and low N with linalool, with an intermediate profile for HNS. In-sample quadratic model fits yielded R 2 values of 0.64 for linalool, 0.82 for eugenol, and 0.73 for eucalyptol. The model-predicted candidate combinations of N, P, and associated K were 62.2, 17.1, and 80 mg L −1 for linalool; 105, 31, and 135 mg L −1 for eugenol; and 58.2, 31, and 93.5 mg L −1 for eucalyptol, respectively. These conditions increased the compound production indices, calculated as aerial fresh weight × relative GC peak area (%)/100, compared with the HNS reference treatment, from 8.46 to 17.43 for linalool, from 5.61 to 14.7 for eugenol, and from 1.29 to 4.10 for eucalyptol. These findings suggest that nutrient solution formulation may influence basil biomass and the relative abundance of selected VOC constituents. The results also highlight the potential of nutrient formulation as a strategy for modulating specific VOC profiles. In addition, RSM may serve as an exploratory approach for identifying nutrient formulations associated with variations in selected VOC compounds.