Sweet basil can be grown hydroponically at low phosphorus and high sodium chloride concentration: Effect on plant and nutrient solution management

Abstract

Agronomic inputs in agriculture easily exceed crop needs causing environment pollution. Phosphorus (P) is a macronutrient largely used in agriculture as a mineral fertilizer that requires an accurate management because it is a finite and non-renewable resource. Growing plants hydroponically can optimize plant nutrition achieving high crop nutrient use efficiency. However, irrigation water of poor quality (saline) interferes with crop performance. In this study, the effects of different P and NaCl levels in the root zone were evaluated on basil plants grown in a deep liquid culture system in a growth chamber. Two experiments with different P (from 0.1 to 1.0 mol m−3) and NaCl (from 0 to 60 mol m−3) concentrations in the nutrient solution were carried out. Plant growth, leaf gas exchanges and fluorescence, uptake of minerals and water, and leaf quality (content of minerals and pigments, and antioxidant capacity) were analysed. The most relevant morphological plant response to the low P (i.e., roughly 0.1 x of a standard nutrient solution) concentration consisted in a greater root/shoot ratio. However, plants growing at low P concentration did not show any reduction in yield and quality. Sodium chloride did not significantly affect plants yield and quality up to a concentration of 30 mol m−3 confirming the tolerance of basil to moderate saline stress. Significant reduction in the total biomass, water uptake and photosynthesis instead occurred at NaCl 60 mol m−3. These results confirmed the hypotheses that basil can be grown hydroponically at low P and high NaCl concentration with proper management of the nutrient solution. The absence of significant interactions between P and NaCl suggests that these two factors can be managed independently with potential benefits for crop economic and environmental sustainability.