Growing ‘Genovese’ and ‘Valentino’ Basil in Pots Using Peat Substrate Combined with Phytoremediated Sediment: Effects on Yield and Nutraceutical Content

Abstract

Climate change is causing a decline in the availability of crucial resources such as water and fertile soil, leading to a detrimental impact on crop yields. Basil (Ocimum basilicum L.), an annual aromatic plant used worldwide for culinary, cosmetic, and medicinal purposes, is especially at risk due to its high water demand and specific growing requirements typical of the Mediterranean climate. In Italy, basil is an essential part of any herb garden and is also commonly found in households as a potted plant. Nowadays, the conventional practice of growing basil in pots with peat as the primary medium is not environmentally sustainable, which underscores the need for alternative and sustainable cultivation techniques to ensure the continued growth of this majestic king of herbs. A greenhouse factorial experiment was conducted to study the impact of peat replacement and reduced water supply on the growth and biochemical traits of basil plants. The study included two cultivars (‘Genovese’ and ‘Valentino’), three substrate mixes with phytoremediated dredged sediment (TS) at varying volume percentages (0%, 12.5%, and 25%), and three levels of water irrigation (normal, reduced by 25%, and reduced by 37.8%). Increasing the TS percentage resulted in higher germination rates and greater biomass production in both cultivars compared with the control. ‘Valentino’ potted plants produced a higher yield than those of ‘Genovese’, while the latter had higher pigment contents due to its genetic characteristics. All combinations of substrates mixed with the highest water amounts of irrigation positively impacted seed germination and biomass-based outputs, while control peat with reduced water availability led to lower plant yields and germination capacity. Substrates with TS had suitable physicochemical characteristics for plant development. Our findings suggest that using peat–TS mixtures can produce quality results comparable to or even better than conventional soilless culture using only peat. Thus, replacing peat with moderate percentages of TS can be an effective and sustainable practice for recycling phytoremediated sediments.