Biosolids application improves mineral composition and phenolic profile of basil cultivated on eroded soil

Abstract

A possible solution for improving the fertility of the eroded soils could be the use of biosolids because of their high content of organic matter (OM), micro- and macronutrients. However, limited information is available concerning the mineral nutrition, physiology, and synthesis of secondary compounds in plants in response to eroded soils and biosolids amendments. Therefore, the aim of this study was to assess how cultivation of basil (Ocimum basilicum L.) in different soil types (eroded soil, biosolids, and eroded soil 75% + biosolids 25% v/v) would affect mineral composition of soil and plant tissue, yield, physiology, and synthesis of phenolic compounds in basil plants. Elemental analysis revealed that application of biosolids to the eroded soil increased the content of macro and micronutrients (phosphorus, (P) by 327%, magnesium (Mg) by 17%, copper (Cu) by 83%, zinc (Zn) by 1062%, and molybdenum (Mo) by 64%) in the substrate compared to the unfertilized control (growth medium). Biosolids had positive effects on gas exchange parameters (CO2 assimilation rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration) as well as chlorophyll fluorescence and chlorophyll content, while the eroded soil decreased these parameters, suggesting a photoinhibition stress effect on the photosystem II. Fresh yield was increased by 206% in plants grown on eroded soil + biosolids and decreased by 43% in those grown on eroded soil in comparison with the control. The synthesis of total phenolics and the antioxidant activity was higher in plants grown on eroded soil. Phenolic profiling of basil leaves revealed 17 compounds. Rosmarinic acid was the main phenolic compound and was higher in plants grown on eroded soil compared with all other treatments. The Zn bioconcentration factor ranged from 1.4 (biosolids) to 14.3 (control), while the Zn translocation factor ranged from 0.43 (eroded soil) to 0.86 (eroded soil + biosolids). This suggests that the investigated basil cultivar is tolerant to Zn, and biosolids fertilization can be used in biofortification of basil crop and products. Application of biosolids to eroded soil improved the mineral content of the substrate and had positive effects on basil yield and physiology.