Nanobiochar Application in Combination with Mulching Improves Metabolites and Curd Quality Traits in Cauliflower

Sustainable nutrient management approaches could improve production and quality without affecting soil health. We conducted a field experiment to investigate the interactive effects of mulching (no mulch, plastic mulch, and straw mulch) and nanobiochar (NBC) foliar application on biomass, nutrient contents, and metabolites in the leaf and curd of cauliflower (Brassica oleracea var. botrytis). After 20 days of transplantation, NBC (0.1% w/v) was applied as a foliar spray for four consecutive weeks (one spray per week). At the curd initiation stage, changes in chlorophyll, carotenoids, and metabolite concentrations in leaves and curd were determined. The application of nanobiochar significantly enhanced the curd weight and improved curd morphology. Yield traits including curd weight, curd diameter, basal diameter, and stalk length were increased by 30, 13, 16, and 20% by NBC application compared to control. Plastic mulching also increased the aboveground biomass by 32% when compared to no mulching. Moreover, plastic mulching and nanobiochar prominently enhanced root dry weight, curd weight, rough solidity index, total soluble sugar in leaf and curd, calcium in curd, and potassium in leaf and curd of cauliflower. Overall, this study revealed the potential of the foliar application of NBC in promoting the biomass and nutritional properties of cauliflower.