Bioproducts (BPs) derived by municipal biowaste are increasingly recognized as a sustainable practice of reducing mineral fertilizers use. The current study assessed the effects of BP in different levels and application methods for the possible substitution of fertilizers during endive (Cichorium endivia L.) growth. A range of fertilizer treatments were tested: no fertilization (NF); base dressing with conventional (CF), organic (OF), and BP (BP1, BP2; 150, 300 kg ha− 1) applications and their combinations (50% contribution); and supplementary fertigation with conventional (CF-S), organic (OF-S) or BP (BP1-S, BP2-S; 24, 48 g L− 1) solution applications. Application of BP provided comparable or enhanced intermediate plant growth, contingent on rates or application method. Sole BP application declined plant growth due to the inadequate N supply. Interestingly, BP2 elevated intermediate leaf N content compared to BP1, but this difference subsided by the final sampling. Fertigation of BP increased the soil electrical conductivity and nutrient content, by the final sampling, but this was not reflected to plants benefit. The sole BP application may not have sufficiently addressed endive’s nutrient demands, with nutrient limitation increasing hydrogen peroxide and malondialdehyde levels. In response, bioactive compounds were enhanced, including total phenolics content, antioxidant activity, and flavonoid content compared to the use of CF. The combination of CF and BP promoted growth compared to sole BP use, attributed to enhanced nutrient uptake, including increased leaf N accumulation. Interestingly, combined CF and BP improved the content of total phenols, flavonoids, and the antioxidant activity, compared to sole CF. Combined CF and BP maintained endive growth and increased bioactive compounds, suggesting that BPs can be used to reduce the consumption of mineral fertilizers while also enhancing produce quality in a sustainable manner.
Neofytou et al. (Wed,) studied this question.