Effects of Bioproducts on Tomato Performance across Two Cultivation Cycles under Reduced Mineral Fertilization

The overuse of mineral fertilizers represents significant environmental and economic concerns, highlighting the necessity of sustainable nutrient management. This study evaluated the biostimulant potential of bioproducts (BPs) from solid anaerobic digestate in greenhouse tomato cultivation to maintain productivity with reduced fertilization. Trials were conducted over two cycles, with soil application of BPs, combined with 100 or 60% of standard mineral fertilization (MF). Reducing MF by 40% resulted in a decrease in marketable yield; however, the combination of BPs with 60% MF compensated for this reduction, achieving yields comparable to the control in both growing cycles. Pigment content decreased under reduced MF, but BP-treated plants exhibited higher protein accumulation and increased enzymatic activities involved in nitrogen assimilation, suggesting enhanced nitrogen use efficiency. Overall, BPs acted as effective plant biostimulants, enabling a 40% reduction in mineral fertilizer input without compromising total yield or fruit quality, supporting a more sustainable tomato production.