The effect of highly porous biochar on the properties of greenhouse peat substrates

Peat is a key component of substrates in greenhouse cultivation, and enhancing its properties through the addition of organic components is a common practice. This study compares highly porous biochars derived from pine nut shells, produced under slow pyrolysis and high-temperature conditions with subsequent activation, as additives partially replacing peat in substrates. The carbon content and degree of organic matter decomposition were determined in peat mixtures with biochars of different concentrations (10% and 20% by volume) and forms (ground and unground). It was found that 20% ground biochar leads to the greatest increase in the C/N ratio, typically observed in undrained or deeper peat layers, indicating a higher intensity of humification that optimally stimulates microbial activity, yet suggesting a possible reduction in nitrogen availability for plants. The concentrations of macro- and micronutrients in mixed peat substrates were determined. The results showed that the addition of ground activated biochar (10–20% by volume) significantly increases the concentration of key macronutrients in the substrate, such as phosphorus, potassium, and calcium by factors of 4.9–5.9, 3.3–3.9, and 1.7–1.8, respectively, demonstrating the promising potential of activated biochar for improving the nutrient properties of peat substrates. Particular attention was paid to analyzing the impact of biochars on the content of heavy metals and non-metals, confirming their potential effectiveness and environmental safety. The data obtained suggest the possibility of partially replacing peat with highly porous biochars, especially in ground form, which may contribute to increased crop yields and enhanced plant resistance to stress conditions.