Effects of peanut shell biochar and fermented cow manure on plant growth and metabolism of tomato

Background This experimental study used peanut shell biochar and fermented cow manure as the main raw materials forming a substrate for tomato plants. Results Substrates were created from peanut shell biochar, fermented cow manure, slag, and vermiculite mixed in volume ratios of 6:0:1:2, 5:1:1:2, 4:2:1:2, and 3:3:1:2, respectively. Comparisons were made to a control substrate composed of peat, slag, and vermiculite in a volume ratio of 6:1:2, respectively. As the proportion of biochar in the substrate increased, the bulk density showed a downward trend while the total porosity, aeration porosity, and water holding capacity showed upward trends. As the proportion of cow manure increased, the total N, available K, Ca, and Mg in the substrate increased. Tomatoes demonstrated similar or better growth than the control at experimental substrate composition ratios of 6:0:1:2 and 5:1:1:2. This was reflected in seedling strength index, seedling growth, chlorophyll content, root growth, plant carbohydrates, purine metabolism, caffeine metabolism, galactose metabolism, and starch and sucrose metabolism. The results of this study indicate the experimental substrate composition ratios of 6:0:1:2 and 5:1:1:2 were the most beneficial in terms of supporting the growth of tomato plants. Conclusions The study confirms biochar in composite substrate promotes plant growth by improving the root environment and plant metabolism. This investigation provides new information to moderate the use of peat and support efforts to achieve carbon neutrality through the creative utilization of agricultural waste. Graphical abstract