Effects of Biochar Addition into Substrate on Tomato Plug Seedlings and Its Working with Automatic Transplanting

Abstract

Vegetable seedling transplantation has become a beneficial and specialized procedure, and a vegetable-specific study on seedling qualities for compatibility with automatic transplanting is needed. In this study, biochar prepared from corn straws was used as the auxiliary material to cultivate seedlings. Firstly, physicochemical properties of compound substrates with different composite of biochar (volume ratio 0, 10, 20~50%) and growth indices of seedlings were measured according to agpronomic conditions. Then, mechanical properties of root lumps and transplanting integrity were investigated. Finally, the optimal seedling qualities for automation of seedling transplanting were comprehensively evaluated with Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). In the results, the rich porous structure and surface area of corn straw biochar can regulate the physicochemical properties of the matrix, which significantly affected the growth of seedling roots and plants. The biochar addition of 10% and 20% in volume ratios was beneficial to the root formation and plant growth. More than 30% biochar-treated substrates had a tendency to inhibit seedling growth. Under the same seedling conditions, the appropriate addition of biochar can improve the twisting strength of root lumps and prevent axial deformation. In conclusion, the comprehensive evaluation coefficient of addition with 10% biochar was 0.67, which was significantly higher than other treatments. Under this treatment, tomato seedlings were stockily grown with rich roots, and the integrity rate of automatic transplanting was above 96%. The biochar of corn straws may be an effective application for the necessary qualities of seedlings for automatic transplanting.