Combinations of waste seaweed liquid fertilizer and biochar on tomato (Solanum lycopersicum L.) seedling growth in an acid-affected soil of Jiaodong Peninsula, China

Biochar application is an effective strategy for improving soil degradation and productivity. However, the effects of the combination of biochar and other fertilizers to improve seedling growth in abiotic stress-affected soils remains unknown. We investigate the effect of biochar derived from reed straw (RBC) and waste seaweed liquid fertilizer (SLF) on tomato (Solanum lycopersicum L.) seedling growth in an acid-affected soil of Jiaodong Peninsula, China. The results revealed RBC, SLF, and the combination of RBC with SLF (RBC+SLF) significantly elevated the dry weight of tomatoes by 23.33 %, 29.93 %, and 63.66 %, respectively. The malondialdehyde content in the tomato seedling roots, stems, and leaves was significantly lower in the RBC+SLF treatment, which might be related to the enhanced contents of proline, soluble sugar, and soluble protein. The synthesis and accumulation of zeatin riboside, indole-3-acetic acid, and gibberellic acid 3 in tomato under RBC+SLF amendment may be attributed to the enhanced plant growth. Moreover, RBC, SLF, and RBC+SLF improved the soil status (including ammonium nitrogen, nitrate nitrogen, laccase, and urease) in the acid-affected soil. Biochar and waste seaweed liquid fertilizer significantly increased the relative abundance of Pseudomonas and Azospira (beneficial bacteria) in tomato rhizosphere. The microbial amino acid metabolism was associated with changes in soil properties and enzyme activities. Consequently, biochar and waste seaweed liquid fertilizer are viable soil conditioners for acid-affected soil.