Biochar and organic fertilizer amendments improved soil microbial biomass, soil quality, and wheat yield of saline-alkali soils in a three-year field trial

The objective of this study was to examine the effects of biochar compared to organic fertilizer on soil quality and microbial biomass as well as wheat yield in the saline-alkaline lands. A three-year field trial was conducted on moderately saline-alkaline land in the Yellow River Delta region (YRD) with six treatments: biochar (B1: 5 t, B2: 10 t, B3: 20 t ha − 1 year − 1 ) and organic fertilizer (OF1: 5 t, OF2: 7.5 t ha − 1 year − 1 ) as well as control (CK). The results showed that both biochar and organic fertilizer increased total organic carbon (TOC), total nitrogen (TN), NH 4 + -N, and NO 3 − -N, and reduced pH, thereby increasing soil microbial biomass carbon (MBC) and nitrogen (MBN), MBC/TOC ratio, and MBN/TN ratio, but organic fertilizer increased soil nutrients and microbial biomass better than biochar. Correlation analysis revealed that soil water content (SWC), soil salt content (SSC), and Na + were the most important factors influencing wheat yield. When compared to CK, the SSC and Na + decreased by 5.55–7.52% and 3.86–9.39%, respectively, and SWC increased by 5.14–5.62% in the biochar treatment, while they increased by 1.07–10.19%, 1.08–7.58%, and 2.96–3.84% in the organic fertilizer treatment, respectively. Accordingly, wheat yield in biochar treatment was 0.90–14.20% higher than organic fertilizer treatment (4.49–4.80 t ha − 1 ). Collectively, B2 had the lowest SSC and Na + and the highest yield, as well as efficiently increasing soil nutrients and microbial biomass, suggesting that it may be a better agricultural practice for improving soil quality and increasing wheat yield in the YRD.