Effects of continuous biochar application on soil chemical properties and tomato yield and quality in an arched shed

Biochar is a promising soil amendment, but its long-term consecutive effects on greenhouse tomato systems are insufficiently explored. To investigate the dynamic and accumulative effects of consecutive biochar application on soil chemical properties and tomato (<i>Solanum lycopersicum</i> L.) yield and quality, a three-year arched shed field experiment was conducted with five biochar rates: 0 (CK), 0.5 (T1), 1.0 (T2), 2.0 (T3), and 4.0 (T4) kg·m^-². Soil chemical properties, tomato growth, yield components, and fruit quality were analyzed. Results showed biochar slightly increased soil electrical conductivity (all below salinization threshold); only T4 significantly raised soil pH (by 0.4 units) and organic matter (by 132.8%) <i>vs</i>. CK. Annual differences in soil available potassium diminished to non-significance, while available phosphorus was 50.8% (T2) and 63.0% (T3) higher than CK. Tomato plant height and dry matter increased with biochar rate; T1-T4 improved fruits per plant (2.0%-17.0%) and single fruit weight (7.0%-16.0%) over CK, with T2 (13.7%-24.1%) and T3 (19.8%-33.2%) achieving the highest significant yield increases. For quality, T2 had the highest comprehensive index, followed by T1 and T3, with their three-year average scores up by 33.1%, 15.4%, and 15.4% respectively. In conclusion, 1.0-2.0 kg·m^-² biochar optimally enhanced tomato yield and nutritional/organoleptic quality, with no significant interannual cumulative effects of biochar rate on yield or quality-providing theoretical and technical support for high-quality greenhouse tomato production.