Improvement of Photosynthesis by Biochar and Vermicompost to Enhance Tomato (Solanum lycopersicum L.) Yield under Greenhouse Conditions

Chlorophyll fluorescence is an important tool in the study of photosynthesis and its effect on the physiological indicators of crop growth is worth exploring. The trial was conducted to investigate the effect of biochar (CK, 0%; BA(3), 3%; BA(5), 5%; by mass of soil) and vermicompost (VA(3), 3%; VA(5), 5%) on photosynthesis, chlorophyll fluorescence, and tomato yield under greenhouse condition. Results revealed that photosynthetic parameters and chlorophyll fluorescence traits of BA(3), VA(3), BA(5), and VA(5) were significantly higher than those of CK, and the improvement of vermicompost was more effective than biochar at the same application rate. VA(3) treatment had the highest net photosynthetic rate (Pn), intercellular CO(2) concentration (Ci), variable fluorescence (Fv), maximum fluorescence (Fm), PSII maximum photochemical efficiency (Fv/Fm), PSII potential photochemical activity (Fv/Fo), absorption flux per cross section (CS; ABC/CSm), trapped energy flux per CS (TRo/CSm), and electron transport flux per CS (ETo/CSm), which increased by 49%, 65%, 17%, 12%, 4%, 25%, 10%, 15%, and 30%, respectively, compared with CK. The study also found that BA and VA rates could effectively improve tomato yield and water use efficiency (WUE). The yield under BA(3), VA(3), BA(5), and VA(5) treatments was 21%, 33%, 23%, and 25% higher than that under CK, and the WUE increased from 31.2 kg·m(−3) under CK to 41.4 kg·m(−3) under VA(3). Pearson correlation analysis indicated that the increment of photosynthesis showed a highly significant correlation with Fv/Fo, ABC/CSm, TRo/CSm, and ETo/CSm and enhanced the light energy absorbed, trapped, and transported per CS of plant leaves, thereby contributing to the increase in tomato yield. Therefore, for one-season tomato production, the application of 3% vermicompost was considered economical with regard to improving photosynthesis, enhancing WUE, and increasing tomato yield.