Abstract:Tomato has become one of the most widely grown vegetables in China due to special nutritive value of its fruit, while waterlogging stress has significant negative effects on tomato yield and quality, a long-term problem facing agricultural production in southern China. In order to explore the means to support the high quality and efficient production of tomatoes, and the possibility of improving crop quality by adding biochar to the soil under waterlogging stress, we conducted soil column test in the Water-Saving Park (WSP) of Hohai University (31°57'N, 118°50'E) in China, from March to August in 2017 to reveal the effect of different biochar application rates (3%, 5%, 10%) on tomato yield and quality. A total of 5 treatments designed included T1 (the control without waterlogging), T2 (waterlogging), T3 (3% biochar application), T4 (5% biochar application), and T5 (10% biochar application). T1 represented conventional planting with groundwater depth of -80 cm. Treatments of T2-T5 were the application of 0, 134, 227 and 480 t/hm2 biochar to the soil affected by waterlogging with groundwater depth of -40 cm, respectively. Effects of biochar application on yield and water use efficiency (WUE) of tomato were studied. The quality indices, such as, single fruit weight, single fruit volume, fruit shape index, fruit color index, soluble sugar, soluble solids, organic acids, vitamin C and fruit hardness of tomato fruit, were also measured. Finally, the 5 treatments were evaluated based on indices of yield, WUE and fruit quality of tomato. By comparing T1 and T2, we found that: 1) waterlogging stress could significantly decrease water requirement and deteriorate fruit quality, but didn’t significantly affect yield and WUE (P>0.05); 2) there was a significant decrease in soluble sugar, soluble solids and organic acids content, by 24.1%,18.1% and 30% (P<0.05), respectively. However, the external quality indices such as single fruit quality, single fruit volume, and single fruit density were not significantly (P>0.05) decreased under waterlogging stress. Increasing biochar application to 10% could increase water use efficiency of tomato suffering from waterlogging stress. In addition, it could also significantly improve fruit internal quality, such as soluble sugar, organic acids and vitamin C content. Compared with T2, all the biochar treatments markedly increased organic acids. Moreover, treatments with 5% and 10% addition biochar application amount significantly increased soluble solids. After the principal component analysis of quality index, we found that the comprehensive principal component scores of external and internal principal components of quality enhanced with the increase amount of biochar application in soil. By mean of comprehensive evaluation method, the treatments ranked from high to low by T5, T1, T4, T3 and T2. The treatment with 10% biochar application in soil had the highest evaluation value with the comprehensive consideration of high yield, water-saving capacity and high quality of tomato under different treatments, while the treatment under waterlogging stress without biochar application had the lowest value. The research provides valuable information for good quality and high efficient production of tomatoes in the areas prone to waterlogging stress, such as the south of China