Yield, fruit quality and water use efficiency of tomato for processing under regulated deficit irrigation: A meta-analysis

Tomato is one of the most widely grown vegetables in the world because of special nutritive value of its fruit. Regulated deficit irrigation (RDI) is widely applied in tomato production due to the water shortage. A lot of studies demonstrated that certain degree of deficit irrigation decreased the tomato yield but improved the fruit quality. The purpose of this paper is to use a meta-analysis to: 1) estimate the effect of RDI on processing tomato yield, water use efficiency and fruit quality; 2) identify soil texture, growth stage and deficit severity that benefit yield and increase water use efficiency compared to full irrigation. We analyzed 25 research articles with 561 experimental groups and 145 control groups. Overall, RDI decreased processing tomato yield with mean difference of 18.61 t ha(-1), increased water use efficiency with mean difference of 2.33 kg m(-3), and improved fruit quality. The yield decreased with mean difference of 19.79 t ha(-1 )in loamy soil and 14.26 t ha(-1) in non-loamy soil. The soil texture had no significant effects on yield and water use efficiency under severe RDI. Application of RDI at the first stage is recommended because of no significant yield loss and significant increase of water use efficiency. RDI can improve processing tomato total soluble solids and Vitamin C. Moreover, both of them were increased more when RDI was applied at the third stage than at previous two stages. Our findings can be helpful on how to use RDI correctly to balance the processing tomato yield, water conservation and fruit quality.