Study of regulated deficit irrigation regime based on individual fruit weight and quality response to water deficit duration: A case study in tomato

Water resources scarcity is an important factor limiting agricultural development in arid and semi-arid areas. In addition, arid and semi-arid regions are often accompanied by soil salinization. This suggests that water-saving irrigation is necessary in salinized soils. Regulated deficit irrigation (RDI) is an important water-saving irrigation technology. However, for tomato, which has prolonged flowering period and whose yield and quality are both sensitive to water deficit and salt stress, RDI regime for stabilizing yield and improving quality needs to be further explored, especially for salinized soils. In this study, two soil salinity treatments: S3 (mixed salt was added to the soil at 3 g Kg−1 dry soil) and S5 (mixed salt was added to the soil at 5 g Kg−1 dry soil), and two RDI treatments: W1, 60 % θf was set as the upper limit of soil water content during the reproductive growth period; W2, 60 % θf was set as the upper limit of soil water content during fruit ripening. The effect of RDI on water consumption, fruit yield and fruit quality of tomato was studied in mildly and moderately salinized soils. The effect of the period water deficit suffered by fruits in salinized soils on their weight and quality was quantified. Clarified the effectiveness of the single crop coefficient approach in the application of RDI for tomato in salinized soils. Water productivity (WP), fruit dry weight (DW), tatal soluble solids (TSS), sugar-acid ratio (SAR), lycopene (Ly) and color index (CI) of tomato were obtained under different RDI scenarios in salinized soils based on tomato flowering pattern, single crop coefficient approach and quantitative relationship between the period water deficit suffered by fruits and their weight and quality. Different RDI scenarios were evaluated to determine the optimal RDI regime through the CRITIC-TOPSIS integrated evaluation method using tomato WP, DW TSS, SAR, Ly, and CI as evaluation indexes. The results of the CRITIC-TOPSIS comprehensive evaluation showed that water deficit carried out 45–75 days after flowering facilitates water saving and quality improvement with yield assurance in mildly and moderately saline soils.