Effect of saline water drip irrigation on tomato yield and quality in semi-humid area and arid area of China

To alleviate the contradiction between the shortage of freshwater resources and the rapid development of industries and agriculture in China, field experiments were conducted to study the response of tomatoes to different water salinity (ECi) levels under drip irrigation in coastal semi-humid areas and arid areas. The effects of water salinity on salt accumulation in the root zone, tomato growth, yield, yield components, and quality response were investigated. The results indicated that the electrical conductivity of the soil saturation extract (ECe) increased with the irrigation water salinity. In semi-humid area, the maximum ECe was not higher than 5 dS/m, and the value was lower in wet year, at approximately 2 dS/m. In arid area, the ECe increased in the first year and then tended to balance. The ECe exceeded 4 dS/m when the ECi is higher than 6.6 dS/m. Salinity hindered the yield of tomatoes, which was mainly manifested by a reduced fruit diameter, fruit number, and single fruit weight. The salinity thresholds that tomato can endure without yield reduction 1.8 dS/m in semi-humid area and 2.1 dS/m in arid area, when ECe of root zone exceeded the threshold, for every 1 dS/m increase in ECe, the relative yield decreased by 14% and 12%, respectively. Nevertheless, tomato fruit quality is improved under saline water irrigation. Vitamin C (VC) content shows a significant quadratic curve relationship with ECe, and the maximum appeared at 4.0 dS/m in semi-humid area and 5.9 dS/m in arid area. Total sugar (TS) and total acid (TA) contents were significantly improved in arid area, for every 1 dS/m increase in ECe, the relative TS and TA increased by 12.8% and 20.3%, respectively. From the comprehensive point of saving water, avoiding yield reduction, and improving tomato fruit quality, saline water of about 6.3 dS/m and 4.9 dS/m is suggested for drip irrigation of tomatoes in semi-humid areas and arid areas in China.