Effect of dynamic unequal distribution of salts in the root environment on performance and Crop Per Drop (CPD) of hydroponic-grown tomato

Due to water shortage, application of saline water for irrigation is an urgent requirement in agriculture. The aim of this study was to investigate the effects of NaCl-induced salinity stress on the growth and Crop Per Drop (CPD) of tomato (Lycopersicon esculentum var. Falcato F1) in a dynamic split-root hydroponic system. Roots of tomato seedlings were separated into approximately two equal parts, half was grown in a box containing aerated nutrient solution (A-half), and the other half was grown in a similar box containing aerated saline water (B-half). Four salinity levels (0, 40, 80, and 120 mM NaCl) were applied at the B-half. At the static split-root hydroponic system, significant difference was found between the tomato roots supplied with the nutrient solution and those supplied with saline waters in the root volume and fresh and dry matter weight. By increasing NaCl concentration in the B-half, the root growth was decreased. At the dynamic split-root system, interchanging the split roots between the nutrient solution and the saline water at 3-day intervals resulted in significant reduction of tomato growth, fruit yield and CPD. The highest CPD was found at the treatment where in a 7-day dynamic split-root system, half of the roots were exposed to the nutrient solution and the other half was immersed in the 40 mM NaCl solution. At the 7-day intervals treatments, exposing the split root to 80 and 120 mM NaCl concentrations resulted in significant reduction of the plant growth, fruit yield and the CPD. The results showed that the dynamic split-root hydroponic system is an applicable technique for using saline waters; although the success of this system is strongly dependent on the salinity level and the exchange interval of root parts between the nutrient solution and saline water.

► Tomato growth and yield was dependent on the interchanging intervals of the split roots.
► Interchanging the split roots at 3-day intervals resulted reduction of tomato fruit yield and CPD.
► The highest Crop Per Drop (CPD) was found at 7-day dynamic split-root system.
► Dynamic split-root hydroponic system is an applicable technique for using saline waters.