Effects of uneven vertical distribution of soil salinity under a buried straw layer on the growth, fruit yield, and fruit quality of tomato plants

Soil salinity is often heterogeneous, but plant response to uneven salt distributions in the vertical direction (USDVD) of the root-zone under buried straw layer is seldom studied in tomato (Solanum lycopersicum Lvar. Yazhoufenwang). Our objective in this study was to evaluate the effects of USDVD under a buried straw layer on changes in water consumption, root distribution, yield, fruit quality, K+ Na+, Ca2+ concentrations of leaves and fruits as well as stable carbon isotopic compositions (VC) of leaves for tomato plants grown in the greenhouse. To achieve this objective, pot experiments were conducted from April to July in 2014 and 2015. The treatments, Tin, T-2:4 and T-3:3, were established by setting the upper soil layer with EC1:5 (the electrical conductivity of a 1:5 dry soil: water mixture) 0.38 ms cm(-1), 038 ms cm(-1), 0.76 ms cm(-1) and 1.14ms cm(-1), respectively, and the lower soil layer with EC1:5 0.38 ms cm(-1), 1.90 ms cm(-1), 1.52 ms cm(-1), and 1.14ms cm(-1), respectively. In addition, a capillary barrier, made of straw, at a depth of 17 cm and with a thickness of 3 cm, was set between the upper and lower soil profile. The roots could penetrate through the straw layer, even though the soil salinity in the lower soil layer was relatively high (T-1:3). Compared to equal salinity distribution treatments (Tin and T-3:3), there was a significant compensatory water uptake and root growth from the low salinity soil profile under USDVD treatments (T-1:5 and T-2:4). In 2014, the water consumption and root density in the upper soil layer under USDVD treatments (Ti:s and T2:4) were 1.20 times and 1.38 times those of the equal salinity distribution treatments (Tin and T33), respectively. The Na* concentrations of leaves for Tis and T-2:4 were 15.1% and 48.9% of T-33, respectively, whereas the lc concentrations of leaves for Ti:5 and T2:4 were 2.1 times and 1.4 times that of T-3:3, respectively, resulting in significantly higher K+/Na+ ratios for Ti:s (10.17) and T2:4 (2.06) than T-3:3 (0.72); the delta C-13 value of T-3:3 (-28.46) was significantly higher than that of Tts (-29.17), whereas there was no significant difference for 613C between 113 and T-1:1 (-29.12). Across the two years, the average yields of Ti3, T2:4 and T3:3 were 20.3%, 47.1%, and 64.9% lower than that of Tin, respectively, whereas the soluble sugar contents of the fruits in T-1:5, T-2:4 and T-3:3 were 21.3%, 76.5% and 97.6% higher than that of Ti:i. The overall results suggest that the USDVD treatments under a buried straw layer could relieve the salt stress and benefit the quality and quantity of tomato plants grown in saline soil. (C) 2016 Elsevier B.V. All rights reserved.