Yield-compatible salinity level for growing cotton (Gossypium hirsutum L.) under mulched drip irrigation using saline water

Abstract Mulched drip irrigation using saline water has the potential to alleviate pressure on crop production from limited freshwater resources in arid and semi-arid regions. To explore the potential of saline water irrigation, it is necessary to investigate how salt stress caused by saline water irrigation affects soil physico-chemical properties and the physiology and growth of crops. The effects of salt stress caused by saline water irrigation are complex and, to date, they are not well understood. We aimed to analyse the distribution and dynamics of these properties to assess their effects on cotton growth, yield, and water productivity during a two-year field experiment using saline water irrigation with various salinity levels (1, 3, 6, 9, and 12 g L−1). Cotton yield, water productivity, and their related components were significantly affected by the different salinity levels. (1) Irrigation water-derived salt accumulated in the soil, especially in the surface soil layer (0–20 cm), but not in the 60–80 cm layer. It was possible to rank cotton main root length based on salinity level as follows: 3 > 1 > 6 > 9 > 12 g L−1. (2) During the growth stage, plants in the 3 g L−1 salinity treatment had transpiration rates 10–30% higher, net photosynthetic rates 20–40% higher, and yields 25–55% higher than those in the other treatments. (3) The 3 g L−1 salinity treatment provided the optimal watering conditions for cotton, and plants in this treatment displayed no salt stress symptoms in terms of their physiology or growth. Therefore, this salinity level is suitable for the mulched drip irrigation of cotton using saline water. Our research provides guidance for further exploitation and utilisation of brackish and saline water resources and sustainable development of irrigated agriculture in semi-arid and arid areas.