Effect of salinity on oleic sunflower (Helianthus annuus Linn.) under drip irrigation in arid area of Northwest China

To achieve secure and efficient saline water irrigation in arid areas, a field experiment was conducted to evaluate the salt distribution in the soil profile and response of sunflower (Helianthus annuus L.) to salinity from 2018 to 2020. The experiment included five levels of irrigation water salinity (ECi = 0.5 dS/m, 3.3 dS/m, 4.9 dS/m, 6.6 dS/m and 8.2 dS/m). The results indicated that the soil salinity rose slightly and was maintained in balance in the first two years owing to the moderate freshwater irrigation after planting. In 2020, surface salinity accumulation occurred when the ECi was greater than 3.3 dS/m. The average soil salinity at 0–100 cm soil depth was near that of the irrigation water. The effects of irrigation water salinity on plant growth and yield were also investigated. Salinity hindered the growth of the sunflower, which was indicated by a decrease of plant height, biomass, and plant water content. Salinity also reduced sunflower yield by reducing the disk diameter and 100-grain weight. IWP increased in the first two years and then decreased in the third year with an increase in the irrigation water salinity. The salinity threshold for oleic sunflower was 1.3 dS/m, and the sunflower seed yield decreased by 4.9% for every 1 dS/m increase in soil salinity. To ensure a seed yield of over 75%, the soil salinity should be less than 6.4 dS/m. It was concluded that for oleic sunflower drip irrigation in arid areas, the plant, should be irrigated with 80 mm of freshwater to leach salt after planting. This not only ensures that the seed yield is no less than 85% but also maintains a balanced soil salinity after harvest when the ECi increases to 8.2 dS/m.