Effect of Planting Density on the Growth and Yield of Sunflower under Mulched Drip Irrigation

A field experiment was conducted to test the suitability of growing sunflower under mulched drip irrigation with saline water in the HID (Hetao Irrigation District), North China. The experiment included five planting densities in which the plant spacing was 30, 35, 40, 45, and 50 cm with the same spacing (50 cm) between rows. The results indicated that mulched drip irrigation with saline water was more water-saving than traditional ground irrigation using fresh water, while the irrigation quota increased with the increase of planting density. Little difference of soil salinization was found for the treatments in the 50–100 cm soil layer, which indicated that additional measures should be taken for salt balance with saline water irrigation. The height and leaf area index (LAI) of sunflower increased in response to the increase of plant density, and the head dry matter transferred to the stem at plant densities higher than 47,619 plants/hm2. Though the grain weight and 1000-seed weight decreased with increasing plant density, the achene yield and biomass production increased. This research suggests that a plant spacing of 35 cm with 50 cm of row spacing is more suitable for sunflower mulched drip irrigation with saline water at concentrations of 3.0 g∙L−1