Splitting irrigation into two applications: Hetao saline–alkali soil achieves both water supply and desalination

The Hetao Irrigation District is an important grain production base in the arid region of northwest China and a key area for the coordinated development of ecological protection and agriculture in the Yellow River Basin. However, strong evaporation, scarce precipitation, and extensive traditional flood irrigation have exposed large areas of cultivated land to the threat of secondary salinization. The dual constraints of water shortage and soil salinization restrict the sustainable development of regional agriculture. Although mulched drip irrigation has been proven to be an effective alternative to flood irrigation, the commonly used single 30-mm drip irrigation has obvious shortcomings—rapid soil water depletion and surface salt accumulation after irrigation—making it difficult to meet crop water requirements throughout the seedling stage. How to optimize the drip irrigation regime under a limited irrigation quota to achieve coordinated water saving, salinity control, and yield increase is an urgent production problem in the region.

The research team led by Prof. Rongjiang YAO at the Institute of Soil Science, Chinese Academy of Sciences, published a study titled “Effect of split drip irrigation with limited water supply on soil water-salt dynamics and crop growth in a saline soil” in ENGINEERING Agriculture (DOI: 10.15302/J-FASE-2026679). Through experiments and Hydrus-2D simulations, the study confirmed that under the same limited water supply, split mulched drip irrigation, compared with single drip irrigation, better maintains soil water conditions in the root zone, promotes salt leaching, and improves crop growth at the seedling stage, providing technical reference for water saving and salinity control in saline–alkali irrigation districts of northwest China.

To explore a suitable mulched drip irrigation regime for the Hetao Irrigation District, the research team took silty clay loam as the study object and combined soil box simulation experiments, field validation experiments, and Hydrus-2D numerical simulations. They systematically compared two irrigation modes: single irrigation of 30 mm and split irrigation (15 mm on Days 1 and 15). In addition, two increased irrigation scenarios of 40 and 50 mm were set up to examine the regulatory effects of higher water volume and frequency on water and salt distribution. The study focused on soil water–salt dynamics in the 0–50 cm soil layer and comprehensively evaluated the effects in combination with sunflower growth indicators at the seedling stage, such as plant height, stem diameter, and leaf area index.

In terms of water–salt dynamics, after single drip irrigation, the peak water content near the drip emitter reached 0.22 cm³·cm⁻³, but water rapidly infiltrated vertically to a depth of 35 cm and then dissipated quickly. Although split drip irrigation reduced the peak to 0.19 cm³·cm⁻³, it maintained water stability in the 0–25 cm root zone for a longer period. Regarding salinity changes, the final total desalination rates of the two modes were similar (about 86% vs. 85%), indicating that the total amount of salt leaching was dominated by the total irrigation volume. However, because of two infiltration events, split drip irrigation produced better localized desalination around the drip emitter. Scenario simulations showed that increasing the total irrigation volume to 40–50 mm improved the stability of shallow soil water content but provided limited benefit for deep salt leaching, indicating no need for a blind increase in irrigation volume under water-saving conditions. Crop growth responses showed that 30 days after sowing, sunflower plant height (49.2 cm) and leaf area index (1.7) under split drip irrigation were significantly better than those under single drip irrigation (41.1 cm and 1.2), confirming that split drip irrigation promoted seedling growth by optimizing the spatiotemporal distribution of water and salt.

This study directly responds to the practical needs of agricultural water saving in the Hetao Irrigation District. Its core value lies in the fact that, without increasing the total irrigation water volume, merely adjusting irrigation frequency—splitting a single 30-mm application into two 15-mm applications—can significantly improve water use efficiency, optimize water and salt distribution in the root zone, and promote crop growth at the seedling stage. This conclusion provides direct, actionable scientific evidence for optimizing existing drip irrigation regimes in irrigation districts under increasingly rigid water resource constraints.