Seasonal differentiation and drivers of vertical soil moisture variation in farmland of the middle Heihe River

Abstract

Soil water scarcity constitutes a pivotal environmental challenge across arid and semi-arid zones both in China and globally. Driven by ongoing climate change coupled with anthropogenic disturbances, such drought-prone areas keep undergoing continuous spatial expansion. The middle reaches of the Heihe River, as a typical irrigated oasis area in arid area, face prominent contradictions between water supply and demand. Farmland soil moisture dynamics play a vital role in ecological security and agricultural sustainability. Understanding the spatiotemporal characteristics and driving mechanisms of soil moisture is urgently needed to optimize agricultural water resource management. Based on multi-depth soil moisture and meteorological observation data from 2012 to 2024 at the Daman farmland station, redundancy analysis (RDA), multiple linear regression, and hierarchical cluster analysis (HCA) were comprehensively employed to systematically identify the driving factors of soil moisture during the growing and non-growing seasons and characterize their seasonal differentiation patterns. We concluded: 1) Soil moisture is significantly greater variability in shallow soil of 2–20 cm than in deep soil of 120–160 cm, and distinct differences in moisture dynamics between different years; 2) RDA analysis indicated that during the growing season, soil moisture variation was mainly correlated with net radiation (Rn) and air temperature (Ta), whereas in the non-growing season it was dominated by soil temperature (Ts) and photosynthetically active radiation (PAR); 3) Regression analysis further showed that Rn had the greatest impact on the moisture of shallow soil, and Ts showed a significant influence during the non-growing season; 4) Cluster analysis revealed distinct seasonal differentiation features: high temperature and humidity in the growing season, and low temperature water storage in the non-growing season, reflecting the region’s typical climatic characteristics. Soil moisture in the middle reaches of the Heihe River is correlate with energy inputs and water replenishment, with markedly different driving mechanisms between seasons. During the growing season, irrigation should be strengthened to mitigate water loss caused by high temperature and intense radiation, while in the non-growing season emphasis should be placed on low-temperature water retention. These findings provide a scientific basis for sustainable water resource utilization and agricultural water management.