Effect of stratified soil mixed with sand on photosynthesis and transpiration of alfalfa

【Objective】Stratifying soil with sand is an engineering technique commonly used to improve the drainage and aeration of fine-textured soils. This study investigates its effects on the growth, transpiration, and photosynthesis of alfalfa.【Method】A field experiment was conducted to compare intact soil (FUS) and soil treated with a sand-stratification technique (ALS). In each treatment, physiological traits, photosynthetic traits, transpiration, and water consumption of alfalfa were measured. The hydrothermal balance of each soil type was analyzed using the soil-heat-water model.【Result】Under identical conditions, ALS significantly influenced the physiological and ecological traits of alfalfa. Specifically, compared to FUS, ALS increased average plant height by 8.5%, stem diameter by 10.4%, stem-to-leaf ratio by 18.2%, and dry mass by 7.1%. Under natural conditions, ALS increased the daily average net photosynthetic rate by 8.69% to 109.39%, with maximum increases ranging from 9.27% to 64.23%. Moreover, ALS significantly enhanced transpiration and stomatal conductance compared to FUS. The total evapotranspiration of alfalfa was 576.85 mm under FUS and 381.45 mm under ALS. Additionally, ALS reduced soil-surface evaporation by 51.22% during the peak water-demand period of the growing season.【Conclusion】Stratifying fine-textured soil with sand improved water infiltration, reduced soil surface evaporation, and enhanced the water use efficiency of alfalfa, thereby increasing its yield.