Effects of soil structure and hydrodynamic properties on the growth of Camellia sinensis in the main producing areas of the Qinba Mountains

Abstract

To enhance the soil hydrological properties of tea plantations, this study applied the Van-Genuchten model to assess various parameters, including the soil water characteristic curve, specific water capacity curve, soil porosity, and particle mechanical composition in the primary tea-producing areas of the Qinba Mountain region. Relationships among soil water retention capacity, water release properties, unsaturated hydraulic conductivity, soil water diffusivity, and porosity across different tea plantation growth zones were investigated. Analysis revealed that the soil texture of the four distinct growth regions in the Qinba Mountain area tea plantations is predominantly silty loam. In areas with poor growth, both water content and bulk density were significantly higher compared to other growth regions, while sand content, organic matter, and porosity were lowest. Conversely, luxuriant growth areas exhibited the highest sand content and lowest silt content, presenting an inverse pattern to that of poor growth areas. The soil moisture characteristic curve was accurately fitted using the V-G model with an R² value exceeding 0.99. Additionally, the index K(x) = a*exp(b*x) effectively described water suction and unsaturated hydraulic conductivity, yielding an R² value exceeding 0.90. Soil volume moisture content and soil water diffusivity were adeptly modeled by the exponential function D(θ) = ae^bθ, with an R² value surpassing 0.99. Across the total suction range, water holding capacity ranked as follows: poor growth > moderate growth > well growth = luxuriant growth. Optimal water release capacity was observed in poor growth areas, contrasting with the least favorable performance in well growth areas. The ranking of unsaturated hydraulic conductivity across the four regions was as follows: luxuriant growth, well growth, moderate growth, and poor growth. Furthermore, soil water diffusivity exhibited a gradual increase with rising soil volume moisture content, approaching infinite increase when volume moisture content neared saturation.