Characteristics of Soil Aggregates and Factors Influencing Bingsugar Orange Orchards

Abstract

[Objective] The soil aggregates of Bingsugar orange orchards and the factors affecting them were characterized in order to reduce soil erosion and increase the water and fertility retention capacity of citrus orchards. [Methods] Soil samples were collected from weathered slate, weathered purple sandstone, sandstone, and weathered Quaternary laterite developed in a Bingsugar orange orchard. Related tillage and geographic information were collected simultaneously. ANOVA and correlation analysis were performed on the agglomerated data and their organic carbon contents using soil structural stability indexes R 0.25, GWD, MWD, fractal dimension (D), and soil erodibility K value. [Results] ① Agglomerates with particle sizes >0.25 mm accounted for 78%~85% of the total agglomerates. Graded soil content gradually decreased with decreasing agglomerate particle size. ② The GWD of the soils developed by the four matrices ranged from 0.536~0.797; MWD ranged from 0.890~1.208; fractal dimension (D) ranged from 2.434~2.480; and soil erodibility K value ranged from 0.060 8~0.0 697. ③ Organic carbon content decreased with increasing particle size and then increased, with an overall V-shaped distribution. Organic carbon content of the 0.250~0.053 mm microaggregates was the lowest. The relative contribution of organic carbon of large agglomerates was 82%~87%. ④ Soil structure stability indexes R0.25, GWD, and MWD significantly increased with increasing number of planting years and the continuous input of exogenous organic carbon. Fractal dimension (D) and soil erodibility K values significantly decreased at the same time, indicating increasing soil structure stability. [Conclusion] Soil stability was high with high content of large agglomerates in a Bingsugar orange orchard in Hu’nan Province. The soil stability of each parent material was at the same level. Sand content of the soil-forming parent material and anthropogenic disturbance directly affected the role of agglomerate stability, exogenous organic carbon, and planting years. Latitude and altitude jointly influence soil stability by organic colloidal material. The sand content of the parent material and anthropogenic disturbance directly contribute to the stability of the aggregates. Exogenous organic carbon, age of cultivation, latitude and altitude combine to influence soil stability through the organic cementing material.

Keywords

• bingsugar orange orchard
• soil-forming matrix
• aggregate
• organic carbon
• soil stability