Abstract
Remote sensing has shown its potential to assess soil properties and is a fast and non-destructive method for monitoring soil surface changes. In this paper, we monitor soil aggregate breakdown under natural conditions. From November 2014 to February 2015, images and weather data were collected on a daily basis from five soils susceptible to detachment (Silty Loam with various organic matter content, Loam and Sandy Loam). Three techniques that vary in image processing complexity and user interaction were tested for the ability of monitoring aggregate breakdown. Considering that the soil surface roughness causes shadow cast, the blue/red band ratio is utilized to observe the soil aggregate changes. Dealing with images with high spatial resolution, image texture entropy, which reflects the process of soil aggregate breakdown, is used. In addition, the Huang thresholding technique, which allows estimation of the image area occupied by soil aggregate, is performed. Our results show that all three techniques indicate soil aggregate breakdown over time. The shadow ratio shows a gradual change over time with no details related to weather conditions. Both the entropy and the Huang thresholding technique show variations of soil aggregate breakdown responding to weather conditions. Using data obtained with a regular camera, we found that freezing–thawing cycles are the cause of soil aggregate breakdown.
Highlights
Soil aggregate breakdown is a function of soil strength and the kinetic energy of the rainfall [1,2].Soil strength depends on soil particle distribution, structure, soil organic carbon, ionic bridging, clay and carbonates
To monitor aggregate breakdown under natural conditions, we designed an outdoor experiment consisted of a RGB Single-lens reflex (SLR) camera and a weather station both mounted on a tripod
Soil aggregate stability was performed on soils according to ISO
Summary
Soil aggregate breakdown is a function of soil strength and the kinetic energy of the rainfall [1,2]. Soil strength depends on soil particle distribution, structure, soil organic carbon, ionic bridging, clay and carbonates. Different land cover or land use, such as forest or agriculture, influences soil structure and organic matter content [3]. Aggregate stability decreases when water dispersible clay content increases in relation to total clay, as reported in [4]. Weather conditions influence soil aggregate, especially when both rainfall and freezing–thawing cycles occur [5]. While rainfall induces soil aggregate breakdown, compaction and crusting, freezing–thawing cycles affect formation and destruction of soil structure [6,7]
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