Transformation of Open Soil Surface Under the Impact of Rainfall in Model Experiment

Abstract

During the model experiment we exposed samples from surface layer of leached chernozem, grey forest and soddy-podzolic soils to study the impact of raindrop action on their surface. According to our results, surface of leached chernozem and grey forest soil transformed similarly forming the crust separated by the cracks. The crust consisted of light (washed silt fraction) and dark (compacted fine material) areas. As for the soddy-podzilic soil, we observed surface accumulation of sand and washed mineral grains. Surface image classification showed that cracks generally tended to increase in area during the surface drying. However, leached chernozem cracked quicker and heavier compared to grey forest soil. In addition, the proportion between light and dark areas of the crust for these two types of soil changed differently as well. In conditions of different transformation cycles divided by heavy rainfalls, the changes of cracks position and the increase of light crust area was observed, while dark area moved to the cracks. Such spatial rearrangement resulted in the increase of average reflectance in RGB channels. The inequality between reflectance in different channels increased as well. During the experiment significant surface lightening occurred. It mainly affected the light area of crust and led to significant rise in reflectance in red channel.

Influence of Soil Background on Spectral Reflectance of Winter Wheat Crop Canopy

“…However, the transformation of the open soil surface of arable lands is not a simple process of change in moisture content or in surface roughness. It results in the formation of a surface layer with different properties (organic matter content, texture, porosity, mineralogical composition) [49] and spectral reflectance [50,51]. We observed increased scattering of soil surface reflectance values in NIR-Red spectral space at the shooting and milky ripeness stages.…”

“…As the measurements were made in sunny weather (near midday time), optically active soil surface layer (1-2 mm) was dry. Therefore, the main factor of soil surface spectral variations within soil type was a transformation of the surface under the impact of rainfall which is known to result in changes of soil surface organic matter content and mineralogical composition or in the development of biological crust [49][50][51][52]65,67].…”

“…This result suggests that the ability of soil-line-based indices to correct for soil background variations is limited by temporal soil line variability. composition or in the development of biological crust [49][50][51][52]65,67].…”

“…The introduction of a temporal dimension into the studies requires the consideration of the soil surface dynamics. Soil surface properties was found to change under the impact of rainfall during the vegetative season (not only soil surface moisture or roughness, but also soil surface mineralogical composition, organic matter content, salts content and so on) [48][49][50][51][52]. Corresponding changes in soil surface spectral reflectance will create a site-specific soil line dynamics, introducing additional uncertainty in the assessment of the crop state from remote sensing data.…”

Some Peculiarities of Arable Soil Organic Matter Detection Using Optical Remote Sensing Data

“…Rainfall splash causes the breakdown of soil surface aggregates and the redistribution of formed soil material which is partially transported as a lateral surface flow and partially washed in soil surface pores, causing the sealing of the soil surface and the formation of the soil crust [30][31][32][33][34]. Studies on the impact of rainfall on the soil surface show that it results in changes in the soil surface organic matter content, mineral composition, and texture as well as soil surface reflectance [35][36][37][38][39][40][41]. The longer the surface of non-irrigated arable soils is left untreated under the influence of atmospheric precipitation, the more its spectral properties and material composition change and the greater the difference between its properties and the properties of the underlying part of the arable horizon becomes [40,42].…”