Soil-Water-Atmosphere Effects on Soil Crack Characteristics under Field Conditions in a Semiarid Climate

Soil's physical and hydrological properties influence the proper modeling, planning, and management of water resources and soil conservation. In areas of vertic soils subjected to wetting and drying cycles, the soil-water-atmosphere interaction is complex and understudied at the field scale, especially in dry tropical regions. This work quantifies and analyzes crack development under field conditions in an expansive soil in a semiarid region for both the dry and rainy seasons. Six 1 m(2) plots in an experimental 2.8 ha watershed were photographed and direct measurements were taken of the soil moisture and crack area, depth and volume once a week and after a rainfall event from July 2019 to June 2020. The rainfall was monitored for the entire period and showed a unimodal distribution from December to May after five months without precipitation. The cracks were first sealed in the plots with a predominance of sand and when the soil moisture was above 23% and had an accumulated precipitation of 102 mm. The other plots sealed their cracks when the soil moisture was above 32% and with an accumulated precipitation in the rainy season above 222 mm. The cracks redeveloped after sealing upon a reduction of 4% in the soil moisture. The depth of the cracks showed a better response to climatic variations (total precipitation, soil moisture and continuous dry and wet days). The higher clay content and the higher plasticity index plots developed more cracks with greater depth and volume.