Desiccation and cracking behaviour of clay loam subjected to different irrigation methods during wetting–drying cycles

Abstract

AbstractDesiccation cracking is a common phenomenon of soil, which potentially affects irrigation and crop growth in farmland. Understanding cracking behaviour aids in developing an effective means of crack prevention or utilization. In the present paper, we report on a phenomenological investigation aimed at exploring the effects of irrigation methods on the cracking behaviour of soil during wetting–drying cycles. Nine identical specimens were prepared and subjected to three irrigation methods (surface irrigation, sprinkling irrigation and drip irrigation) and three wetting–drying cycles. Specimen cracking was monitored by a digital camera and crack patterns were delineated by geometric parameters calculated using image processing techniques. The results showed that the evaporation process of specimens could be roughly divided into three stages according to the variation of evaporation rate. Most cracks were generated during the constant rate stage, although the soil matrix zone was nearly saturated. Surface irrigation increased the cracking water content and cracking degree, in contrast to sprinkling irrigation and drip irrigation. The contribution of crack length propagation and crack width broadening to crack area growth was nearly the same when the soil water content decreased to low values. Stabilized crack networks varied from fractal regimes to uniform distribution regimes with the increasing‐length scale, and the crossover length was independent of irrigation methods and wetting–drying cycles. Under sprinkling irrigation and drip irrigation, cracks formed in the first drying remained as failure zones and most of them reappeared during subsequent drying. However, after surface irrigation most cracks did not propagate in previously cracked zones during subsequent drying, giving rise to shifting crack networks between wetting–drying cycles. Our results provide new insights regarding crack development and evolution in agricultural soil, which will be useful in crack management and irrigation arrangement during crop production.Highlights Effects of irrigation methods and wetting–drying cycles on cracking were investigated. Most cracks initiate and propagate when the soil matrix zone is nearly saturated. Different irrigation methods result in reappearing or shifting crack networks between cycles. This study provides new insights regarding crack development and evolution in agricultural soil.