Soil fragmentation properties as influenced by induced compaction in Asian clayey hydragric anthrosols conditions

Abstract Compaction of clayey hydragric anthrosols (paddy soil) caused by field traffic can seriously jeopardize the sustainability of intensive rice–wheat rotation systems. This study aimed to investigate the effect of applied stress and compaction times on the soil fragmentation properties for Asian clayey hydragric anthrosols. A specific in situ soil sinkage test bench was used to quantitatively simulate various types of wheel traffic. Experimental treatments included no compaction (control), and 20 combinations of five different applied stresses (50, 100, 150, 200, and 300 kPa) and four different compaction cycles (1, 3, 6, and 12). Intact soil cores with a diameter of 100 mm and a height of 100 mm at depths of 0–100 and 100–200 mm were collected for drop‐shatter testing. Three soil fragmentation state parameter indicators, including mean weight diameter (MWD), specific surface area (SSA), and mass fractal dimension (MFD), were measured. With the increase of applied stress and compaction cycles, the MWD of hydragric anthrosols for 0‐ to 100‐mm and 100‐ to 200‐mm soil layers gradually increases, and the SSA and MFD gradually decrease. Referring to the definition of the soil compression curve, we propose a soil fragmentation curve to characterize soil fragmentation behavior and a pre‐compression stress of soil structures to represent the bearing capacity that does not affect soil fragmentation. Soil drop‐shatter tests also indicated that soil compaction increased soil tillage energy consumption. For 0‐ to 100‐mm and 100‐ to 200‐mm soil layers, the pre‐compression stress of soil structures based on MWD, SSA, and MFD is basically the same, and the average coefficient of variation is 3.86% and 5.64%, respectively. This result indicates that the value of pre‐compression stress of soil structures by using the soil fragmentation state parameters is very stable. It can be used for prediction of soil compaction risks of clayey hydragric anthrosols affecting soil fragmentation.