Soil water retention dynamics in a Mollisol during a maize growing season under contrasting tillage systems

A Soil water retention curve (SWRC) provides pore structure information and is usually measured in the laboratory on soil cores. In field, the dynamics of SWRC is affected by pore structure changes due to tillage operations and wet-drying cycles (WDs). While the temporal changes of SWRCs during WDs have long been reported, the dynamics of SWRC under different tillage systems are poorly understood. A field experiment was conducted on a Mollisol to determine the SWRC dynamics of conventional tillage (CT), no tillage (NT), and rotational tillage (RT) in the maize growing season of 2018. Volumetric water content and matric potential dynamics at three depths were monitored continuously, and the temporal changes of SWRCs were compared with laboratory data measured on soil cores. Results showed that SWRCs measured under field conditions varied with WDs and tillage treatments, especially in the wet range (0 hPa to -100 hPa). The water retention capacity of the tilled soils (i.e., CT and RT) gradually increased with WDs while that of NT in 0􀀀 5 cm was slightly decreased. Compared with the laboratory data, the dynamics of SWRC under field conditions were more prominent. During the observation period, NT showed the highest water retention capacity under both laboratory and field conditions when the matric potential of soil water was more negative than -100 hPa. The high rigidity of soil pore system and straw mulch on soil surface in NT maintained a relatively higher soil water retention capacity and reduced the temporal variation of SWRC in the maize growing season.