Performance of surface, subsurface and trench-type drainage systems in paddy fields for non-rice farming

Effective drainage is a crucial factor in paddy fields, especially in regions with waterlogging or heavy clay soils. Identifying an effective drainage system is essential for the successful removal of excess soil water from paddy fields to prepare them for subsequent crops. This study aimed to evaluate three different drainage systems, shallow surface drainage (shallow ditch), conventional subsurface pipe drainage and trench-type subsurface drainage (French drain), in paddy fields in terms of drainage water volume, water table depth, drainage intensity, soil moisture and cracks. Experiments were carried out in a physical model capable of simulation with a 7.5 m drain spacing. The findings indicated that trench-type drainage was more effective in reducing soil moisture due to its higher drainage water volume compared to other systems. The time required for the topsoil to reach its lower plastic limit in the subsurface, trench-type and shallow surface drainage systems was 14, 11 and 15 h after the depletion of excess water over the soil surface, respectively. Although shallow surface drainage represented faster depletion of excess water, trench-type drainage eventually proved to be the most effective alternative for providing appropriate qualifications for secondary cultivation. Crack areas on the soil surface were twice as extensive in trench-type and subsurface drainage systems as in shallow surface drainage systems, indicating their superior performance.