Subsurface drainage technology may offer a useful option in improving crop productivity by preventing water-logging in poor drainage paddy fields. The present study compared two paddy fields with and without sheet-pipe type subsurface drainage on land and water productivities in Indonesia. Sheet-pipe typed is perforated plastic sheets with a hole diameter of 2 mm and made from high-density polyethylene. It is commonly installed 30–50 cm below the soil surface and placed horizontally by a machine called a mole drainer, and then the sheets will automatically be a capillary pipe. Two fields were prepared, i.e., the sheet-pipe typed field (SP field) and the non-sheet-pipe typed field (NSP field) with three rice varieties (Situ Bagendit, Inpari 6 Jete, and Inpari 43 Agritan). In both fields, weather parameters and water depth were measured by the automatic weather stations, soil moisture sensors and water level sensors. During one season, the SP field drained approximately 45% more water compared to the NSP field. Thus, it caused increasing in soil aeration and producing a more significant grain yield, particularly for Inpari 43 Agritan. The SP field produced a 5.77 ton/ha grain yield, while the NSP field was 5.09 ton/ha. By producing more grain yield, the SP field was more effective in water use as represented by higher water productivity by 20%. The results indicated that the sheet-pipe type system developed better soil aeration that provides better soil conditions for rice.

Sheet-pipe is a sort of perforated mole drain placed horizontally between 30–50 cm below the land surface commonly having a water-logged problem. The sheet-pipe can be installed with a heavy machine mole drainer. The primary purpose of installing sheet-pipe is to maintain or control the expected water table in farmlands. Sheet-pipe having a diameter of 5 mm has been installed at a depth of 40 cm with a drain spacing of 4 m and length of 100 m covering a paddy field of 1 hectare located in Sukamandi District, Subang Regency, West Java, Indonesia. Field investigation and numerical studies were undertaken to figure out water head profiles surrounding the sheet-pipe. The paddy field installed with sheet-pipe can be drained faster (2 times), and in consequence, its water level can be managed easier. Right after an effective rainfall event (34 mm), the rainwater immediately infiltrates downward resulting in a parabolic curve of infiltration rate (maximum rate 0.94 cm/h) which differs with a standard infiltration curve (steady state 0.121 cm/h). Water level profile is horizontally flat except at the points closer to the sheet-pipe, which is showing the presence of outward gradients of the water head. The electrical conductivity was low (0.33 Ms/cm) due to the leaching effect.

The present study is part of the development of an environment-friendly water management system based on sub surface drainage technology. It is aimed at creating a multipurpose farmland with expectation of increase in both benefits and productivity. Sub-surface drainage pipes which are installed inside mole-drain, functions as water channel that flows water into the drainage channel. Simulation was run using a 2D numerical soil water flow model based on Richard’s equation. It integrates varying soil textures with aim of figuring the optimum setting of sub-drains in response to soil textures. The depth of sub-drain was established at 40cm beneath the surface for all conditions as it is the current installation available in Indonesia. Our simulation shows the variation of soil moisture and pressure over distance, time and different textures under specified spacing of sub-surface installation.

Sheet pipe is a type of perforated pipe used for drainage designed initially for drainage but has the potential for sub-surface irrigation. The objectives of this study were to experiment and observe the performance of the sub-surface irrigation control system with sheet pipe. This investigation covered the observation of water table control and its effect on soil moisture. The detailed process of water flow during the setting of the water table was numerically modeled in 2 dimensions to observe the distribution of soil moisture, soil pressure, and flux. The results showed that the system successfully controlled the water table at the desired level in the experiment. The developed two-dimensional numerical simulation showed the distribution of soil moisture in the model center as a response to the water table increase, represented by the variable head. The soil wetting advances toward soil surface driven by the water table, which was increased gradually and reached saturation at the height of water table setpoint.

For the sustainable restoration of wet farm land degraded by the climate change-induced rise of ground water level (GWL) and soil salinity etc., the sheet pipe system is one of the most useful technologies which reduces cultivation obstacles due to the poor drainage by controlling the rapid drainage function and enabling farmers to produce profitable crops. This system is characterized mainly as a perforated polyethylene rolled-band sheet 180 mm in width and 1 mm thick which is drawn into the subsurface layer while transforming a drainage pipe with φ = 50 mm. The major advantage of this system is that since the sheet pipe is installed without trenching, the disturbance of land is minimized and the construction period can be shortened to about 1/4 (which reduces the cost approximately by 50%). In this study, by using the sheet pipe installed miniature-type model soil box, the drainage capacity of the sheet pipe was confirmed as being the same as the pipe-shaped standard drainage pipes. Based on the observations of the saturated–unsaturated flow and the maximum lowering rate of GWL was predicted. Finally, at the farm land wherein the free board of the adjoining canal was limited, the effectiveness of the sheet-pipe system was confirmed.