Mole drain performance in a clay loam soil in Ireland

Abstract

There is uncertainty regarding the suitability of some soils for mole drainage. Soils with questionable potential for the formation of stable mole channels generally have <45% clay and >20% sand, and gravel mole drainage is an alternative. However, this technique is unattractive due to its relative cost (2014 price: €1500-2800 ha −1 versus €125-300 ha −1 ). The performance of conventional mole drains and gravel mole drains was compared on a clay loam soil in the south of Ireland over 12 rainfall events. The installation dates of mole drainage treatments were staggered (January versus July) to assess how soil moisture status during installation affected performance. Treatments were (A) undrained control, (B) mole drainage installed in January 2011 (suboptimal), (C) mole drainage installed in July 2011 (optimal) and (D) gravel mole drainage installed in July 2011. Gravel mole drains were consistently more efficient in removing excess water than mole drains. Mean total drain flow (DF) during rainfall events was greater (P < .05, standard error 0.56 mm) in gravel mole drains (7.4 mm) than any mole drainage treatment irrespective of installation conditions (B [3.8 mm] and C [4.2 mm]). Initially, DF volumes exceeded overland flow (OF) in all treatments (Events 1-4, mean total OF was 0.47 [±0.08] of mean total DF). From Event 5 onwards, this relationship changed with OF being greater than DF (mean total OF was 2.02 [±0.41] of mean total DF). Results showed that across treatment replicates, the water table depth was consistently shallower in control plots. Mole drains were effective for a period of approximately 2 years. Although gravel mole drains were more effective, they were also subject to significant deterioration during the study. Installation conditions had no effect on mole drain performance. The results suggest that on this site conventional mole drainage repeated every 2 years could provide adequate drainage at low cost.

Storm Event Suspended Sediment-Discharge Hysteresis and Controls in Agricultural Watersheds: Implications for Watershed Scale Sediment Management

“…The sediment loss risk may consequently be offset particularly in upland and midchannel reaches where no woodland riparian corridor is present. Reducing hillslope connectivity by increasing subsurface pathways through appropriate subsurface drainage or increasing soil water storage capacity by aeration may reduce surface flows but efficacy over time is spatially variable . Interception of surface pathways through buffer strips encourage deposition of sediments and reduction of flow pathways, but can require agricultural land to be set-aside from production .…”

“…Reducing hillslope connectivity by increasing subsurface pathways through appropriate subsurface drainage 48 or increasing soil water storage capacity by aeration 24 may reduce surface flows but efficacy over time is spatially variable. 48 Interception of surface pathways through buffer strips encourage deposition of sediments and reduction of flow pathways, but can require agricultural land to be set-aside from production. 47 Therefore, rural sustainable drainage systems (RSuDS) are a viable alternative to minimize the area set-aside where land use pressure exists.…”

Soil and Crop Management Practices to Minimize the Impact of Waterlogging on Crop Productivity

“…This drainage system is generally installed to manage rising groundwater levels and land salinization problems (Robinson et al, 1987; Castanheira and Serralheiro, 2010; Kolekar et al, 2014). Mole drainage relies on closely spaced channels and subsoil cracks to quickly send surplus soil water to the tile or agricultural (ag) pipe drainage system throughout the season (Childs, 1943; Hallard and Armstrong, 1992; Tuohy et al, 2015, 2016). Mole drains are installed in close proximity to tile drains and are most suitable for low-permeability heavy soils such as clay (Monaghan et al, 2002; Monaghan and Smith, 2004).…”

Modeling Performance of a Tile Drainage System Incorporating Mole Drainage

“…During installation, the mole plow forms cracks in the soil as the soil is displaced forward, sideways, and upward along well defined rupture plains (Smedema and Rycroft, 1983). Mole drainage relies on this network of closely spaced channels and subsoil cracks to rapidly convey excess soil water to the tile drainage system during rainfall events (Childs, 1943;Spoor, 1982;Hallard and Armstrong, 1992;Tuohy et al, 2015Tuohy et al, , 2016. Stable mole channels can only be formed in fine, plastic, stonefree horizons, and their performance and lifespan are largely determined by soil type and installation conditions (particularly soil moisture content during installation).…”