Mole drainage performance in a clay loam soil
2015
Tuohy, P., Teagasc, Animal and Grassland Research and Innovation Centre, Cork (Ireland) | Humphreys, J., Teagasc, Animal and Grassland Research and Innovation Centre, Cork (Ireland) | Holden, N., University College Dublin (Ireland). UCD School of Biosystems Engineering | Fenton, O., Teagasc, Environment Research Centre, Wexford (Ireland)
The objective of this study was to compare the effectiveness of mole and gravel mole drainage in removing excess water and controlling the watertable position from a soil with 35-45% clay content in the south of Ireland to determine the effectiveness of both treatments and establish whether the increased cost of the gravel mole drains can be justified in such a soil. Also the installation dates of mole drainage treatments were staggered (January versus July) to assess how soil moisture status during installation affected performance. The study site was poorly drained grassland (2.5 ha), with slope of 1.4% and perched watertable consistently is less 1m below ground level (BGL). An open drain was excavated to 2 m BGL adjacent to the site to act as a collector drain for the drainage treatments. The experimental area was hydrologically isolated by a 1m deep ditch. Inside this area four blocks (60 m wide x 100 m long) were established. These were further sub-divided into four plots (15 m x 100 m). The experiment was laid out in a randomized complete block design with four replicates.. The response of treatments to rainfall was analysed for 12 events from June 2012 to March 2013. Data were analysed using ANOVA with treatment as a fixed effect. Both mole and gravel mole drainage were found to be effective in the removal of excess water off site. Drain performance varied between treatments and between events but general trends were evident: Drain flow from gravel mole drains had consistently higher peak flow rates and greater total flows than in other treatments. Therefore, gravel mole drainage was generally more effective than mole drainage in removing excess water.
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