Tile can drain water from an up-slope, wet area or from a spring however, as the water makes its way down the tile to drier areas the water can leave the tile through perforations. The water can re-enter the soil in another area before reaching the drain outlet. In these situations, and unknown to a farmer, trees planted close to tiles that have standing or flowing water could cause root-plugging problems. At a low field elevation, plugging in tile by roots may encourage proliferation of roots of other trees upstream in the line since water remains present until the plug is noticed and subsequently released. By transpiration, trees, like crops, can remove significant amounts of water from soil.
Trees remove little soil water during times of critical farming activities.
In order to remove soil water through transpiration, water must evaporate through photosynthesizing deciduous leaves or needles of conifers. Trees remove water from soil when crops absorb water from soil, during the growing season, from mid-spring to early autumn. At other times of the year, trees transpire very little water out of the soil. Although some moisture evaporates from trees during winter dormancy, the amount is small. Trees remove very little water from soil before early spring and after mid-autumn since leaves are absent or are no longer functional, and for most conifers, needles are either ending or beginning their winter dormant period.