Construction details and microclimate modifications of a permanent rain-sheltered lysimeter system
1990
Clark, G.A. | Reddell, D.L.
A set of 12 field lysimeters were constructed at College Station, TX, to study deficit irrigation and crop water stress. The lysimeters were constructed with a shallow soil depth and filled with a sandy soil to minimize plant available water and to facilitate the establishment of a water stress in crops. Permanent rain shelters were constructed over the lysimeters to provide continuous protection from rain. The initial construction cost of a permanent rain shelter was much less than the cost of a fully automatic rain shelter that would cover the lysimeters only during rainfall events. An initial permanent rain shelter system, constructed in 1984 using lightweight electrical conduit, was damaged by wind. A second permanent rain shelter system, constructed in 1985 using structural steel tubing with several internal supports, has provided continuous rain protection since 1985 with no problems. A semi-rigid polycarbonate panel system was used to roof the 1985 rain shelter system. The roofing panels reduced solar radiation under the rain shelters by 35 to 40%. Wind run under the rain shelters was reduced as the crop height increased during the growing season, decreasing the ventilation area between the crop canopy and the rain shelter roof However, temperature and relative humidity remained essentially the same under the rain shelters as in an adjacent unsheltered buffer area. This article describes the construction details of this lysimeter and permanent rain shelter facility. In addition, solar radiation, temperature, relative humidity, and wind run under the permanent rain shelters are compared with those measured in a surrounding unroofed buffer area.
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