The Effect of Colored Plastic Covers on Transpiration Rate of Water

Abstract

Water hyacinth (Echhornia crassipes) is one of the invasive and is considered as one of the most notorious aquatic weeds because of its fast spread and crowded growth. Manual removal of the plant is considered to be the most environmentally friendly way of controlling the plant but it is laborious when the plant covers large area. Field experiment study was conducted on water hyacinth plants collected from Ziway Lake to estimate the effect of colored plastic covers on the transpiration rates of the plant. In addition, crop factors (Kc) and coefficients of evaporation (Cp) of the covered plants were also compared with the uncovered plants. Transpiration losses were determined from the difference in the volume of water from the pan containing the treatment and control plants and the volume of water lost from the pan evaporation. The water losses from the pans were calculated from the differences in the depths of water in the pans before and after the successive measurement days. For this, calibration was done to correlate the depth of water level (in the pan) to the volume of water lost by evapotranspiration. Besides, water loss measurements, pictures were also taken for visual observation of the plants at every level during the experiment. Data analysis was made using Microsoft Office Excel. Comparisons were made using one-way ANOVA followed by pair comparisons Evapotranspiration estimation for Zeway area was done using the modified and optimized Temesgen-Melesse’s method.
The result showed that the mean ET of the uncovered plant, those covered by Black plastic (Bpc) and transparent plastic covered (Tpc) plants were 2.25L/d (7.96mm/d), 0.26L/d (0.92 mm/d) and 0.35L/d (1.24mm/d), respectively, compared to the mean daily pan evaporation of 0.88 L/d (3.11 mm/d). The transpiration rate from the control plants was 1.37L/d (4.85 mm/d), but those covered by Tp and Bp did not show any transpiration. Additionally, the Cp calculated showed 1.09, 0.40 and 0.30 for the control, Tpc and Bpc plants, respectively. The Kc result showed 1.42, 0.22, and 0.16 for the control, Tpc and Bpc plants, respectively. ANOVA results of T, Cp showed significant differences between treatments and the control but no differences within treatments. Out of the two, the transparent plastic cover showed superior performance in adversely affecting the performance of the plant and in terms of its endurance in resisting the external environment. This study showed promising result in killing the plant so that it would be easy to remove the plant from the water body. However, we recommend the study to be conducted in the real environment of the plant (on lakes, or dams infested with water hyacinth).