| Abstract: | Results of field experiments to measure the influence of shelterbelts on wind velocity, air temperature, soil temperature, soil moisture and yield of millet in a semi-arid environment are presented. It was found that the shelterbelt reduced wind velocity (measured at 2 m above the ground surface) on the leeward side. The reduction in wind velocity ranged from 20 to 10% at distances of 20 and 150 m, respectively, from the belt. Maximum air temperatures were 0.8 to 1.5°C higher at 20 m from the belt on the leeward side than in the open field. Minimum temperatures were, however, of the same magnitudes in both the open and sheltered areas. It is estimated that the moderating influence of the belt on wind extends to a distance of 15 times the height of the trees, while the effect of the belt on air temperature does not extend beyond 10 times the height of the trees.The influence of the shelterbelt on soil temperature was minimal. Maximum soil temperatures at 5 cm depth were 0.5 to 1.0°C higher close to the belt than in the open. Also, the shelterbelt had little influence on the soil moisture during the rainy season. However, immediately following the end of the rains, moisture depletion from the top soil was more rapid on the unprotected side than on the leeward side as the higher wind speeds on the unprotected side hastened the process of evaporation. Millet yield was higher in the sheltered area than in the open with peak yield observed at a distance of 4 times the tree height. |
