SOME ECOLOGICAL IMPACTS OF PLANTING EUCALYPTUS IN AGRICULTURAL AREA

Abstract

The study on some ecological impacts of planting Eucalyptus camaldulensis in agricultural area was conducted during 1978 to 1986 at Huay Tha Silvicultural Research Station, Sisaket Province, Northeastern Thailand. It involved comparing with Acacia auriculiformis under the practice of agroforestry land-use system. The obvious results drawn from this study during the four and eight years rotations were shown that Eucalyptus camaldulensis gave no harmful effects on the site and crop yields compared to A. auriculiformis during the four years rotation. Crop yields gained from the Eucalyptus plot were higher than the Acacia plot. These were due to the considerable large amount of annual nutrients uptake with the amount of two times provided by Acacia compared to Eucalyptus plot. On the other hand, Eucalyptus gave the significantly decrease corn yield at eight years and lower than the yield gained from Acacia. Corn yield was also increasing significantly higher at the eight years compared to the four years rotation in Acacia plot. These were due to a higher rate of nutrients to the soil by the Acacia with the amount of 48.38% compared to 32.67% provided by Eucalyptus plot at the 8 years period. However, the yield of peanut was higher in Eucalyptus plot through the whole range of these study period than the Acacia were. These would be clearly indicated that the harmful effects on soil productivity were not accounted greatly by Eucalyptus. It was also clearly indicated that both tree species had the common effect on lowering the ground water table with the rate of 1.50 cm/day or decreasing 1.21 m of water table during the 3 months period in the dry season.