Author : Pitaya Petmak

Summary : Three species showed different effects on each crop yield. All agricultural crops intercropped with Peltophrum dasyrachis gave the lowest yield value. Yields were high when intercropped with Acacia auriculaeformis and Eucalyptus camaldulensis, but higher when intercropped with Leucaena leucocephala during the third year of intercropping practices. All of the equations derived by the allometric model for the various biomass components estimated for each tree species were closely correlated with each particular stem diameter. The coefficient of correlation (r) was also highly correlated with an average value of 95 percent in all equations. This showed that the model is applicable for A. auriculaeformis, P. dasyrachis, L. leucocephala, and E. camaldulensis with stem diameters of 5, 5, and 130 cm above the ground, respectively. A. auriculaeformis had the highest value both in the estimated net aboveground production rate and in the average fuelwood dry weight with 35.85 t/ha/yr and 43.94 t/ha, respectively over the four year period. It also increased over 600 percent on the monoculture trial compared with the other three tree species. Production rate of the litterfall at four years of age was highest in ACACIA with 4.03 t/ha/yr and lowest in LEUCAENA (1.91 t/ha/yr). However, the annual return/uptake ratio (percent) in dry matter of ACACIA (11.24 percent) was far lower than LEUCAENA with (44.11 percent). The rate ofleaf litter decomposition was found fastest in LEUCAENA stand (1.84 gm/m (superscript 2)/month) and slowest in ACACIA stand (0.12 gm/m (superscript 2)/month) during the rainy season.