I wish to express my sincere gratitude to FAO/NACA for providing me the opportunity to participate in this program.
I am also grateful to Dr. Mali Boonyaratpalin as coordinator Secondment for Young Scientist - RLCT for the guidance given during this research program.
I am thankful to Dr. C. Kwei Lin and Ms. Jiamjit Boonsom for their constructive comments. Special recognition is thank due to Mr. Warawudh Jakngoen for his sustained guidance in carrying out the lab works. To Ms. Wipa Chaiwisitkul, Mr. Wech Thongnak and Mr. Pisanu Thongnak, who were of much assistance during the field works.
I would also like to take this opportunity to thank Mr. Nopadol Chotisasitorn for his assistance on data processing, and to Mr. S.K. Naido who helped going through the manuscript critically. Finally, thanks to Ms. Chujit Thongprapai for the typing on this research paper and all the staff at NIFI and NACA for their kind cooperation.
