Surachart Pechkeo, Jampen Onthong, Manoon Sae-Ong, and Narong Malee

pp. 669 - 683

Abstract

The major problems of longkong (Aglaia dookkoo Griff.) production in Thailand are poor quality and low quantity of yield, which may be caused by the imbalance or deficiency of essential nutrients in soils. The objective of this study was to investigate soil properties and land suitability for longkong growth in southern Thailand. Ten private longkong orchards in Songkhla and Narathiwat province were selected as the experimental sites. The soil samples were taken at 2 depths; 0-15 and 15-30 cm, around the middle of the longkong canopy and outer longkong canopy at the pre-flowering period, then analyzed for some important chemical and physical properties. Results indicated that longkong soils in the study areas were suitable for longkong plantation. However, some study still had limitation on slope factors especially those located on the low terrace areas. All of the longkong soils (0-30 cm, inner and outer canopy) were the extremely acid to slightly acid soil (soil pH = 3.72-6.16; soil: water = 1: 5), with medium soil organic matter level (6.25-30.28 g kg^-1) and very low soil electrical conductivity level (0.041-0.081 dS m^-1). The inner canopy soils (0-15 cm)
were of medium fertility level (237.80 mg kg^-1 of available P and 0.23, 2.33, 0.70 and 0.12 cmol_c kg^-1 of exchangeable K, Ca, Mg and Na, respectively) when compared to the medium to low fertility level (26.77 mg
kg^-1 of available P and 0.13, 1.46, 0.22, and 0.08 cmol_c kg^-1 of exchangeable K, Ca, Mg and Na, respectively) in the outer canopy soils. However, longkong soils contained a large amount of available P.