Family Variation in Early Growth Characteristics of Thai Neem (Azadirachta indica var. siamensis Valeton) in Lad Krating Plantation, Chachoengsao

Abstract

12-month-old Thai Neem grown in the progeny trial in Lad Krating Plantation, Chachoengsao had average survival percentage, height, and diameter at ground level values as 91.65%, 31.77 cm, and 5.04 mm, respectively.  Monthly height growth pattern of Thai Neem was slightly increased in the dry season and accelerated in the rainy season.  On the other hand, the diameter growth increased continuously by months.  While, in the dry season, the genetic factors showed less effect on growth performances than environmental factors, in the rainy season, the genetic factors stimulated the growth increments but environmental factors (site or replication) still had more effect.  Not only monthly rainfall and mean air temperature were influenced to height increment but also factors as genetics, other environments, and silvicultural practices were collaborated in monthly height growth.  Besides, monthly rainfall and mean air temperature showed the intimate correlation with diameter increment, thus, the monthly diameter growth of Thai Neem progenies were expected to be controlled by climatic factors and associated with other environmental and genetic factors.  In an early growth evaluation, progenies of Plus Tree No. 1, 9, 23, 25, 32, and 33 showed superior growth characteristics when planted in Lad Krating Plantation, Chachoengsao.  However, the growth investigation should be done until the time of a half rotation.

Key words: family variation, early growth, thai neem (Azadirachta indica var. siamensis Valeton)