PRELIMINARY RESEARCH RESULTS ON PLANTING METHODS AND FERTILIZATION FOR Cupressus tonkinensis Silba. J. IN LANG SON AND PHU THO PROVINCES

Abstract

Cupressus tonkinensis Silba. J. is one of the ten priority conifer species for conservation in Vietnam. This is a rare, narrow-endemic species, classified as Critically Endangered (CR A1a, d) in the Vietnam Red Data Book (2007) and listed in Group IA (List of endangered, precious and rare forest plants and animals) under Decree No. 84/2021/NĐ-CP dated September 22, 2021, by the Government. In the wild, the species is currently distributed in very limited numbers, with only a few individuals remaining in remote limestone mountain areas within the Huu Lien Nature Reserve, and almost no natural regeneration seedlings have been observed. Preliminary research results on planting methods and basal fertilization showed that agroforestry planting (intercropping with short-term crops such as maize) during the first three years produced significantly better results compared to scattered planting or mixed planting. Basal fertilization had a positive effect on the early growth of C. tonkinensis at both experimental sites in Lang Son and Phu Tho provinces. The best fertilization formula was: 2 kg of well-rotted manure + 0.5 kg of superphosphate + 0.5 kg of NPK, applied into the pit 15 days before planting. The experiment conducted in Lang Son gave better results than in Phu Tho in terms of survival rate, diameter and height growth, and overall quality of planted trees.