1 9 9 5 . ▁The ▁knowledge ▁about ▁the ▁gen etic ▁divers ity ▁is ▁therefore ▁limited . ▁Today , ▁available ▁information ▁about ▁gen etic ▁resources ▁is ▁too ▁little ▁that ▁improvements ▁occur ▁by ▁plant ▁bre eding . ▁ ▁Cl imate ▁and ▁soil ▁requirement ▁▁ ▁Cl im atic ▁requirement ▁ ▁So il ▁requirements ▁ ▁Best ▁germ ination ▁success ▁can ▁be ▁observed ▁on ▁a ▁mixture ▁of ▁river ▁sand ▁and ▁forest ▁soil ▁with ▁a ▁ratio ▁of ▁ 1 : 3 . ▁ ▁Cult iv ation ▁technique ▁ ▁Pro pag ation ▁Pro pag ation ▁of ▁nj ang sa ▁is ▁possible ▁by ▁se eds , ▁by ▁veget ative ▁propag ation ▁or ▁by ▁gra ft ing . ▁The ▁advantage ▁of ▁propag ation ▁by ▁se eds ▁is ▁that ▁the ▁tree ▁develop s ▁a ▁strong ▁tap root . ▁This ▁is ▁important ▁for ▁the ▁stability ▁of ▁the ▁tree ▁as ▁well ▁as ▁for ▁big ▁expl oration ▁zone ▁for ▁water ▁and ▁nut ri ent ▁u pt ake . ▁ ▁Because ▁nj ang sa ▁is ▁dio ec ic , ▁it ▁is ▁difficult ▁to ▁identify ▁male ▁and ▁female ▁trees ▁before ▁the ▁re product ive ▁phase . ▁Because ▁of ▁high ▁gen etic ▁vari ability , ▁se eds ▁may ▁have ▁different ▁characteristics ▁compared ▁to ▁the ▁parent ▁plant . ▁Veg et ative ▁propag ation ▁allows ▁reprodu cing ▁trees ▁with ▁exactly ▁the ▁same ▁characteristics ▁as ▁the ▁selected ▁female ▁tree . ▁ ▁N j ang sa ▁can ▁also ▁be ▁propag ated ▁by ▁gra ft ing . ▁A ▁shoot ▁or ▁bud ▁( the ▁sc ion ) ▁is ▁un ited ▁with ▁an ▁already ▁established