When I am in Japan on a buying trip the only fertiliser I see being used in nurseries is IB. It is formed into a oval pellet which does not break down or give of odours unlike rape seed ,naruko and other types and brand names,. it also repels animals, birds and pets It is sold in Japan as Nurseryace and remains active for 8-12 months.
IB is used on all bonsai varieties the N P K is 12, 6 ,6
PLEASE EMAIL FOR SHIPPING COSTS OUTSIDE THE UK MAINLAND