S. Kuo et al., FISHWASTE COMPOST EFFECTS ON RHODODENDRON GROWTH AND NITROGEN LEACHING AND TRANSFORMATION, Journal of environmental quality, 26(3), 1997, pp. 733-739
Availability and leachability of N in fishwaste compost should be cons
idered before it is used as growing media for nursery stock. This stud
y examined N availability and leaching, and transformation of organic
N constituents in fishwaste compost (HGF) as well as the effect of the
compost on growth of rhododendron (Rhododendron fortunei 'Scintillati
on'). With an initially high inorganic N concentration, the compost en
hanced growth of rhododendron during its first bush of growth. Because
of extensive N leaching, this beneficial effect was short-lived. Peri
odic additions of N fertilizer at 150 mg N kg(-1) were required to imp
rove growth of rhododendron. Approximately 45% of inorganic N present
initially in the HGF was leached regardless of the proportions of HGF
in the mixtures. With N uptake by the plants representing a small frac
tion of inorganic N added, the inorganic N lost not accounted for prob
ably was lost by denitrification and/or ammonia volatilization. Most N
fertilizer applied as NH4NO3 to 100% bark was also leached. Concentra
tions of labile amino acids changed significantly in 4 mo, from 53.6%
to <5% of total organic N in the HGF. Similar reduction also occurred
for amino sugars. Even with such a magnitude of change in the two labi
le N fractions, there was no marked increase in inorganic N in the lea
chate 2 wk after transplanting and in growth of rhododendron. A large
proportion of amino acids and amino sugars present in the compost init
ially were probably transformed to a more stabilized organic N form.