Nutrient Availability and Response of Sago Palm (Metroxylon sagu Rottb.)
to Controlled Release N Fertilizer on Coastal Lowland Peat in the Tropics
Benito H. P., K. Kakuda, H. ando, J.H. Shoon, Y. Yamamoto, A. Watanabe and
T. Yoshida
Soil Science Plant Nutri.tion 48-4, 529-537 (2002)
Sago palms (Metroxylon sagu Rottb.) growing on peat soils were found to grow
more slowly and to show a lower production than palms growing on mineral
soils. This difference was related to the physical and chemical constraints
of peat soils, which include low bulk density, high acidity, and low N, P,
K, Ca, Zn, and Cu levels. In coastal lowland peat soils, the distance from
the sea has been found to be an important determinant of soil elemental composition.
We predicted that a sufficient supply of N at the rosette stage would improve
sago palm growth and that the availability of N in soil to which controlled
release N fertilizer was applied might be higher than that in soil treated
with soluble fertilizer. To investigate the changes in the nutrient composition
of peat soils at various distances from the sea and the effect on sago palm
growth, we studied sago palm areas in Indonesia and Malaysia. To observe
the influence of N on the growth performance, we also conducted a fertilizer
experiment on coastal lowland peat soil in Indonesia.
Distance from the sea had no significant effect on the cation concentration
in the soil solution (with the exception of Mg) or on the levels of soil-exchangeable
cations. No significant differences were observed between the concentrations
of exchangeable cations in surface peat soils and those in mature leaves.
However, the concentrations of K, Na, and Ca in mature leaves increased significantly
with their concentrations in the soil solution. This finding implies that
the concentrations of cations in sago palm leaves depend directly on the
concentrations of cations in the soil solution.
No significant effect of N fertilizers on plant height and leaf formation
was observed. N fertilizers applied twice a year did not affect appreciably
the foliar concentration of N determined in December 1998 (5 months after
the initial application) and December 1999. In June 2000, we detected a significantly
higher concentration of N (p < 0.01) in young leaves of the palms treated
with LP-100 or urea than in control leaves. However, no significant difference
was detected between the LP-100 and urea treatments in the concentration
of N in both mature and young leaves. This finding indicated that the concentration
of N in sago palm leaves increased with the level of soil-applied N, regardless
of whether N was applied as controlled release fertilizer or in the soluble
form. We anticipate that a significant difference in the effects of these
N fertilizers may occur during the next rainy season, when there should be
a considerable loss of soluble N.
Key Words: distance from sea, exchangeable cations, foliar N concentration,
soil solution