Abstract

Nipa (Nypa fruticans Wurmb) frond biomass is the cruicial factor for sap/sugar production. An allometric equation was firstly formulated for estimating frond biomass from the length (L) and the diameter at breast height (DBH) of a frond. And subsequently the L-DBH relationship was applied for L estimation at five nipa farms. As a result, the allometric equation was expressed as Log DW = 0.85 x Log D²L + 1.54 (r² = 0.94). The highest above-ground biomass was 83 t/ha, whereas the average biomass in other farms was 32 t/ha, which was almost the same as that in young oil palm plantation. The physical and chemical properties of soils in the nipa farms were analyzed using 80 soil samples to elucidate the factors determining nipa soil properties by principle component analysis (PCA). Consequently, organic matter, salt content and brackish water were considered to be the key factors determining nipa soil properties. Daily sap production (ml/day) (DSP) was well explained by frond biomass and above-ground biomass with the equations: DSP = 17.6 x frond biomass (kg) + 256.1 (r² = 0.48) and DSP = 11.4 x above-ground biomass (t/ha) + 263.4 (r² = 0.57), respectively. When soil properties are included, sap production is better explained, as shown by multivariate analysis followed by PCA with the equation, DSP = 609.7 – 92.9 x PC1 – 58.5 x PC2 (r² = 0.93). As PC1 and PC2 correspond to the organic matter factor and the salt content factor, sap production would be controlled by the nipa growth and the amount of Na in soil.

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