Abstract:
Eppawala apatite has low available phosphorus which acts as a barrier to use it as an efficient
phosphorus fertilizer. Acidulation is a process which commonly uses to increase available
phosphorus in apatite. Biological acidulation is a more environmentally and economically
friendly process than chemical acidulation. Coconut water (CW) is a household waste in Sri
Lanka with pH < 5.5. CW contains acids such as citric, acetic acids. The objective of this study
was to increase the available phosphorus in apatite using CW due to its acidic nature. CW was
subjected to ferment under controlled air by covering the CW contained container for three days
with monitoring pH. Then apatite + soil mixture was treated in three different ways as Fresh CW,
One-day fermented CW, two-days fermented CW using two different types of CW volumes; (a)
first, with a minimum CW [Sample (g): CW (mL) = 6:1] to wet the sample (promoting aerobic
fermentation) and (b) second with an excess CW [Sample (g): CW (mL) = 3:1] to cover the
sample (suppressing aerobic fermentation). Apatite + Soil mixture was used as a controlled
sample. Randomized complete block design (RCBD) was used with 3 replicates as an
experimental design. Two percent citric acid-soluble phosphate content was measured using the
vandomolybdate method with 2-day intervals for 10 days. Data were analyzed by using two-way
ANOVA with a 95 % confidence interval. The results revealed that it is having a significant
difference (p<0.05) of available phosphorus between the controlled and all other CW treated
samples which type (a). The highest available phosphorus content (1.52 %) was reported in
fresh CW treated samples (controlled showed 0.95-1.1 % of available phosphurus) and it was
decreased with time. Results concluded that CW can be used to increase the available
phosphorus content with a considerable level in apatite.
