IJERD – International Journal of Environmental and Rural Development (2012) 3-2

Research articleerd

Nitrogen and Phosphorus Released from Coconut Husk
during Retting Treatment
JULIAN E. TORILLO JR.
Graduate School of Agriculture, Tokyo University of Agriculture, Tokyo, Japan
Email: juliantorillo@yahoo.com

MACHITO MIHARA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan
Email: m-mihara@nodai.ac.jp
Received 14 January 2012

Accepted 12 March 2012(*: Corresponding Author)

Abstract Upland fields in Bohol of the Philippines are mostly located on areas with highslopes resulting in soil erosion. Although coconut husk has been applied as buffer strips
for eliminating soil erosion, attention has been paid to the loss of nitrogen and phosphorus
components not only discharged from synthetic fertilizer applied in upland fields but also
those released from coconut husk. The leached nutrients associated with surface runoffand percolation water may cause pollution downstream. Thus, efficient utilization of thenutrient components from coconut husk is necessary from a view point of conservation
agriculture in Bohol, Philippines. This study sought to find out the amounts of nitrogenand phosphorus in coconut husk, to quantify the amounts of nitrogen and phosphorus
released from coconut husk during the pretreatment by retting process and to observe theoptimum period of releasing nutrients from coconut husk. Retting of coconut husk werecarried out for 140 days and small amounts of ret liquor was sampled at certain days ofinterval for nitrogen and phosphorus analyses. Based on the experimental results, it wasobserved that releasing nutrients from coconut husk rapidly increased from the starting day
up to ten days of retting. Even after ten days, nutrient components released from coconut
husk tended to increase gradually. It was also proven that about 87% of its phosphorus and
10% of its total nitrogen was released from the coconut husk. Therefore, it was concluded
that coconut husk has a high tendency to release nutrients during the retting process,particularly for phosphorus component that can be a source for bio-fertilizer.
Keywords coconut husk, retting, nitrogen, phosphorus, bio-fertilizer

INTRODUCTION
Upland fields with protruding stones and rocks on ground surfaces as well as abandoned farmlands
are dominant particularly in the southwestern part in the island of Bohol (Torillo and Mihara, 2011).
Moreover, these lands are mostly located on slopes of areas with 8-18% and even some portions
with more than 18% slope, particularly for subsistence agriculture (OIDC, 2006). Together withhigh squalls, uplands in the island are susceptible to soil erosion causing rapid degradation of landwith the decrease of crop quality and yields.
To replenish the nutrients required by crops and to increase crop yields, local farmers choose
to apply synthetic fertilizers. However, high prices of synthetic fertilizers lead to scarcity of theseresources, particularly on phosphorus. Cordell et al. (2009) reported that phosphorus is mainly
obtained from mined rock phosphate and its reserves could be exhausted in the next 50-100 years(Steen, 1998; Smil, 2000b) thus an effective approach to the management of phosphorus cycle isnecessary. On the other hand, coconut husks that were installed as buffer strips for soil erosion
control tended to release nitrogen and phosphorus. This tendency was observed during the slopemodeling under artificial rainfall simulator (Torillo and Mihara, 2011). Those nutrients released
from the coconut husk may leach through percolation and surface runoff resulting water pollution
in downstream. Therefore, treating of coconut husk before its installation as buffer strips throughⒸISERD94

IJERD – International Journal of Environmental and Rural Development (2012) 3-2

retting has been recommended. However, improper management on the treatment process maycause pollution to surface waters as well. Bijoy (1997) reported that coconut husk retting activity
has caused large scale organic pollution with the mass destruction of flora and fauna, foul smelling
stagnant waters in Kerala, India. Also, Ambika and Gopalakrishna (1990) added that pectin,
pectosan, fat, tannin and also toxic polyphenols are liberated into ambient water by the activity ofbacteria and fungi in the coconut husk retting area in backwaters at Cochin, India.
Thus, making use of the nutrient component in coconut husk for liquid bio-fertilizer has been
desired. The objectives of this study were 1) to find out the amounts of nitrogen and phosphorus incoconut husk at different portions and layers, 2) to quantify the released amounts of nitrogen andphosphorus from the coconut husk during the retting treatment, and 3) to determine the optimum
period for retting of coconut husk.
MEHODOLOGY
To find out the total amounts of nitrogen and phosphorus in the coconut husk, a preliminary
analysis was carried out. The following procedure was also aimed to find out which portions andlayers of the coconut husk have lower concentration of total nitrogen (T-N) and total phosphorus(T-P) that could be applicable as buffer strips for soil erosion control in order to mitigate thereleasing of nutrients from coconut husk. As shown in Fig. 1, coconut husk were cut into three
portions as bottom, middle and top then were sliced into three layers as inner, middle and outerthen the bark layer. Pith and fiber were segregated, and were crushed into powder. Crushed pithand fiber were then analyzed for T-N and T-P components.
Pedicel and SepalTopMicropyle

FiberEmbryoMiddlePithBottoma) Cross-section ofcoconut huskb) Segregated fiber, pith and barkc) Pulverizing of fiber, pith and barkFig. 1 Preparation process for preliminary analysis of total nitrogen (T-N) and total
phosphorus (T-P) in coconut husk

First day of rettinga) Minor pounding by hammer

Fourth day of rettingb) Retting into cylinders with distilled water

Fig. 2 Procedure of pretreating coconut husks
The coconut husks utilized as buffer strips for soil erosion control had released nutrient
components, so it was proposed to carry out the pretreatment of the coconut husks by retting before
installing into the site. To quantify the amount of T-N and T-P released from the coconut husk
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during the retting treatment, the analysis of those nutrients in the ret liquor was carried out. Rettingof coconut husk was performed using the following procedures; firstly, coconut husks weremoderately pounded by hammer (Fig. 2) to produce porous material similar to that being installed
into the site as buffer strips. Pounded coconut husks of 119.22 g in dry mass were then immersed
into the 4,600 ml of distilled water.
Secondly, sampling of water soaked with coconut husk or so called ret liquor was done atcertain days of intervals within 140 days. Thirdly, ret liquor samples were analyzed for T-N and TP after the decomposition with sodium hydroxide (NaOH) and potassium peroxodisulfate (K2S2O8)
then the concentrations of T-N and T-P were measured by spectrometric methods (Mihara andUeno, 2000).
RESULTS AND DISCUSSION
Amount of nitrogen and phosphorus in coconut husk

T-N per mass of husk (mgN/g)

Coconut husks were portioned, layered and then pith, fiber and bark were segregated for analyzing
the amount of total nitrogen (T-N) and total phosphorus (T-P). Based on the experimental results, it
was found out that every portion of the coconut husk has different concentrations of T-N and T-P(Figs. 3 and 4).
0.30
0.25

a**

a**

0.20

a**
a**,b**

a**,b**

a**,b**

0.15

b**

b**

0.10

b**

0.05

b**
b**
b**

0.00

Portion of coconut husk

Weighted mean of nitrogen mass** Significant difference at 99%

T-P per mass of husk (mgP/g)

Fig. 3 Amount of total nitrogen (T-N) per dry mass of pith, fiber and barkat top (T), middle (M) and bottom (B) portions of coconut husk
0.70

a**

0.60
0.50
0.40
0.30
0.20
0.10

b**

c**

c**,d**c**c**

b**,c**

c**,d**
c**,d**

c**,d**
d**

d**

0.00

Portion of coconut husk

Weighted mean of phosphorus mass** Significant difference at 99%

Fig. 4 Amount of total phosphorus (T-P) per dry mass of pith and fiber, and barkat top (T), middle (M) and bottom (B) portions of coconut husk

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Most of the top portions showed significantly higher in the amounts of T-N and T-P than thatof the middle and bottom portions. Top portion of the coconut husk is highly concentrated with TN and T-P, it may be because of the pedicel and embryo (Fig. 1a) that are located in the top portionof the husk and nut. As Rancic et al. (2010) reported that water and nutrients which fruit growthdepends on is transported from the stem into the fruit through the pedicel by xylem and phloem.
The embryo which germinates at microphyle (Chan and Elevitch, 2006) develops a haustorium thatprovides a conduit for the supply of nutrients from kernel into the germinating embryo (Foale,2003). These conditions might be the factors that most nutrients are accumulating at the top portionof the coconut husk.
As shown in Fig. 3, the weighted mean of T-N in the coconut husk was 0.1138 mgN/g and asignificant difference at 99% was observed among portions. For the amounts of T-P, a weighted
mean at 0.3037 mgP/g and also a significant difference at 99% were observed among the portionsof coconut husk (Fig. 4).
Optimum retting period of coconut husk

0.02

Mass of T-P per mass of husk
(mgP/g)Mass of T-N per mass of husk
(mgN/g)Coconut husks were retted within 140 days and then the ret liquor samples were collected at certain
days of interval for nitrogen and phosphorus analyses. It was observed that a remarkable increase intotal nitrogen (T-N) and total phosphorus (T-P) components in coconut husk ret liquor from thestarting day of retting up to a certain period of time then tended to increase gradually further.

y = 0.0035ln(x) + 0.0394
R² = 0.9791

0.01

Deflection point
0.01

0.00

0.30

y = 0.0592ln(x) + 0.628
R² = 0.9129

0.20

Deflection point
0.10

0.00
020

4060

80

1001201400Time (day)

20406080

100120140

Time (day)Fig. 5 Amount of T-N released from coconut
husk into ret liquor

Fig. 6 Amount of T-P released from coconut
husk into ret liquor

Based on the logarithmic curve as shown in Figs. 5 and 6, the deflection point lies approximately on the tenth day of retting. This trend indicates that up to the tenth day from the starting dayof retting, T-N and T-P rapidly released from coconut husk. After then, the trend changed to release
gradually of those nutrients. The results suggested that ten days of retting is an adequate period of
pretreating the coconut husk when its nutrient components are mostly released.
Amounts of nitrogen and phosphorus released from coconut husk during the retting
treatment
Coconut husks were retted in distilled water and ret liquor samples were collected at certain days ofinterval for total nitrogen (T-N) and total phosphorus (T-P) analyses. It was suggested that ten days
retting of coconut husk is an adequate period of pretreating the material. As shown in Fig. 5, theamount of T-N released into the ret liquor was 0.0114 mgN/g during the tenth day. Based on theweighted mean of T-N in coconut husk as shown in Fig. 3 was 0.1138 mgN/g therefore it wasproven that 10.01% of T-N was released from the coconut husk during the retting treatment.
Fig. 6 shows the amount of T-P in the ret liquor where 0.2639 mgP/g was released into the retliquor during the tenth day of retting which is 86.89% in the weighted mean of 0.3037 mgP/g thatis being shown in Fig. 4. Although, it was clearly observed that T-N and T-P were released fromⒸISERD97

IJERD – International Journal of Environmental and Rural Development (2012) 3-2the coconut husk during the retting treatment, a confidence interval was not observed. It was also
indicated that the amounts of T-P released from the coconut husk during the retting period wassignificantly higher than that of T-N.
CONCLUSION
For sustainable use of resources, utilizing the nutrient components from the coconut husk which islocally available and a renewable resource in the region has good value. So, this study dealt withthe optimum retting period of coconut husk to release its nitrogen and phosphorus components. The
quantification of the amounts of nitrogen and phosphorus released from coconut husk into the ret
liquor during the retting treatment were also sought to be found out of this study. However, as afundamental basis on the quantification of nitrogen and phosphorus released into the ret liquor,
finding out the amounts of T-N and T-P in the coconut husk is necessary. Thus, analyses on theamounts of T-N and T-P in the coconut husk were also carried out.
It was found out that the weighted mean of T-N and T-P in coconut husks were 0.1138 mgN/g
and 0.3037 mgP/g, respectively. The experimental results also indicated that rapid release ofnutrient from coconut husk during the tenth day of retting. During the tenth day period, 0.0114
mgN/g accounted for about 10% of 0.1138 mgN/g in coconut husk was released into the ret liquor.
Meanwhile, phosphorus component was 0.2639 mgP/g accounted for about 87% of 0.3037 mgP/g
in coconut husk has been released from the retted coconut husk into the ret liquor.
Therefore, it was concluded that ten days is enough period of treating the coconut husk byretting treatment. At this period, about 87% of T-P component from the coconut husk while about
10% of T-N were released during the retting treatment. Thus, rich amount of nutrient component
particularly on phosphorus could be extracted from the coconut husk by retting method within tendays which could be the suitable source for bio-fertilizer.
ACKNOWLEDGEMENT
We would like to acknowledge the support of President Dr. Elpidio T. Magante of Bohol Island
State University for his meaningful guidance and advice.
REFERENCES
Ambika, D.M. and Gopalakrishna, P.N. 1990. Effect of pollution due to coconut husk retting on the southwest coast of India. Indian Journal of Fisheries, 37(2), 145-149.
Bijoy, N.S. 1997. Retting of coconut husk: A unique case of water pollution on the southwest coast of India.
International Journal of Environmental Studies, 52, 335-355.
Chan, E. and Elevitch, C.R. 2006. Cocos nucifera (coconut). Species Profiles for Pacific Island Agroforestry,
2-1, 1-27.
Cordell, D., Drangert, J.O. and White, S. 2009. The story of phosphorus: Global food security and food forthought. Global Environmental Change, Elsevier, 19, 292-305.
Foale, M. 2003. The coconut odyssey: the bounteous possibilities of the tree of life. Australian Centre forInternational Agricultural Research, 44-46.
Mihara, M. and Ueno, T. 2000. Nitrogen and phosphorus transfer in soil erosion processes, IAHS Publication,
No. 263, 109-115.
Orient Integrated Development Consultants Inc. 2006. Bohol Agriculture Master Plan, CY2006-2026.
Rancic, D., Pekic, S. and Pecinar, I. 2005. Anatomy of tomato fruit and fruit pedicel during fruit development. Microscopy: Science, Technology, Applications and Education, 851-861.
Smil, V. 2000b. Phosphorus in the environment: Natural plows and human interferences. Annual Review ofEnergy and the Environment, 25, 53-88.
Steen, I. 1998. Phosphorus availability in the 21 st Century: Management of a non-renewable resource. Phosphorus and potassium, 217, 25-31.
Torillo, J.Jr. and Mihara, M. 2011. Soil erosion control by coconut husk buffer strip in Bohol island of Philippines. International Journal for Environmental and Rural Development, 2(1), 25-30.
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