東京農業大学リポジトリ

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Study on Utilizing Coconut Husk for

Conservation Agriculture in

Bohol of Philippines

2014

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Doctoral Dissertation

Study on Utilizing Coconut Husk for

Conservation Agriculture in

Bohol of Philippines

Julian E. TORILLO, Jr.

Supervisor : Professor Dr. Machito MIHARA 印

Advisor : Professor Dr. Fumio WATANABE 印

: Associate Professor Dr. Shinji SUZUKI 印

: Professor Dr. Elpidio T. MAGANTE 印

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Summary

The areas with 8-18% slopes, accounted for 29% or 120,636 ha in the island of Bohol, are mostly upland, open or grass dominated and eroded land areas. Along with high squall, those sloped-land areas are affected by soil erosion resulting in rapid degradation of farmlands. Thus, soil erosion control strategies such as buffer strips are necessary to be implemented. Meanwhile, around 5 million coco trees are cultivated in the island producing large amount of coconut husk during copra production. However, these coconut husks are considered with no use and left to rot in the site. In this study, utilizing locally available material has been focused from a view point of conservation agriculture. The aim of this dissertation is to discuss the most convenient, effective and adoptable erosion control system utilizing coconut husk as buffer strips. For achieving the above goal, following researches were conducted; a) to evaluate the capability of coconut husk buffer strips on mitigating soil and nutrient losses through slope modeling and field application, b) to find out an adaptable method on eliminating the release of nutrient components from coconut husk buffer strips, and c) to evaluate the effectiveness of nutrient component from coconut husk for liquid bio-fertilizer.

1. Capability of coconut husk buffer strips on mitigating soil and nutrient losses through slope modeling experiment

Soil erosion causes serious environmental problems in Bohol of Philippines. Considering the agricultural socio-economic situation of the island, utilizing the available materials in the region to mitigate soil erosion has been focused. The objectives in this chapter were to investigate the capability of coconut husk on mitigating soil and nutrient losses, and to evaluate two-ply and four-ply coconut husk buffer strips to trap soil and nutrient losses. Thus, slope modeling experiments with

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coconut husk buffer strips were conducted under artificial rainfall simulator. Coconut husks were slightly pounded by hammer to make them porous. Three slope model plots were prepared; Plot I as control (C), Plot II as two-ply husk buffered plot (2pCHB), and Plot III as four-ply husk buffered plot (4pCHB). Local soil sampled in Bohol was filled up into stainless slope model plots. Simulated rainfalls were given to slope model plots at 60 mm/h intensity within two hours. Three repetitions of rainfall simulation were carried out in separate days. Based on the experimental results, the coconut husk buffer strips were more effective in trapping soil losses compared to controlled plot with significant difference at 99% level. However, there was no significant difference in soil loss between two-ply and four-ply coconut husk buffered plots. Nutrient losses from the plots with coconut husk buffer strips were higher than that from control plot, particularly during the first rainfall simulation.

It was concluded that coconut husk buffer strips were considerably effective on mitigating soil losses, although the effects between two-ply and four-ply coconut husk buffer strips showed no significant difference. Therefore, two-ply of coconut husk can be efficient thickness as buffer strips. On the other hand, coconut husk buffer strips tended to release nutrients therefore attention has been paid to suitable method for mitigating the release of nutrients from coconut husk buffer strips. Thus, strategies on mitigating the release of these nutrients are discussed in Chapters 4 and 5.

2. Capability of coconut husk buffer strips on mitigating soil losses in situ

It was found out that coconut husk buffer strips were highly capable on mitigating soil losses through slope modeling experiment under rainfall simulation. To find out the effects of coconut husk buffer strips on mitigating soil losses in the field, actual installation has been implemented into upland fields in Bohol of Philippines. This chapter aimed to evaluate the capability of coconut husk on mitigating soil losses under

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field conditions. Coconut husk were also slightly pounded by hammer as well as the condition carried out in the modeling experiment. Furrows were dug across slopes on ground surfaces in upland fields. Two-ply of coconut husk were installed into furrows as buffer strips. There were two upland fields chosen for this research; one is Cabawan at 4 degrees gentle slope, and the other Sambog at 21 degrees steep slope. Level surveys were carried out on December 2011, March 2012, September 2012, and February 2013. Data was gathered by measuring ground surface level to observe the accumulation of soil sediments behind the buffer strips. In addition based on topographical features, RUSLE model was employed to evaluate the effects of coconut husk buffer strips on mitigating soil losses, especially focusing on LS factors.

The results of the calculation based on the Revised Universal Soil Loss Equation (RUSLE) model indicated that 73.7 to 83.2% of soil loss was reduced with installation of coconut husk buffer strips in Cabawan at 4 degrees gentle slope, also 65.5 to 68.7% in Sambog at 21 degrees steep slope. Additionally, soil amounts around 83 t/ha/year were captured by coconut husk buffer strips in Cabawan, also around 35 t/ha/year were captured by coconut husk buffer strips in Sambog. It was considered that coconut husk buffer strips contributed to divide long sloping farmland into several parts, so soil loss could be reduced with installation of coconut husk buffer strips.

3. Analyzing distribution of nitrogen and phosphorus concentrations in coconut husk for segregation of high concentration parts

Coconut husk buffer strips have released nitrogen component in the slope modeling experiment as discussed in Chapter 2. So, research interests have been focused on the distribution of nitrogen and phosphorus concentrations in coconut husk as well as the possibility to segregate higher concentration parts before installing coconut husk as buffer strips. This chapter aimed to analyze nitrogen and phosphorus

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components in cross-section of coconut husk and to discuss the possibility to segregate higher in nitrogen and phosphorus concentrated parts of coconut husk. Coconut husk were divided into three portions as bottom, middle and top, then sliced into 4 layers as inner, middle, outer and bark. Pith and fiber were segregated and crushed into powder. Also, crushed pith and fiber were analyzed for nitrogen and phosphorus components.

Experimental results indicated that nitrogen and phosphorus concentrations in the top portion tended to be higher than that in the middle and bottom portions. Also, the concentrations significantly differed among layers; inner, middle, outer and bark. However there was a big individual difference in distribution of nitrogen and phosphorus concentrations among coconuts. Accordingly, it was concluded that the segregation of higher concentrated parts before installing coconut husk as buffer strips is difficult as there was no certain tendency in the distribution of nitrogen and phosphorus concentrations in coconut husk. Thus, it was considered that whole coconut husk, in which weighted mean of nitrogen and phosphorus concentrations in coconut husk were 0.1138 ± 0.0193 mgN/g and 0.3037 ± 0.0546 mgP/g, must be utilized for installing as buffer strips. So, attention has moved to other strategies to eliminate nitrogen and phosphorus components in coconut husk.

4. Eliminating nitrogen and phosphorus components from coconut husk by retting

treatment

This chapter dealt with retting treatment for eliminating nitrogen and phosphorus components from coconut husk. The aims of retting treatment experiment conducted were to observe optimum period of retting treatment and to quantify the amounts of nitrogen and phosphorus components released from coconut husk. Coconut husk of 199.22 g in oven-dry mass was pounded by hammer to make the structure porous, and then was immersed into 4,600 mL of distilled water within 140 days. Water soaked with

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coconut husk, so called ret liquor, was sampled at a certain interval, and nitrogen and phosphorus concentrations of sampled water were analyzed.

Experimental results indicated that nitrogen and phosphorus concentrations in ret liquor increased remarkably from initial to 10 days passed, and then increasing tendency became gentle after 10 days passed in retting treatment of coconut husk. Same tendencies were observed when coconut husk of 0.15 g in oven-dry mass was immersed into 500 mL of distilled water. So, it was considered that retting treatment for 10 days may be adequate to release nitrogen and phosphorus components from coconut husk. At 10 days passed of retting treatment, the amounts of nitrogen component released from coconut husk into ret liquor was 0.0114 mgN/g which was equivalent to 10% of total nitrogen component in coconut husk. Also, the amounts of phosphorus component released from coconut husk into ret liquor was 0.2639 mgP/g at 10 days passed of retting treatment which was equivalent to 87% of total phosphorus component in coconut husk.

5. Capability of ret treated coconut husk buffer strips on mitigating soil and

nutrient losses

In this chapter, capability of ret treated coconut husk buffer strips on mitigating soil and nutrient losses was discussed. Three slope model plots were prepared; Plot I as control (C), Plot II as two-ply untreated coconut husk buffered plot (U), and Plot III as two-ply of ret treated coconut husk buffered plot (T). Local soil sampled in Bohol was filled up into stainless slope model plots. Simulated rainfalls were given to slope model plots at 60 mm/h intensity within two hours. Three repetitions of rainfall simulation were carried out in separate days.

The experimental results showed that the coconut husk buffer strips either treated or untreated were effective to trap soil losses compared to controlled plot with

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significant difference at 99% level. Also, the amounts of nitrogen component released from the plot (T) with ret treated coconut husk buffer strips was significantly lower than that of plot (U) with untreated husk buffer strips at 99% level. Therefore, it was concluded that retting treatment of coconut husk for buffer strips was effective for eliminating the release of nutrients, particularly nitrogen component.

6. Utilization of nutrient components from coconut husk as liquid bio-fertilizer for

crop growth

Pretreatment of coconut husk by retting before installing in farmlands has been proposed in the former chapter. However improper management of retting process may cause eutrophication in water systems, a serious phenomenon of water pollution. Attention has been paid to efficient utilization of nutrient components from coconut husk. Therefore in this chapter, application of fermented ret liquor as liquid bio-fertilizer for crop growth was discussed. Molasses of 300 mL were added into ret liquor at ratio of 15 (ret liquor) : 1 (molasses) to enhance fermentation process. Fermented ret liquor at 150 mL as liquid bio-fertilizer containing 3 mg/L of total nitrogen and 21 mg/L of total phosphorus were then broadcasted into each pot five days before sowing of water spinach (Ipomoea aquatica), a leafy vegetable crop. Based on crop growth experimental results, a delay of seed germination in the pots applied ret liquor bio-fertilizer was observed, however their growing rate were higher than those in controlled pots, without applying any fertilizer. In addition, the average weight of Ipomoea aquatica applied ret liquor bio-fertilizer was significantly higher than that of controlled pots at 99% level. Therefore, it was suggested that bio-fertilizer from coconut husk ret liquor is applicable to plant growth.

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和文要約フィリピン共和国ボホールにおけるココナッツ殻の適用による保全型農業の推進に関する研究フィリピン共和国ボホールにおける土壌侵食の抑制を目指したココナッツ殻の緩衝帯として適用を扱った。模型斜面実験の結果、土壌流亡量の軽減にあたってはココナッツ殻緩衝帯の設置が効果的であると判断できた。現地の傾斜面畑にココナッツ殻緩衝帯を設置して流亡土壌の捕捉能を調べた結果、4 度の緩傾斜畑地ではココナッツ殻緩衝帯によって 83 t/ha/y の流亡土量を補足でき、21 度の急傾斜畑地では 35 t/ha/y の流亡土量を補足できたことが明らかとなり、 RUSLE モデルによる解析と併せて、土壌侵食の抑制の点からココナッツ殻緩衝帯の有効性を確認できた。しかし模型斜面実験の結果、ココナッツ殻の緩衝帯を設置した試験区から流出する窒素成分はコントロール区を大きく上回り、緩衝帯として設置したココナッツ殻から窒素成分が流出していると判断できた。そこで緩衝帯として設置する前に、ココナッツ殻における高濃度部位を分離する方法と浸水処理を行う方法について検討した結果、浸水処理によるココナッツ殻に含む窒素・リン成分の削減が効果的であると判断できた。再度、模型斜面実験を実施して、浸水処理したココナッツ殻緩衝帯による土壌および窒素・リン成分の流出抑制効果についての評価に取り組んだ結果、浸水処理したココナッツ殻緩衝帯を設置した試験区からの窒素成分の流出量は無処理のココナッツ殻緩衝帯の試験区を 99%の有意水準で大きく下回る結果となり、ココナッツ殻の浸水処理は窒素成分の流出抑制において有効であると判断できた。併せて、ココナッツ殻浸出液を 発酵し液肥としてヨウサイ（Ipomoea aquatica）に施用した結果、その優位性を 確認できた。

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Acknowledgement

This dissertation was successfully formulated mainly because of the support from many individuals. I would like to express my deepest gratitude to Professor Dr. Machito Mihara, for his great advices and guidance throughout my study in Tokyo University of Agriculture. He kindly shared his time in outlining the research`s procedure, analyses and site application technique. With his generous support through ERECON, I had enough opportunities to conduct field research monitoring in Bohol, Philippines. I would like also to thank Professor Dr. Fumio Watanabe, Associate Professor Dr. Shinji Suzuki and Professor Dr. Elpidio T. Magante for their suggestions and comments.

I am so grateful to all of my colleagues in the Laboratory of Land and Water Use Engineering, Mr Yuta Ishikawa and others for taking part throughout my research particularly on experiments. To the land owner of research sites in Bohol, Engr. Antonio Camelo P. Tompar in Sambog, Corella and Mr. Eustaqiuo Escabosa in Cabawan, Tagbilara City, my deepest thanks to them for providing their upland field as research field sites for this dissertation.

My heartfelt gratitude to my sister Beth for giving me the opportunity to study in Japan and with her enormous support I able to obtain this degree. Also, thanks to my brother-in-law Takao, nephews Ruichi and Ryuji. To my sisters, Belinda, Bebie, brother Elmer and brother-in-law Tayodes who are in my hometown who kindly help and provide my needs either in personal and field research matters. To other members of my family who also influenced me to pursue this degree, Mama Maria and Papa Juli, sisters Grace and Fe, brothers Emie, Boy and Al and to all sister-in-laws, brother-in-laws, nephews and nieces. Thanks also to my relatives and friends, who took part of my study. Finally, I dedicate this accomplishment to my wife Karina.

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Table of contents (continuation)

Chapter 3 Capability of coconut husk buffer strips on mitigating soil losses in situ

3.1.2 Objective 3.2 Research methods

3.2.1 Research sites

3.2.2 Preparation and installation of coconut husk 3.2.3 Site monitoring

3.2.4 Ground surface and slope measurements

3.2.5 Slope length factor (L) and slope steepness factor (S) in RUSLE model

3.3 Results and discussion

3.3.1 Changes of slope length (L) and slope steepness (S) factors 3.3.2 Soil sediments accumulated at the back of coconut husk

buffer strips 3.3.3 Discussion

Chapter 4 Analyzing distribution of nitrogen and phosphorus concentrations in coconut husk for segregation of high concentration parts

4.2.1 Segregation of fiber and pith in coconut husk 4.2.2 Total nitrogen and total phosphorus analyses 4.3 Results and discussion

4.3.1 Total nitrogen concentration 4.3.2 Total phosphorus concentration 4.3.3 Discussion

38 39 39 40 40 40 44 44 45 47 48 48 49 53 54 55 56 57 57 57 58 58 60 61 61 65 65 67 68

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Table of contents (continuation)

Chapter 5 Eliminating nitrogen and phosphorus component from coconut husk by retting treatment

5.2.1 Preparation of coconut husk 5.2.2 Retting treatment of coconut husk

5.2.3 Total nitrogen and total phosphorus analyses of ret liquor 5.3 Results and discussion

5.3.1 Optimum period on retting of coconut husk

5.3.2 Amount of total nitrogen and total phosphorus leached into the ret liquor

5.3.3 Discussion

Chapter 6 Capability of ret treated coconut husk buffer strips on mitigating soil and nutrient losses

6.2.1 Coconut husk buffer strip preparation 6.2.2 Retting treatment of coconut husk 6.2.3 Slope model plot preparation 6.2.4 Artificial rainfall simulation 6.2.5 Analyses items

6.3 Results and discussion

6.3.1 Total nitrogen and total phosphorus released from coconut husk during retting treatment

6.3.2 Soil losses

6.3.3 Total nitrogen and total phosphorus losses 6.3.4 Discussion 69 70 70 70 71 71 71 72 73 73 73 75 77 78 79 80 80 81 81 81 81 82 83 84 84 84 85 87 90

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Table of contents (continuation)

6.4 Conclusion of this chapter References of this chapter

Chapter 7 Utilization of nutrient components from coconut husk as liquid bio-fertilizer for crop growth

7.2.1 Fermentation of ret liquor

7.2.2 Ret liquor bio-fertilizer application and irrigation 7.2.3 Monitoring and data collection

7.3 Results and discussion 7.3.1 Growth of crops

7.3.2 Effects of ret liquor bio-fertilizer to crops 7.3.3 Discussion

7.4 Conclusion of this chapter References of this chapter

Chapter 8 Conclusions Appendix 91 92 93 94 94 95 95 95 96 97 98 98 101 101 102 103 105 109

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Fig. 1-1 Fig. 1-2 Fig. 1-3 Fig. 1-4 Fig. 1-5 Fig. 1-6 Fig. 1-7 Fig. 1-8 Fig. 1-9 Fig. 1-10 Fig. 1-11 Fig. 1-12 Fig. 2-1 Fig. 2-2 Fig. 2-3 Fig. 2-4 Fig. 2-5 Fig. 2-6 Fig. 3-1 Fig. 3-2 Fig. 3-3 Fig. 3-4

List of Figures

Map of Philippines

Four climatic types in the Philippines Land use vegetation map in Bohol Province Land use in Bohol Province

Slope map in Bohol Province

Traditional slash-and-burn farming in Tagbilaran, Bohol Upland field of maize on steep slope in Corella, Bohol

Rolled erosion control systems made from coconut husk fiber of a) random fiber coir, b) open weave coir, and c) rolled erosion control or coir geotextile installed on slope ground surface to protect from erosion

Pile of unused coconut husk in Panglao, Bohol Parts of coconut fruit

Bark, fiber and pith component of coconut husk Research structure of this dissertation

Trimmed coconut husk of 12 cm long by 5 cm wide equivalent to one-ply coconut husk buffer strip

Slight pounding of coconut husk to make the material poruos Slope model plots of (C) controlled, (2pCHB) two-ply coconut husk buffered, and (4pCHB) four-ply coconut husk buffered plots set at 8 degrees in slope

Slope model plots under artificial rainfall simulator

Amount of soil losses from (C) controlled, (2pCHB) two-ply coconut husk buffered, and (4pCHB) four-ply coconut husk buffered plots during the first, second and third rainfall simulation

Amount of total nitrogen and total phosphorus losses through surface discharge and percolation during the first, second and third rainfall simulation

Location of two research sites for evaluating coconut husk buffer strips under field conditions

Rainfall amount in Cabawan and Sambog research sites Research site 1 located in Cabawan, Tagbilaran City, Bohol Coconut husk buffer strips stabilized through furrows

3 3 5 5 7 9 9 11 12 12 13 15 27 27 28 29 31 33 40 41 42 42

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Fig. 3-5 Fig. 3-6 Fig. 3-7 Fig. 3-8 Fig. 3-9 Fig. 3-10 Fig. 3-11 Fig. 3-12 Fig. 4-1 Fig. 4-2 Fig. 4-3 Fig. 4-4 Fig. 4-5 Fig. 4-6 Fig. 4-7 Fig. 4-8

List of Figures (continuation)

Coconut husk buffer strips stabilized through furrows Poles and baseline on ground surface measurements Measuring ground slope by the use of hose level

Slope length (L) and slope steepness (S) values at 4 and 21 degrees ground slopes

Ground slope section of upland field with coconut husk buffer strips at research site 1 located in Cabawan, Tagbilaran City, Bohol

Ground slope section of upland field with coconut husk buffer strips at research site 2 located in Sambog, Corella, Bohol

Accumulated soil at the back of coconut husk buffer strips installed at 4 degree slope upland field in Cabawan, Tagbilaran City, Bohol

Accumulated soil at the back of coconut husk buffer strips installed at 21 degree slope upland field in Sambog, Corella, Bohol

Cutting of portions and layers of coconut husk Segregated fiber and pith

Pulverized coconut fiber and pith

Total nitrogen and total phosphorus analyses through spectrometric method

Amount of total nitrogen per dry mass of pith, fiber and bark at top, middle and bottom portions of coconut husk

Cross sectional details of husk a) designated portions and layers of coconut husk, b) color gradient where darker color shows higher T-N concentrations on pith and fiber as well as in c) bark

Cross sectional details of husk a) designated portions and layers of coconut husk, b) color gradient where darker color shows higher T-P concentrations on pith and fiber as well as in c) bark

Amount of total phosphorus per dry mass of pith, fiber and bark at top, middle and bottom portions of coconut husk

45 46 46 48 50 51 52 52 58 58 59 60 61 62 62 64

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Fig. 4-9 Fig. 5-1 Fig. 5-2 Fig. 5-3 Fig. 5-4 Fig. 6-1 Fig. 6-2 Fig. 6-3 Fig. 6-4 Fig. 7-1 Fig. 7-2 Fig. 7-3 Fig. 7-4 Fig. 7-5 Fig. 7-6 Fig. 7-7

List of Figures (continuation)

Whole coconut fruit showing a) the pedicel, and b) parts of the nut

Retting treatment of coconut husk

Amount of T-N released from coconut husk into ret liquor Amount of T-P released from coconut husk into ret liquor Amount of T-N and T-P a) leached from coconut husk during the slope modeling experiment, and b) leached from coconut husk into the water during the retting treatment

Slope model plots of (C) controlled, (U) untreated coconut husk buffered, and (T) treated coconut husk buffered plots set at 8 degrees in slope

Slope model plots under artificial rainfall simulator Amount of soil losses from (C) controlled, (U) untreated coconut husk buffered, and (T) treated coconut husk buffered plots during the first, second and third rainfall simulation

Amount of total nitrogen and total phosphorus losses through surface discharge and percolation during the first, second and third rainfall simulation

Fermentation of ret liquor for liquid bio-fertilizer Water spinach (Ipomoea aquatica)

Grown water spinach (Ipomoea aquatica) at 12 days old Rack compartment enclosed with polyethylene sheet for potted crop`s protection

Average height of water spinach (Ipomoea aquatica) Average weight of water spinach (Ipomoea aquatica) after harvesting in 28th days

Water spinach (Ipomoea aquatica) as control at left and ret liquor bio-fertilizer applied at right

66 72 74 74 76 82 83 86 88 95 96 97 98 99 100 100

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Table 2-1 Table 2-2 Table 3-1 Table 3-2 Table 6-1

List of Tables

Physical properties of Philippine soil

Physical and chemical properties of Philippine soil

Physical and chemical properties of soil in research sites at Cabawan and Sambog

Value of slope length (L) and slope steepness (S) factors in Cabawan and Sambog

Amounts of total nitrogen (T-N) and total phosphorus (T-P) in coconut husks and in ret liquor

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Chapter 1

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1.1 Background

1.1.1 Overview of environment and agriculture in the Philippines

The Philippines is an archipelago of about 30 million hectares situated in the Southeast Asian region. The country is divided into three major island groups: Luzon, Visayas and Mindanao. It is composed of 7,107 islands with 11 of them are large islands taking up about 95% of the total land area. One of those 11 bigger islands is Bohol which is the tenth largest island in the country with a total land area of 411,636 hectares. Bohol Island is located in the central part of the Philippines belonging to the Visayas group of islands (Fig. 1-1).

The country has a tropical climate dominated by rainy and dry seasons. It is divided into four climatic types, depending on how rainfall is distributed throughout the year as shown in Fig. 1-2. Based on rainfall, temperature and other parameters such as elevation and land form, three agro-ecological zones are identified (Moog, 2006). The zones are: wet zone, moist zone and dry zone. Wet zone are those regions dominated mostly in the Type I and Type II climate areas (Fig. 1-2) with rainfall intensity usually greater than 2,500 mm annually. Moist zone are those regions in Type II and Type III climate areas. Moist zone includes regions with annual rainfall ranging from 1,500 to 2,500 mm. Dry zone are those low rainfall regions with precipitation of less than 1,500 mm annually and with considerable moisture deficit during the dry season. Dry zone includes regions in Type IV climate areas.

Bohol Island falls under the Type IV climatic classification. The intertropical convergence zone and the island`s topography highly influenced the distribution of rainfall. Based on the thirty year data (OIDCI, 2006) from 1971-2000 of PAGASA-Tagbilaran Station, it shows a mean annual rainfall of 1,360.2 mm.

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Fig. 1-1 Map of Philippines

Fig. 1-2 Four climatic types in the Philippines

0 200 km

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The lowest monthly average rainfall occurs in March at 62.8 mm with about 10 rainy days, while the highest rainfall occurs in November at 182 mm with 18 rainy days. The interior mountainous areas are seemed to be receiving greater rainfall as compared to the coastal and offshore islands.

The Philippine economy is highly dependent on agriculture. About 32% or 9.5 million hectares of the total land area is under intensive cultivation, where 51% and 44% of these intensive cultivated land areas are arable and permanent croplands, respectively (Amongo et al., 2011). In 2010, the major agricultural land utilization by area harvested is devoted to rice, corn and coconut (BAS, 2013). Daily living of Filipino people also greatly rely on agriculture. About 86% of the 94.01 million population with a rate of 2.04% (NSO, 2010) are living in the rural areas, and 75% of them depend on agriculture for employment and income (Stads, Faylon and Buendia, 2007). Meanwhile, 66.54% or 273,950 hectares in the island of Bohol are utilized for agricultural production, mainly rice, corn, coconut and oil palm, vegetables and rootcrops (OIDCI, 2006). Although agricultural sector plays a bigger role on socioeconomic status in the country, poverty still surge particularly in the rural areas. This situation is influenced by low productivity and low incomes from agriculture (Briones, 2011). This is further aggravated by low prices of agro-products in the market but high retail prices of food and other basic needs (Cororaton and Corong, 2009).

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Fig. 1-3 Land use vegetation map in Bohol Province

Fig. 1-4 Land use in Bohol Province

Agricultural land 66.54% Forest & woodland 24.60% Others 8.86%

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1.1.2 Land degradation in the Philippines

Soil is the foundation of basic ecosystem function. It supports different forms of life by providing habitat for billions of organisms contributing to biodiversity. Soil acts as a water filter and helps regulate the earth`s temperature as well as many of the important greenhouse gases. Finally, soil endows a lot of service to human being as a growing medium of crops providing food, fiber and fuel.

However, soil degradation occurs because of rapid changes in the normal processes of soil formation influenced by human activities (Asio et al., 2009) which gives an alert worldwide that soil degradation is now widely recognized as a serious threat to agricultural productivity (Lal, 1998; Eswaran, Lal, and Reich, 2001). In the Philippines, soil degradation is a major threat to food security as identified by the National Action Plan (NAP) for 2010-2020. It was also reported by NAP (2010) that about 5.2 million hectares are severely degraded resulting 40 to 50% reduction in soil productivity. While part of these areas which is situated in Bohol of about 120,636 hectares accounted for 29% of island`s total land area are mostly coconut, corn and subsistence crops, open or idle land, grass dominated land and eroded land areas (OIDCI, 2006). Newby and Cramb (2007) reported that Bohol is characterized by typically highly degraded, shallow, calcareous soils.

Water erosion, physical degradation and chemical degradation are the major soil degradation processes in Southeast Asia as the result of assessment study by Van Lynden and Oldeman (1997). The natural factors affecting soil erosion by water include rainfall, vegetative cover, the slope of the land, and soil erodibility (Lal, 1984; Presbitero et al., 2005), hence the factors in Universal Soil Loss Equation and the Revised Universal Soil Loss Equation (Schwab et al., 1992) were derived. As mentioned above that an area of about 120,636 hectares or 29% of the total land area

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in Bohol that are usually utilized for coconut, corn and root crops are situated in 8 to 18% slope of land areas as shown in Fig. 1-5.

Fig. 1-5 Slope map in Bohol Province

The most common type of land degradation in the Philippines is soil erosion (NAP, 2010). Soil erosion removes the usually fertile topsoil resulting in the reduction of the productive capacity of the soil (Asio et al., 2009). It also led to significant offsite effect mainly by nutrient losses in runoff water resulting euthrophication in downstream water (Midmore et al., 1997). It is noted that Philippines has a tropical climate influence by monsoon and intertropical convergence zone. These conditions are also aggravated by the occurrence of an average 15 to 20 typhoons per year (Asio, 2009). Mihara (2001) stated that around 40% of annual nitrogen loads from upland fields were lost by one typhoon event alone. In the Philippines, loss of nutrient and organic matter are commonly observed

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in areas where low-input agriculture is practiced like in most upland areas in the country, which is primarily the result of soil erosion (Briones, 2009).

Rola and Coxhead (2005) stated that traditional farming method with high demand of basic commodity from the increasing population lead to rapid resource degradation. Furthermore, expansion into the uplands is occurring due to declining productivity in lowland agriculture. This situation highly engaged on clearing of forest areas to pave way for agricultural activities which is commonly related to slash-and-burn farming. Urich et al. (2001) reported that shifting agriculture with slash-and-burn farming in Bohol widely increased due to fast degradation of upland fields on slope areas. Newby and Cramb (2007) added that a combination of shallow soils, intense rainfall events, and traditional land-use practices results in high level of erosion and land degradation in Bohol. They also reported that about 80% of upland farmers in Bohol attested that soil erosion is the problem on their farms, even the entire soil profile in some places had been removed exposing the underlying bedrock. Because of this soil degradation that is continuously occurring in Bohol and throughout the Philippines, necessary strategy should be given in priority to conserve agricultural land particularly on soil erosion problem. Careful and rationale considerations on promoting soil erosion strategy which can be adaptable to the local community. In order to meet this condition, technology should be economically favorable to the adapter as well as to the environment. This may include; utilization of locally available materials, easy application method, and ecofriendly biodegradable materials.

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Fig. 1-6 Traditional slash-and-burn farming in Tagbilaran City, Bohol

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1.1.3 Coconut husk`s potential for conservation agriculture

The coconut palm (Cocos nucifera) is widely exists in tropical and subtropical regions either cultivated or wild. Coconut is an important orchard crops in tropical countries hence coconut palm can provide almost all the necessities of life in the absence of other land-based natural resources (Chan and Elevitch, 2006). It provides drink, oil, medicine, fiber, timber, fuel, utensils, artifacts and others. In the Philippines, coconut is one of the most widely cultivated food crops that cover 4.25 million hectares (Quilang, 2011) bringing Philippines the second highest producer of copra for export and domestic use.

According to OIDCI (2006), Bohol have existing coconut palm of about 5 million palm trees. As shown in Fig. 1-3, coconut palm trees are sparsely cultivated across the island. This high numbers of coconut palm trees produce large amount of coconut husk during copra production (Fig. 1-8). Although a few of these coconut husks are locally used as growing medium in backyard gardening such as orchid growing and potted plants, most of these residues are considered as waste material and left rotten in the site.

Coconut husk is a biodegradable material and because of its plentiful amount in tropical and subtropical regions therefore it has a high potential as resource for environmental and agricultural development. Van Dam et al. (2004) noted that coconut husk is composed of 30 wt.% fiber or coir and 70 wt.% pith (Fig. 1-11). Manufactured soil erosion control materials made from coconut husk fiber was introduced in the middle of nineteenth century (Ziegler and Sutherland, 1997). Sutherland and Ziegler (2007) reported that natural fiber rolled erosion control systems usually applied on bare slopes and are increasingly favored, as they are biodegradable, less costly to produce and to apply, environmentally friendly, equally

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effective in reducing erosion, and generally provide a favorable microclimate for biomass production. Batthacharyya et al. (2010) stated that natural fibers including coconut fiber or coir can help to decrease the penetration of intense solar radiation to the ground, suppress extreme soil temperature fluctuations, reduce water loss through evaporation, and thus conserve soil mosture, which can created ideal conditions for plant establishment and growth.

Fig. 1-8 Rolled erosion control systems made from coconut husk fiber of a) random fiber coir, b) open weave coir, and c) rolled erosion control or coir geotextile installed on slope ground surface to protect from erosion

a) b)

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Fig. 1-9 Pile of unused coconut husk in Panglao, Bohol

Fig. 1-10 Parts of coconut fruit

Husk (Mesocarp)

Shell (Endocarp) Meat (Endosperm) Bark (Exocarp)

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Fig. 1-11 Bark, fiber and pith component of coconut husk

To make use of coconut husks available in the island of Bohol, utilizing this material for mitigating soil erosion has been proposed. For finding out the capability of coconut husk to its utilization purpose in this research, slope modeling under artificial rainfall simulator and onsite installation of coconut husk buffer strips were carried out.

Pith Fiber Bark

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1.2 Objectives

1.2.1 Overall objectives of this dissertation

Discussing the most convenient, effective and adaptable erosion control systems through utilizing coconut husk as buffer strip has been sought in this dissertation entitled ‘Study on Utilizing Coconut Husk for Conservation Agriculture in Bohol of Philippines’. In achieving the goal of this dissertation, objectives were implemented as follows:

(1) To evaluate the capability of coconut husk buffer strips on mitigating soil and nutrient losses through slope modeling and field application

(2) To find out applicable method on eliminating the release of nutrient component from coconut husk buffer strips

(3) To evaluate the effectiveness of nutrient component from coconut husk for liquid bio-fertilizer

1.2.2 Objectives of each chapter

To achieve the overall objectives and making clear the flow of this dissertation, research structure was formulated as shown in Fig. 1-9. It was stated in this chapter that soil erosion is the most serious problem causing rapid land degradation throughout the Philippines particularly in the island of Bohol. Thus, strategy on mitigating soil erosion has been focused through the utilization of abundant unused coconut husk in the island.

With the aim of promoting the proposed technology that would be adaptable to the local farmers in Bohol, utilizing the coconut husk for soil erosion control with low cost and low labor input were sought. In this connection, coconut husks were utilized as buffer strips by installing across slopes on upland field with very low labor cost on preparing the coconut husk as well as its installation into the field.

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Fig. 1-12 Research structure of this dissertation Chapter 1

Background and objectives

Chapter 2

Capability of coconut husk on mitigating soil and nutrient losses through slope modeling experiment

Chapter 7

Utilization of nutrient component from coconut husk as liquid bio-fertilizer for crop growth

Chapter 6

Capability of ret treated coconut husk buffer strips on mitigating soil and nutrient losses

Chapter 3

Capability of coconut husk on mitigating soil losses in situ

Chapter 8 Conclusions

Chapter 4

Analyzing distribution of nitrogen and phosphorus concentration in coconut husk for segregation of high concentration parts

Chapter 5

Eliminating nitrogen and phosphorus components from coconut husk by retting treatment

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In this connection, Chapter 2 deals with the evaluation of the capability of coconut husk buffer strips on mitigating soil and nutrient losses through slope modeling experiment under artificial rainfall simulator. Also, for finding out the efficient amount of coconut husk as buffer strip, and the capability of two-ply and four-ply coconut husk buffer strips on trapping soil losses were also examined. It was observed that coconut husk buffer strips were effective to trap transported soils however there was no significant difference between the two-ply and four-ply of coconut husk buffer strips. Therefore, installation of two-ply coconut husk buffer strips were carried out in situ as discussed in Chapter 3.

Chapter 3 discusses the installation of coconut husk as buffer strips for soil

erosion control in the field. In Chapter 2, it was found out that coconut husk buffer strips were highly capable on mitigating soil losses through slope modeling experiment under rainfall simulator. Therefore, installation of coconut husk buffer strips has been implemented in the upland fields in Bohol of Philippines. The aimed of this chapter was to evaluate the capability of coconut husk on mitigating soil losses under field condition. The results showed that sediments were notably accumulated at the back of coconut husk buffer strips. Also, a reduction of soil losses after the installation of coconut husk buffer strips was clearly indicated.

Coconut husk buffer strips tend to release total nitrogen (T-N) and total phosphorus (T-P) which were observed during the slope modeling experiment covered in Chapter 2. Thence, it was asserted that specific portion of coconut husk may have lower concentration of total nitrogen and total phosphorus that might be usable portion for buffer strips. So Chapter 4 discusses the concentration of total nitrogen and total phosphorus at different portions and layers in coconut husk. However, it was concluded that different portions and layers in coconut husk had

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complex concentration of those nutrients therefore cutting a specific layer of coconut husk for buffer strip installation is unmanageable method. In this regard, it has been considered that coconut husk must be utilized for buffer strips by its natural structure. So there is a need to look for another method on treating the coconut husk in order to eliminate its nutrient component from releasing as discussed in the next chapter.

As mentioned above, an assertion that specific portion of coconut husk may have lower concentration of T-N and T-P which might be a usable portion for buffer strips for mitigating its nutrient release. However, it was proven that complex concentration of nutrients at different portions and layers in coconut husk. In this manner, cutting out a specific layer of husk having low concentration of nutrient is impossible. Thus, Chapter 5 deals with other method for eliminating the release of nutrient component through soaking of coconut husk into distilled water called retting treatment method. It was concluded that high amount of nutrient component were extracted from coconut husk particularly on T-P component within the optimum period of about ten days in retting. However, concerning on improper management of ret liquor may cause pollution to water bodies. Thus, efficient utilization of extracted nutrients from coconut husk has been desired. In this regard, Chapter 7 discusses the utilization of nutrients from coconut husk.

Chapter 6 covers the evaluation of ret treated coconut husk buffer strips on

mitigating soil and nutrient losses through slope modeling experiment under artificial rainfall simulator. A significant amount of nutrient component from coconut husk was extracted during the retting treatment. From that trend, finding out the effect of retting treatment of coconut husk buffer strips on eliminating its total nitrogen and total phosphorus release was the objective in this chapter.

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liquor, efficient utilization of this nutrient was given of importance. Consequently, fermentation of the ret liquor for liquid bio-fertilizer has been desired. In the course of utilizing this extracted nutrient component, Chapter 7 deliberates the effects of liquid bio-fertilizer made from coconut husk`s ret liquor. The objective of this chapter was to find out the effect of ret liquor bio-fertilizer on plant growth. Ret liquor bio-fertilizer applied Ipomoea aquatica indicated a significant weight higher than that of controlled crop.

Chapter 8 summarizes the outcome from each chapter stating the overall

conclusions in this research entitled ‘Study on Utilizing Coconut Husk for Conservation Agriculture in Bohol of Philippines’.

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References of this chapter

Amongo, R.M., Amongo, L. and Larona, M.V. 2011. Mechanizing Philippine agriculture for food sufficiency. Paper presented during the UNAPCAEM and FAO joint roundtable meeting on sustainable agricultural mechanization in Asia, Bangkok, Thailand.

Asio, V., Jahn, R., Perez, F., Navarette, I. and Abit, S.Jr. 2009. A review of soil degradation in the Philippines. Annals of Tropical Research 31-2, 69-94.

Bhattacharrya, R., Smets, T., Fullen, M.A., Poesen, J. and Booth, C.A. 2010. Effectiveness of geotextiles in reducing runoff and soil loss: A synthesis. Catena 1-12.

Bureau of Agricultural Statistics, 2013. Quick graphs, utilization of agricultural area by type of utilization, facts and figures on the Philippine economy.

http:// countrystat.bas.gov.ph /index.asp?cont=factsandfigures. Accessed July, 30, 2013.

Briones, A. 2009. Land degradation and rehabilitation in the Philippines. Final report to the World Bank, Philippine Institute for Development Studies, 18-20.

Briones, A. 2011. National study: Philippines. Organic agriculture and rural poverty alleviation: potential and best practices in Asia, 119-145.

Chan, E. and Elevitch, C.R. 2006. Cocos nucifera (coconut). Species profiles for Pacific Island Agroforestry, 2-1, 1-27.

Cororaton, C. and Corong, E. 2009. Philippine agricultural and food policies, implications for poverty and income distribution. International Food Policy Research Institute, Research Report 161.

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Eswaran, H., Lal, R. and Reich, P. 2001. Land degradation: an overview. In: Bridges, E.M., I.D. Hannam, L.R. Oldeman, F.W.T. Pening de Vries, S.J. Scherr, and S. Sompatpanit (eds.). Responses to Land Degradation, Proc. 2nd International Conference on Land Degradation and Desertification, Khon Kaen, Thailand, Oxford Press, New Delhi, India.

Lal, R. 1984. Soil erosion from tropical arable lands and its control. Advances in Agronomy, 37, 183-248.

Lal, R. 1998. Soil quality and sustainability. In: Lal R. Blum W.E.H. (eds.) Methods for assesment of soil degradation, Advances in Soil Science. CRC Press, Boca, Raton, 17-30.

Mihara, M. 2001. Nitrogen and phosphorus losses due to soil erosion during a typhoon, Japan. Journal of Agricultural Engineering Research, 78-2, 209-216. Moog, F.A. 2006. Country pasture/forage resource profiles: Philippines. Food and

Agriculture Organization, 9-11.

National Action Plan, 2010. The updated Philippine National Action Plan to combat desertification and, land degradation and drought FY2010- 2020, Department of Agriculture, Bureau of Soils and Water Management, Department of Agrarian Reform, Department of Environment and Natural Resources, Department of Science and Technology, 12-17.

National Statistics Office, 2010. Summary of projected population by sex and by single calendar year interval, Philippines.

http://www.census.gov.ph/content/2010-census-population-and-housing-reveals -philippine-population-9234-million, Accesed July 30, 2013.

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Newby, J.C. and Cramb, R.A. 2007. Economic impacts of landcare in the Central Philippines: A preliminary report, working paper number 10, Philippines- Australia Landcare Project, 2-4.

Orient Integrated Development Consultants Incorporated, 2006. Bohol Agriculture Mater Plan, CY2006-2026.

Presbitero, A.L., Rose, C.W., Yu, B., Ciesiolka, C.A.A., Coughlan, K.J. and Fentie, B. 2005. Investigation of soil erosion from bare steep slopes of the humid tropic Philippines. Earth Interactions, 9-5, 1-30.

Quilang, R. 2011. Philippine policies on agribusiness and rural development to adapt to climate change. Journal of ISSAAS, 7-1, 29-39.

Rola, A., and Coxhead, I., 2005. Economic development and environmental management in the uplands of Southeast Asia: Challenges for policy and institutional development. Agricultural Economics 32-1, 243-256.

Schwab, G.E., Fangmeier, D.D., Elliot, W.J. and Frevert, R.K. 1992. Soil and water conservation engineering, fourth edition. John Wiley & Sons, Inc., 97-107. Stads, G., Faylon, P. and Buendia, L. 2007. Agricultural research and development in

the Philippines: Policy, investments and institutional profile. Agricultural Science and Technology Indicator, 1-3.

Sutherland, R. and Ziegler, A. 2007. Effectiveness of coir-based rolled erosion control systems in reducing sediment transport. Applied Geography 27, 150-164.

Urich, P.B., Day, M.J. and Lynagh, F. 2001. Policy and practice in karst landscape protection: Bohol, the Philippines. The Geographical Journal, 167-4, 305-323.

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Van Dam, J.E.G., Van Den Oever, M.J.A, Teunissen, W., Keijsers E.R.P. and Peralta A.G. 2004. Process for production of high density/high performance binderless boards from whole coconut husk, Part 1: Lignin as intrinsic thermosetting binder resin. Industrial Crops and Products 19, 207-216.

Van Lynden, G.W.J. and Oldeman, L.R. 1997. The assessment of the status of human-induced soil degradation in South and Southeast Asia. International Soil Reference and Information Centre, Wageningen, 17-20.

Ziegler, A.D. and Sutherland, R.A. 1997. Reduction in interrill sediment transport by rolled erosion control systems. Soil and Tillage Research 45, 265-278.

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Chapter 2 Capability of coconut husk buffer strips on

mitigating soil and nutrient losses through

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2.1 Introduction of this chapter

2.1.1 Background

Soil erosion causes serious environmental problems in Bohol of Philippines. 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 (OIDCI, 2006). Together with torrential rain, uplands in the island are susceptible to soil erosion causing rapid degradation of land with the decrease of crop quality and yields.

Considering the agricultural socio-economic situation of the island, utilizing the available materials in the region to mitigate soil erosion is an essential factor to be considered. Coconut husk is locally available and abundant in the province of Bohol. So, utilizing of this residue for soil erosion control has been focused in this research. Meanwhile, there were reports dealing with previous studies on manufactured products from coconut husk for soil erosion control. Sutherland and Ziegler (2007) stated that many studies had found coconut fiber rolled erosion control systems (RECS) are effective in reducing erosion at degraded hillslopes. Also, utilization of coconut fiber mat or geotextile as buffer zones on bare soil was highly effective on reducing runoff and mitigating soil losses (Bhattacharyya, 2010). However, these manufactured products from coconut husk fiber for erosion control system are economically expensive for the local farmers. Thus, this technology is difficult to be adapted particularly by the local farmers in Bohol. In this connection, application of non-manufactured products, low labor cost, convenient method were considered in making use of coconut husk for soil erosion control systems. Thus,

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buffer strip installation of coconut husks has been proposed in this research as a strategic method for soil erosion control.

To find out the capability of coconut husk as buffer strip for soil erosion control, a preliminary investigation has been carried out through slope modeling experiment under artificial rainfall simulator.

2.1.2 Objectives

The objectives of this chapter were 1) to investigate the capability of coconut husk on mitigating soil and nutrient losses, and 2) to evaluate two-ply and four-ply coconut husk buffer strips to trap soil and nutrient losses.

2.2 Research methods

2.2.1 Slope model plot preparation

There were three stainless slope model plots utilized for the slope modeling experiment. Size of each plot was 130 cm long and 11 cm wide. Philippine soil of 7.7 kg was filled up into each plot then slightly compacted and leveled by hand up to 5 cm deep from the bottom of stainless slope model plot. The amounts of soil weighing 7.7 kg that were filled up into each slope model plot was based on the product of dry bulk density at 0.8 g cm-3 and wet density at 1.08 g cm-3 of Philippine soil, and the volume of soil required into stainless slope model plot at 7,150 cm3.

Philippine soil was obtained from the abandoned corn field at Tiptip District, Tagbilaran City in the province of Bohol. The soil had clay, silt and sand percentages of 63.8%, 8.1% and 28.1%, respectively as shown in Table 2-1. It has the dispersion ratio of 22.4% indicating that the soil is susceptible to erosion. The soil had an ignition loss of 16.5% meaning lower amounts of organic content. It also has the amount of total nitrogen at 118×10-5 kg•kg-1 and total phosphorus at 8.67×10-5 kg•

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kg-1.

Table 2-1 Physical properties of Philippine soil

Soil

Specific gravity

Particle size distribution % _Soil

texture

Sand Silt Clay

Faraon clay soil 2.73 8.8 24.2 67.0 C

Table 2-2 Physical and chemical properties of Philippine soil

Dispersion ratio % Ignition loss % Total nitrogen (×10-5 kg•kg-1) Total phosphorus (×10-5 kg•kg-1) 22.4 16.5 118 8.67

The prepared slope model plots were set up at 8 degrees in slope. This slope steepness of 8 degrees was employed in correspond to the maximum slope required in farmland management (Yasutomi et al., 1999). Plot I was the controlled plot (C) and Plot II was installed with two-ply coconut husk buffer strips (2pCHB). Plot III was installed with four-ply coconut husk buffer strips (4pCHB).

2.2.2 Coconut husk buffer strip preparation

Coconut husks were obtained from Bohol, Philippines. Those were cut and trimmed into 12 cm long and 5 cm wide (Fig. 2-1) which is equivalent to one-ply coconut husk buffer strip. Trimmed coconut husks were slightly pounded by hammer. Pounding was carried out to make the coconut husk a porous material allowing runoff water to pass through the buffer medium. Two pieces of pounded coconut husk were installed at the lower toe of the plot. This plot was the two-ply husk

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buffered plot or 2pCHB. Another four pieces of coconut husk were prepared for the four-ply husk buffered plot or 4pCHB.

Fig. 2-1 Trimmed coconut husk of 12 cm long by 5 cm wide equivalent to one-ply coconut husk buffer strip

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Fig. 2-3 Slope model plots of (C) controlled, (2pCHB) two-ply coconut husk buffered, and (4pCHB) four-ply coconut husk buffered plots set at 8 degrees in slope

2.2.3 Artificial rainfall simulation

Slope model plots were set under artificial rainfall simulator (Fig. 2-4) at Artificial Rainfall Facilities in the Department of Bioproduction and Environment Engineering, Faculty of Regional Environment Science, Tokyo University of Agriculture, Agricultural Engineering facilities. Rainfall of 60 mm hr-1 based on the intensity gathered from the research site in Bohol was employed within two hours.

Three repetitions of rainfall simulation were carried out for about a week of interval in each simulation. Slope model plots were covered while not in use to protect from rain, wind and severe sunshine exposure. During the rainfall simulation, surface water discharge was measured and sampled every fifteen minutes for the first hour from the start of simulation and every thirty minutes for the second hour. However, percolation water was collected and sampled twenty-four hours after the end of simulation.

C

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2.2.4 Analyses items

Suspended water samples collected from surface water discharge were analyzed for soil, total nitrogen (T-N) and total phosphorus (T-P) losses. Suspended water samples collected from percolation were analyzed only for T-N and T-P losses. Soil loss analysis was carried out by oven drying method. T-N and T-P analyses were carried out by decomposing of water samples with sodium hydroxide (NaOH) and potassium peroxodisulfate (K2S2O8) then T-N and T-P concentrations were measured by spectrometric method (Mihara and Ueno, 2000).

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2.3 Results and discussion

2.3.1 Soil losses

Suspended water samples collected from surface discharge were analyzed for soil losses by oven drying method. Quantitative data were statistically analyzed by Fischer`s T-test. The results showed that coconut husk buffered plots of two-ply (2pCHB) and four-ply (4pCHB) had lower amounts of soil losses than that of controlled plot (C) as shown in Fig. 2-5. It was indicated that coconut husk buffer strips were able to mitigate soil losses (p<0.01) throughout the three rainfall simulations.

Comparing the two-ply and four-ply coconut husk buffered plots, it was observed that the two-ply coconut husk buffered plot have no significant difference with that of four-ply coconut husk buffered plot during the first and third rainfall simulation. It could be presumed that thickness of four-ply coconut husk buffer strip had less influence on improving its capability to trap soil losses than that of two-ply thickness of coconut husk buffer strips.

Even though during the second rainfall simulation, the four-ply coconut husk buffer strip tended to mitigate soil losses than that of two-ply coconut husk buffer strip (p<0.05), it could be considered that two-ply of coconut husk could be an efficient thickness for buffer strips.

2.3.2 Total nitrogen and total phosphorus losses

Suspended water samples collected from surface discharge were also analyzed for total nitrogen (T-N) and total phosphorus (T-P) losses. Figure 2-6 showed the amount of T-N and T-P losses at controlled plot (C), two-ply coconut husk buffered plot (2pCHB) and four-ply coconut husk buffered plot (4pCHB).

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Fig. 2-5 Amount of soil losses from (C) controlled, (2pCHB) two-ply and (4pCHB) four-ply coconut husk buffered plots during the first,

second and third rainfall simulation

First ra

infa

ll

sim

ula

ti

on

0 100 200 300 400 0 30 60 90 120 Cu m u lat iv e am o u n t o f so il lo ss es (g /m 2) Time (min) a** b** b**

S

ec

ond

rai

nfall

sim

ula

ti

on

0 100 200 300 400 0 30 60 90 120 Cu m u lat iv e am o u n t o f so il lo ss es (g /m 2) Time (min) a** b*,** c*,**

T

hi

rd

ra

inf

al

l

simul

at

ion

0 100 200 300 400 0 30 60 90 120 Cu m u lat iv e am o u n t so il lo ss es (g /m 2) Time (min) a** b** b**

* Significant difference at p<0.05, ** Significant difference at p<0.01 Controlled plot (C) Two-ply husk buffered plot (2pCHB) Four-ply husk buffered plot (4pCHB)

First rainfall simulation

Second rainfall simulation

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At the right side of the figure, arrows pointing up and down are indicating from zero x-axis, the darker colors in histogram are the amounts of T-N and T-P through percolation while the light colors are the amounts of T-N and T-P through surface discharge.

Based on the experimental results, it was found out that during the first rainfall simulation, the amount of T-N losses at 2pCHB plot and 4pCHB plot were higher at 31.9 and 16.4% respectively than that of C plot. This result had figured out that coconut husk buffer strip itself releases a considerable amount of T-N component. It showed that 2pCHB significantly released T-N component (p<0.01) as well as 4pCHB (p<0.05) compared to C plot. Even though the 2pCHB plot appeared to be higher amount of T-N losses than that of 4pCHB however, it was proven that there was no significant difference between these two plots.

During the second rainfall simulation, it was observed that the amount of T-N losses at 2pCHB plot was higher at 20.8% significantly higher (p<0.05) than that of C plot. However, 4pCHB showed no significant difference compared to C and 2pCHB plots. During the third rainfall simulation, the 2pCHB plot tended to mitigate T-N losses (p<0.05) than that of C plot. While there was no significant difference was observed between 4pCHB plot and 2pCHB plot as well as to that of C plot.

Meanwhile, phosphorus losses from the coconut husk buffered plots (2pCHB and 4pCHB) were lower compared to C plot as shown in Fig. 2-6. Although the amounts of T-P losses were very little compared to T-N losses which clearly shown in histogram ranges, 2pCHB and 4pCHB plots tended to mitigate T-P losses. Even significant differences (p<0.05 and p<0.01) were observed than that of C plot throughout the three rainfall simulations.

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Loss of T-N Percolation Surface discharge 0.0 0.0 Surface discharge Loss of T-P Percolation -0.6 -0.4 -0.2 0 a*,**b** b* -0.6 -0.4 -0.2 0 a** b** b** (0.6) (0.4) (0.2) 0.0 0.2 0.4 0.6 a*,** c*,** b* Amo un t of T -P losse s 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 b*,** a** a* Amo un t of T -N losse s (g/m 2 ) C 2pCHB 4pCHB 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 b* a* a,b C 2pCHB 4pCHB 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 b** a** a,b C 2pCHB 4pCHB First rainfall simulation Second rainfall simulation Third rainfall simulation

Two-ply husk buffered plot (2pCHB) Four-ply husk buffered plot (4pCHB) Controlled plot (C)

*Significant difference at p<0.05, **Significant difference at p<0.01

Fig. 2-6 Amount of total nitrogen and total phosphorus losses through surface discharge and percolation during the first, second and third rainfall simulation

It was suggested that based on the statistical analysis, coconut husk buffer strips tended to mitigate T-P losses. However, there was no significant difference between 2pCHB and 4pCHB on T-P losses particularly during the second and third rainfall simulation.

31.9%

16.4%

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2.3.3 Discussion

The experimental results on slope modeling showed that the amount of soil losses at two-ply (2pCHB) and four-ply (4pCHB) coconut husk buffered plots were significantly lower than that of controlled (C) plot. This result indicated that coconut husk buffered plots remarkably mitigated soil losses. However, there was no significant difference was observed between 2pCHB plot and 4pCHB plot during the first and third rainfall simulation. This might be due to the sizes of eroded soil particles and spaces between fibers and piths of coconut husk.

Based on the slope modeling experiment that was carried out for determining the sizes of eroded soils with the same type of soil and the same rainfall intensity employed into slope model plots (Torillo and Mihara, 2011), it was found out that around 70% of the whole eroded soils were fine soil particles of less than 106 μm. In the same experiment, it was also observed that coconut husk buffer strip was less capable to trap soil particles of less than 106 μm.

This tendency illustrated that fine soils had passes through the spaces between fibers and piths in 2pCHB and 4pCHB. Very fine soil particles were passing through the spaces with the same tendency either in two-ply and four-ply thickness of coconut husk buffer strips. This tendency also indicated that fibers and piths in The 4pCHB may have more ability to retard the surface runoff water than that of 2pCHB however four-ply thickness of coconut husk buffer strips does not influence on trapping eroded fine soil particles than that of two-ply thickness of coconut husk buffer strips.

Remarkable amount of T-N losses was observed from 2pCHB and 4pCHB plots than that of T-P losses even though the weighted mean mass of T-N per mass of

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coconut husk was lower than that of the weighted mean mass of T-P (Figs. 4-5 and 4-8).

For phosphorus losses, although the weighted mean mass of T-P per mass of coconut husk was higher than that of weighted mean mass of T-N in coconut husk as mentioned above, the amounts of T-P losses from coconut husk buffered plots tended to be much lower. In Chapter 5, it was also observed that by soaking of coconut husk into the water, the amount of T-P released from coconut husk into the water was remarkably higher than that of T-N. In the latter condition where higher amount of released T-P by longer period of soaking the coconut husk in an ambient water, it indicates that T-P component in coconut husk could not be easily released by just with runoff water that passes through fibers and pith in coconut husk buffer strips in a short period. Thus, the tendencies of T-P release from coconut husk buffered plots were much less.

2.4 Conclusions of this chapter

This chapter dealt with the investigation on the capability of coconut husk on mitigating soil and nutrient losses. Also, evaluating the two-ply and four-ply coconut husk buffer strips to trap soil and nutrient losses was also aimed.

Based on the experimental results, it was clearly observed that coconut husk buffer strips significantly effective on mitigating soil losses. However, there was no significant difference observed between the two-ply coconut husk buffered plots (2pCHB) and the four-ply (4pCHB) coconut husk buffered plots. Therefore, it was suggested that two-ply was an efficient thickness of coconut husk for buffer strip installation.