STEP 1: Submitted Via OJS to “Journal Water Conservation and Management”

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KORESPONDENSI

STEP 1: Submitted Via OJS to “Journal Water Conservation and Management”

(10-2-2022)

STEP 2: Notification of article status from editor (14-2-2022)

STEP 3: Reviewer 1: First revision: Accepted with mayor revision (26-5-2022) STEP 4: Manuscript ID: WCM-02-2022-0015 revisions sent back (4-6-2025) STEP 5: Accepted (18-6-2022)

STEP 6: Galley Proof I (22-6-2022)

STEP 7: Galley Proof II (23-6-2022)

STEP 8: Available online (23- 6-2022)

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STEP 1:

Submitted Via OJS to “Journal Water Conservation and Management”

(10-2-2022)

COVER LETTER

I am enclosing herewith a manuscript entitled "SOIL INFILTRATION IN VARIOUS LAND USE AS A BASIS FOR DETERMINING LAND USE DIRECTION" submitted to journal Water Conservation and Management for possible evaluation.

With the submission of this manuscript I would like to undertake that the above mentioned manuscript has not been published elsewhere, accepted for publication elsewhere or under editorial review for publication elsewhere; and that my Institute’s Faculty of Forestry, Tadulako University representative is fully aware of this submission.

Type of Submitted manuscript Original Research Article

*Corresponding Author E-mail: nahar.pailing@gmail.com Date: February 10, 2022

Best Regards,

Dr. Naharuddin

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STEP 2:

Notification of article status from editor (14-2-2022)

Submission Confirmation - WCM-02-2022-0015

Water Conservation and Management <onbehalfof@manuscriptcentral.com> Sel, 15 Feb 00.33 14-Feb-2022

Dear Dr. Naharuddin Naharuddin,

Your manuscript entitled "SOIL INFILTRATION IN VARIOUS LAND USE AS A BASIS FOR DETERMINING LAND USE DIRECTION" has been successfully submitted online and is presently being given full consideration for publication in the Water Conservation and Management.

Your manuscript ID is WCM-02-2022-0015.

Please mention the above manuscript ID in all future correspondence or when calling the office for questions. If there are any changes in your street address or e-mail address, please log in to Manuscript Central

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Please note that you are required to clear permission to re-use any material not created by you. If there are permissions outstanding, please upload these when you submit your revision. We are unable to publish your paper with permissions outstanding.

Thank you for submitting your manuscript to the Water Conservation and Management.

Yours sincerely,

Prof. Dr. Muhammad Aqeel Ashraf

Water Conservation and Management Editorial Office

ashraf@inwascon.org.my

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STEP 3:

Reviewer 1: First revision: Accepted with mayor revision (26-5-2022)

ZIBELINE INTERNATIONAL PUBLISHING SDN BHD

26 Mei 2022 03.15

Dear Dr. Naharuddin

Pls revise your paper and email us back Reviewer 1:

The analysis of the paper is interesting. However, there are comments on the work need to be addressed in the next revisions as follows:

1. The abstract must provide enough a brief overview of the paper. Here, the abstract is not telling what actually in the main text. Thus, it should be re-written and should be to the point. What the problem is, what you did to solve it and what the results are and why are important?

2. Related Literature is very poor and should be rewritten and improved. I can't see the related work section? Thus, please provide several solid literature reviews (discussion and argument). Prefer to be updated with recent studies.

The overall recommendation is accept this paper.

Reviewer 2:

1.The abstract should be written in the way of purpose, method, result and conclusion, and kept within 150 real words.

2. It is suggested that key words should be extracted from the important content of the article rather than some words in the title.

3.The introduction of this paper analyzes the previous research needs, in order to put forward this point of view.

4. In the experiment part, we need to explain the experiment environment, experiment index, experiment scheme and so on.

5.The experiment is lack of data analysis. Please supplement this part to ensure the credibility of the article

6.Please point out the direction of future research and the shortcomings of this study.

Yours sincerely,

Prof. Dr. Muhammad Aqeel Ashraf

Water Conservation and Management Editorial Office ashraf@inwascon.org.my

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STEP 4:

Manuscript ID: WCM-02-2022-0015revisions sent back (4-6-2022)

Naharuddin Sumani <nahar.pailing@gmail.com>

4 Jun 2022 20.13

Kepada ZIBELINE Dear Editor-In-Chief

Journal Water Conservation & Management (WCM)

Thanks for the editor's responses and comments, reviewers. The authors have revised it for a long time with the aim of improving the quality of the article for possible publication in the Journal of Water Conservation and Management.

Attached, the author sends back the article that has been revised and has been proofread. Revised sections are highlighted in yellow.

The author hopes that the quality of the article can be improved so that it can be accepted for publication in the next volume

Best regards

Dr. Naharuddin

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SOIL INFILTRATION IN VARIOUS LAND USEAREAS AS A BASIS FOR DETERMINING LAND USE DIRECTION IN THE TOBOLI WATERSHED, CENTRAL SULAWESI, INDONESIA

ABSTRACT

The heterogeneity of infiltration has a strategic influence on the hydrological process in the watershed. One, and one of the factors that may the infiltrationaffecting its rate is land use. Land use has an impact on and soil compaction and has a direct impact on infiltration rate. Thisis land use. Therefore, this study aimedaims to compare infiltration rates in three land uses such as-use areas, namely secondary forest, agroforestry, and moor. The method used was aA survey method, was used, where field data observations were carried out at three locations, namely secondary forest, agroforestry, and moor. . The infiltration rate measurement was carried outperformed using a double-ring infiltrometer with five times repetitionrepetitions at each location.sampling site. The results , it showed that moor had the lowest infiltration with an averagevalue of 4.72 cm h^-1while the was recorded on the moorland, while agroforestry had the highest was agroforestry land at of 12.87 cm h^-1. LandThese findings indicate that land use hadhas a strategicsignificant role in the process of changing soil physical properties and soil compaction. Therefore, a, hence, sustainable soil and water conservation strategy isstrategies are needed.

Keywords:

Land use, soil infiltration, watershed management. Secondary forest, agroforestry, moor 1. INTRODUCTION

Land conversion in mostseveral watersheds becomeshas become a serious problem. It may cause, because it causes a disturbance in the hydrological cycle to be disturbed including the, such as land damage and infiltration rate reduction due to soil compaction, as well as land damage (Wang et al, 2018; Peña-Arancibia et al, 2019; Purba et al, 2020; E. Al-Esawi et al, 2021). Watershed is a basic concept in hydrology and, and one of its integral parts is the rate of water inflow into the soil. Furthermore, it is the basis for understanding hydrological processes forwhile planning and managing water resources. Infiltration is part of the hydrological process in the watershed.

An understanding of various hydrologicalthese processes and groundwater quality in a watershed is very important to maintain thewatershed health of the watershed (Flotemersch et al, 2016; Aryafar, 2017), through rainwater management, infiltration processes, surface runoff, andas well as groundwater and soil erosion (Bhardwaj, 2019).

Infiltration capacity is one of the main components of the hydrological cycle (Khalid et al, 2017), as well as an important variable for understanding and predicting various soil processes (Yimer et al, 2008; Tesemma et al, 2015; Devia et al, 2015; Chyba et al, 2017).

Infiltration is one of the main components of the hydrological cycle (Khalid et al, 2017). In watershed management, flood and erosion predictions depend on runoff raterunoffs (Naharuddin et al, 2021), which is directly affected by infiltrationthe rate of water inflow (Yan et al, 2015).

In the watershed ecosystemFurthermore, infiltration has a strategic role in watershed ecosystem because it becomesdetermines the key to how muchamount of therunoff and rainfall that can penetrate the soil and how much it becomes surface runoff. Increasing the.

Furthermore, increasing its value of the infiltration rate will be useful for infiltratinghelps to infiltrate rainwater into the soil which is useful for , and this serves as groundwater reserves induring the dry season (Fauzan and Rusli, 2018). Infiltration quantification is also needed to determine water availability for plant growth and, development (Fischer et al., 2015; Basche and DeLonge, 2019), as well as irrigation, and other uses for domestic household purposes (Al-Ismaili et al, 2017).

Land use controls soil infiltration (Návar and Synnott, 2000). Land use that isthat does not as expected withfollow soil and water conservation principles, such as soil compaction can affect soil infiltration. rate (Návar and Synnott, 2000). The grazing of livestock in pastures has the potential effect of reducing soil infiltrationthe inflow of water due to disturbances in soil and plant cover. Pressure on forests andas well as non-regulation of conservation efforts can remove shrubs, herbs, trees, and grasses, and canas well as reduce above-ground organic matter, all of which are parameters for infiltration and minimizing surface runoff.

Land-use change and rainfall are often considered the main factor affecting soil infiltration (Sun et al, 2018; Aliramayee et al, 2019).

However, the difference in soil infiltrationthe capacity for several types of land use is not widely known, especially in the use of

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secondary forest landforests, agroforestry, and moor. ChangesForest conversion is often accompanied by changes in soil structure caused by compaction of surface soil due to the use of tillage systems that doesdo not use soilfollow conservation principles are the main factors that cause . This causes compaction of the soil surface, thereby leading to a decrease in the infiltration capacity and soil water content after forest conversion to other land uses (Owuor et al, 2018).

Infiltration from a hydrological aspect is a very important, as hydrological parameter, and it marks the transition of fast -moving surface water to slow -moving groundwater from groundwater. Various. Several studies related to infiltration rates onhave also explored its rate in various land uses have been carried out, for exampleuse areas, such as the impact of land use on increasing soil infiltration capacity using meta-analysis (Sun et al, 2018), infiltration capacity model (Hamman et al, 2018), Effectthe effect of soil moisture and plant roots on soil infiltration capacity (Liu et al, 2019; Liu et al, 2020), Assessmentassessment of infiltration capacity based on the spatial distribution for evaluation of storm runoff in forestedforest catchments (Miyata et al, 2019), Variationand variation of soil infiltration capacity after vegetation restoration (Tang et al, 2019). SomeHowever, none of these infiltration studies, none of them have compared infiltrationthe rates in various land uses, generally the object is only one landuse areas.

In the tropical area, especially in Central Sulawesi, there are dynamic changes in land use from primary forest land to secondary forest land, agroforestry, and other forms of land use, this is very important to study and estimate . There are also no studies on the infiltration rate in these various land uses, there is no previous research done onareas. Therefore, this issue. This study aimedaims to determine and compare the rate of infiltration rate in secondary forest land useforests, agroforestry, and moor as a basis for directing land use and management in the context of preservingto preserve the hydrological function of the watershedwatersheds.

2. MATERIALS AND METHODS 2.1 Study area

This researchstudy was conductedcarried out from January to August 2021 in the Toboli watershed, Central Sulawesi, Indonesia, but.

However, the supporting data retrieval research has been done study was conducted in 2020, in the production Forest Management Unit (FMU) Model Dolago Tanggunung, the area of the Trans Sulawesi Poros Road, Coffee Plantation, that is the Pangi Binangga Nature Reserve Conservation Area, Central Sulawesi (. This study area is geographically located at 0⁰43'39” S and 119⁰59'17” E with an altitude of 165 m from above sea level).. Although the research locationit is a conservation area, there isare still occurred land conversionconversions from primary forest to secondary forest, agroforestry, and moor. The conversionThis is due to road accessconstruction (Trans Sulawesi) from Palu, the capital of Central Sulawesi province to other areas like, such as North Sulawesi and Gorontalo. Analysis of soil physical properties was carried out at the Soil Science Laboratory, of the Faculty of Agriculture and as well as the Forestry Laboratory, of the Faculty of Forestry, Tadulako University.

2.2 Sample Collection and Method of Sampling

TheThis study used a survey method. Field, where field observations were carried out at 3 locations, namely secondary forest, agroforestry, and moor. The infiltration rate measurement was carried outperformed using a double-ring infiltrometer with 5 repetitions at each measurement location, and the infiltration rate data was obtained were calculated using the Horton method. Soil Subsequently, soil samples were taken at each location of secondary forest, agroforestrycollected and moor then analyzed in the laboratory. Sampling was carried out using the undisturbed soil sample method and the disturbed soil sample method (disturbed soil sample) with a depth of 0-40 cm and 40-60 cm., respectively. The distance of the sampling depth used is related to the soil's ability to infiltration capacity of the area (Wang et al, 2015)

The parameters analyzed for soil physical properties were, such as soil texture, organic matter, bulk density, porosity, and permeability based on instructionswere analyzed using various methods, as shown in Table 1 (Arthur et al, 2013; Worku and Bedadi, 2016). Variables of observation of soil physical properties and method of analysis (Table 1)

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Table 1. Variable observation of soil physical properties and analysis method

Observational variables Method of analysis

soil texture

pipette

organisorganic matter walkeley and black say

bulk density gravimetric

porosity gravimetric

permeability constant head permeameter

2.3 Data analysis

Permeability; SoilThis is the ability of the soil to carry water or air. Permeability, and it is generallyoften measured in terms of the rate of flow of water flow rate through the soil in a mass ofwith time and is expressed as (cm h^-1. Permeability is). Furthermore, it was analyzed based onusing the equation below:

K ( ) (1)

Description :

K : permeability (cm h^-1)

Q : the amount of water flowing per measurement (ml) t : measurement time (hours)

L : thickness of soil (cm) H : Head ring height (cm) A : ground surface area(cm²)

Bulk density (BD); bulk density was determined based on the equation below:

(2)

Description :

V : value of ring volume (cm³)

Porosity; porosity was determined based on the equation below:

x 100%) (3)

Soil infiltration; The infiltration rate was analyzed using the Horton method. This method, which is a time-dependent methodtechnique (Abdulkadir et al, 2011; Beven, 2021; Kim et al, 2021).

F(t) = fc + (f0 – fc) e ^–kt (4)

Description :

f(t) :): infiltration rate at t- time (cm h^-1) fc : constant infiltration rate (cm h^-1 sec^-1) f0 : initial infiltration rate (cm ^h-1 sec^-1) e : exponential number (2.718) k : constant (-1/(m log 2. 718) t : time (sec^-1)

To obtain k value performed formula derivation of, the Horton infiltration equation was derived.

f = fc + (f0 – fc) e –kt (5)

f – fc = (f0 – fc) e ^–kt (6)

Right and left side alghoritmedalgorithmed log (f – fc) = log (f0 – fc) – kt log e log (f – fc) – log (f0 – fc) = - kt log e

t ( ) 𝑙𝑜𝑔 ( 0 – ) 𝑘𝑡 𝑙𝑜𝑔 (7)

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t ( ) 𝑙𝑜𝑔 ( – ) ( ) 𝑙𝑜𝑔 ( – ) (8)

Change to equation : 𝑦 𝑚𝑥 𝑦 𝑡 m x = log (f – fc)

𝑙𝑜𝑔 ( 0 – ) (9)

So the k value is the equation 𝑘

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The value of m is the gradient obtained from plotting of the graph between the actual infiltration f withand log ( – )

Classification of infiltration rates according to the criteria (Table 2),rate was carried out based on the instructions of Soil Conservation Services, as shown in Table 2 (Jury and Horton, 2004).

Table 2. Classification of Infiltration Rate

Criteria Infiltration rate (cm h^-1)

Very fast

>25.4

Fast 12.7 – 25.4

Rather fast 6,3 – 12.7

FairlFairly fast 2 – 6.3

Rather slow 0.5 – 2

Slow 0.1 – 0.5

Very slow < 0.1

Source: Asdak, 2018

3. RESULT AND DISCUSSION

3.1 Physcial CharacteristicPhysical Characteristics of Soil

Soil physical properties are related to theits shape or condition of the original soil, including conditions, such as texture, structure, bulk density, organic matter, porosity, and permeability. Soil propertiesFurthermore, they have a role in plant root activity, both in terms of including nutrient absorption, water, and oxygen absorption as well as constraint of plant root movement (Hu et al, 2018). SoilThe soil physical properties in the 3 land -use asareas are presented in tableTable 3 below.

Table 3. PhyscialPhysical properties of Soil

Soil physical properties LanduseLand-use Unit

Secondary forest Agroforestry Moor

Soil texture 32.1 29.1 27.6 % sandy

60.3 52.1 42.2 % dusty

7.6 18.8 30.2 % clay

Texture class Dusty Clay Dusty Clay Loamy clay -

Bulk density 1.14 1.22 1.75 g/cm³

Organic matter 2.72 6.35 1.28 %

Porosity 46.17 49.15 28.26 %

Permeability 27.48 12.75 9.83 cm h^-1

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Table 3, shows that the land use of secondary forest and agroforestry hasland use areas have a dusty clay texture class, for, while moorland it has a loamy clay texture that influences the , which influenced their infiltration raterates. A soil with fine soil texture has more dense soil pores compared to athan coarse or sandy soil texture (sand),, and this factor greatly affects the speed of water penetration into the soil.

The value of bulk density on the secondary forest land use was 1.14 g/cm³, and on, agroforestry land, and moor was land use areas were 1.14 g/cm³, 1.22 g/cm³, and 1.75 g/cm³. These results showed that moor had a high bulk density compared to secondary forest and agroforestry land., respectively. The existence of repeated pressure on land will causecauses soil compaction so that, which leads to an increase in the value of bulk density will be higher, it. This finding is in line with the Shah et al, (2017) that Soil compaction is an important problem because it is related to soil quality for crops, agricultural production, and infiltration rates.

Low Furthermore, low to medium bulk density is influenced by a texture that is dominated by dusty and sandy that textures, which causes an increase in the number of pores. The occurrence of soil pores to form. There is soil compaction so thatincreases the bulk density value will increase further which results in, and this leads to a slow infiltration rate (Irmak et al, 2018). This is also clarified by consistent with Franza et al, (2019) that the higher the density, the denser the soil, and the lower the porosity of the soil.

The analysis results of organic matter (Table 3) showshowed that inthe secondary forests 2.72%,, agroforestry , and moor contain 2.72%, 6.35%, and moor 1.28%. The largest organic matter value was found on agroforestry land, followed by secondary forest and the lowest was on dry land% organic matter respectively, as shown in Table 3. Chaudhari et al, (2013) stated that an increase in soil organic matter content was followed by led to a decrease in bulk density, and on the other hand, it was able to as well as an increase the value of soil in porosity. The low value of bulk density and high value of soil porosity will be This condition is advantageous in terms of because it causes an increase in the infiltration speed.

The results of soil porosity analysis showed that the secondary forest had a porosity of 46.17%, agroforestrywhile 49.15%,% and moor 28.26%.% were recorded in the agroforestry and moor, respectively. The highest value was foundobtained in the agroforestry, so land use, which indicates that water enterscan enter the soil faster. According to Fu et al, (2019),) reported that the more porous a soil is, the higher the porosity value, the higher theits infiltration rate. The lowest value was in the moor. Based on the results of research by Gopal et al, (2019), it is shown) also revealed that the smalllow porosity of the soil causes may reduce the infiltration reduced the rate. of water flow.

Permeability is the ability of the soil to pass water to the lower layers of the soilits profile. The results of the study (Table 2) show revealed that secondary forest land had a high permeabilityhighest value of 27.48 cm h^-1compared towas recorded in the secondary forest, followed by agroforestry and low which weremoor with 12.75 cm h^-1 and 9.83 cm h^-1., respectively. Soil structure and texture have anplay a very significant important role in the high permeability. Soils with high permeability of the soil, which causes an increase in the rate of infiltration. It will reduceAn increased inflow of water into the soil reduces surface runoff which has an impact on soilas well as erosion.

3.2 Infiltration Rates in Various Land Use

Infiltration is defined as the percolation of water through the soil, and it is an important parameter in hydrological modeling mainly, such as surface runoff, as well as watershed management, and irrigation management (Singh et al, 2017). TheFurthermore, the infiltration rate is the amount of water per unit time that enters the soil surface. When the soil, and low values are obtained when the it is in a dry state, the infiltration rate is high. Based on the . The results, showing the infiltration rates showed that there were differences in the rates of the three land use had differences (areas, as shown in Table 4)..

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14

10.4 8.5

7.4 6.4

3.9 3.6

14 14.2

13.6 10.4

7.6 5.1 4.3

14

6.2 4.5

3 1.9 1.7 1.5

02 46 108 1214 16

0 1 2 3 4 5 6 7 8

Infiltration (cm h-1)

Time (t) (Sec)

14

10.4 8.5

7.4 6.4

3.9 3.6

14 14.2

13.6 10.4

7.6 5.1

4.3 14

6.2 4.5

3 1.9 1.7 1.5

02 46 108 1214 16

0 1 2 3 4 5 6 7 8

Time (t) (Sec)

Table 4. Infiltration rate of various land use

Time (t) (Sec)

Infiltration Rate (cm h^-1)

Secondary forest Agroforestry Moor

0.00 14 14 14

0.16 10.4 14.2 6.2

0.33 8.5 13.6 4.5

0.50 7.4 10.4 3

0.66 6.4 7.6 1.9

0.83 3.9 5.1 1.7

1.00 3.6 4.3 1.5

The infiltration rate in the secondary forest was categorized as rather fast (Figure 1). In contrast to and agroforestry, land has were included in the rather fast and fast criteria.categories, respectively. Vegetation in the secondary forest had a high number of species, but this isit was not the only thingfactor that can affect the rate of infiltration. Another thing that can affectaffected water inflow.

Furthermore, the infiltration rate is the soil's physical properties.

The bulk density of secondary forestin this land-use area was also greater than that of agroforestry, while the but it had a lower soil porosity of secondary forest was lower than that of agroforestry. According to. Hussain et al, (2020) reported that the increase in the number of cavities in the soil causes water to more easily infiltrate into the soil.led to a high infiltration rate

Figure 1. Infiltration rate in secondary forest land, agroforestry, and moor

SoilThe highest soil porosity of 49.15% was obtained in the agroforestry was the highest compared to secondary forest and moor which was 49.15%. As stated by. Ngadisi et al, (2020) revealed that the high porosity ofvalues in the soil will beare directly proportional to the infiltration rate.

In additionFurthermore, the vegetationvegetations on agroforestry lands withhave more than one type of plant with overlapping crowns, which can block the impact (kinetic energy) of falling rainwater (Delima et al., 2018), thus triggering a high chancethereby increasing the inflow of water being properly infiltrated into the soil. TheA low infiltration rate of 4.73 cmh^-1 was recorded on dry land includes the lowest infiltration of 4.72 cm h^-1 compared to agroforestry and secondary forest with , which were included in the fast and rather fast criteria (categories, respectively, as shown in Figure 2).. The activity or frequency of tillage in the moormoorland was higher, it causes the highestand this led to an increase in its bulk density to occur that also causes very low soil, as well as a decrease in the porosity.

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Vegetation and litter layers protect the soil surface from direct raindrops that can destroy soilits aggregates, resulting inand cause soil compaction andas well as blockage of soil pores which. The condition can also inhibit soil infiltration, resulting in athereby leading to soil erosion accompanied along with an increase in surface runoff increase (Darja et al, 2002; Masnang, 2014; Naharuddin et al, 2020).

The vegetationvegetations on the moor is slight, themoorland are few, and their roots are short so that, hence, they cannot absorb much a large amount of water. As stated by Delima et al., (2018) stated that low vegetation can provide open space making, and this increases the impact of rainwater high so that , as well as causes low water cannot be infiltrated properly and becomesabsorption, and excess runoff. Other factors that affect infiltrationInfiltration capacity areis also influenced by vegetation. Vegetation affects the size of infiltration (Tang et al, 2019), which affects the protection of the soil against erosion (Kaloper et al, 2020), eroded landand worsens the physical properties of the soil (Telak and Bogunovic, 2020). TheFurthermore, the amount of vegetation that exists in agroforestry, including candlenut and teak, results inled to the low density and high porosity so that water infiltration in the soil is highof the area.

4. CONCLUSION

The largesthighest infiltration rate of 12.83 cm h^-1 was found on obtained in the agroforestry land, which was 12.83 cm h^-1 included in the fast criteriacategory with a dusty clay texture. The second-largest infiltration rate was found inFurthermore, the secondary forest which was had the second-largest rate of 7.28 cm h^-1, which was included in the criteria rather quicklyfast category, with a dusty clay texture. The The moor land-use area with a loamy clay soil type had the lowest infiltration rate was found in the moor value of 4.72 cm72cm h^-1, and it was included in the medium criteria with a loamy clay texture. Infiltration category. Based on the results, infiltration heterogeneity is the most important factor, and it is mainly related tomajorly influenced by land use. Land use has a major impact on the characteristics of this infiltration, especially onin moor use.areas

ACKNOWLEDGEMENTS ACKNOWLEDGMENTS

The author would likeauthors are grateful to thank the Rector and, Chairman of Research Institutions, and Director of Postgraduate, Tadulako University for research funding this study through the grants flagship research scheme fiscal year 2021 DIPA

Tadulako University.

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Response by Authors to Reviewer’s Remarks/Comments

SOIL INFILTRATION IN VARIOUS AREAS AS A BASIS FOR DETERMINING LAND USE DIRECTION IN THE TOBOLI WATERSHED, CENTRAL SULAWESI, INDONESIA

Naharuddin Naharuddin^a*, Abdul Wahid^b, Golar Golar^c, Imran Rachman^d, Akhbar Akhbar^e, Sudirman Daeng Massiri^f

a,b,c,d,e,f Department of Forestry, Faculty of Forestry, Tadulako University, Palu-Central Sulawesi 94118, Indonesia * Corresponding author. Tel: +0621-81145202229, *Email:

nahar.pailing@gmail.com

The authors have summarized their replies to the Reviewers’ comments in this response letter in a two column format. A revised manuscript is submitted addressing all the comments to the Journal of Water conservation and management for possible publication.

No R 1 Comments Authors Response

1 The abstract must provide enough a brief overview of the paper. Here, the abstract is not telling what actually in the main text. Thus, it should be re-written and should be to the point. What the problem is, what you did to solve it and what the results are and why are important?

Thank you for the response, the abstract has been written to the point, tells what actually happened and at the end of the abstract the implications of the research findings have been explained

2 Related Literature is very poor and should be rewritten and improved. I can't see the related work section? Thus, please provide several solid literature reviews (discussion and argument).

Prefer to be updated with recent studies.

Thank you for the response, has been proofreaded by a native English speaker from the title to the References section

R 2 Comments Authors Response

1 The abstract should be written in the way of purpose, method, result and conclusion, and kept within 150 real words

Thank you for the response Repairs have been made

2 It is suggested that key words should be extracted from the important content of the article rather than some words in the title

Thank you for the response, fixed and added keywords according to the contents of the manuscript

3 The introduction of this paper analyzes the previous research needs, in order to put forward this point of view

Thank you for the response Repairs have been made

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4 In the experiment part, we need to explain the experiment environment, experiment index, experiment scheme and so on

Thank you for the response, has been fixed, especially in the Sample Collection and Method of Sampling section

5 The experiment is lack of data analysis.

Please supplement this part to ensure the credibility of the article

Thank you for the excellent response, several data analyzes have been added including Permeability, bulk density, Porosity

6 Please point out the direction of future research and the shortcomings of this study.

Thank you for the good response, it has been described in the introduction, there is also a conclusion as an implication of this researchof this research

The authors appreciate the valuable comments from the Reviewers.

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SOIL INFILTRATION IN VARIOUS AREAS AS A BASIS FOR DETERMINING LAND USE DIRECTION IN THE TOBOLI WATERSHED, CENTRAL SULAWESI, INDONESIA

Naharuddin Naharuddin^a*, Abdul Wahid^b, Golar Golar^c, Imran Rachman^d, Akhbar Akhbar^e, Sudirman Daeng Massiri^f

a,b,c,d,e,f Department of Forestry, Faculty of Forestry, Tadulako University, Palu-Central Sulawesi 94118, Indonesia * Corresponding author.

Tel: +0621-81145202229, *Email: nahar.pailing@gmail.com

ABSTRACT

The heterogeneity of infiltration has a strategic influence on the hydrological process in the watershed, and one of the factors affecting its rate and soil compaction is land use. Therefore, this study aims to compare infiltration rates in three land-use areas, namely secondary forest, agroforestry, and moor. A survey method was used, where field data observations were carried out at three locations. The infiltration rate measurement was performed using a double-ring infiltrometer with five repetitions at each sampling site. The results showed that the lowest value of 4.72 cm h^-1 was recorded on the moorland, while agroforestry had the highest of 12.87 cm h^-1. These findings indicate that land use has a significant role in changing soil physical properties and compaction, hence, sustainable soil and water conservation strategies are needed.

Keywords:

Land use, soil infiltration, watershed management. Secondary forest, agroforestry, moor 1. INTRODUCTION

Land conversion in several watersheds has become a serious problem, because it causes a disturbance in the hydrological cycle, such as land damage and infiltration rate reduction due to soil compaction (Wang et al, 2018; Peña-Arancibia et al, 2019; Purba et al, 2020; E. Al- Esawi et al, 2021). Watershed is a basic concept in hydrology, and one of its integral parts is the rate of water inflow into the soil.

Furthermore, it is the basis for understanding hydrological processes while planning and managing water resources. An understanding of these processes and groundwater quality is very important to maintain watershed health (Flotemersch et al, 2016; Aryafar, 2017), through rainwater management, infiltration processes, surface runoff, as well as groundwater and soil erosion (Bhardwaj, 2019).

Infiltration is one of the main components of the hydrological cycle (Khalid et al, 2017), as well as an important variable for predicting various soil processes (Yimer et al, 2008; Tesemma et al, 2015; Devia et al, 2015; Chyba et al, 2017). In watershed managemen t, flood and erosion predictions depend on runoffs (Naharuddin et al, 2021), which is directly affected by the rate of water inflow (Yan et al, 2015).

Furthermore, infiltration has a strategic role in watershed ecosystem because it determines the amount of runoff and rainfall that can penetrate the soil. Furthermore, increasing its value helps to infiltrate rainwater into the soil, and this serves as groundwater reserves during the dry season (Fauzan and Rusli, 2018). Infiltration quantification is also needed to determine water availability for plant growth, development (Fischer et al., 2015; Basche and DeLonge, 2019), irrigation, and other domestic household purposes (Al-Ismaili et al, 2017).

Land use that does not follow soil and water conservation principles, such as soil compaction can affect infiltration rate (Návar and Synnott, 2000). The grazing of livestock in pastures has the potential effect of reducing the inflow of water due to disturbances in soil and plant cover. Pressure on forests as well as non-regulation of conservation efforts can remove shrubs, herbs, trees, and grasses, as well as reduce above-ground organic matter, which are parameters for infiltration and minimizing surface runoff.

Land-use change and rainfall are often considered the main factor affecting soil infiltration (Sun et al, 2018; Aliramayee et al, 2019).

However, the difference in the capacity for several types of land use is not widely known, especially in secondary forests, agroforestry, and moor. Forest conversion is often accompanied by changes in soil structure due to the use of tillage systems that do not follow conservation principles. This causes compaction of the soil surface, thereby leading to a decrease in the infiltration capacity and water content (Owuor et al, 2018).

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Infiltration is a very important hydrological parameter, and it marks the transition of fast-moving surface water to slow-moving groundwater. Several studies have also explored its rate in various land use areas, such as the impact of land use on increasing soil infiltration capacity using meta-analysis (Sun et al, 2018), infiltration capacity model (Hamman et al, 2018), the effect of soil moisture and plant roots on soil infiltration capacity (Liu et al, 2019; Liu et al, 2020), assessment of infiltration capacity based on the spatial distribution for evaluation of storm runoff in forest catchments (Miyata et al, 2019), and variation of soil infiltration capacity after vegetation restoration (Tang et al, 2019). However, none of these studies have compared the rates in various land use areas.

In the tropical area, especially Central Sulawesi, there are dynamic changes in land use from primary to secondary forest land, agroforestry, and other forms. There are also no studies on the infiltration rate in these various areas. Therefore, this study aims to determine and compare the infiltration rate in secondary forests, agroforestry, and moor as a basis for directing land use management to preserve the hydrological function of watersheds.

2. MATERIALS AND METHODS 2.1 Study area

This study was carried out from January to August 2021 in the Toboli watershed, Central Sulawesi, Indonesia. However, the supporting data retrieval study was conducted in 2020, in the production Forest Management Unit (FMU) Model Dolago Tanggunung, Trans Sulawesi Poros Road, Coffee Plantation, Pangi Binangga Nature Reserve Conservation Area, Central Sulawesi. This study area is geographically located at 0⁰43'39” S and 119⁰59'17” E with an altitude of 165 m above sea level. Although it is a conservation area, there are still land conversions from primary forest to secondary forest, agroforestry, and moor. This is due to road construction (Trans Sulawesi) from Palu, the capital of Central Sulawesi province to other areas, such as North Sulawesi and Gorontalo. Analysis of soil physical properties was carried out at the Soil Science Laboratory of the Faculty of Agriculture as well as the Forestry Laboratory of the Faculty of Forestry, Tadulako University.

2.2 Sample Collection and Method of Sampling

This study used a survey method, where field observations were carried out at 3 locations, namely secondary forest, agroforestry, and moor. The infiltration rate measurement was performed using a double-ring infiltrometer with 5 repetitions at each location, and the data obtained were calculated using the Horton method. Subsequently, soil samples were collected and analyzed in the laboratory.

Sampling was carried out using the undisturbed and disturbed soil sample method with a depth of 0-40 cm and 40-60 cm, respectively.

The depth used is related to the infiltration capacity of the area (Wang et al, 2015)

The soil physical properties, such as soil texture, organic matter, bulk density, porosity, and permeability were analyzed using various methods, as shown in Table 1 (Arthur et al, 2013; Worku and Bedadi, 2016).

Table 1. Variable observation of soil physical properties and analysis method

Observational variables Method of analysis

soil texture pipette

organic matter walkeley and black say

bulk density gravimetric

porosity gravimetric

permeability constant head permeameter

2.3 Data analysis

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Permeability;This is the ability of the soil to carry water or air, and it is often measured in terms of the water flow rate through the soil with time (cm h^-1). Furthermore, it was analyzed using the equation below:

K ( ) (1)

Description:

K: permeability (cm h^-1)

Q: the amount of water flowing per measurement (ml) t: measurement time (hours)

L: thickness of soil (cm) H: Head ring height (cm) A: ground surface area(cm²)

Bulk density (BD); bulk density was determined based on the equation below:

(2)

Description:

V: value of ring volume (cm³)

Porosity; porosity was determined based on the equation below:

x 100%) (3)

Soil infiltration; The rate was analyzed using the Horton method, which is a time-dependent technique (Abdulkadir et al, 2011; Beven, 2021; Kim et al, 2021).

F(t) = fc + (f0 – fc) e ^–kt (4)

Description:

f(t): infiltration rate at t- time (cm h^-1) fc: constant infiltration rate (cm h^-1 sec^-1) f0: initial infiltration rate (cm ^h-1 sec^-1) e: exponential number (2.718) k: constant (-1/(m log 2. 718) t : time (sec^-1)

To obtain k value, the Horton infiltration equation was derived.

f = fc + (f0 – fc) e –kt (5)

f – fc = (f0 – fc) e ^–kt (6)

Right and left side algorithmed log (f – fc) = log (f0 – fc) – kt log e log (f – fc) – log (f0 – fc) = - kt log e

t ( ) 𝑙𝑜𝑔 ( 0 – ) 𝑘𝑡 𝑙𝑜𝑔 (7)

t (

) 𝑙𝑜𝑔 ( – ) (

) 𝑙𝑜𝑔 ( – ) (8)

Change to equation:

𝑦 𝑚𝑥 𝑦 𝑡 m

x = log (f – fc)

𝑙𝑜𝑔 ( 0 – ) (9)

So the k value is the equation 𝑘

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The value of m is the gradient of the graph between the actual infiltration f and log ( – )

Classification of the rate was carried out based on the instructions of Soil Conservation Services, as shown in Table 2 (Jury and Horton, 2004).

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Table 2. Classification of Infiltration Rate

Criteria Infiltration rate (cm h^-1)

Very fast >25.4

Fast 12.7 – 25.4

Rather fast 6,3 – 12.7

Fairly fast 2 – 6.3

Rather slow 0.5 – 2

Slow 0.1 – 0.5

Very slow < 0.1

Source: Asdak, 2018

3. RESULT AND DISCUSSION 3.1 Physical Characteristics of Soil

Soil physical properties are related to its shape or conditions, such as texture, structure, bulk density, organic matter, porosity, and permeability. Furthermore, they have a role in plant root activity, including nutrient, water, and oxygen absorption as well as constraint of root movement (Hu et al, 2018). The soil physical properties in the 3 land-use areas are presented in Table 3 below.

Table 3. Physical properties of Soil

Soil physical properties Land-use Unit

Soil texture 32.1 29.1 27.6 % sandy

60.3 52.1 42.2 % dusty

7.6 18.8 30.2 % clay

Texture class Dusty Clay Dusty Clay Loamy clay -

Bulk density 1.14 1.22 1.75 g/cm³

Organic matter 2.72 6.35 1.28 %

Porosity 46.17 49.15 28.26 %

Permeability 27.48 12.75 9.83 cm h^-1

Table 3 shows that secondary forest and agroforestry land use areas have a dusty clay texture, while moorland has a loamy clay, which influenced their infiltration rates. A soil with fine texture has more dense pores than coarse or sandy soil, and this factor greatly affects the speed of water penetration.

The bulk density on the secondary forest, agroforestry, and moor land use areas were 1.14 g/cm³, 1.22 g/cm³, and 1.75 g/cm³, respectively. The existence of repeated pressure on land causes soil compaction, which leads to an increase in the density. This finding is in line with Shah et al, (2017) that compaction is an important problem because it is related to soil quality for crops, agricultural production, and infiltration rates.

Furthermore, low to medium bulk density is influenced by dusty and sandy textures, which causes an increase in the number of pores.

The occurrence of soil compaction increases the value, and this leads to a slow infiltration rate (Irmak et al, 2018). This is consistent with Franza et al, (2019) that the higher the density, the lower the porosity.

The analysis results showed that the secondary forests, agroforestry, and moor contain 2.72%, 6.35%, and 1.28% organic matter respectively, as shown in Table 3. Chaudhari et al, (2013) stated that an increase in soil organic matter led to a decrease in bulk density as well as an increase in porosity. This condition is advantageous because it causes an increase in the infiltration speed.

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14

10.4 8.5

7.4 6.4

3.9 3.6

14 14.2

13.6 10.4

7.6 5.1

4.3 14

6.2 4.5

3 1.9 1.7 1.5

02 46 108 1214 16

0 1 2 3 4 5 6 7 8

Time (t) (Sec)

The secondary forest had a porosity of 46.17%, while 49.15% and 28.26% were recorded in the agroforestry and moor, respectively. The highest value was obtained in the agroforestry land use, which indicates that water can enter the soil faster. Fu et al, (2019) reported that the more porous a soil is, the higher its infiltration rate. Gopal et al, (2019) also revealed that low porosity reduced the rate of water flow.

Permeability is the ability of the soil to pass water to the lower layers of its profile. Table 2 revealed that highest value of 27.48 cm h^-1 was recorded in the secondary forest, followed by agroforestry and moor with 12.75 cm h^-1 and 9.83 cm h^-1, respectively. Soil structure and texture play a very significant important role in the high permeability of the soil, which causes an increase in the rate of infiltration.

An increased inflow of water into the soil reduces surface runoff as well as erosion.

3.2 Infiltration Rates in Various Land Use

Infiltration is defined as the percolation of water through the soil, and it is an important parameter in hydrological modeling, such as surface runoff, as well as watershed and irrigation management (Singh et al, 2017). Furthermore, the infiltration rate is the amount of water per unit time that enters the soil surface, and low values are obtained when the it is in a dry state. The results showed that there were differences in the rates of the three land use areas, as shown in Table 4.

Table 4. Infiltration rate of various land use

Time (t)

(Sec)

Infiltration Rate (cm h^-1)

Secondary forest Agroforestry Moor

0.00 14 14 14

0.16 10.4 14.2 6.2

0.33 8.5 13.6 4.5

0.50 7.4 10.4 3

0.66 6.4 7.6 1.9

0.83 3.9 5.1 1.7

1.00 3.6 4.3 1.5

The infiltration rate in the secondary forest and agroforestry were included in the rather fast and fast categories, respectively. Vegetation in the secondary forest had a high number of species, but it was not the only factor that affected water inflow.

Furthermore, the bulk density in this land-use area was also greater than that of agroforestry, but it had a lower soil porosity. Hussain et al, (2020) reported that the increase in the number of cavities in the soil led to a high infiltration rate