LAND DEGRADATION EVALUATION IN MEDAN CITY, NORTH SUMATRA PROVINCE, INDONESIA

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Land Degradation Evaluation in Medan City North Sumatra Indonesia by: Rauf and Rahmawaty| 1

LAND DEGRADATION EVALUATION IN MEDAN CITY, NORTH

SUMATRA PROVINCE, INDONESIA

ABDUL RAUF1*_{AND RAHMAWATY} 2

1_{Agroecotechnology Study Program, Faculty of Agriculture, University of Sumatera Utara, Jl.}

A.Sofyan No. 3 Kampus USU, Medan 20155, Indonesia email: arauf17@yahoo.co.id

2_{Forestry Study Program,Faculty of Agriculture, University of Sumatera Utara, Jl. Tri Dharma Ujung}

No. 1 Kampus USU, Medan 20155, Indonesia email: rahmawaty1974@yahoo.com

*Corresponding author

ABSTRACT

As the capital city of North Sumatra Province, Medan’s dense population and settlements as well as its flourishingindustrial and trading activities are significantly contributing to rapid land degradation. This study was aimed to evaluate the land characteristics and uses , analyze the main causes of land degradation, and explore efforts in preventingland degradation in Medan City. Conducted in June to October 2014, the study coveredresidential, industrial, and commercial areasas well as the areas for food crops, horticulture, permanent vegetated lands (parks, green open spaces, mangrove forests and urban forests). Survey method was used to collect primary data and soil samples by purposive sampling. From each type of land use, at least three observed points were taken as a minimum of 30 sample points. The results showed that the rate of erosion on dry land in the area ranged from 1.86 to 29.06 tons/ha/yr.The critical area of 5.15 ha (0.02%) while the potential critical of 21219.35 ha (74.99%) and the moderate critical area of 7,071 ha (24.99% of the total land area of Medan). These findings provided options to maintain the quality of land in Medan City, such asproper land use according to land characteristics and capability, increasing the of number of trees, prevention of pollution, both by domestic sewage and industrial waste through the application of environmentally friendly technologies, maintaining mangrove forests andland utilization balance between the interests of technical civil (building) and aspects of vegetative (green open space). In order to mitigate climate change in Medan City, it is important to evaluate land degradation as one of the efforts of climate change mitigation.

Keywords: Climate change, environmental, Medan City, mitigation, prevention

INTRODUCTION

Medan city, the capital of North Sumatra province, has an area reaching 26,510 hectares (265.10 km2_{), or 3.6% of the total area of the province. A large part of the City is}

in the lower reaches of the Deli watershed, a small portion is in the lower reaches of the Belawanwatershed (West) and in the downstream Percutwatershed (eastern). Medan city has 21 sub-districts and 151 villages with a large population of 2,109,339 people million. Being in the downstream of Deli Percut and BelawanWatersheds which have dense population and settlements, as well as high and diverse economic activities (mainly industry and trade), environmental degradation is inevitable particularly in the form of pollution, land compaction, and inundation. Such environmental degradation affects the capacity of the soil for better production and health status of the public.

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decline in soil structure that leads to hardening / compaction, erosion, desertification, anaerobisme, and environmental pollution. Significant chemical degradation includes acidification, washing, salinization, decreased cation capacity, and decreased fertility. Biological processes including the reduction of total biomass carbon, and soil biodiversity decline.

Based on the explanation above, this study was thus conducted to determine the rate of land degradation, extent of damage that occurred, underlying causes of the damage, and the needed efforts to prevent further environmental damage in Medan city.

MATERIALS AND METHODS

This study was conducted in June to October 2014 on various types of land use, such as residential, industrial, and commercial area and the area for food crops, horticulture, permanent vegetated lands (parks, green open spaces, mangrove forests and urban forest). The study used the survey method in collecting field data and soil sampling was done purposively. The methods of analysis of soil samples for each parameter followed the Government Regulation No. 150 of 2000 on Damage Criteria Raw Land for Biomass Production (PP No. 150 of 2000).

RESULTS AND DISCUSSION

Depth of Solum

One of the criteria for a level of degraded land, especially in dry land can be viewed from the thickness / depth of solumsoil .The soil is considered good l when the depth / thickness of solum can meet the needs of plants for nutrients and the plant’s root system is able to establish medium optimal anchorage. The depths of solumobserved for each soil sample locationin Medan are presented in Table 1. From this Table, it can be seen that Medan City has dry lands and wetlands which are located at an elevation (altitude) ranging from 2 to 67 meters above sea level. Most common uses for dry lands includeforest, tree plantation (e.g., coconuts) and garden / forest parks.

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Table 1. The geographical position, elevation, land use type, spatial regions and depth of solum soil sample sites on dry land Medan

No. Sampel Code

Coordinate (LAT)

Coordinate

(LONG) Village Sub DIstrict Land Cover

Elevasi

4 D07 3.52292 98.60843 KemenanganT

ani

Medan

Tuntungan Hutan 52 45

5 D08 3.51860 98.66699 Gedung Johor Medan Johor Hutan 44 40

6 D10 3.53558 98.60569 TanjungSelam

at

10 D17 3.68848 98.63600 Terjun Medan Marelan SawidanKan

gkung 6 45

16 D29 3.55585 98.68313 KampungBaru Medan Maimun

Taman

25 D39 3.62174 98.66562 KarangBeromb

ak Medan Barat Ubi kayu 18 48

26 D40 3.60089 98.65898 SeiPutih

Tengah Medan Petisah Ubi kayu 22 40

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of the sample points are observed at a depth relatively shallow solum. The facts above show that although the lands in Medan no one has entered the category below the critical threshold based PP. No. 150 (2000), but the distribution of land belonging to the superficial criteria of reaching 81% of the sample locations are spread from upstream to downstream and categories were only 19%, while classified in the category (> 90 cm) no (0%) then the tendency to Further degradation reaches a critical threshold is likely to occur.

Setbacks soil depth in Medan can occur as a result of intensive erosion, especially in the upper reaches of Medan as in the district of Medan and Medan Johor Tuntungan up to the middle of the city of Medan as in MedanAmplas, Medan Selayang, Sunggal and Medan Helvetia Sub-Sistrict. While the decline of soil depth in the lower reaches of the city of Medan may occur mainly caused by compaction (compection) due to the intensity of human activity is very high as well can be caused by erosion.

Shallow Groundwater Depth

Shallow ground water is underground water (ground water or water table) that can be close to or above the soil surface. Shallow ground water appeared in regions or landscapes basin which is then referred to as wetlands. Wetland itself is defined as land that is the source of water comes from ground water (ground water) that the landscape may be in the rice fields, marshes, ponds, lakes or reservoirs, so that water could inundate or close to the ground throughout the season. While the land is the source of water comes from rainfall (only inundated during the rainy season) and the water becomes very deep soil of> 90 cm during the dry season the land belonging to the dry land.

Shallow depth of ground water in wetlands in Medan ranged between 0-6 cm. The range of the depth of shallow ground water is not entering into the critical threshold criteria based Damage Criteria Raw Land for Biomass Production (Indonesian Government Regulation No. 150 of 2000) due to the depth of the shallow ground water is still smaller (shallower) than 25 cm.

Distributions of shallow groundwater depth in Medan are evenly from the upstream area, central to the downstream area of the city of Medan. The existence region with a depth of groundwater largely (9 locations in the sample) in a state of stagnant (0 cm) and just 5 sample points that are below ground level but does not exceed 6 cm describe in the area of Medan there are potential sites for development as land the production of food crops (paddy rice), vegetables (spinach), pool/pond fish and water-based tourist areas , in addition to the development of mangrove forests, particularly in the downstream is in the district of Medan Belawan and Medan Labuhan .

Composition Fraction Land

The composition of the soil fraction is the most permanent and important characteristics of the soil in biomass production systems (agriculture, fisheries and forestry) (Arsyad, 1979; Djaenuddin, 1994). Soil mineral particles size varies from coarse diameter of more than 2 mm until very smooth with a size of less than 2 lm. Soil particles are grouped based on the size of the particles into the rock (gravel) with a diameter of> 2 mm, sand (diameter 0.05 to 2 mm), dust (diameter (.05 to .002 mm), and clay (diameter <0.002 mm). Composition fractions of land that can only be obtained through the analysis of soil samples in labooratorium using these Hydrometer methods will then determine the type of soil texture.

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on the clay content of the sample, there are about 14 points (53.85%) on dry land clay containing <18% were classified into critical thresholds based on PP. No. 150 of 2000 on Damage Criteria Raw Land for Biomass Production.

The existence of soil clay fraction consisting of clay minerals and oxides amorphous silicates are very important because the role of the clay fraction is the active ingredient making up the ground and determine the nature and capabilities in the provision of land and plant nutrient exchange. While the sand fraction and dust are largely composed of SiO2 is not much role in supplying plant nutrients, and even the presence of

excess soil fraction (> 80%) describe land degradation in the form of desertification.

Sandy soil, namely the soil with sand content of> 70% causes the soil porosity to be low because most of the large-sized pore space (macro) so that good soil aeration, water conductivity fast, but the ability of soil to retain water and keep nutrients low. Excellence sand soil easily processed so as so-called soft ground.

Land with very high levels of clay fraction (> 45%) is also not good. This soil is relatively high porosity, but is mostly a small-sized pore (micro), so permeability is low and air circulation is less smooth. Clayey soil's ability to store water and nutrients are high, but the water is bound by clay strong enough, so it was difficult absorbed by plants when dry. The clay also called heavy soils because it is difficult processed.

Argillaceous soil is a land with a proportion of sand, silt, and clay such that its located between sandy and clayey soil. Such land has aeration or air and water system is quite good, the ability to store and provide water for crops is high, and the most optimum soil for plant growth. Thus, based on Table 6 it can be seen that the lands in the city of Medan that is almost entirely memili argillaceous texture (only in two locations textured clayey), so it can be said that the lands in the city of Medan has a good soil fertility levels for biomass production ,

Weight Fill Land

Soil bulk density (ρb) or bulk density is the ratio between the total mass of land in the dry state with a volume oven undisturbed soil (soil lumps), provides an overview of the level of friability / soil density. Soil friability level is inversely proportional to the value of soil bulk density. Land with a large bulk density values describe the soil denser than the soil that has a bulk density value is smaller. In other words, the greater the value of the unit weight of the soil, the soil is getting solid and conversely the smaller the value of soil bulk density, soil more friable.

The location of the soil samples dry land in the city of Medan that the value of the unit weight of the soil into the critical threshold that is greater than 1.40 g / cm3 (according to the PP. No. 150 of 2000 on Damage Criteria Raw Land For Biomass Production) there are only The four locations, as can be seen in Table 2.

Soil Porosity

Porosity (η), which is the proportion of the total pore space contained in the unit volume of soil or the ratio of pore space to the total volume of soil is a condition of drainage and soil aeration. This pore space can be occupied by water and soil air. Soil nests (porous) means having adequate soil pore space for air and water movement into and out of the matrix / body ground freely.

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to withstand higher water, but the strength of adsorption clay and high water can inhibit the absorption of water by plants. This means land with total soil pores (pororsitas) land that is too high (> 70%) and too low (<30%) are equally poorly and are at a critical threshold by PP. No. 150 of 2000 on Damage Criteria Raw Land For Biomass Production. soil porosity value of all the locations of soil samples on dry land Medan no entry / belonging to the critical threshold according to the PP. No. 150 of 2000, due to the porosity values in the range of> 30% and <70%.

The Degree of Release of Water (Permeability) Land

The degree of release of water or soil permeability that describes the amount of water per unit of time that goes through the surface and move in the soil (cm / h) is an important indicator in conjunction with the ground water system. The dominant soil contains clay fractions will be slower to pass water in the soil mass than the dominant soil containing sand fraction. Soil with a high clay content of the dominant faction have micro pores that are less porous, which in turn would be difficult to pass water, otherwise the soil with a high content of sand fraction will easily pass the water because it has a macro pores that much.

Soil permeability is too large (> 8.0 cm / hour) with the same lack of good permeability of the soil that is too small (<0.7 cm / hour) and this limit is by PP. No. 150 of 2000 as land critical threshold in terms of the degree of release of water (permeability) soil. only one soil sample point location that has the degree of release of water (permeability) that fall within the critical threshold in Medan, namely in Sub Acid Beetle district of Medan Selayang with a permeability value of 8.52. The soil permeability values exceed the criteria (> 8.0 cm / hour) as the critical threshold based PP. No. 150 of 2000 on Damage Criteria Standard Quality Land for Biomass Production.

Electrical Conductivity (EC)

Parameter electric conductivity (EC) is an indicator for lands that have high levels of dissolved salts. Naturally, soils with high levels of dissolved salts like this a lot happening in the climate of the area is very dry (arid), lands in coastal areas that are affected seawater (salt water), and can also occur due to accumulation of salts due irrigation water.

In the arid regions of dissolved salts in the subsoil can be transported to the soil surface due to evaporation are very strong. The type of soil that is formed here is saline soils, saline-sodic and sodic by varying the amount of content and comparison of types of salts.There are 7 locations of sample points that have a value that goes beyond DHL threshold specified in the PP. No. 150 of 2000 on Damage Criteria Raw Land for Biomass Production amounted to more than 4.0 mS / cm. While the value of the land DHL wetlands in Medan which exceeded the critical threshold reached 8 locations of sample points from 14 sample points wetlands locations were observed.

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Facts on the ground indicate that many rice water coming from irrigation channels, which constitute a drainage ditch from residential areas (water is black and foul smelling) and some dry land used for the cultivation of dry land farming also has / drainage ditch alongside the people who advance shallow drainage water.

DHL high at locations downstream of the sample can be ascertained due to the runoff of the tide as it happened in the sub-district of Medan Belawan and Medan Labuhan Sub-district.

Acidity (pH) Soil

Soil acidity expressed with soil pH can be used as an indicator of fertility and degradation of soil chemistry, because it can reflect the availability of nutrients in the soil and cause poisoning micro elements and heavy metals for cultivated plants. In addition to greatly affect the availability of inorganic nutrients, low pH also affects the activity of soil microorganisms to decompose organic matter soil. pH value on all soil samples dry land in Medan no classified into critical threshold as defined in the PP. No. 150 of 2000 on Criteria Raw Biomass Production Damage To Soil with a pH ranging between <4.5 and> 8.5. Some factors that may affect the value of soil acidity in both the area of Medan them by base saturation, colloidal properties of soil, and the kinds of cations are adsorbed on soil colloids. As described earlier that DHL relatively high ground in soils existing with high salt solubility allows the pH value of the soil also be high due to the high solubility of the salt.

Number of Soil Microbes

Microbes (microorganisms) soil plays an important role in the dynamics of reactions in the soil and in support of the availability of nutrients and organic matter recycling (Alexander, 1977). The main roles of the microbes are as decomposers of organic matter and leaching of nutrients from the mineral soil. Thus, the presences of microorganisms in the soil become an important indicator of the quality of the soil. the amount of soil microbes in the dry land Medan no one is under the critical threshold, even much higher than the critical threshold limits as defined in the PP. Number: 150 2000 Raw Damage Criteria neighbor Land For Biomass Production of <102 cfu / g soil. The same thing happens on the ground wetland in the city of Medan. Although no one goes into the categories below a critical threshold, but there is a tendency that the lands are polluted by domestic waste or industrial waste, both on dry land and in wetlands, has a number of microbes that is smaller than the ground or slightly polluted.

Soil Erosion

The computation of soil erosion in dry land Medan using USLE get that value the highest erosion only 29.066 ton/ ha/year and the value that can be tolerated erosion (erosion is allowed) ranged from 8.688 to 19.345 ton / ha / year. Thus the rate of erosion on dry land in the city of Medan is low to moderate.

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the soil and water conservation, especially land use that does not comply with the conditions and ability to land the potential area this critical time will turn into critical areas.

Some things need to be done in maintaining the soil and land in the city of Medan in order not degraded or being critical is the way to use the land according to their ability and spatial established, multiply the tree stands, both in areas specifically designated for it, such as parks and forests the city, as well as in residential areas and along the river-banks, as well as pollution control domestic waste and industrial waste. In the coastal land (department tidal) retained important mangrove forests that sea water intrusion into inland regions can be prevented.

CONCLUSIONS

Soil properties in Medan that do not fall within the critical threshold according to the PP. No. 150 of 2000 include depth of the soil solum (on dry land), depth of the shallow ground water (wetlands), percentage of sand fraction (on dry land and wetlands), soil porosity (on dry land ), and number of microbes (on dry land and wetlands).

The rate of erosion on dry land in Medan City was low to moderate (i.e., 1.86 to 29.06 ton/ha/year) such that the critical area covers of 5.15 ha ( 0.02 % ); not critical consists of 21219.35 ha ( 74.99 % ); and the somewhat critical area comprises of 7,071 hectares ( 24.99 %) of the total land area of Medan .

REFERENCES

Alexander, M.1977. Introduction to Soil Microbiology. John Wiley & Sons. New York.

Arsyad, S. 1979. Soil Conservation (Konservasi Tanah). Faculty of Agriculture, Bogor Agricultural University. Bogor.

Djaenuddin, dkk. 1994. Kesesuaian Lahan untuk Tanaman Pertanian dan Tanaman Kehutanan (Land Suitability for Crop Agriculture and Forestry Plant). Technical Reports 7 version 1.0 Centre for Soil and Agroclimate Research. Bogor.

Djaenuddin, et al. 1994. Land Suitability for Crop Agriculture and Forestry Plant. Technical Reports 7 version 1.0 Centre for Soil and Agroclimate Research. Bogor.

Foth, H.D. 1984. Fundamentals of Soil Science. (Translation). GadjahMada University Press. Yogyakarta.

Hardjowigeno, S., dan S. Sukmana. 1995. Menentukan Tingkat Bahaya Erosi (Determining Erosion Hazard Level). Centre For SoilandAgroclimate Research. Bogor.