Soil Conservation Instructions Against Environmental Damage Due to Erosion Rates in the Krueng Seulimeum Sub-watershed

Soil is an important natural resource for ecosystems because it provides habitat for humans, animals, and plants. Soil erosion is strongly influenced by a region's geological conditions, such as the slope and length of the land, the type of rock and sediment, the permeability of the land, vegetation, climate, and the activities of living things. The aims of this research were to assess the degree of erosion risk in the Krueng Seulimuem Sub-watershed and the Krueng Aceh Watershed, as well as the environmental consequences of the damage. Direct observations at the research site and soil sample analysis were used to conduct the investigation. The erosion was estimated using the USLE (Universal Soil Loss Equation). The effects of slope length and steepness factors, program management aspects, and conservation methods, as well as a variety of other research criteria, were assessed. It was carried out in three stages: (1) secondary data processing and map preparation; (2) analysis of the research site; and (3) soil analysis and data evaluation. According to the results of the soil type, slope, and land use overlay map, the research site had nine land mapping units (LMU) covering a total area of 26,497.07 hectares. The largest potential erosion was at LMU 9, with 2,857.72 tons ha -1 yr -1 , while the largest actual erosion occurred at LMU 8, with 254.06 tons ha -1 yr -1 . There were three degrees of erosion risk: low, moderate, and very high. The low level was present in LMU 1, 2, 4, 5, 6, 7, 8, and 9. The moderate level was present in LMU 1, 2, 3, and 6. LMU 2 was present to the very high-level index. The recommended strategy for soil conservation was reforestation of protected areas at LMU 4 and 8. Conservation methods may be used in agricultural fields at LMU 1, 2, 3, 5, 6, 7, and 9


INTRODUCTION
An essential natural resource for ecosystems is soil.(Singer & Warkentin, 1996) and is a major provider of habitat for humans, animals and plants.Soil erosion could indeed occur when the rate of erosion greater than the rate of formation.If future sediment management plans are not taken into consideration, the risk of soil erosion in catchments connected by high hydrosurfaces would increase.(Borrelli et al., 2020) One of the most significant types of soil degradation, soil erosion, creates environmental issues in many places of the world (Luetzenburg et al., 2020).The movement and transportation of soil through diverse mechanisms, such as water, wind, and mass movement, is known as soil erosion (Tarr et al., 2005).Soil erosion is the loss of the topsoil layer caused by either water or wind movement.In addition to soil productivity and soil carrying capacity being reduced, environmental quality can be negatively impacted by this erosion process.The surface of the earth's crust will always experience an erosion process.Erosion will take place in some areas, while accumulation will take place in other areas.Therefore, its shape will always change from time to time.This event occurs naturally and takes place slowly so that the effects only appear after tens or even hundreds of years later (Asdak et al., 1998).
Generally speaking, there are four types of soil erosion: water, wind, gravity, and soil erosion.Nevertheless, water is responsible for 50% of all global soil erosion (Blanco-Canqui & Lal, 2008).Water, precipitation, and runoff all contribute to water erosion by releasing, moving, and depositing soil and other primary materials (Foster et al., n.d.).Many elements, such as rainfall and intensity, land use, vegetation cover, soil characteristics, slope, and slope angle, among others, have an impact on soil erosion.
Climate change, changes in land use, regional differences, and soil characteristics are only a few of the causes of water erosion (Wu et al., 2018).The most important factors among others include climate change and land use (Panagos et al., 2015).
Erosion destroys a fertile layer of soil that is beneficial to plant growth and reduces the soil's ability to absorb and hold water.The transported soil will be carried to water sources (sediments) and will be deposited in places where the water flow slows down in rivers, reservoirs, lakes, reservoirs, irrigation canals, above agriculture, and so on.Thus, damage due to erosion occurs in two places, namely on the soil where erosion occurs, and on the final destination of the deposited haulage (Noeralam et al., 2003).
Aceh Province has 316,637 ha of critical land, which is classified as very critical level of 190,399 ha and critical level of 126,238 ha (BPS Aceh Province, 2019).Aceh Besar District has a critical land area of 5,914 ha and a slightly critical area of 24,193 ha (BPS Aceh Besar, 2019).There are five categories of land criticality level and its area based on the Krueng Seulimeum sub-watershed, namely very critical land covering an area of 647.01 ha (2.44%), critical land covering an area of 11,782.32ha (44.27), slightly critical land covering an area of 4,560.36ha (17.21%), potential critical land area of 7,184.22 (27.11%), and non-critical land area of 2,323.17ha (8.77%) of the total area of Krueng Seulimeum Sub-watershed 26,497.08 ha (BPDAS Krueng Aceh, 2019).
A watershed is a land area that is topographically bounded by mountains that accommodate and store rainwater to then be channeled to the sea through the main river.The land area is known as a water catchment area (DTA), and it is an ecosystem with natural resources (soil, water, and plants) and human resources as users of natural resources (Asdak et al., 1998).
Aceh Province has 15 watersheds, which include Krueng Aceh.This catchment area is 207,496 ha and is located in two administrative areas, namely Banda Aceh City and Aceh Besar District (BPDAS Krueng Aceh, 2009).The Krueng Aceh watershed has several watersheds, one of which is the Krueng Seulimuem watershed.Geographically, Krueng Seulimuem District is located between 5º15' -5º30' North Latitude and 95º30' -95º45' East Longitude.The Krueng Seulimuem sub-watershed covers approximately 26,497.08 ha (BPDAS Krueng Aceh, 2009).The Krueng Seulimeum sub-watershed covers an area of 26,494.07ha with a critical area of 11,782.32ha (44.27%).It is critical to investigate the environmental damage caused by erosion in the Krueng Seulimuem watershed because there has been little research done in the area so far, and it is currently lacking.

MATERIALS AND METHODS
This research was carried out in the Krueng Seulimeum Sub-watershed, Seulimum Sub-district, Lembah Seulawah Sub-district, Jantho Sub-district, Aceh Besar District.Furthermore, the soil analysis was carried out at the Laboratory of Soil Physics and Environment and Laboratory of Soil Chemistry, Faculty of Agriculture, Universitas Syiah Kuala.Research site of this study can be seen in Figure 1.The research took place from September to November 2021.

Rainfall Erosivity Factor (R)
Rainfall erosivity was the rain potential to erode the soil (Wischmeier & Smith, 1978).If there was no maximum daily rainfall data in the month where the erosivity would be calculated and only monthly rainfall data that was available, then the Lenvain formula (Asdak et al., 1998)  The calculation results show that the value of the rainfall erosivity index for one year at the research site is 799.48 cm yr -1 .Because the speed and distribution of raindrops are the main factors that cause soil particles to peel off from soil aggregates, high rainfall is the cause of erosion, so it can be said that rainfall is a determinant of the amount of soil erosion (Asdak & Supian, 2018).

Soil Erodibility Factor
Erodibility was the sensitivity of the soil to erosion (Hudson, 2015).The value of K was determined by the texture, structure, permeability, and organic matter of the soil.Determination of the value of K (Table 1) could be done using Wischmeier & Mannering's formula (1978) as follows:

RESULTS AND DISCUSSION Type of soil
The type of soil found in the research site was based on the type of soil sourced from the Watershed Management Center of Krueng Aceh's soil type map (2019) and the results of a soil survey in the field.Soil type map can be seen in Figure 2.

Figure 2. Soil type map
The figure 2 shows that the research location is dominated by Entisol soil type which is 47.92% of the total area.This type of soil is a type of soil that is very sensitive to the risk of erosion, because it has a shallow soil layer with a texture of dust and sand that is easily carried away by surface runoff.Andisols are fertile soils, but their P absorption rate is high because most of them consist of amorphous minerals such as allophane, imogolite, ferrihydrite and hydrated oxides of Al and Fe with a relatively large specific surface (Uehara & Gillman, 1981).Inceptisols are immature soils, their profile development is weaker than that of mature soils, but still has characteristics similar to the parent material.Soils previously classified as forest brown soils may be included (Hardjowigeno, 1993).

Territory Shape and Land Steepness
The territory shape at the research site consisted of a flat area with a land slope of 0 -8% and an area of 20,523.14ha or about 77.46%, sloping with a land slope of 8 -15% and an area of 3,878.95ha or about 14.64%, slightly steep with a land slope of 15 -25% and an area of 1,555.45ha or about 5.87%, steep with a land slope of 25 -45% and an area of 182.58 or about 0.69%, and very steep with a land slope > 45% and an area of 353.95 or about 1.34%.Monitoring changes in slope erosion rates is an important factor in planning soil conservation measures such as in biological treatments (Zhang et al., 2020).The slope map can be seen in Figure 3.The decrease in forest area, into developed land and agricultural land causes changes in the increasing level of erosion hazard in the Krueng Pase watershed (Muntazar et al., 2021).Land management systems and technological approaches are needed to reduce erosion.

Land Mapping Unit
Based on maps of soil types, slopes and land use maps, the Krueng Seulimeuem subwatershed consists of 4 (four) soil types, namely Andisol, Entisol, Inseptisol, and Red Yellow Podsolic (Ultisol).secondary forest areas, agricultural dry land, rice fields, shrubs.Meanwhile, the area has five degrees of slope, namely: 0-8%, 8-15%, 15-25%, 25-45% and >45%.Based on the results of overlaying the three types of maps, 9 units of land mapping unit (LMU) were obtained.The description of the land map unit is shown in Table 1, and the land map unit map is shown in Figure 5.

Prediction of Actual and Potential Erosion
The actual erosion prediction was obtained using the USLE.Actual erosion was predicted as erosion that occurred in the field where the values of C and P corresponded to the current state of the soil, while potential erosion was obtained by calculating the value of A = R. K. LS without entering the values of C and P. In this condition, the soil was in a state of open without any land conservation action so that the CP value was considered one.The main factor causing actual erosion at LMU 3 was the high CP value (0.3) due to shrubs that did not apply conservation methods.Furthermore, it was supported by very steep slopes > 45%.Then, a high erodibility resulted in high erosion that also occurred very heavily, while in primary forest areas such as LMU 2, 3, 4, and 5 with the actual erosion values of 1.80 tons ha -1 yr -1 , 4.63 tons ha -1 yr -1 , 0.64 ton ha -1 yr -1 , 0.20 ton ha -1 yr -1 .The erosion that occurred was not so great even though it was on a very steep slope.It was due to good land cover in primary forest areas so that rainwater that fell did not directly hit the ground.The results of the calculation of actual and potential erosion that occurred at the study site are presented in Table 2.
Table 2 shows the highest erosion of actual was found at LMU 8, namely 254.06 tons ha -1 yr -1 with heavy category.High erodibility and steep slope factors, together with improper management of plant cultivation carried out on land with slightly sloping slopes, are to blame for an high erosion value at LMU 8. Soil with high dust content is easily eroded, because the size of the dust is finer, and easily carried away by water when it rains, while the greatest potential for erosion occurs in LMU.Erosion usually increases with increasing slope and slope length as a result increase in the velocity and volume of runoff (Morgan, 2009).Slope and the length of the slope can affect erosion, the runoff coefficient increases, the kinetic energy and carrying capacity of surface runoff become greater, soil stability and slope stability decrease and will increase the rate of erosion (Zachar & Bingham, 1982).n addition to the physical properties of the soil, the management or treatment of the soil will also greatly affect the erodibility of the soil (Hudson, 2015).
Management of soil and plants that accumulate plant residues has a good influence on soil quality, namely increasing soil aggregate stability, soil resistance, and soil resistance to rain crushing power (Rachman et al., 2003).Map of actual and potential erosion can be seen in Figures 6 and 7.One of the issues associated with increasing the rate of erosion is the eroding area of forest land, which results in a reduction in the conservation value of forest land (Syafjanuar et al., 2021).Soil's physical properties, the management or treatment of the soil also had a significant effect on the soil erodibility.It was related to the effects of soil management factors on soil properties (Marriott et al., 1997) .The distribution of Total Suspended Sediments (TSS) using Landsat 8 imagery shows large fluctuations of erosion value and sedimentation that occur in land use.So that it can make it easier to observe erosion and sedimentation in an area (Ramli et al., 2022).

Erosion Hazard Index (EHI)
Based on the soil properties at the research site, it was known that the effective depth in shallow soil was 25-50 cm, the allowable erosion value was 9.6 tons ha -1 yr -1 , and the moderate depth was 50-90 cm above the weathered matters.Meanwhile, the allowable amount of erosion was 14.4 tons ha -1 yr -1 (Noeralam et al., 2003), a high level of erosion hazard will get a high critical land (Fachruddin et al., 2021).By using USLE equation, the value of EHI can be seen in Table 3 and Figure 8. Table 3. Classification of the erosion hazard index that occurs in the Krueng Seulimeuem sub-watershed LMU Actual (A) (ton ha -1 yr -1 ) TLS (ton ha

Soil Conservation Instructions
Based on the results of the analysis of erosion parameters and erosion hazard index that occurs in each LMU, it can be concluded that the factors causing erosion are erodibility, slope, plant factors and conservation measures, so it is important to make changes to the factors that cause erosion.The appropriate directions for soil conservation in LMU are crop rotation, intercropping and the use of crop residues as mulch that can increase organic matter.Organic matter that is still in the form of litter, such as leaves and twigs that have not been eroded and covers the soil surface, is a protection for the soil against the damaging power of rainwater.Organic matter can also impede surface runoff, making the flow rate slower and less damaging (Dariah et al., 2002).The main role of organic matter is to slow down run off, increase the amount of infiltration and stabilize soil aggregates (Arsyad, 2009).The appropriate conservation directions according to each LMU are presented in Table 4.

CONCLUSION
At the research location, there were nine land mapping units with a total area of 26,497.07ha.Actual erosion estimated at 254.06 tons ha -1 yr -1 in LMU 8 and 196.95 tons ha -1 yr -1 in LMU 7 were the highest.LMU 9 has the largest potential for erosion, with a rate of 2,587.72 tons ha -1 yr -1 and LMU 4 which was 1,828.88tons ha -1 yr -1 .Three categories of erosion hazard index were used: low erosion hazard level at LMU 1, 2, 4, 5, 6, 7, 8, and 9, moderate erosion hazard index at LMUs 1, 2, 3, and 6, and extremely high erosion hazard index at LMU 2.
Reforestation in protected areas was identified as the soil conservation strategy that needed to be implemented.Meanwhile, in cultivation areas, the agricultural system must apply a system of conservation methods, such as planting according to contour lines, using organic mulch, intercropping plants, agroforestry, and terracing.
Based on the findings of the study, it was recommended to the relevant agencies that they should be able to carry out conservation efforts, particularly at LMU 4, 8, and 9, in order to prevent further erosion.

Figure
Figure 3. Slope map

Figure 4 .
Figure 4. Land use map

Table 1 .
Description of the land mapping unit in the Krueng Seulimuem Sub-watershed, Aceh Besar District.

Table 2 .
The actual and potential erosion values that occurred in the Krueng Seulimeuem Sub-watershed in each LMU.

Table 4 .
Conservation directions for each land mapping unit in the Krueng Seulimeum Sub-watershed, Aceh Besar District.