Application of Flow Coefficients to Support High Economical Plant Cultivation (Case Study: Kwanyar Bangkalan, Indonesia)

: The initial study that we carried out regarding the Kwanyar sub-district area, Bangkalan, East Java, shows the need to optimize land productivity and analyze the potential for farming to build the welfare of the people of the Kwanyar subdistrict. Preliminary spatial data analysis related to the topography as a result of Digital Elevation Model (DEM) data processing shows that: the Kwanyar sub-district is dominated by flat slopes (0-8°) compared to the northern region of the Kwanyar sub-district, while runoff water analysis shows a low flow coefficient (0-0.25) which means that most of the Kwanyar area has low absorption capacity and a high potential for stagnant water. In addition, the Kwanyar region has a Regosol soil type. Regosol soil has a coarse texture and low organic matter, which makes it unable to properly hold water and minerals for plants, so it tends to be infertile. The initial study then became the basis for this research.


Introduction
Cultivating food crops in the Kwanyar sub-district faces various challenges, one of which is land degradation (Yunianti et al., 2022).Intensive agricultural and plantation cultivation can reduce soil fertility, especially a decrease in soil organic matter content (Wihardjaka et al., 2020), which is an essential element in the soil (Wihardjaka et al., 2022).The organic matter content in the soil greatly influences soil physical properties such as the stability of soil structure, soil density, and also water holding capacity (Arpino et al., 2023;Jiao et al., 2020;Luna Juncal et al., 2023).The availability of organic matter can increase the availability of macro-and micro-nutrients, as well as increase the cation exchange capacity, so that nutrients can be available to plants (Dhaliwal et al., 2019;Kizuka et al., 2023;Yorlano et al., 2022).The availability of organic matter also supports the activity of soil microorganisms to secrete enzymes that play an important role in the availability of plant nutrients such as N, P, and K (Debele, 2020; Lu et al., 2020;Ndabankulu et al., 2022).Decreasing soil fertility without being offset by adequate return of organic matter in the long term can result in land degradation and have an impact on decreasing crop productivity (Kopittke et al., 2019;Purwanto & Alam, 2020).
One of the parameters that affect the level of soil fertility is the slope and flow coefficient (Utama et al., 2022).The slope's slope shows the flow direction based on the height and pitch of the hill with the upstream to the downstream system.The coefficient of flow or water runoff shows the percentage of stagnant water absorbed into the soil.Both of these parameters indirectly affect soil erosion, where erosion is one of the causes of land degradation (Andrade et al., 2021;Kopittke et al., 2019;Y. Liang et al., 2020;Yang et al., 2022).
This research was conducted to determine the effect of the slope of the slope on the runoff of the research area with the existing conditions of the area being developed for agriculture in high economical plant cultivation (Ahmad Zubairi et al., 2022;K. Liang et al., 2023;Sabzi et al., 2022).Thus, the further development of this research becomes significant in the analysis of decision making regarding the development and management of agricultural land for the cultivation of high-economy crops.

Method
The research area is in Bangkalan Regency, especially in Kwanyar District.The following details the research location Figure 1.Next, determine the flow direction to determine the direction of flow on the surface.The coefficient of land flow is obtained from the slope of the land.

Slope Classification
Clip DEM, generate slope, reclassify, dissolve SHP, and continue with slope classification analysis are all slope classification steps that are performed after the coordinate system conversion.Data are converted to UTM by the coordinate system.Clipping DEM is the process of combining SHP data from the research site with DEM data.Reclassification is a step in the classification method.The disintegration procedure converts the reclassified data into shapefile data.Using color settings as symbols for each category, data from the dissolve operation is organized (Marin et al., 2020;Setyoko, 2019).

Flow Coefficient Classification
The coefficient of water flow on the surface of the land was estimated using data regarding land cover and slope.Using the straightforward model shown below, the flow coefficient is computed: with C as the flow coefficient, Lbl as the area (km2) of a specific land class, and LT as the total study area (km2).This method processes the intersection, including the calculation.The results of intersection processing provide information for the classification of flow coefficients (Ayu Saputri et al., 2018;Bujung, 2020;Indriatmoko & Wibowo, 2018;Nganro et al., 2019).

Result and Discussion
Preliminary studies that have been conducted show that based on slope and flow coefficient data processing it is found that Kwanyar sub-district is dominated by low-lying areas, compared to other areas in the northern part of Bangkalan district, as shown in Figure 2. In addition, the results of analysis of runoff water show that 100% of the water in the zone flows to the ground surface and 0% of the water is absorbed into the soil surface (Rugendo et al., 2023;Spangler et al., 2019a).Based on the slope, most of the flow coefficient in the study area is 0.2.The flow coefficient value indicates that 20% of the water flows to the ground surface and 80% of the water is absorbed or infiltrated into the soil.This shows that most of the flow coefficients are low with low absorption and high potential for waterlogging, as shown in Figure 2 (Indriani & Utama, 2023).
If viewed from the water runoff map in Figure 3, the northern region has a high runoff value, namely with an interval of 0.5-0.75.In this area has a land classification, namely fields.If viewed from the results obtained, the water will run off faster so that the water absorbed on the land is quite a bit.On average, the kwanyar area has land with a low slope so that a low flow coefficient is obtained.In addition, the land is used for rice fields (Abas et al., 2022;Page et al., 2023;Zhang et al., 2021).So that the rice fields in the Kwanyar subdistrict act as rain-fed rice fields.However, this has a weakness in the dry season, the lack of water distribution.In addition, land with steep slopes and high flow coefficients has the potential for high-level land degradation, so that it can affect the thickness of the soil layer getting thinner (Cui et al., 2020;Spangler et al., 2019b).The thickness of the soil layer is getting thinner can indicate the level of soil fertility is decreasing (Chen et al., 2023;Guo et al., 2021).In the future, with development, this value will increase significantly which means in controlling water in the area (Ayu Saputri et al., 2018;Bujung, 2020;Indriatmoko & Wibowo, 2018;Nganro et al., 2019).This research was conducted to determine the effect of the slope of the runoff of the research area with the existing conditions of the area being developed for agriculture in high economical plant cultivation.Thus, the further development of this research becomes significant in the analysis of decision making regarding the development and management of agricultural land for the cultivation of high-economy crops based on Figure 4 (Arpino et al., 2023;Ordonez et al., 2020).

Conclusion
Most of the kwanyar area has land with a low slope so that a low flow coefficient is obtained.In addition, the land is used for rice fields.So that the rice fields in the Kwanyar sub-district act as rain-fed rice fields.However, this has a weakness in the dry season, the lack of water distribution.In addition, land with steep slopes and high flow coefficients has the potential for highlevel land degradation, so that it can affect the thickness of the soil layer getting thinner.The thickness of the soil layer is getting thinner can indicate the level of soil fertility is decreasing.In the future, with development, this value will increase significantly which means in controlling water in the area.This research was conducted to determine the effect of the slope of the slope on the runoff of the research area with the existing conditions of the area being developed for agriculture in high economical plant cultivation.Thus, the further development of this research becomes significant in the analysis of decision making regarding the development and management of agricultural land for the cultivation of high-economy crops.

Figure 1 .
Figure 1.The boundaries of the research area use administrative boundaries