Indonesia is composed of islands and volcanoes formed by tectonic plate movements. There are approximately 500 volcanoes in the country, with some located in the horseshoe region of East Java, such as Mount Semeru, Mount Ijen, Mount Raung, and Mount Argopura. Mount Argopura has a peak at 3,088 meters above sea level, and its base borders the Indian Ocean. The volcano is currently inactive, so the central area, behind the foot of the mountain, is used for agriculture and plantations, including oranges, watermelons and durian, while plantation crops include sugarcane, tobacco, coffee, rubber and cocoa. Oranges are mostly planted in the volcanic soil area of the lower slopes of the mountain, located in three administrative districts: Tanggul, with an area of 9840.48 ha; Balung District, with an area of 4999.82 ha; and Bangsalsari District, with an area of 12750.24 ha. Geographically, the study area is located between 113°25'0"–113°35'30" E and 8°05'0"–8°08'0" S (Figure 1a). Land use in the three sub-districts consists of plantations covering 10,258.53 ha (44.48%), rice fields covering 2,189.93 ha (9.49%), and rice fields covering 10,617.19 ha (46.03%) (Figure 1b).

Mount Argopura significantly influences the environment and the resulting soil. Based on the great group level soil classification system, four subgroups are present, namely Andic Dystrudepts, which covers an area of 2,661.39 ha; Typic Epiaquepts, which covers an area of 8,523.55 ha; Typic Eutrudepts, which covers an area of 6,725.18 ha; and Typic Hapludands, which covers an area of 5,155.52 ha (Figure 1b). The depth characteristics of the large Andic Dystrudepts group (> 75 cm) consist of a fine soil texture fraction (silt and clay) of at least 30%. Typic Eutrudepts contains 0.2% or more organic carbon at a depth of 125 cm below the mineral soil surface (Ogg et al., 2017). In the Typic Epiaquepts subgroup, the soil is very fine with a clay content of 66-83%, and the soil temperature is 50 cm below the isohyperthermic surface. The Typic Hapludands subgroup is soil formed from volcanic material, especially volcanic ash, which has a solum ranging from 30 to 40 cm from the surface (Jimoh et al., 2020). Rainfall in the Mount Argopura region ranges from 1,500 to 4,000 mm/year. It occurs between September and February, with peak rainfall occurring in December. The dry season occurs between April and August, with the optimal period in June, when evapotranspiration exceeds soil moisture. These rainfall conditions correlate with temperature, with air temperatures ranging from 20 to 27 degrees Celsius, increasing closer to the coast. The development of horticultural plants in the region continues to improve and is conducted in surrounding/satellite areas.

The study employed a descriptive exploratory method, with activities divided into three stages: preparation or pre-survey, survey, and analysis, to determine actual and potential land suitability using the AHP method (Figure 2). The first pre-survey activity was conducted to develop a working map, gather tools and materials, and collect quantitative data. The map was compiled based on land differentiation factors, which served as the initial basis for identifying factors limiting citrus plant growth and development. It was compiled by overlapping three land characteristic maps: land use, slope, and soil type. This overlap produced land units that were a combination of the three factors. The land use characteristics used in the overlapping working map, designed to produce land units, were limited to plantations, dry rice fields and rice paddies; settlements and forests were not included. The overlap of these three land characteristics resulted in seven land units (Table 1).

The second activity, a field survey, was conducted to collect soil samples and biophysical data for each of the prepared land units. The collection was conducted across all seven land units, with four replicate sampling points for each subunit. Each point was randomly selected to represent the subunit, with soil sampling ranging from 0 to 40 cm from the surface (Figure 3). Five replicate samples were then combined into one sample and labelled. The collected soil samples were used for chemical and physical soil analysis in the laboratory. The analysis began with the preparation of 2 mm air-dried soil samples. Observed soil characteristics included pH (H₂O), EC, available P, total N, available K, CEC, organic C, base saturation, and soil texture. The soil chemical analysis method is shown in Table 2.

Biophysical observations conducted in each land unit included temperature, drainage, effective soil depth, rainfall, slope and erosion hazard. Temperature was measured using the Braak formula, which correlates temperature with altitude (Table 2). The average sea surface temperature is 26.3°C, and for every 100 meters of altitude above sea level, the temperature decreases by 0.6°C. Soil drainage was assessed in the field by observing the reduction and oxidation processes, indicated by visual rust or color on the soil surface (Figure 4). Soil depth was measured from the surface to the C horizon (100 cm) using a profile drill, then with a tape measure. Slope was measured using a DEM analysis in ArcGIS software. Erosion hazard was determined using USLE (Universal Soil Loss Equation) analysis (Table 2). This is a mathematical modelling method for predicting the long-term average annual soil erosion rate (A) based on factors such as rainfall (R), soil erodibility (K), slope length/slope (LS), and crop/conservation management (CP). The method is commonly used to evaluate erosion hazards in an area and plan appropriate soil conservation techniques.

Land evaluation assessment to determine the level of suitability of citrus crop commodities in Indonesia in line with environment and soil parameters was adopted from the FAO modifications developed by  (Sys et al., 1991) and Balittan Bogor, Indonesia (Basuki et al., 2026). The criteria for land suitability for citrus plants are the result of matching the soil and environmental characteristics associated with citrus productivity. The assessment utilized AHP, which matched the results of biophysical field analysis and laboratory analysis with citrus land suitability criteria as a basis for identifying factors that influence citrus productivity in the research area  (Nuru et al., 2025).

AHP analysis is used to evaluate and prioritize factors by comparing their relative importance. Pairwise comparisons were made between the criteria, and a weight assigned to each based on their significance in determining land suitability (Negussie et al., 2024). This allowed for a systematic and objective way of ranking the criteria based on the land suitability for citrus cultivation. The AHP method is used to compare land characteristics pairwise based on the results of field and laboratory analysis, and provide weights to prioritize the influence of each factor on citrus crop productivity.

AHP is a decision-making technique that is used for evaluation and shows priority choices. It relies on pairwise comparisons to determine the relative importance of each criterion or option. Some experts argue that by giving weights first, followed by analysis using AHP, the technique is easier. AHP often has a weight range of 1-9 as a basis for ranking variables (Sadiq et al., 2025). The pairwise comparison matrix was used to generate priority weights, with the consistency ratio (CR) used to assess the reliability of the paired analysis. Equation (2) evaluates the CR, which ranges from 0 to 1, as described by Saaty  and Malczewski (Negussie et al., 2024). The assessment is acceptable if it is less than 0.1. The consistency index (CI) was used as the basis for evaluation according to equation 1.

(1)

where λ max is the highest eigenvalue of the pairwise model comparison, and n indicates the total number of classes (Abate et al., 2024). The CR value was obtained according to Equation (2).

(2)

The index ratio (RI) value was determined by considering a random matrix of average CI values as described in the Saaty scale (Abate et al., 2024).

Land suitability assessment is based on multi-criteria decision analysis utilizing GIS technology with Quantum-GIS (Q-GIS) applications, particularly overlay models of weighted factors (Abuzaid & Abdelatif, 2022).The prerequisite criteria used to assess land suitability for citrus crops are shown in Table 3. Decision-making in assessing land suitability is divided into four classes for actual land suitability status, while for assessing potential land suitability status, AHP analysis is utilized. The results of the AHP analysis serve as the basis for management improvements and to determine the distribution of land suitability status, based on the S1 (highly suitable), S2 (moderately suitable), S3 (slightly suitable), and N (not suitable) classes.

1. Temperature

The temperature data used were obtained from the calculation results of the Braak formula (26.3oC-(0.01 X elevation X 0.6 oC) (Chen et al., 2021). Temperature is a triggering factor in the physical process in the formation of clay from parent material minerals in the soil (Zhong et al., 2019). The study's temperature distribution map, especially along the slopes of Mount Argopuro, is shown in Figure 5a. Based on the figure, land unit 1 has the lowest temperature value, 24.61°C, with an area of ​​2,441.61 ha, or 10.59% of the total area. The highest temperature was found in land unit 3, with a value of 26.26°C, and an area of ​​2,661.40 ha, or 11.54% of the total area. Variations in temperature can occur due to different topographic positions (How Jin Aik et al., 2021). On different land maps, they can be influenced by differences in altitude, which is an important parameter used to evaluate the adequacy of land as a growth factor for the cultivation of plants. Temperature can also affect plant productivity (Dornik et al., 2024). Safe temperatures for citrus plants are generally at 19 - 33°C; if the temperature is higher than 33°C, the plant will experience damage to the coloring of the fruit due to a decrease in nutrient content and consequently affect the taste of the fruit, making it less fresh.

2. Precipitation

Rainfall (mm) is the amount of rainwater expressed in mm. It is used as a physiological factor in plants, and as an indicator to determine their water needs in the event of drought (Ng et al., 2024). Moreover, rainfall is an indicator of humidity, which is an important factor in the plant growth process and affects plant productivity (Getachew et al., 2021). The distribution of average rainfall over the last 10 years is shown in Figure 5b. Based on the figure, the highest rainfall is in Tanggul sub-district, with 2665.86 mm/year, affecting 35.67% of the total area (9840.48 ha), while the lowest is in Balung sub-district, with 2154.88 mm/year over an area of 4999.82 ha, 18.12% of the total area. Annual rainfall has a strong influence on crop management and is therefore an important factor, as rainwater functions as a solvent and transporter that can influence soil properties, soil minerals, and soil profile depth differentiation. Rainfall of between 1,000 -3,000 mm/year is the optimal level for citrus plants (Li et al., 2024).

3. Drainage

The cultivation of plants can be optimized by good drainage, which maintains soil moisture and aeration (Sadiq et al., 2025). The distribution of soil drainage in the research area is divided into two drainage classes: good and somewhat obstructed. Land units 1, 4 and 7, with an area of ​​8,915.11 ha, or 38.65% of the total area, have good drainage, while land units 2, 3, 5 and 6, with an area of 14,150.54 ha, or 61.35% of the total, are classified as having somewhat obstructed drainage. Soil with good drainage is characterized by a homogeneous soil color and no rust (manganese) or gley-related color at depths> 120 cm in the lower layer. This is in line with (Aburas et al., 2017), who state that a homogeneous soil color without spots (rust) can be a characteristic of good drainage, especially in layers up to > 100 cm. In citrus plants, soil drainage conditions greatly affect whether they grow well. Citrus plants can grow optimally with good drainage conditions at a soil depth of up to 120 cm.

4. Slope

Slope is a measure of an area in degrees or percentage. In addition to determining the level of land suitability, slope also affects the level of erosion and landslides (Dutta et al., 2024). Determination of plant types on each slope also needs to be made, as plants are protectors of the soil surface (Miao et al., 2022).

Therefore, the selection of plant types in line with the slope gradient is very important to maintain slope stability. The distribution of slopes in the research area is shown in Figure 5e. Based on the figure, there are four slope gradient classes: a flat class covering an area of 4,283.57 h; a gentle area of 10,425.77 ha; a slightly sloping area of 7,292.94 ha; and a sloping area of 1,063.36 ha. Very steep land will affect the level of soil erosion (Yeneneh et al., 2024). Steep land is not suitable for planting agricultural commodities because of the high erosion value, which will subsequently affect the nutrient content of the soil. An increase in surface runoff flow velocity can be caused by the steepness of the slope; this will also increase the surface flow transport energi (Sugianto et al., 2022).

5. Erosion Hazard

Erosion refers to the loss of the top soil layer due to the movement of water and wind. Steep slope conditions increase the volume of surface runoff, which causes erosion (Basuki et al., 2024). The distribution of erosion hazards are shown in in Figure 5d. The figure indicates that at the research location there are four classes of erosion hazard: very severe, covering an area of 1,063.36 ha; severe, covering an area of 7,292.94 ha; moderate, covering an area of 4,092.15 ha; and very low, covering an area of 10,617.19 ha. The erosion hazard class that dominates the research area is that of very low, with 46.03% of the total area.

6. Effective Soil Depth

The depth of the soil layer that can be used for plant root growth is referred to as effective depth. If this is limited by barriers such as hard rock, solid rock, or other layers, it will inhibit root growth (Hofmann et al., 2024). The distribution of effective depth in the research area is shown in Figure 5f, which indicates that the effective depth in this area is quite varied, with depths of 55-100 cm. Land units 1, 6 and 7 have the same depth, 100 cm, which is included in the deep category. Land units 2 and 3 are included in the medium category, with depths of 55 cm and 60 cm. Effective depth can be measured in the field by observing the fine roots of plants compared to the coarse ones, and other roots growing within them. Effective depth is influenced by the presence or absence of parent material, gravel or boulders, which cannot be penetrated by roots (Cyio, 2008). 82.93% of the research area has an effective depth in the deep category, while 17.07% has a medium effective depth. Soil depth is divided into deep (>75 cm), medium (50-75 cm), shallow (20-50 m), and very shallow (<20 cm) classes (Subardja et al., 2016).  Effective depth can be influenced by root development; if the soil depth is shallow, this will inhibit such development. Depths of up to 120 cm are suitable for citrus plants.

1. Texture

Soil texture in a soil mass is defined as the ratio of the content of sand, silt, and clay fractions. The percentage of particles determines the soil texture, with the texture class determined according to the USDA (Sadiq et al., 2025). The distribution of soil texture is shown in Figure 6.a. It is divided into four texture classes sandy clay, covering 39% of the total area (8,995.02 ha); sandy loam, with an area of 6,752.18 ha (29.16%); silty clay loam covering an area of 2,189.93 ha (9.49%); and silty clay with an area of 5,155.52 ha. (22.35%). Each land unit has a different texture rsulting from differences in the soil formation process and the soil management practiced. Soil texture affects the availability of nutrients and water due to its ability to bind and exchange cations in the soil. Soil with a clay texture stores nutrients and has sufficient water to allow air circulation (Nuru et al., 2025). Because ofo the many micropores in the sand, air and water movement is very fast. A good texture for citrus growth is soil that is fine in texture and dominated by some dusty and clayey textures.

2. Cation Exchange Capacity

Cation exchange capacity (CEC) is a process that occurs in the soil by which cations are exchanged for available cations and vice versa. Cation exchange capacity is influenced by the presence of clay, nutrients and organic matter. A higher CEC value indicates better soil fertility status and vice versa (Mustofa et al., 2024). Its role is very complex, as the formation and maintenance of soil fertility are supported by soil pH, soil C-organic factors, and the availability of organic material. The cation exchange capacity of each land unit in the study area is shown in Figure 6b. As shown in the distribution map in the figure, the CEC value in the research area has only two classes: low and medium. Land units 1, 2, 3, 4 and 5, with a total area of 12,448.46 ha (53.97%), are included in the low grade, while land units 6 and 7, with a total area of 10,617.19 ha (46.03%), are included in the medium grade. The lowest CEC value is in land unit 2, at10.37 cmol/kg, with an area of 1,063.37 ha, and the highest CEC value was in land unit 7, namely 19.08 cmol/kg corresponding to an area of 4,283.57 ha. The cation exchange capacity in the study area is low as the soil colloids contain clay and a low level of organic matter. Furthermore, CEC is influenced by soil moisture, with the ideal soil moisture for cation exchange being > 60%.

3. Base Saturation

Base saturation refers to base cations such as magnesium, calcium, sodium and potassium in the soil colloids. It can increase as a result of increased soil organic matter content (Jimoh et al., 2020). The base saturation distribution map is shown in Figure 6c, which indicates that there are various base saturation values ranging from low to medium and high categories. Land unit 7, with an area of 4,283.57 ha, or 18.57% of the total area, is included in the lowest category, with a value of 36.83%. Land unit 2, with an area of 1,063.37 ha, or 4.61% of the total area, is in the highest category, with a base saturation value reaching 67.21%. The medium category includes land units 1, 3, 4, 5 and 6, with vulnerable values of 42.23–56.71%. The base saturation value can be influenced by rainfall and soil pH. High rainfall in Indonesia results in high levels of nutrient leaching, so alkalis in the soil are leached out. Low base saturation causes the bases in the soil to become acidic. Apart from rainfall, a high pH in soil usually corresponds tohigh base saturation, and vice versa.

4. Soil pH

Soil pH depends the presence of compounds in the soil, which can be acidic, neutral and alkaline. The level of soil acidity is used to define the suitability of land for certain crops (Tantuoyir et al., 2025). Soil pH affects plant growth. If high H+ ion values are found in the soil, soil pH decreases, causing plants to be contaminated with microelements and increasing the solubility of iron and aluminum ions. Based on the pH distribution map shown in Figure 6d, the soil pH distribution ranges between 5.64 and 7.14, corresponding to the neutral and slightly acidic categories. Land unit 4, with an area of 2,189.93 ha, and land unit 5, covering 4,092.15 ha, are classified as having slightly acidic pH, while land units 1, 2, 3, 6 and 7 are classified as having neutral pH. Citrus plants can grow in various types of soil. The ideal pH is between 5 and 6; if the pH is less than 5, then the plant roots do not develop well, and the plant cannot absorb nutrients. On the other hand, soil with a pH of more than 6 usually has many bound macroelements, which is disturbing and abnormal for plant growth due to the lack of nutrients ((Basuki et al., 2022); (Basuki & Sari, 2020)).

5. Soil Organic Carbon

Soil organic carbon (C-Organic) in the soil increases soil fertility and the process of nutrient availability, which ultimately boosts the productivity of cultivated plants (Mustofa et al., 2024). The C-Organic content supports the availability of organic materials derived from the decomposition of living things. Its distribution on the slopes of Mount Argopuro is shown in Figure 6e, ranging from 1.18 to 1.94%, with a low value; this indicates that the C-Organic content across all land units is very similar. Soil fertility is indicated by the presence of soil organic carbonin the soil, which is food for organisms; the number and diversity of types of organisms working in the soil also increase. Low soil organic carbon content in soil can be caused by intensive land cultivation (Mustofa et al., 2024). Low C-organic content in soil can reduce productivity and plant growth. One way to overcome this is by adding fertilizer or organic material.

6. N-Total

Nitrogen is an important element for plants. Its level in soil varies greatly due to factors such as land cover, climate, landform, and soil chemical-physical properties. In turn, many factors influence the nitrogen content of plants, such as climate, vegetation, topography, and chemical-physical properties of the soil (Zhao et al., 2023). The distribution of N-total in the study area can be seen in Figure 6f. The highest value of 0.18% is in land unit 2, with an area of 1,063.37 ha, and the lowest of 0.11% in land unit 1, with an area of 2,441.61 ha; however, both values are still in the low category. Another factor that influences the N-total value is organic matter. A low value in soil is a result of several factors, such as leaching with water, evaporation, and absorption by plants (Zhu et al., 2024). The efficiency of N element absorption relates to the denitrification of N₂ gas.

7. P₂O₅

Phosphorus is a nutrient needed by plants. The P element content is usually lower than that of other nutrients, such as nitrogen and potassium. Plants absorb P in the form of primary orthophosphate (H₂PO₄) and secondary orthophosphate ions (HPO₄) (Oliveira et al., 2021). The distribution of P2O5 in the study area can be seen in Figure 6g. Its value in all land units on the slopes of Mount Argopuro is in the low category (Figure 6g). The highest P2O5 value is 10.3 mg/100 g in land unit 2, with an area of 1,063.37 ha (4.61%), and the lowest available p-value is 7.83 mg/100 g in land unit 6, with an area of 6,333.62 or 27.46% of the total area. Several factors, such as soil texture, organic matter and soil pH influence the level of P values (Xu et al., 2016). Low available P content is due to low phosphorus content in organic and mineral matter; poor pH also affects P elements. Low P levels in soil indicate leaching of phosphorus. Generally, phosphorus dissolves more easily in soil that has an acidic pH.

8. K₂O

The element potassium is one of the essential elements needed by plants to grow and develop. It functions, for example, by helping the development of roots in the soil and increasing plant resistance (Oliveira et al., 2021). Based on Figure 6h, which shows the K₂O distribution map of each land unit in the research area, the K₂O value is in the very low category. The highest K value, 9.68 mg/100 g, is in land unit 4, with an area of 2,189.93 ha or 9.49% of the total area, while the lowest value, 9.25 mg/100 g, is in land unit 6, with an area of 6,333.62 ha or 27.46% of the total. The K₂O value in each land unit is very low. Low K content occurs because of the low efficiency of the leaching of potassium fertilizer, which is caused by the increased binding or leaching capacity of potassium (Zhu et al., 2024).

This also corresponds to the land conditions at the research location, which have low c-organic and CEC values, meaning the K reserves or stores are low. Another factor leading to low K values is the intensity of processing and fertilization. Fertilization needs to be balanced, with the extraction of biomass, especially organic material, and appropriate timing also needs to be considered, so that fertilizer absorption occurs optimally (Hofmann et al., 2024). If a citrus plant lacks at least 16% of the K element, the leaves will fall off, and the fruit will also fall before it is ripe.

This study shows that although current citrus land suitability in Agropuro is predominantly moderately acceptable, the AHP-based evaluation indicates that any limitations can be substantially mitigated through prioritized management interventions, leading to meaningful improvements in potential suitability across several land units. According to the AHP and GIS-based suitability analysis, 18.57% of the land area studied was highly suitable; 65.28% moderately acceptable for citrus agriculture, and 16.15% marginally suitable. The AHP-based potential suitability analysis demonstrated acceptable decision consistency (CR = 0.089 < 0.1) and identified rainfall (18%), temperature (16%), and drainage (15%) as the most influential criteria, suggesting that targeted interventions (fertilization, terracing, and soil filling) could improve suitability classes from S3/N to S2, S3, and even S1 in selected land units.

Land suitability assessment is a crucial factor in cultivation techniques, as it helps identify the appropriate zone, both for planting locations and management technique (Fu et al., 2025). Land evaluation methods are divided into matching and AHP approaches. It can be inferred that the AHP method has good flexibility and considers various factors, with a high accuracy rate of up to 85% ((Agrawal et al., 2024); (Negussie et al., 2024); (Sadiq et al., 2025)). Land evaluation using a mapping model provides accurate information regarding the zoning of growth-inhibiting factors, including both soil characteristics and environment-related ones (Zaniboni et al., 2025). The environment and soil characteristics strongly support the growth and development of citrus productivity (Gizawu Garbaba & Negasa Wolteji, 2024). Environmental characteristics that play a role include erosion hazard, water availability and temperature. Erosion hazards related to soil movement are primarily caused by other environmental and soil characteristics ((Dessalegn et al., 2014); (Gizawu Garbaba & Negasa Wolteji, 2024)). Environmental characteristics include topography, slope percentage, and rainfall, while soil characteristics that influence erosion hazards include the percentage of dominant texture fractions ((Nath et al., 2021); (Wang et al., 2022); (Zhang et al., 2022)). It has been reported that gentle slopes (>3%) affect groundwater conditions ((Abuzaid & Abdelatif, 2022); (Bhandari et al., 2021); (Marghmi et al., 2024)). Water affects productivity, particularly the quantity of citrus fruit ((Baker et al., 2024); (Elshahat et al., 2025)). Water availability during the flowering period influences the number of flowers produced; in addition, water supports the formation of sucrose, which affects the fruit's sweetness. Studies show that inadequate watering during the fruit-forming phase can cause flower and fruit drop (Xing et al., 2025). Managing land erosion risks with appropriate conservation techniques can increase water infiltration and reduce runoff (Ma et al., 2025). Appropriate conservation techniques, such as terraced benches using grassy border plants, can reduce groundwater loss by 40% (Rijsdijk et al., 2007).

Crucial soil characteristics for citrus productivity include pH and nutrients (nitrogen, phosphate, and potassium). The ideal pH for citrus cultivation is a minimum of 5 and a maximum of  6-7   (Karki et al., 2024). Soil pH correlates with the availability of nutrients, both macro and micro ((Cheng et al., 2023); (Freidenreich et al., 2022); (Ng et al., 2024)). Sufficient nitrogen can be obtained from rainwater, irrigation water, and inputs in the form of inorganic fertilizers ((Li et al., 2024); (Nuru et al., 2025); (Wang et al., 2022)). In the research area, nitrogen was not a limiting factor for citrus cultivation, but phosphate and potassium. Phosphate and potassium are mostly present in the soil at high total concentrations but low availability. Phosphate is available at a soil pH of 6.5-7.5, but below or above this range it will be bound by cations such as iron (Fe²⁺), aluminum (Al³⁺), magnesium (Mg²⁺) or calcium (Ca²⁺) ((Bao et al., 2024); (Jerand et al., 2016); (Madsen, 2019); (Zhu et al., 2024)). The role of phosphate in horticultural crops is vital in increasing sugar content in citrus and influencing fruit ripening time. Phosphate fertilization recommendations are based on field conditions, with most phosphate values in the low category (Bio-based fertilisers can replace conventional inorganic P fertilisers under European pedoclimatic conditions, 2025). For citrus cultivation, it is necessary to add P fertilizer such as SP-36 at 157.20 kg/ha/plant. Phosphate fertilizer is applied based on plant age: if the plant is 0-3 years old, apply 3-4 times; at 3-4 years old, apply 2-3 times; and at > 4 years old, apply twice per year. Potassium nutrients at the research location are categorized as low, so 495.75 g/plant is needed; at medium nutrient status, 458.72 g/plant is needed. The addition of potassium nutrients also depends on plant age: for plants aged 0-2 years, 3-4 times; for those aged 2-3 years, 3 times; and at age 3-4 years, twice per year (Choudhary et al., 2024). Future research is recommended to examine land suitability at the varietal or clone level for specific crops, such as citrus varieties or clones, such as Semboro, tangerines (SoE, Tejakula, Monita Agrihorti), Siamese oranges (Pontianak, Madu), and new varieties such as Karisma Agrihorti, which produces sweet fruit with yellow flesh.