Evaluation of land suitability and potential production of sorghum (Sorghum bicolor L.) as a biomass energy crop in West Sumatra, Indonesia

Avaliação da adequação do solo e potencial de produção de sorgo (Sorghum bicolor L.) como cultura de bioenergia em Sumatra Ocidental, Indonésia

Abstract

Research findings establish sorghum as an ideal choice for enhancing the productivity of arid, acidic, or otherwise unproductive lands, including reclaimed former mining areas. Sorghum serves as an alternative food ingredient, containing high levels of carbohydrates and calories, making it a viable solution for food security and biomass energy challenges. A study on sorghum cultivation in West Sumatra, Indonesia, reports yields of approximately 8 t ha⁻¹, with wheat seeds produced at a rate of 10 t ha⁻¹. The outcomes of these sorghum plantations include processed products such as flour and sugar derived from sorghum stems. By assessing land characteristics suitable for sorghum development as a biomass energy crop in West Sumatra, this research aims to promote the sustainable growth of sorghum cultivation in the region. This research aims to evaluate the suitability of land for sorghum (Sorghum bicolor L.) in West Sumatra, Indonesia, using purposive sampling and survey methods. To assess land suitability, a quantitative model from the Food and Agriculture Organization (FAO) is employed, which combines environmental data, climate, and the physical and chemical characteristics of the land. The estimation of Radiation Thermal Production Potential (RPP) is conducted, with each data point measured (rated) individually and incorporated into several mathematical formulas. Subsequently, the potential production of land based on climate, referred to as Climate Production Potential (CPP), is quantitatively determined. By modifying specific variables within this model, it can accurately predict the outcomes of sorghum cultivation in various regions. By inputting actual data on land plant production, this model can forecast the real plant production potential of the land, known as Land Production Potential (LPP). The West Sumatra region is classified as S1 land suitability, indicating it is highly suitable for growing sorghum. The potential actual sorghum production in West Sumatra, Indonesia, is estimated at 5 t ha⁻¹, which exceeds the current levels of sorghum production. The results indicated that the land in West Sumatra, Indonesia, has potential for the development of sorghum plants, characterized by an average temperature of 25-27 °C, rainfall of less than 200 mm, air humidity below 75%, good drainage, soil depth greater than 60 cm, and a pH range of 4.4 to 6.1.

Keywords:
CPP; LPP; land evaluation; RPP; sorghum (Sorghum bicolor L.)

Resumo

Resultados de pesquisas estabelecem o sorgo como escolha ideal para aumentar a produtividade de terras áridas, ácidas ou improdutivas, incluindo áreas de mineração recuperadas. O sorgo serve como ingrediente alimentar alternativo, contendo altos níveis de carboidratos e calorias, tornando-se uma solução viável para os desafios da segurança alimentar e da energia de biomassa. Um estudo sobre o cultivo de sorgo em Sumatra Ocidental, Indonésia, relata rendimentos de aproximadamente 8 t ha⁻¹, com sementes de trigo produzidas a uma taxa de 10 t ha⁻¹. Os resultados dessas plantações de sorgo incluem produtos processados, como farinha e açúcar, derivados dos caules do sorgo. Ao avaliar as características do solo adequadas para o desenvolvimento do sorgo como cultura de energia de biomassa em Sumatra Ocidental, esta pesquisa visa promover o crescimento sustentável do cultivo de sorgo na região. Esta pesquisa visa avaliar a aptidão do solo para o cultivo de sorgo (Sorghum bicolor L.) em Sumatra Ocidental, na Indonésia, utilizando amostragem intencional e métodos de levantamento. Para avaliar a aptidão do solo, emprega-se um modelo quantitativo da Organização das Nações Unidas para a Alimentação e a Agricultura (FAO), que combina dados ambientais, climáticos e as características físico-químicas do solo. A estimativa do Potencial de Produção Térmica por Radiação (RPP) é realizada, com cada ponto de dados medido (avaliado) individualmente e incorporado em diversas fórmulas matemáticas. Posteriormente, o potencial de produção do solo com base no clima, denominado Potencial de Produção Climática (CPP), é determinado quantitativamente. Ao modificar variáveis ​​específicas dentro desse modelo, é possível prever com precisão os resultados do cultivo de sorgo em diversas regiões. Ao inserir dados reais sobre a produção vegetal do solo, este modelo pode prever o potencial real de produção vegetal do solo, conhecido como Potencial de Produção do Solo (LPP). A região de Sumatra Ocidental é classificada como de aptidão de solo S1, indicando alta aptidão para o cultivo de sorgo. O potencial de produção real de sorgo na Sumatra Ocidental é estimado em 5 t ha⁻¹, o que excede os níveis atuais de produção de sorgo. Os resultados indicaram que as terras no oeste de Sumatra Ocidental têm potencial para o desenvolvimento de plantas de sorgo, caracterizadas por temperatura média de 25-27 °C, precipitação inferior a 200 mm, umidade do ar inferior a 75%, boa drenagem, profundidade do solo superior a 60 cm e faixa de pH de 4,4 a 6,1.

Palavras-chave:
CPP; LPP; avaliação fundiária; RPP; sorgo (Sorghum bicolor L.)

1. Introduction

The production of bioethanol from sorghum biomass is feasible in temperate climates and does not compete with food production, as sorghum can be cultivated after rye (Batog et al., 2020). Bioethanol can be derived from various raw materials, including wood, straw, wheat, sugarcane, sugar beets, corn grains, corn stalks, and sweet sorghum, using several processing methods such as acid hydrolysis followed by fermentation, enzymatic hydrolysis followed by fermentation, malting followed by fermentation, and fermentation alone (Ariningsih et al., 2023).

Sorghum is a drought-resistant food crop with significant potential for development in Indonesia (Human and Sihono, 2010). Research findings indicate that sorghum is an ideal choice for enhancing the productivity of arid, acidic, or otherwise unproductive lands, including reclaimed former mining areas (Juniarti et al., 2020). Indonesia aims to increase renewable energy contributions within its national energy mix. Sorghum biomass could serve as a feedstock for bioethanol or biogas production, supporting national commitments to reduce reliance on fossil fuels. Sorghum biomass can be converted into bio-briquettes or bioethanol for local use, enabling rural communities to access affordable and sustainable energy while reducing dependence on imported fuels.

The information and data regarding natural land resources for developmental planning are crucial. Land resources are one of the primary physical factors considered in the planning, arrangement, and construction of spatial settings, particularly in inland areas. Certain regions present numerous physical challenges related to land, which adversely affect the social and economic well-being of communities. Therefore, data on natural resources play a significant role and must be taken into account when utilizing land.

The potential for developing food crops on dry land in West Sumatra is significant, covering approximately 590,450 hectares. Dry land with a slope of less than 8% is suitable for sorghum cultivation (Sihono, 2013). Furthermore, the cultivation, research, and development of sorghum in West Sumatra remain limited due to a lack of information regarding superior seeds, sorghum utilization, cultivation practices, and effective methods for growing high-quality sorghum. Expanding sorghum cultivation on degraded lands provides carbon sequestration benefits and reduces greenhouse gas emissions through the substitution of fossil energy with bioenergy.

Furthermore, Juniarti conducted experiments of cultivating sorghum in various soil types, including Andisols, Entisols, and Regosols, over two seasons (winter and summer) in Shobara, Hiroshima Prefecture, Japan. The sorghum yields biomass that can serve as an energy source for greenhouse strawberry cultivation and household energy consumption in the Shobara-Hiroshima region. Promoting sorghum cultivation not only enhances land productivity but also contributes to the advancement of sustainable agriculture and strengthens Indonesia's food production.

Previous research has been conducted by the Cereal Maros and the Isotope and Radiation Technology Application Center (PATIR) of the National Nuclear Energy Agency (BATAN). This study specifically focused on sorghum and aimed to enhance the available germplasm through Cobalt-60 gamma irradiation, targeting the development of superior crops based on desired criteria.

Agronomically, there have been several promising developments, including high production, drought resistance, and clear white seeds. A number of mutant sorghum lines from the PATIR-BATAN collection have been tested for resistance to acidic soils. The study was conducted in Lampung, Indonesia, in areas where soil pH levels ranged from 4.2 to 4.7, with aluminum saturation levels between 30% and 39%. The results indicated that several sorghum strains exhibited high resistance (or high tolerance), and some showed moderate tolerance to acidic soils. The acid-resistant sorghum strains are currently undergoing purification and seed propagation (Sari and Juniarti, 2023).

One of the predicted causes is the use of inappropriate land. The lack of alignment between land use and its supporting resources leads to land degradation, making it unsuitable for continuous use. To assess land suitability, a quantitative model developed by the Food and Agriculture Organization (FAO, 1976) is employed, which integrates environmental data, climate factors, and the physical and chemical characteristics of the land (Sys et al., 1991).

Every data point is measured (rating) individually and included in various mathematical formulas. Subsequently, the potential production of land based on climate, referred to as Climate Production Potential (CPP), is quantitatively determined. By adjusting specific parameters within this model, it can predict the potential yield of crops in different regions (Fiantis, 2001). By inputting actual data on land crop production, this model can forecast the real crop yield, known as Land Production Potential (LPP) (Sys et al., 1993).

This modeling program facilitates local governments and farmers in developing effective planning strategies. Findings from land suitability assessments could guide provincial governments in formulating land-use policies that integrate food, feed, and energy security. Incentives such as subsidies for biomass processing facilities or guaranteed feed-in tariffs for bioenergy could accelerate adoption.

This work contributes to innovation and scientific advancement by introducing an integrated spatial-biophysical framework for evaluating sorghum’s suitability and biomass energy potential in West Sumatra, thereby advancing the science of sustainable land-use planning and renewable energy resource assessment in tropical regions.

The novelty of this study lies in its first comprehensive application of established FAO and Van Ranst land-evaluation models to assess the biophysical suitability and production potential of sorghum as a biomass energy crop in West Sumatra, Indonesia. By integrating Radiation-Thermal Production Potential (RPP), Climatic Production Potential (CPP), and Land Production Potential (LPP) with high-resolution local climatic, soil, and topographic datasets, the study produces a spatially explicit and region-specific analysis that has not been previously conducted. This integrated modelling framework provides new baseline insights into sorghum’s feasibility as a renewable-energy feedstock in humid tropical environments

The aim of this research is to assess land suitability levels in West Sumatra, Indonesia, in order to determine the area that is suitable for growing sorghum (Sorghum bicolor L.) as biomass energy crops in West Sumatra, Indonesia.

2. Material and Method

2.1. Study area

The study was conducted in Pesisir Selatan Regency, West Sumatra Province, Indonesia, a region characterized by humid tropical climate conditions and heterogeneous landforms relevant to biomass crop development. The area was selected to represent major agro-ecological zones currently used or potentially suitable for sorghum (Sorghum bicolor L.) cultivation as a biomass-energy crop.

2.2. Data sources

The evaluation integrated primary and secondary data. Primary data included field-based soil observations and production data obtained through structured interviews with farmers cultivating sorghum or comparable annual crops within the study area. Secondary data were derived from geological, soil, slope, and land-use maps, as well as relevant technical reports and published literature, and were used to support land-unit delineation and parameter threshold selection.

2.3. Land unit delineation and sampling design

Land units were delineated using a stratified approach based on the overlay of geological maps, slope classes, and existing soil maps. This approach ensured that sampling locations captured the dominant variations in parent material, topography, and soil type across the study area. Within each land unit, representative sampling sites were selected to reflect relatively homogeneous land characteristics, thereby minimizing internal variability and improving the reliability of land suitability classification.

2.4. Field survey and soil sampling

Field surveys were conducted to characterize soil morphology and environmental conditions at each sampling site. Soil profiles were described through augering and profile excavation, with observations of horizon depth, texture, structure, color (using the Munsell Soil Color Chart), drainage condition, and rooting depth. Soil samples for laboratory analysis were collected from representative horizons.

Composite soil samples were prepared for chemical analyses to reduce microscale variability while maintaining representativeness at the land-unit level. Undisturbed soil samples were collected using ring samplers for analyses requiring intact soil structure. All sampling locations were georeferenced using a Global Positioning System (GPS) to ensure spatial accuracy and reproducibility.

2.5. Laboratory analysis

Laboratory analyses were conducted using standardized and widely accepted methods appropriate for evaluating soil properties relevant to sorghum biomass production. Analytical procedures and instruments were selected according to the physical and chemical parameters measured, ensuring consistency and comparability with previous land-suitability studies.

2.6. Land suitability evaluation

Land suitability was evaluated using the FAO land evaluation framework, adapted for biomass-oriented Sorghum bicolor production under humid tropical conditions. Suitability classes and limiting factors were determined by comparing observed land characteristics with crop-specific requirements derived from literature and regional agronomic references. Actual Production Potential (RPP) was assessed based on existing land constraints, while potential improvements through feasible land management practices were incorporated into the evaluation of Current Production Potential (CPP). The Land Production Potential (LPP) was derived by integrating biophysical constraints with achievable management inputs, allowing differentiation between manageable and permanent limitations.

2.7. Observation and survey

The method involved conducting experiments and surveys in the designated area (Pesisir Selatan Region, West Sumatra, Indonesia). The data consist of primary data (production data obtained from interviews with farmers) and secondary data (analyzing reference materials from available reports). Conducting surveys and collecting soil samples were done. The selection of soil sample locations was based on information from geological maps, slope maps, and soil maps of the research area.

Soil sampling was conducted within three delineated land units representing the dominant soil landscape conditions of the study area. Within each land unit, soil samples were collected at a depth of 0-30 cm (upper) and 30-60 cm (lower), corresponding to the effective rooting zone for sorghum during early to mid-growth stages. Sampling was performed at six locations per land unit, with three repetitions at each location to account for local spatial variability.

At each sampling point, soil morphology and environmental conditions were documented through augering and profile observation, including horizon depth, texture, structure, drainage, and soil color (using the Munsell Soil Color Chart). Composite soil samples were prepared from the repeated subsamples for chemical analyses to ensure representativeness at the land-unit scale, while minimizing microscale heterogeneity. Undisturbed soil samples were collected using ring samplers for analyses requiring intact soil structure. All sampling locations were georeferenced using a Global Positioning System (GPS) to ensure spatial accuracy and reproducibility.

Standard tools, including drills, hoes, chopping knives, measuring meters, GPS (Global Positioning System), Munsell Soil Color charts, plastic sampling bags, and ring samplers, were commonly used in the field. These tools were employed to survey and collect samples. In the laboratory, tools were selected based on the specific analyses to be conducted. The environment and morphology of the soil were observed in the field by creating soil profiles and drilling. The soil samples used for chemical analysis were composite samples, ensuring that they did not affect the physical characteristics of the soil.

2.8. Analysis of soil in the laboratory

Observation of soil properties and characteristics includes:

1. Analysis of organic matter using the Walkley and Black method.

2. The Kjeldahl method is used for the analysis of total nitrogen (N).

3. The dry ashing method is used for the analysis of total phosphorus (P).

4. The electrometric pH meter electrode method is utilized for the analysis of soil pH.

5. 1 N ammonium acetate washing method is employed for CEC (Cation Exchange Capacity) and determining base cations.

2.9. Analysis of land suitability for sorghum (data interpretation)

Data is analyzed by comparing land characteristics with the production of sorghum as a biomass energy crop, based on land condition and production of sorghum:

1. The measurement of land suitability is conducted at a semi-detailed level using a map scale of 1:50,000. In this category of semi-detail, the following data is required:

2. Climate data includes the mean duration of sunlight (n, hours/day), the mean maximum air temperature (Tmax, °C), the mean minimum air temperature (Tmin, °C), the mean humidity (RH, %), and the mean wind velocity (U, m/s). Additionally, it encompasses the total monthly rainfall (P, mm) and the total number of rainy days (RD).

3. Environmental data related to soil, such as drainage, soil depth, flood duration, land slope, and surface rock (rock outcrop), are important factors to consider.

4. Data on soil characteristics, including CEC, pH, total nitrogen (N), available phosphorus (P₂O₅), available potassium (K₂O), salinity, aluminum saturation, structure, and consistency.

2.10. Estimation of radiation thermal production potential (RPP)

To determine the Renewable Power Potential (RPP), data on the production of clean biomass are utilized. RPP is calculated using the mathematical Formula 1 provided below (Van Ranst, 1991):

$\text{RPP}=\text{Bn}\times \text{Hi}$ (1)

or

$$RPP=\frac{0.26\times bgm\times KLA{I}^{\text{R}}Hi}{1/2+(0.25:ct)}$$

$$bgm=fxbo=\left(I-f\right)xbc$$

where: f = Fraction of the daytime that the sky is overcast; bo = Maximum gross biomass production on overcast; bc = Maximum gross biomass production on clear days; Hi = Harvest Index.

The RPP calculation mentioned above was integrated into a Geographic Information System (GIS) using ArcGIS.

2.11. Estimation of climatic production potential (CPP)

CPP estimation starts with the calculation of the parameters listed below (Van Ranst, 1991) (Equation 2):

1. Evapotranspiration of referential crop (ET_o)

2. Evapotranspiration of aero (ET_aero)

3. Evapotranspiration of radiation (ET_rad)

4. Evapotranspiration maximum (ET_max)

5. Crop coefficient (kc)

6. Total of water available (Sa), i.e. amount of water between spacious capacity and permanent wilt point.

7. Rainfall- effective (P_eff)

   $$CPP=RPP\left[1-E{T}_a\right]/E{T}_{max}]$$(2)

Ky is a factor of harvest respond and ET_a is actual evapotranspiration.

2.12. Estimation of land production potential (LPP)

LPP is calculated by first obtaining the CPP value by considering index of soil data (Sy) and the land management index (My). The Formula 3 for LPP is as follows (Van Ranst, 1991):

$$LPP=CPPxSy$$ (3)

where: My = Ya/( CPP x Syp); Ya= crop production in the land (kg/ha); Syp= index of soil, which is obtained from approach formula in parametric; while My is obtained from the table of FAO about rating of land management.

3. Results and Discussion

Based on climate data, the land designated for this research can be categorized as an area with high potential for growing sorghum. The available water supply for this plant is adequate, and the air temperature is suitable, indicating that the land suitability classification is highly suitable (S1). In West Sumatra, Indonesia, precipitation exceeds the potential for evapotranspiration, as noted by Papadakis; this information is illustrated in Table 1.

Table 1
Monthly and Annual Precipitation Rates in West Sumatra, Indonesia.

Month	Precipitation rate (mm)	Evapotranspiration (mm)	Water surplus (mm)
January	282.98	149.70	133.28
Feb	294.19	146.97	147.22
Mar	220.65	162.89	57.76
April	216.13	152.98	63.15
May	208.34	162.27	46.07
June	172.91	159.90	13.01
July	388.66	165.46	223.20
August	248.01	147.51	100.50
Sept	260.79	138.89	121.90
Oct	209.56	134.71	74.85
Nov	339.69	120.60	219.09
Des	372.21	135.56	236.65
Total	3214.12	1428.546	1436.68

Based on the data presented in Table 1, West Sumatra experiences a high total annual rainfall of 3,214.12 mm. According to Aldrian and Dwi Susanto (2003), this region falls under the equatorial rainfall pattern, influenced by its geographical position near the equator. The highest rainfall occurs in July (388.66 mm) and December (372.21 mm), while the lowest is recorded in June (172.91 mm).

The monthly rainfall distribution indicates that West Sumatra does not experience a distinct dry season, as monthly rainfall consistently remains above 150 mm throughout the year. Hermawan (2018) notes that this condition is highly favorable for agricultural activities requiring a continuous water supply but may also lead to drainage problems on certain soil types. Ameliawati et al. (2022) suggest that in areas with high rainfall, such as West Sumatra, sorghum planting should be scheduled during months with lower rainfall, such as May (208.34 mm) or June (172.91 mm), to avoid waterlogging during critical growth phases.

The total annual evapotranspiration in West Sumatra reaches approximately 1,428.55 mm, with a monthly average of about 119 mm. The highest evapotranspiration values occur in March (162.89 mm) and July (165.46 mm), while the lowest values are recorded in November (120.60 mm) and October (134.71 mm). According to Kusumastuti et al. (2021), elevated evapotranspiration rates in certain months are associated with higher air temperatures and increased wind speeds during those periods.

The total annual water surplus in West Sumatra reaches approximately 1,436.68 mm. The highest surpluses occur in July (223.20 mm) and November (219.09 mm), indicating potential risks of flooding or waterlogging during these months. Even in June, which has the lowest surplus (13.01 mm), there is still excess water. According to Meijide et al. (2020), effective management of water surplus is essential to prevent soil erosion and support water resource conservation. Hariprabowo et al. (2019) note that excessive water surplus can lead to nutrient leaching and disrupt aeration in the sorghum root zone, as sorghum plants are highly sensitive to anaerobic conditions caused by prolonged waterlogging.

To address the challenges posed by excess water, Tari et al. (2022) recommend developing sorghum varieties with enhanced tolerance to wet conditions or implementing cultivation practices such as planting on raised beds combined with effective drainage systems.

Data shows that West Sumatra experiences abundant water availability year-round, which is highly significant for agricultural activities. However, good water management is still needed to address water surplus in certain months and optimize crop productivity. Pratiwi et al. (2019) suggest developing an effective drainage system and selecting crops suitable for local climate conditions to enhance agricultural production in high-rainfall regions like West Sumatra.

3.1. Evaluation of climate for growing and production of sorghum in West Sumatra, Indonesia

West Sumatra experiences a consistent water surplus throughout the year, with no distinct dry season. This stable rainfall pattern provides sufficient water to grow sorghum. Adequate water availability facilitates the dissolution of nutrients in soil, making them accessible for plant uptake. Conversely, during dry periods, plant roots may struggle to absorb nutrients effectively, potentially affecting sorghum production (Fiantis, 2001) (Figure 1).

Figure 1
Water Balance in West Sumatra, Indonesia.

Based on the calculation, the amount of evapotranspiration (ETo) estimated using the Doorenbos and Pruitt (1977) method is higher than the PET calculated using the Papadakis method. This discrepancy arises because the Papadakis method primarily considers precipitation and average air temperature, whereas the Doorenbos and Pruitt method incorporates additional parameters such as relative humidity of air, wind speed, duration of sunlight, day length, and radiation. This observation aligns with the findings reported by Fiantis (2001), who reported that the amount of evapotranspiration of oil palm (ETO), calculated using the Doorenbos and Pruitt (1977) method, ranges daily from approximately 3.23 to 8.58 mm, and monthly values range from about 100.14 to 257.56 mm, which are higher than those obtained using the Papadakis method.

The dry and hot valley area of Jinsha River exhibits minimal temperature difference across seasons and receives annual rainfall between 850 and 1,200 mm. The dry and wet seasons are distinct, belonging to the subtropical monsoon climate, which is suitable for planting sorghum and other crops. Sorghum thrives in warm conditions with ample sunlight, requiring optimal temperatures ranging from 20 °C to 30 °C throughout its growth period (Yang and Zhong, 2022). In the Agamsa sub-watershed of northeastern Ethiopia, land suitability assessment for sorghum cultivation has been conducted using soil, climate, and topographic characteristics as primary criteria (Tadesse and Negese, 2020). Sorghum is recognized as a climate-resilient crop, particularly favored by rainfed farmers in regions experiencing severe moisture stress (Chadalavada et al., 2022).

In Pesisir Selatan Regency, West Sumatra, Indonesia, suboptimal land is commonly found in hilly and coastal areas. The land is generally cultivated with perennial crops such as coconut, rubber, and coffee. However, the productivity of these crops is relatively low due to some factors (Sefano et al., 2024).

Based on the calculated climate parameters—including precipitation, maximum and minimum air temperatures, average air temperature, sunlight duration, day length, wind speed, and relative humidity—the potential for sorghum production in the study area is classified as suitable (S). This classification is supported by the results of the Climate Production Potential (CPP) and Land Production Potential (LPP) assessments for sorghum, as presented in Table 2. Additionally, spatial data illustrating the Regional Production Potential (RPP), CPP, and LPP across the research location are provided in Table 3.

Table 2
Value of RPP, CPP and LPP of sorghum (Sorghum bicolor L.) per month in West Sumatra, Indonesia.

Sample	Real Production (t ha−1)	RPP (t ha−1)	CPP (t ha−1)	Management Index (My)	Soil Index (Sy)	LPP (t ha−1)
I	10	5	3.7	0.67	0.5	1.2395
II	8	5	3.7	0.38	0.5	0.7030
III	8	5	3.7	0.67	0.5	0.8695

• RPP = Radiation Potential of Production; CPP = Potential Production based on climate; LPP = Potential Production based on Management and Land Management.

Table 3
Value of RPP, CPP and LPP of sorghum (Sorghum bicolor L.) per year in West Sumatra, Indonesia.

Sample	Real Production (t ha−1)	RPP (t ha−1)	CPP (t ha−1)	Management Index (My)	Soil Index (Sy)	LPP (t ha−1)
I	120	60	44.4	8.04	6	21.45
II	96	60	44.4	4.56	6	12.16
III	96	60	44.4	5.64	6	15.02

• RPP = Radiation Potential of Production; CPP = Potential Production based on climate; LPP = Potential Production based on Management and Land Management.

Table 2 indicates that RPP and CPP values for sorghum in West Sumatra, Indonesia, differ despite the use of the same variety. The RPP value, which is 5 t ha⁻¹ in the location, is higher than the CPP value, which is 3.7 t ha⁻¹. RPP value (5 t ha⁻¹) represents the ideal production of sorghum, which is influenced by solar radiation. Thus, based on the climate conditions at West Sumatra, Indonesia, the region should result in the production of sorghum reaching 5 t ha⁻¹. The lower CPP value, i.e., 3.7 t ha⁻¹, shows a production that is influenced by rainfall in West Sumatra, Indonesia. This condition shows that production of sorghum at the location is influenced by climate, mainly duration of sunlight and rainfall, which will influence the photosynthesis process of sorghum (Amoah and Antwi-Berko, 2020). Climatic variation is documented as among the most noteworthy problems encountered by human beings with respect to worldwide food security and ecological stability (Godfray and Garnett, 2014).

Sorghum exhibits remarkable adaptability to various environments, especially under water-deficient conditions (Abreha et al., 2022). Due to this characteristic, the crop is a great crop with valuable utility in the region with irregular rainfall distribution and high air temperature (Griebel et al., 2019). Sorghum is a highly drought-tolerant crop and has been increasingly used as a model cereal to identify genes that confer tolerance (Abdel-Ghany et al., 2020). The higher photosynthetic rate under elevated CO₂ conditions in rice was observed in the overexpression of Ribulose Bisphosphate Carboxylase (RuBisCo) RbcS sorghum and knocked-out rice RbcS by the CRISPR/Cas9 system (Matsumura et al., 2020).

Furthermore, Table 3 indicates that LPP of sorghum in location I.E. ranges from approximately 0.703 to 1.239 t ha⁻¹, which is lower than the RPP and CPP values. The LPP value represents the real production of sorghum in the location. The difference occurs because of climate, management, and soil factors. Notably, in sloping areas, the LPP value is higher than at the base of the slopes, which is typically utilized for rice cultivation.

Figure 2and 3, Tables 2and 3 show that the land is highly suitable for growing sorghum in the research location in West Sumatra, Indonesia. This assessment is based on observed land characteristics and calculated land suitability indices. The actual sorghum yield in the study area closely aligns with the estimated CPP and LPP values of sorghum in West Sumatra, Indonesia, suggesting that the environmental and management conditions are conducive to optimal sorghum growth. Therefore, the result of research shows that West Sumatra, Indonesia, is suitable for growing sorghum since there are optimal supporting factors such as fertile soil and appropriate climatic conditions (Tables 4 and 5).

Figure 2
Potential production of Sorghum (Sorghum bicolor L.)in West Sumatra, Indonesia.

Figure 3
Land evaluation of Sorghum (Sorghum bicolor L.) and potential production in West Sumatra, Indonesia.

Table 4
Climate Suitability Rating for Sorghum (Sorghum bicolor L.) in West Sumatra.

Sim	Climate parameters	Value	Class	Level limit	Rating
C	Rain (mm)	2.238.773	S1	0	100
C	Average temperature	267.525	S1	0	100
C	Max Temperture	332.708	S1	0	100
C	Min Temperaure	201.898	S1	0	100
C	n/N	976.686	S1	1	85
	Climate Index	Storie Method/Square Root Method			75/78
	Climate Rating	Storie Method/Square Root Method			85/92
	Climate class		S1/S1	S1

Table 5
Soils properties Chemical at West Sumatra, Indonesia.

Soil’s Chemical	Upper *	lower*
pH	4.4 m	4.75 m
C-organic (%)	2.6 s	3.89 s
N- tot (%)	0.25 s	0.27 s
P (ppm)	7.00 sr	9.00 sr
CEC (me/100 g)	3.46 r	14.29 r
Base saturation (%)	14.94 sr	16.23 sr
K (me/100 g)	0.29 r	0.35 s
Na (me/100 g)	1.11 s	1.18 s
Ca (me/100 g)	0.28 sr	0.32 sr
Mg (me/100 g)	0.33 r	0.47 r

• ^*
  m = acid; sr = very low; r = low; s = medium; t = high; CEC = Cation Exchange Capacity.

The data in Table 4 shows an evaluation of climate suitability for sorghum cultivation in West Sumatra. Based on both the Storie Method and Square Root Method classifications, the climate condition in this region is highly favorable for sorghum growth. The rainfall parameter reaches 2236.773 mm and is categorized as class S1 (highly suitable) with a rating of 100. The average temperature in this region is 26.75 °C, which is also classified as the S1 category with a rating of 100. This is consistent with findings by Sirappa (2020), who stated that sorghum grows optimally at temperatures between 23 °C and 30 °C. The maximum temperature reaches 33.27 °C, and the minimum temperature is 20.18 °C, both classified as S1 with a rating of 100. Wahyuni et al. (2019) explain that sorghum tolerates high temperatures well, but it still requires a certain minimum temperature for germination and vegetative growth. The n/N ratio of 97.66% is categorized as class S1 with a rating of 85. The parameter relates to the duration of sunshine, which is very important for the process of photosynthesis and sorghum grain development according to Zulkarnain et al. (2017). The climate index is 75 based on the Storie Method, and it reaches 78 with the Square Root Method. The climate rating reaches 85 with the Storie Method and 92 with the Square Root Method. Both methods classify the climate suitability for sorghum in this region as class S1 (highly suitable).

Based on the data in Table 5, the soil in West Sumatra has a pH ranging from 4.4 to 4.75, indicating a very acidic condition. Soil pH below 5,5 can lead to increased solubility of Al and Fe, which can bind phosphorus and cause deficiencies in plants (Mulyani et al., 2021). Acidic soil in Sumatra is generally the result of intensive base leaching due to high rainfall (Subagyo et al., 2018). C-organic content varies between 2.6% to 3.89%, which is classified as medium. Soil with medium organic C content requires additional organic matter to enhance soil microbial activity and nutrient availability (Prasetyo and Suriadikarta, 2019). Total nitrogen (N) ranges from 0.25% to 0.27%, both classified as moderate. Soil with moderate N content still requires nitrogen fertilization to support optimal plant growth (Widowati et al., 2020). Available phosphorus is very low at both levels, ranging from 7.00 ppm to 9.00 ppm. According to Hartono et al. (2022), in acidic soil in Indonesia, phosphorus is often fixed by Al and Fe, forming compounds that are unavailable to plants. Soil CEC varies between 3.46 me/100g to 14.29 me/100 g, indicating a low to medium ability to retain and exchange cations. Soil with low CEC tends to have limited nutrient storage capacity (Hartatik and Setyorini, 2022). Soil base saturation ranges from 14.94% to 16.23%, which is classified as very low. According to Sutandi (2019), soil with low base saturation generally has low fertility and requires liming to increase pH and nutrient availability. The content of exchangeable cations such as K (0.29-0.35 me/100g), Na (1.11-1.18 me//100g), Ca (0.28-0.32 me/100g), and Mg (0.33-0.47 me/100g) is at low to medium levels. Research conducted by Nursyamsi et al. (2018) shows that the low content of basic cations in acidic soil in Indonesia is associated with high rainfall, which causes leaching of bases from the soil profile.

Research about sorghum cultivation in West Sumatra, Indonesia, covered approximately 8 tons/hectares and yielded wheat seed at a rate of 10 tons/hectare (Juniarti et al., 2020). Sorghum is one of the commodities that is expected to serve as a substitute for rice in reducing national food needs. Sorghum production in Indonesia is still very low, and sorghum products are not widely available in the market; therefore, efforts should be made to increase sorghum production, starting with the provision of the right form of cage fertilizer (Ariningsih et al., 2023).

Nitrogen fertilizer is one of the most important and widely used elements. However, losses of nitrogen through leaching and other pathways pose both economic challenges for farmers and environmental concerns for the broader community. Therefore, crops having efficient fertilizer and soil nitrogen utilization efficacy to maximize forage and grain yields are crucial (Saddam Hossain et al., 2022). Sorghum, for instance, contains essential minerals such as phosphorus, potassium, and zinc, with their concentrations varying based on the cultivation location (Shegro et al., 2012).

Although sorghum is recognized as a drought-tolerant crop and for its ability to thrive under low-input conditions, water deficiency can impair its nutrient uptake, nutrient mobilization, and transport mechanism (Sarshad et al., 2021). To elucidate the molecular basis of sorghum's response to drought stress, proteomic studies have gained prominence (Ngara et al., 2021).

The adoption of sorghum as a biomass energy crop in West Sumatra has the potential to generate significant socio-economic and policy impacts. Sorghum’s adaptability to marginal lands, tolerance to drought, and relatively short growth cycle make it a promising alternative for regions with limited suitability for rice or maize. Integrating sorghum into local farming systems could directly affect both rural livelihoods and broader energy policy agendas in Indonesia. Farmers can cultivate sorghum not only for food and feed but also as a biomass resource, creating multiple market outlets. This reduces dependence on single-commodity farming and strengthens household resilience against price fluctuations. By utilizing sub-optimal and degraded lands, sorghum cultivation minimizes competition with staple food production and promotes more efficient land use, turning previously underutilized areas into productive landscapes.

4. Conclusion

The land suitability evaluation conducted in West Sumatra, Indonesia, shows that the region is highly suitable (S1) for cultivating sorghum (Sorghum bicolor L.) as a biomass energy crop. The findings reveal that West Sumatra possesses favorable agroecological conditions, including average temperatures of 25-27 °C, rainfall below 200 mm, air humidity under 75%, well-drained soils, soil depths exceeding 60 cm, and moderately acidic soil pH levels between 4.4 and 6.1. Although the area exhibits low nitrogen, phosphorus, and potassium availability, these limitations can be addressed through targeted soil-nutrient management. The estimated actual sorghum yield potential of 5 t ha⁻¹ exceeds current production levels, indicating significant room for yield improvement.

A key innovation of this study is the development of the first integrated spatial-biophysical model for assessing sorghum suitability and potential production in West Sumatra. By combining Radiation-Thermal Production Potential (RPP), Climatic Production Potential (CPP), and Land Production Potential (LPP) within a unified geospatial framework, this research provides a new, region-specific decision-support tool for renewable-energy crop planning.

The successful integration of sorghum into West Sumatra’s agricultural and energy systems will require coordinated actions among research institutions, local governments, and private investors. Supportive policy frameworks, infrastructure development, and farmer capacity-building programs will be essential to ensure that sorghum adoption advances not only renewable energy expansion but also sustainable rural development across the region.

Acknowledgements

The authors would like to express their sincere gratitude to all parties of both the local community and the local government of West Sumatra, Indonesia, and others involved in this research activity. We also extend our appreciation to Directorate of Down streaming and Partnerships, Directorate General of Research and Development, Ministry of Higher Education, Science, and Technology (KEMENDITISAINTEK) for providing financial support that made this study possible.

Data Availability Statement

The research data analyzed in this study are not publicly available by any means. Data will be available at request.

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Edited by

• Editor:
  Takako Matsumura Tundisi

Publication Dates

• Publication in this collection
  29 May 2026
• Date of issue
  2026

History

• Received
  18 June 2025
• Accepted
  31 Jan 2026