Sensitivity Analysis

A risk model sensitivity analysis can be used to identify the most significant risk factors and to assist in developing priorities for risk mitigation (Frey and Patil 2002). According to (Kumar and Parikh 2001), climatic conditions greatly impact agricultural yields. Climatic anomalies, including those associated with La Nina and El Nino, can affect agricultural productivity. This is one of the factors that need to be considered in conducting a sensitivity analysis. Production costs and changes in the level of productivity of *Indigofera* spp. are parameters that are determined by prevailing conditions.

The Potential Economic and Social Value of the Development of *Indigofera*

Economic value is determined on the basis of the net profit value per hectare multiplied by the size of the area deemed to be most suitable (S1) for *Indigofera* cultivation, with three development target scenarios: 100% planted area (scenario 1); 50% planted area (scenario 2); and 25% planted area (scenario 3). Social value is determined on the basis of the rate of labor absorption associated with the development of *Indigofera* spp.

potential income = net profit value × land deemed suitable for the cultivation of *Indigo f era* spp. (4)

> 2.2.6. Development Strategy for the Sustainable Utilization of *Indigofera* to Produce Natural Dye

Analysis of the strategy for the development of *Indigofera* was conducted through the application of a SWOT-AHP analysis to the descriptive data. This method has previously been used to formulate agricultural and manufacturing product development strategies for a number of commodities (Ali et al. 2021; Santos et al. 2019; Görener et al. 2012; Kazemi et al. 2018).

The analysis is conducted through the systematic identification of both internal factors, including strengths and weaknesses, and external factors, including opportunities and threats. The SWOT analysis is conducted in a number of stages, including: compiling the Internal Strategic Factors Analysis Summary (IFAS) and External Strategic Factors Analysis Summary (EFAS); analyzing the Internal Factor Evaluation (IFE) Matrix and External Factor Evaluation (EFE) Matrix; and analyzing the Strategy Matrix. Factor weights were determined on the basis of pairwise comparisons between factors using the Analytical Hierarchy Process (AHP). AHP is a mathematical method for multi-criteria decision making developed by (Saaty 2008).

#### **3. Results and Discussion**

#### *3.1. Evaluation of the Cultivation and Utilization of Indigofera spp.*

Plant materials used for the production of colored dyes, especially *I. tinctoria* L. and *Morinda citrifolia* L., are collected from nature directly, either by the artisans themselves or by professional collectors (Setiawan and Suwarningdyah 2014). The collection of these plants is informed by different bodies of local wisdom. In Atambua, weavers believe that there is a strong spiritual dimension to the relationship between humans and nature so that they only collect enough plant materials to meet the needs of the producing household income (Siombo 2019). In general, weavers use naturally-growing *Indigofera* spp. grown in their gardens without any intensive cultivations to meet the production needs of the dye's raw materials (Seran and Hana 2018; Agustarini et al. 2021; Murniati and Takandjandji 2015).

Based on information from weavers in the research location, there are two species of *Indigofera* spp. in the region, these being *I. suffruticosa* Mill. and *I. tinctoria* L. (Agustarini et al. 2021). They explained that the species of *Indigofera* used produces a particular type of fruit (*I. suffruticosa* Mill.), as this type is more commonly found in gardens than *I. tinctoria* L. Users of *Indigofera* as a natural dye on Timor Island are weavers who are still on a household scale, so they only rely on plants that exist in nature. However, if in the future the industry becomes more developed to support cultural tourism, it is necessary to use cultivation.

The results of interviews with respondents indicate that the community is more familiar with *Indigofera* for use to produce black dye rather than blue, a finding supported by two other studies (Ledoh et al. 2021; Nomleni et al. 2019). The black color is obtained by mixing clay with *Indigofera* spp. and applying it to the thread. In this area, a synthetic dye is used for blue. Regarding the composition of the raw materials, they produce the dyes based on their needs and their available equipment. Usually, natural dyes are applied directly to the yarn after they are produced, without any attempts to store them.

The people of Timor Island, NTT, rely mainly on farming or animal husbandry for their livelihood. However, *ikat* weaving is another livelihood that is no less important. The activity of making *ikat* has been integrated with the daily activities of the community, especially the women (Buni et al. 2021). In the past, weaving was an activity for leisure time. Nowadays, along with the development of cultural tourism, *ikat* weaving has became a profitable source of income (Samadara 2018).

Women are more dominant in the activity of making *ikat*, which can be seen from the composition of weaver respondents, with a composition of 65% of women and 35% of men (Table 1). This is supported by the myth that developed in the community, especially in terms of processing *Indigofera* as a paste. There is a strict taboo forbidding men from being directly involved in producing dye from *Indigofera*, with a belief that those who violate that taboo will be cursed with infertility (personal communication with Marthen Tualaka, member of Farmer Group in Bosen Village, North Mollo, TTS District on 28 March 2019). Therefore, women dominate the process of manufacturing natural dyes from *Indigofera*, whereas men are more involved in the cultivation of *Indigofera*.

**Table 1.** Respondent information in three (3) research locations.


The main job of the head of the family is generally as a farmer whose sources of income are very small and also depend on the seasons. In general, the role of the women economically adds to the family's income. However, based on the study of (Buni et al. 2021) in Sumba shows that the contribution of women's income to the weaving business and animal rearing is household income is very large, equal to 88%.

Training on the use of *Indigofera* as a natural blue dye is still rarely done. Thread of Life, a social enterprise that promotes the community-scale production of textiles using traditional materials and techniques as a means of achieving poverty alleviation, has made efforts to introduce the use of *Indigofera* in producing natural blue dye. In 2016, the organization conducted training programs and other forms of assistance to enable local communities to produce indigo paste from *Indigofera* with this training. It is expected that there will be an uptake in the use of *Indigofera* to produce good-quality and highly durable blue dye. Thread of Life could also play a role in facilitating access to markets for the indigo paste and the *ikat* that is produced by the community using natural dyes.

The community has responded to these initiatives positively, being open to receiving information and guidance and expressing enthusiasm for cultivating *Indigofera* spp. and the manufacturing of indigo paste. However, ongoing training and assistance will be needed to enable the community to produce indigo paste that meets market requirements. It is expected that these investments in community capacity building will produce positive impacts and benefits for all stakeholders involved in the cultivation and utilization of *Indigofera* spp. and for communities more generally.

#### *3.2. Techniques for the Cultivation of Indigofera spp.*

The system used to cultivate *Indigofera* spp. was similar to one applied in the Philippines (Mann and Garrity 1994). *Indigofera* spp. is never cultivated in monoculture systems but is always intercropped with other food-producing and/or commercial crops, including maize, green beans, and tobacco. It has been suggested that the cultivation of *Indigofera* spp. in multi-crop systems would reduce the need for chemical fertilizers (Garrity et al. 1994). Given that *Indigofera* spp. is a type of legume, intercropping with this plant could play a positive role in the nitrogen fixation process (Nezomba et al. 2008).

These techniques for the cultivation of *Indigofera* spp. could be adjusted to meet the needs of members of local communities on Timor Island on the basis of considerations related to the availability of land and applied where intercropping systems are in place for the cultivation of seasonal crops (maize), with the spacing between the plants adjusted in accordance with the conditions required for this system. In general, farmers on Timor Island plant maize with a distance between plants of 75 × 75 cm, although on dry land, the optimal spacing for maize is 100 × 50 cm (Arifin and Tafakresnanto 2019). For the cultivation of *Indigofera* spp., distances between plants of 100 × 100 cm are applied, intercropped with maize (with a spacing of 100 × 50 cm) (Figure 2).

The techniques applied by the community for the cultivation of *Indigofera* spp. cultivation technique involved a number of stages, from germination to seeding and planting in the field. At each of these stages, the results of the research were applied, with the following identified as the best practice techniques for cultivation:

■ Germination. *Indigofera* seeds are characterized by external dormancy, as is the case with other types of legumes. Thus, they need to be subjected to a process of scarification to overcome this dormancy, with scarification achieved through immersion (Luna et al. 2009). The results of the research demonstrate that the combination of scarification and sowing media had no significant effect on the germination of *I. tinctoria* L. The treatment that had the greatest impact on germination was the sowing media. The three treatments that have the greatest impact on the germination of the *I. tinctoria* L. were without scarification (control), soaking in cold water for 24 h, and soaking in pure coconut water (100%) for 30 min. These treatments resulted in the highest germination rates in sand media, at 73.33%, 77.33%, and 88.00%, respectively (Table S1). By contrast, seeds sown on soil media and on a mixture of soil and sand produced a germination rate below 50%. This indicates that sand is a suitable medium for sowing *I. tinctoria* L. seeds. Even though the sand medium is poor in nutrients, according to (Wiryanta 2007), sand contains a number of minerals essential for the

■ plants' growth. In addition, the porosity of the sand media enables imbibition and adequate aeration, enabling the seeds to germinate rapidly.

Seedling. Based on experience on Timor Island, planting *Indigofera* directly from seeds in the field without going through a nursery will cause delays in leaf harvesting. Planting using seedlings will harvest at the age of 4 months while using direct seedings when the plant is one year old. The successful growth of the plants is heavily dependent on the quality of the seeds, with the quality of the seeds being determined by the media used in the nursery. Therefore, mixed media with a sufficient level of nutrients and porosity results in the production of high–quality seeds. In addition, according to (Fredrick et al. 2020; Onyekwelu et al. 2012; Veloso et al. 2017), light intensity is another environmental factor that affects the survival and growth rates of seedlings with each plant species requiring a different light intensity for growth. Research shows that *I. tinctoria* L. seedlings planted in a mixed media consisting of soil, cocopeat, and rice husk charcoal (1:2:2) and placed in an unshaded location (0%) had the highest TR ratio and SQI, namely 5.53 and 0.0030, respectively (Table S2).

**Figure 2.** Cropping pattern of *Indigofera* spp. with maize on Timor Island.

The high TR ratio indicates that the media used is relatively fertile and that sufficient water is available (Orpa et al. 2019). According to (Rivai et al. 2015), rice husk charcoal has good aeration and drainage properties but low water holding capacity, while coco peat has both high porosity and water holding capacity. Mixing these two media with soil produces an ideal medium for the growth of *I. tinctoria* L. seedlings, particularly in an unshaded location (0% shade). By contrast, *I. tinctoria* L. seedlings planted in a mixture of soil and rice husk charcoal (1:2) and placed in 50% shade resulted in a seed quality index of 0.0030, but with a lower shoot to root ratio value (4.72). According to (Orpa et al. 2019), the low value of the root to shoot ratio indicates that the rate of the growth of shoots is lower than that for roots. This indicates that the level of nutrients contained in the mixed soil and rice husk charcoal media is lower than in the mixed soil, cocopeat, and rice husk charcoal media so that plants concentrate on forming roots to optimize nutrient absorption. Both types of media and shade treatment combinations also produced a relatively high biomass compared to other treatments, at 0.0768 and 0.0798 g, respectively. According to (Orpa et al. 2019), the increase in biomass indicates that photosynthesis is proceeding well, thereby resulting in increased plant growth. This is presumably due to an improvement to the growth media resulting from the addition of rice compost charcoal and/or cocopeat, with an increased soil nutrient content and improved aeration and drainage. However, both types of media require different light intensities to promote optimal seedling growth.

At three weeks of age, the *I. tinctoria* L. seedlings did not meet the criteria for transferring seedlings to the field, with the quality index value of the seeds failing to reach 0.09 (Bogidarwanti and Darwo 2016), with a minimum SQI value of 0.09 required to ensure a high survival rate. According to (Ariyanti and Asbur 2018), *I. tinctoria* L. seedlings are ready to be planted in the field at the age of 4–6 weeks, while *I. suffruticosa* Mill. seedlings are ready at around the age of 6–8 weeks or when the minimum seedling height is 30 cm. The use of ready-to-plant seeds may result in seedlings that are able to compete with those growing in a natural environment, where environmental factors cannot be fully controlled.

■Planting. The viability of *I. suffruticosa* Mill. plants up to the age of 4 months stood at 100% for all spacings, with the results of the research showing that the spacing treatment and the application of fertilizers did not significantly affect the growth of *Indigofera* spp. at 4 months of age. However, *I. suffruticosa* Mill. planted at a spacing of 100 × 100 cm showed better growth than the plants spaced at 75 × 75 cm and 50 × 50 cm. The average increase in height, diameter, and branch of *I. suffruticosa* Mill. planted at a spacing of 100 × 100 cm stood at 25.87 cm, 3.26 mm, and 6.44, respectively (Table S3). According to (Li et al. 2019), plant spacing has an effect on the final yield of a range of different types of plants. Likewise, (Azam-Ali and Squire 2002) reported that plant density depends on the soil, climate, and the type of plant grown. In extreme conditions, with poor soil and in semi-arid areas without irrigation, planting is best conducted at low density to avoid the growth of weak, weedy plants. Not only do these extreme conditions result in low yields; they also create ideal conditions for pests and diseases. With the different fertilizer treatments, the results of the analysis show that fertilizer dose sizes did not result in a significant difference in growth rates but that the application of fertilizer (100, 150, and 200 g per plant) resulted in better growth in diameter and number of branches than in the case of plants planted without fertilizer (0 g plant−1). Similarly, the results of a study conducted by (Setiono and Azwarta 2020) show that the application of cow manure had a significant effect on plant height, stem diameter, number of leaves, and net weight of cobs per plant in maize, with the best results produced with 600 g of fertilizer per plant. This indicates that the soil at the study site required the addition of the appropriate amount of nutrients to facilitate growth, with the application of manure as a basic fertilizer at the beginning of the planting process adding macronutrients and some micronutrients required for plant growth, as well as improving soil structure, aggregating water holding capacity, and increasing soil permeability and the exchange of cations. Found in the study (Nyakpa et al. 2008) manure, as an organic fertilizer, plays an important role in the growth of plants due to its positive effects on the physical and chemical properties of the media. Manure can increase the media's capacity to absorb water and improve the living conditions of the microorganisms in the media, stimulating granulation and enabling available nutrient ions to trigger cell wall growth, resulting in increases to the size of the stem diameter.

The results of the research showed that the most significant factor in the cultivation of *Indigofera* in TTS is planting time, with the planting time having a strong effect on the leaf production of *Indigofera*. According to (Ariyanti and Asbur 2018), the optimal time to plant *Indigofera* is at the beginning of the rainy season. Therefore, the recommended time to plant *Indigofera* on Timor Island is in November, which receives high rainfall.

Planting at this time results in optimal growth and high leaf production. By the time of the arrival of the dry season, the plants have adapted to the environment, so there is no need for watering. However, in cases where the dry season occurs earlier than forecast, watering may be required. Under normal conditions, *Indigofera* leaves can be harvested four months after planting.

*Indigofera* plants are productive for about 2–4 years, depending on the species and growing location. For example, the life cycle of *Indigofera tinctoria* L. on Java Island is 2–3 years (Kurniawan 2020; Ariyanti and Asbur 2018). The development cycle for the cultivation of *Indigofera* spp. described above throughout the four stages (germination, seedling, planting and harvesting) is very different from the cycle traditionally applied by the community (Figure 3A). The community only harvests *Indigofera* spp. plants found in nature, usually once a year, following the commencement of the rainy season (Figure 3B).

**Figure 3.** The production cycle for *Indigofera* spp. over 48 months: (**A**) application of cultivation techniques, (**B**) utilization of *Indigofera* spp. by the community. Notes: I = germination and seeding (1.5–2 months), II = planting (4 months), III = harvesting (4 months after planting, or when the plants are ready), IV = post-harvest maintenance/leaf pruning (4 months).

The initial planting of *Indigofera* is conducted at the beginning of the rainy season (around November) and preceded by germination and seedling (1.5–2 months before). The cultivation of *Indigofera tinctoria* L. on Java Island, harvesting is carried out when the plants are 4–5 months old. The next harvest is carried out 3–4 months after the first harvest or it can be harvested 3 times a year, with the life span of the plant as a dye producer being 2–3 years (Kurniawan 2020; Ariyanti and Asbur 2018). Furthermore, (Ariyanti and Asbur 2018) say that *Indigofera tinctoria* L. grows optimally in areas with rainfall below 1750 mm year<sup>−</sup><sup>1</sup> accompanied by a hot and humid climate. The dry condition of Timor Island (rainfall 1211–1242 mm year<sup>−</sup>1) makes the frequency of harvesting not as often as in Java, a maximum of 2 times a year. Harvesting on Timor Island is conducted 4 months after planting when the plants are in full bloom, and the leaves are colored bluish green (community experience). Harvesting is conducted in the morning at 4–6 am (Ariyanti and Asbur 2018), with the process involving pruning at the bottom (1 m from the bottom) (Muzzazinah et al. 2021).

The initial harvesting takes place in March and a secondary harvest takes place in July. Likewise, maize, which is a staple crop, is planted in November and harvested in April, with the full cycle taking a year. Following the second harvest in July, the dry season arrives, during which period the plants will experience a decrease in growth. However, with the return of the rainy season, the growth of the *Indigofera* increases, enabling harvesting to take place in around March of the following year. Figure 3 depicts the annual production cycle.

#### *3.3. Processing Indigofera Leaves to Produce Indigo Paste*

After harvesting, the leaves of the *Indigofera* are immediately separated from the twigs, after which they are processed. This must be undertaken immediately to obtain a high yield of indigo dye. According to (Ariyanti and Asbur 2018), semi-dried or dry leaves will produce only a low yield because the β-glucosidae enzyme is more active in fresh leaves than in semi-dried or dry leaves. *Indigofera* leaves extract contains indican glucoside, which can be hydrolyzed to glucose and indoxyl. Indoxyl itself is a colorless indigo precursor that, in alkaline conditions, is easily oxidized, resulting in the production of blue indigo pigment.

The production of indigo paste from *Indigofera* leaves involves three processes these being fermentation to release the indigo precursors, removal of the leaves and oxidation of the liquor as a result of aerating under alkaline conditions caused by the addition of slaked lime (Ca(OH)2), and the precipitation of the indigo dye with the slaked lime. Following these processes, the precipitate is used to produce a paste that is ready for use (Figure 4).

**Figure 4.** Process of producing paste from *Indigofera* leaves.

There are a number of differences between the indigo paste processing technique and the community utilization process. More details can be seen in Table 2.


**Table 2.** Differences between the indigo paste processing technique and the community utilization process.

#### *3.4. Potential Cultivation Area of Indigofera spp. on Timor Island, Indonesia*

*Indigofera* spp. plants have a high level of adaptability, often growing in the wild in all types of soil, with high levels of tolerance to drought, flooding, and high salinity (Campos et al. 2018). Many are found growing in coastal regions in soil with clay-sand soil characteristics and with a pH ranging from 6 to 7. It grows well in locations with an average temperature of 22–28 ◦C and with a maximum temperature of 32 ◦C (Bobojonov et al. 2012). For the cultivation of plants, altitude is the first criterion that must be considered out of a number of topographical parameters. Altitude parameters are closely related to temperature parameters, with a relationship between altitude, temperature, and rainfall (Sagredo et al. 2014). *I. suffruticosa* Mill. can be found at altitudes of 1–1800 m asl, while I. tinctoria at 0–800 m asl. Both species grow in areas where the air temperature ranges between 21 and 34 ◦C. Generally, it is recommended that agricultural activities take place in flat areas to minimize soil erosion, in areas with soil of good quality (Kumar and Jhariya 2015). Due to impacts on environmental sustainability, cultivation on steep slopes is not recommended (Malley et al. 2006). Based on these considerations, the areas with the highest suitability scores are those with slopes of 0–3%. Climatic parameters are a critically important factor for plant growth, affecting a wide range of physiological processes (Gruda 2005). Both rainfall and temperature affect plant growth in high-land areas, as shown by a number of studies (Motsa et al. 2015; Naughton et al. 2015). Air temperatures have an impact on chemical reactions and the physical properties of plants, with effects both at the cellular level and at the plant level (Gruda 2005). On Timor Island, temperatures range from between 12.2 and 27.6 ◦C, with a maximum temperature of 33.5 ◦C.

The weight of the criteria generated from the AHP is presented in Table 3. The results showed that the consistency ratio (Cr) stood at 0.03. This value is still below the maximum threshold (Cr) of 0.1. This shows that the results are valid, in accordance with the threshold recommended by (Saaty 2008).

The results show that topographic and climatic conditions have a higher weight than soil quality. These results indicate that soil quality is not a limiting factor for the successful cultivation of *Indigofera* spp. Soil on Timor Island has specific characteristics, as follows: dominated by medium soil texture (±85% of the area); ±47% of the area has soil conditions with pH 7.1, CEC 10.4, and Corg 0.97. A study by (Suriadi et al. 2021) found that soil pH on Timor Island is neutral to alkaline. Although the soil is alluvium, the surrounding parent

material is made entirely of limestone. Soil derived from limestone parent material has a shallow solum of <50 cm, with most of it lithic. The soil also has very low organic carbon content. In terms of topographic conditions, the largest proportion of the land has a slope of <8% ( ±53% of the area), at an altitude of <600 m above sea level ( ±77% of the area). In terms of climatic conditions, the largest proportion of the land has an annual rainfall of 1000–1500 mm ( ±84% of the area), with an average temperature of 24 ◦C ( ±69%) and a maximum temperature of 30 ◦C ( ±48%). Timor Island is characterized by a dry climate (Suriadi et al. 2021).


**Table 3.** Weight of criteria resulting from pairwise comparison.

Notes: Text: texture, CEC = cation exchange capacity, Corg = C organic, Alt = altitude, RF = rainfall, Temp. = temperature, MaxTemp = maximum temperature.

The results of the land suitability analysis for *Indigofera* spp. on Timor Island are presented in Figure 5. Land that is not suitable for the cultivation of *Indigofera* spp. plants covers an area of less than ±1% of the total area of the island. The unsuitable land is mainly located around mountain peaks, characterized by a combination of physical properties that do not permit crop cultivation, including steeper slopes and very low temperatures. This land is generally not cultivated, with the land cover consisting of forests. Thus, almost 99 percent of the land on Timor Island is suitable for the cultivation of indigo plants. The degree of suitability varies, however, from *very suitable* (S1) to *marginally suitable* (S3), with the greatest proportion of the land falling into the very suitable (S1) category, with land in this category covering a total area of ±1.3 million ha.

To determine the suitability of land for the cultivation of *Indigofera* spp., a land availability analysis was conducted, based on considerations related to land cover and land-use conditions. Of the Indonesian territory on the Island of Timor that consists of agricultural land, 453,931 ha has suitable land conditions for indigo cultivation. However, the development of land for this purpose is directed at land not covered by forest and/or that has been used for plantations or other agricultural uses. Thus, 369,836 ha of the Indonesian territories of Timor Island are available for the cultivation of Indigo, with most of this land consisting of abandoned land, mostly either open land or covered with shrubs and grasslands (Figure 6).

In Indonesia, measures to develop the cultivation of *Indigofera* spp. could also play a role in accelerating land rehabilitation, considering that a large proportion of the suitable areas consist of critical land ( ±80%), with more than 60% of this area located outside forest areas (Other Use Area (*Areal Penggunaan Lain*, APL)). Measures to accelerate land rehabilitation initiatives are important, particularly in the context of the threat of deforestation in the tropical mountain forests of Timor (Pujiono et al. 2019). The most suitable land in critical APL areas could be prioritized for the development of *Indigofera* spp. ( ±163 thousand ha). The distribution of the area based on the level of criticality of the land and land function status is presented in Table 4.

**Figure 5.** Land suitability map Indigo on Timor Island.

**Figure 6.** Land availability map for the cultivation of Indigo on Timor Island.


**Table 4.** Area available for the cultivation of indigo cultivation based on land function status and land criticality for the prioritization of rehabilitation efforts.

Remark: S1 = suitable, S2 = moderately suitable, S3= marginally suitable.

#### *3.5. Economic Analysis of the Cultivation of Indigofera spp.*

#### 3.5.1. Feasibility Analysis

A business feasibility assessment was conducted to determine the feasibility of the development of *Indigofera* spp., including cultivation activities and the production of indigo paste. *Indigofera* spp. cultivation activities includes nursery, nursery maintenance, planting preparation, planting, and plant maintenance. The production of indigo paste activities includes harvesting and processing the paste.
