Planting patterns in rubber agroforestry (Hevea brasiliensis) developed by the communities of Menggala Mas Village, Lampung Province, Indonesia

The alley planting pattern combines forestry and agricultural crops (Fig. 2). Alley cropping is a planting system where annual plants are planted in an alley between two rows of hedgerows, usually in the form of trees or shrubs (Evizal and Prasmatiwi 2021). The planting pattern for forestry plants resembles an alley (Idris et al. 2019). Plants in the alley include kayu afrika (Maesopsis eminii), pulai (Alstonia scholaris) and mentru (Schima wallichii).

Figure 2.

The dominant plant combinations include rubber–pulai and rubber–mentru–kayu afrika planted in the middle of rows of rubber trees. These plants can complement the rubber plant as an alley plant, which, according to farmers, have benefits for extracting its wood. The spacing between interplants is 6 m. According to farmers, this species of plant is easy to grow and is suitable for planting alongside rubber plants. They can sell the potential wood obtained from kayu afrika and mentru wood species or use them as building materials for their purposes. Pulai plants are usually widely cultivated to be later sold as ornamental plants which are widely used on roadsides or in tourist attractions in Tulang Bawang Barat Regency. Meanwhile, rubber wood can also be sold to make plywood or used simply as firewood.

This agroforestry planting pattern is a pattern for arranging plant space like a fence (Fig. 3). The way to plant forestry plants uses a fence form, namely, the tree components are arranged at the edge of the land and the agricultural plants are in the middle (Idris et al. 2019). The community combines various multipurpose tree species (MPTS) and forestry plants such as akasia (Acacia auriculiformis), jati (Tectona grandis), kapuk randu (Ceiba pentandra), petai (Parkia speciosa), nangka/jackfruit (Artocarpus heterophyllus), cempedak (Artocarpus integer), mango (Mangifera indica), lamtoro (Leucaena leucocephala), jambu (Psidium guajava) and mengkudu (Morinda citrifolia). The dominant plant combinations in this planting pattern are combinations of rubber–akasia, rubber–jackfruit–cempedak and rubber–petai–jati.

Figure 3.

People deliberately plant these plants as garden boundary marks or fences so that the rubber sap is not taken by other people. Selecting the plant species that provide many benefits according to farmers is followed, as the majority plant MPTS species for their fruit and trees for their wood. In line with research (Naharuddin 2018) which states that trees planted around land usually function as fences or land borders. This is under planted edge trees which can act as land ownership boundary markers, living fences, fire breaks, windscreens and can also act as protectors or soil binder if planted on unstable soil/edge of ravines.

The random pattern is the pattern most widely applied by the community because this planting pattern can be said to have no systematic distribution model (Fig. 4). Random mixture is a random agroforestry planting pattern, between forestry plants, agricultural plants, herbs and shrubs that grow unevenly distributed on a land (Willmott et al. 2023). The filler plants are very diverse, such as akasia (Acacia auriculiformis), gaharu (Aquilaria malaccensis), medang (Phoebe hunanensis), pelangas (Aporosa aurita), pulai (Alstonia scholaris), sungkai (Peronema canescens Jack), jengkol (Pithecellobium lobatum), petai (Parkia speciosa), mengkudu (Morinda citrifolia L.), jambu monyet (Anacardium occidentale), durian (Durio zibethinus Murr), coffee (Coffea sp.), kakao (Theobroma cacao), banana (Musa paradisiaca), takokak (Solanum torvum), ketepeng cina (Senna alata), gadung (Dioscorea hispida), lengkuas hutan (Alpinia malaccensis), turmeric (Curcuma longa), kumis kucing (Orthosiphon aristatus), cabe jawa (Piper retrofractum), cincau (Cyclea barbata), sereh (Cymbopogon citratus) and others.

Figure 4.

The dominant plant combinations used include rubber–jengkol, rubber–petai–jengkol–akasia, rubber–jackfruit–cempedak, rubber–pulai–mengkudu–jengkol and rubber–banana–gadung–sungkai. These plants are deliberately planted by the community, and some of them grow naturally. The species of plants that are widely planted are jengkol, petai and banana; this is because many people in this village are from the Lampung tribe and like to eat fresh vegetables. The community said that it often holds celebrations every day, namely, eating a dish of ‘seruit’ (a typical Lampung regional food), many of the ingredients of which are taken from their land. In addition, rubber agroforestry with bananas can increase organic carbon and nitrogen-fixing microbes (Tetteh et al. 2019). Gadung and mengkudu plants are trusted by village communities as natural rubber condensants which make it easier for farmers to process rubber latex traditionally. Jackfruit and cempedak plants are seasonal plants that, if harvested once, will produce very abundant fruit on one tree. The species of plant is suitable for planting with rubber plants. This proves that competition for nutrients is not that significant. Akasia and sungkai plants are those plants whose wood quality is beyond doubt, so many farmers have planted these plants randomly in rubber plantations. Planting woody plant species is for not only obtaining results from the wood, but also as a long-term investment for the community. This random planting also aims to reduce hot temperatures, when farmers work in the dry season. It is usually during the dry season, when rubber loses a lot of leaves. The presence of various species of plants during the rainy season will reduce the risk of flooding in the land and soil erosion (Zhao et al. 2023).

The random mixture planting pattern is the pattern most widely applied in community rubber plantations because it has been a teaching passed down from generation to generation. In general, the reason people choose the mixed gardening pattern is because it has been continued from their ancestors, and thus, it has been carried out from generation to generation. So, most farmers in the area apply the mixed gardening pattern in their forest land. Even though the care or management of a random mixture pattern is more difficult because of the variety of species, farmers choose to use a random mixture planting pattern because according to them, the income they get is higher from a variety of plant species.

The biggest reasons for people to develop rubber agroforestry are income factors and ecological factors for the rubber land itself. Landowners who have other income or do not just work as rubber farmers tend to only grow rubber in monoculture. In contrast, landowners who only depend on their livelihood as rubber farmers, they will maximize their land using agroforestry. The planting distance for rubber monoculture is usually 4 × 5 m, while for agroforestry it is 3 × 6 m. In half a hectare of monoculture, there are usually 300 stems and in 1 ha, there are 600 stems. Meanwhile, for half a hectare of rubber agroforestry, there are around 250 stems and for 1 ha, there are 500 stems.

The phenomenon at the research location is that rubber production always increases every year because the older the rubber tree, the more rubber the tree produces, but the price of rubber itself is often unstable or experiences ups and downs (Jayathilake et al. 2023). Apart from price factors, rubber farmers’ income is influenced by land area. The larger the land cultivated, the income generated will increase (Muthuri et al. 2023). Farmers who have a narrow arable area are racking their brains to improve their narrow land to make it more productive using agroforestry or what farmers usually call mixed rubber plantations. Rubber agroforestry land is usually called ‘Omou’ or ‘Pelan’, which is taken from the Lampung language because most of the population is from the Lampung tribe. Omou is a garden/forest that the community uses as the main source of income to meet its daily living needs. Usually, in managing the community they still use the local knowledge they have, but this knowledge is no longer considered valid and the younger generation is less interested to learn by using it (Febryano et al. 2023). The climate factor is a factor that farmers are very worried about because changing climate is one of the factors that farmers cannot control (Nyagumbo et al. 2017). Therefore, some communities implement an agroforestry planting system that combines forestry plants and agricultural plants (agrisilviculture), namely, a combination of rubber trees with seasonal plants, fruit, herbs and plants that are beneficial to local communities (Fig. 5).

Figure 5.

The dominant plant species combined with rubber trees in Menggala Mas Village are kayu afrika (Maesopsis eminii), pulai (Alstonia scholaris), akasia (Acacia auriculiformis), mentru (Schima wallichii), jengkol (Pithecellobium lobatum), petai (Parkia speciosa), cempedak (Artocarpus integer) and jackfruit (Artocarpus heterophyllus). Combining plant species in the garden is more profitable because it can increase the household income or can be consumed by the family alone, but with affordable capital. This system makes a major contribution to people’s lives in direct income, but with little capital. The uniqueness of agroforestry land is that it can optimize land productivity by varying the species composition within one land and the management system (Langenberger et al. 2016).

The choice of agroforestry plant species depends on the situation, conditions and needs of the local community. Local ecological knowledge is closely related to decision-making in planting and maintaining trees (Salampessy et al. 2017). Priority is given to choosing species of plants that can provide benefits to the welfare of the community, both directly and indirectly. Apart from rubber plants as the main crop, other agroforestry plants managed by the community at the research location consist of woody tree species, MPTS, medicinal plants, fruit, shrubs, vines and other agricultural plants, which are indicators of the species of plants favoured by residents. This species of plant is deliberately planted or grows naturally on a plot of land or garden. From an ecological aspect, farmers’ habit of planting as many plants as this has a positive impact. The more diverse the species planted that made environmentally stable (Xue et al. 2023).

Furthermore, well-managed agroforestry practices can boost crop productivity by creating a favourable micro-climate, controlling pest outbreaks, improving soil structure, fertility and soil water content, enhancing crop pollination and providing habitat (Bentrup et al. 2019; Kim and Isaac 2022). Agroforestry also has many benefits for the society, especially in improving the economy and food security (Herwanti et al. 2022). Community dependence on the surrounding forests is commonplace, especially for communities living close to natural forests that manage local plants (Hidayat 2017). There were 41 plants species of rubber agroforestry on community land, both forestry and agricultural plants, which are presented in Tab. 1.