Creating the oil palm/rubber mosaic

Small family farms very quickly adopted this crop in the 1920s, reaching 85% of the country's total area today. In the 1960’s, some of the large plantations were nationalized to form the state-owned company "PTP" (PT Perkebunan Nusantara). The State implemented concession policies aimed at promoting the development of oil palm in the 1990s, contributing to a massive deforestation. This changed fundamentaly the landscape in Sumatra and Kalimantan, leading to a typical oil palm/rubber mosaic. In the 1990’s, jungle rubber, the historical rubber-based agroforests was covering 3 millions ha. Probably 1 to 2 millions ha of jungle rubber have now diseappeared, to the profit of oil palm (2/3), and rubber monoculture/RAS (1/3).

Assessing RAS on the ground

In 1994, ICRAF and CIRAD jointly launched the SRAP-Smallholder Rubber Agroforestry Project, in order to set up several on-farm trials based on agroforestry systems in the Indonesian provinces of West Kalimantan, Jambi and West Sumatra. Three different designs were adopted, namely:

• RAS1: which involved clonal rubber plantation and forest regrowth in the interline (the most extensive system);
• RAS 2 in which clonal rubber was associated with fruit and timber trees and intercropping during the immature period (the most intensive system),
• RAS 3 which was planted under the same design as RAS 2 but complemented with fast growing shading trees and cover crops (mainly Flemingia congesta) to get rid of alang-alang (Imperata cylindrica).

The idea was to assess if the different combinations of associated trees and crops with clonal rubber had any long-term impacts, in terms of both income diversification and adoption of agroforestry practices.

The main outcomes which were expected from clonal rubber-based agroforestry systems were as follows:

• Income diversification (rubber, fruits, timber …) = better economic resilience;
• No impact of agroforestry practices on rubber production, as long as there are no trees above rubber canopy:
• Reservoir of local biodiversity and « forest effect » on local climate, if widely used, for a better global resilience, better Carbon stock, maintain humidity and rainfall patterns and access to “forest products”;
• Less soil erosion and better use of water;
• Preservation or improvement of soil fertility, if soil surface is covered,
• Possibility of timber production: rubber farmers might be the very next timber producers;
• A more environmentally friendly system in a broad sense, and
• As rubber production does not require any fertilizers nor pesticides: it is thus already « bio compatible », i.e. for organic farming intercropping.

Generating income

A comparison of the various systems under study with ancient and recent jungle rubber, poor/good oil palm plantation and monoculture/RAS systems showed that clonal rubber-based systems provided a good level of income to farmers.

Levels of income per ha were found to be comparable to that of generated by oil palm cultivation (and better than rice or “palawija” or other upland secondary annual crop such as soybean, corn or peanut). RAS showed a longer lifespan than oil palm if tapping practices were correctly adopted (35 years for rubber vs 20 years for oil palm). The income generated by RAS is strongly linked to rubber prices.

Changes in RAS systems were observed in 2019:

• RAS 1 was found to perform as best for soil fertility maintenance, no erosion and low cost of establishment for immature period, either in 1997 and 2007 during survey implemented at these periods as now in the long run by farmers that did maintain their RAS plots (more than 80 %). This is interesting for most smallholders who are reluctant to invest 2,000 US$/ha for new clonal rubber plantation from their own savings (compared to plantation done by local estates for oil palm with a dedicated credit). Establishment cost and maintenance for the first 3 years were estimated in 1997 at 700 US$/ha,
• RAS 2 is the most widely adopted type, due to the production of associated trees (both fruits and timber recently) despite the fact that poor markets for fruits and timber are real constraints for further development,
• RAS 3 did the job in alang-alang (Imperata cylindrica) infested environments, with a very good control through the shading provided by associated trees and cover crop (Flemingia congesta).

The main trends were the following: conversion to oil palm (20 % of SRAP plots) or to clonal rubber monoculture (20 % of SRAP plots mainly in Trimulia), with agroforestry systems maintained in RAS 1 or 2 (50 % of the SRAP plots) and tembawang (10 % of the SRAP plots.

Lessons learned

Rubber agroforestry trials came right in time in 1994, with a strong demand from farmers for systems providing low establishment cost and income diversification: the right time at the place,

Oil palm came in 1997 with a very strong pressure from companies (through the policy of concessions) providing a lucrative alternative to rubber cultivation with full credit (but loss of land) and better return to labor,

Interest in agroforestry practices remains high for old men but poor interest is witnessed from younger generation. It is now time for rubber replanting as trees are old, and the same old story is going on, as the access to improved planting material remains critical. Good tapping practices (tapping schools and continuous training, technical information on panel management, upward tapping ….) are essential if farmers want to maximize tree lifespan up to 35 years long,

The sanitary conditions of rubber stands is worrying, as the impact of white root and other root diseases is observable in areas with forest or old jungle rubber before plantation.

Low rubber prices especially compared to palm oil do not help in stimulating farmers’ dedication in rubber cultivation. Most trial plots are now at the end of their life, due to the high impact of diseases and poor tapping practices.