This report presents the results of a study to assess the potential for adoption of intensified banana/rubber intercropping on smallholdings in Sri Lanka. The study was located within two agro-climatic zones, the Wet and Intermediate zones, which encompass the widest possible range of socio-economic and climatic conditions under which rubber is grown in Sri Lanka. Rubber is grown extensively in the Wet zone and to a more limited extent in the drier regions of the Intermediate zone where livelihoods are largely rural based and chena cultivation still predominates. On-farm trials confirmed the advantages of high density intercropping on growth of rubber and banana. Growth and foliar nutrient content of rubber in the high density banana/rubber intercrop indicated that the benefits of intercropping on rubber could not simply be explained by improved access to soil nutrients when fertiliser was applied to the component banana intercrop. Instead, gas exchange studies implicated a role for the beneficial effects of shade in the intercrops, alleviating high radiation stress thereby allowing leaves to maintain a positive CO2 fixation for a greater duration of the day. In addition to the benefits of intercropping on early growth of rubber, our studies have also shown that intercropping results in long-term benefits in terms of earlier and higher latex yield returns. Discounting analysis showed that whilst rubber and banana may not be as profitable as other crops such tea and pepper, the majority of smallholders preferred to cultivate them because of the low cost of establishment. Smallholders stated a clear preference for rubber due to its relatively low demand in terms of labour inputs (458 labour days ha-1 compared with 1184 total labour days ha-1 for tea). In addition, banana is very popular with smallholders because it is a highly flexible crop that has no particular seasonal demands for activities such as weeding, harvesting etc. Full-time farmers, particularly the land poor in the Intermediate zone where infrastructure is less well developed than in the Wet zone, were identified as having the greatest potential to benefit from high density rubber intercropping. The major constraint to uptake being access to effective extension information and advice. Traditionally, the performance of smallholder rubber has been considered inferior to that produced by the estate sector and governments have attempted to raise productivity by promoting monoculture-based plantation practice. The outputs of this project show this approach to be severely misguided and in the case of smallholders, rubber-based intercropping systems can be developed that are not only compatible with, but also improve the productivity of traditional systems. High density intercropping of rubber offers a win win scenario; rubber can be successfully integrated with traditional cropping systems to provide many benefits to smallholders including earlier and greater latex yield, an additional income from the intercrop and better security of subsidy payments and property rights. Indirect benefits to soil fertility and stability will also accrue from the introduction of trees to traditional annual and perennial cropping systems.
Incorporating local and scientific knowledge in the development and adaptation of intercropping practice for smallholder rubber lands. Final Technical Report.