Snoeck D., Lacote R., Keli Z.J., Doumbia A., Chapuset T., Jagoret P., Gohet E., 2013. Association of hevea with other tree crops can be more profitable than hevea monocrop during first 12 years. Industrial Crops and Products, 43: 578-586. Doi: 10.1016/j.indcrop.2012.07.053
Performance of Tree Crop-Based Systems
Intercropping several tree crops is not only possible, but profitable. This was recently demonstrated by researchers from CIRAD and their partners in Ivory Coast who spent 17 years monitoring a trial in which rubber ― a crop grown in the open that can reach a height of more than 25 metres ― and other cash crops suited to shade, such as coffee and cocoa.
Intercropping rubber with other tree crops can help smallholders diversify their sources of income and make better use of their land during the six years it takes for rubber trees to become productive. To help them choose the most profitable cropping system, researchers from CIRAD, the CNRA and Hévégo compared the profit from rubber monocrop with that from rubber trees intercropped with other tree crops ― coffee, cocoa, lemon, cola nut ― in plots in southwestern Ivory Coast.
The main merit of the study was its duration. It lasted 17 years, and all the data were recorded in the field, without resorting to simulations or estimations, as is often the case.
It comprised rubber plots planted in the traditional design, in single rows seven metres apart, and plots of rubber trees intercropped with another type of tree, in double rows three metres apart, with 16-metre interrows to foster intercrop growth and production.
The four intercrop species, all of which had a commercial lifespan of around 25 years, like rubber, were coffee and cocoa, two trees that grow in the shade and no more than four metres tall when cultivated, and lemon and cola nut, which need sunlight.
All input and labour costs were recorded, along with production, for the 17 years after planting, for each crop and each system ― monocrop and intercrops.
When rubber was grown with an intercrop, its individual yield was not affected by the trees grown in the interrows, and intercrop productivity was sustained by the fact that the interrows were sufficiently wide to prevent competition as a result of the shade cast by the rubber trees. This design served to extend by almost three years the period during which intercrop yields were not penalized.
In view of the planting density of each of the intercrops, rubber production amounted to some 89% of total production compared to monocultures, and that of intercrops to between 24% for cola nut and 32% for coffee. Cumulated yields thus ensured an overall surplus in relation to a rubber monocrop that varied from 17% for the rubber-cola system to 21% for rubber-coffee. This proved that intercropping enabled more efficient use of land.
Rubber-coffee and rubber-cocoa intercropping systems were much more profitable than the other combinations and than the rubber monocrop up until year 12.
However, rubber-lemon and rubber-cola nut systems were never profitable, the former due to the low price of lemons, and the latter because the cola nut trees did not begin to turn a profit until year 7.
The cumulated gross profits for the intercropping systems were positive from year 3 for the rubber-coffee combination and year 4 for rubber-cocoa, whereas for the rubber monocrop at the traditional density of 510 plants per hectare, financial equilibrium was not reached until year 8.
For the intercropped plots as a whole, 88% of total profits came from rubber and between 4% for cola nut and 25% for coffee from the intercrops.
Intercropping rubber with other tree crops is a means of reducing competition for land, while diversifying farmers' sources of income and reducing cash flow constraints in the period until latex production begins. This is particularly the case with cocoa and coffee intercrops.
Such cropping systems could generate real added value and prove more sustainable than monocropping.