Yerba mate afforestation: alternative for adding value with environmental quality

The practice of extensive monocultures has proven to be inappropriate for small family farmers. The devaluation of subsistence production (food, fiber, wood, etc.), dependence on energy and external inputs, environmental risks (pests, diseases and bad weather) and market risks (price fluctuations) have been identified as the main negative consequences of the lack of diversification on small properties.

With yerba mate, monocultures began in the 60s, due to the depletion of a large part of the native herbs, which were exploited only in an extractive way, with subsequent eradication of the forests for agricultural uses.

The domestication of yerba mate for pure plantations was relatively successful, mainly due to the resistance of adult plants to excess sunlight and frost. Although it is a forest species native to shaded environments, the way in which it has always been explored and cultivated, to this day the real radiation needs for the species' maximum productive performance are unknown.

As widespread deforestation currently limits the management of herbs in natural environments, afforestation appears as an alternative to minimize environmental, social and economic problems arising from monoculture areas. This practice can imitate the natural environment with advantages as competition for water, light and nutrients can be controlled, with adequate spacing and management, as well as tree species can be selected for specific uses.

Regarding the profitability of the tree system, there are at least two important aspects to be considered. The protective tree population also implies the productive occupation of vertical space, which will eventually have a due economic return, proportional to the quality of the species chosen for afforestation. On the other hand, the resulting environmental services, mainly carbon sequestration, climate mitigation and water conservation, respond to the call of society, which increasingly values ​​products from this type of system.

Embrapa Florestas, in partnership with the Association of Yerba Mate Producers of Machadinho/RS (Apromate), has been developing monitoring research in herb areas with planned afforestation, with the aim of correlating crop production under the influence of different native tree species , subjected to different management regimes.

This experience was generated through an agreement signed between the company Machadinho Energética S/A (MAESA), a construction company of the Machadinho Hydroelectric Plant, and the Machadinho Yerba Mate Producers Association (APROMATE), as one of the ways found to compensate for the environmental liabilities resulting from the formation of the lake, adjacent to that municipality (Rio Pelotas, border between Santa Catarina and Rio Grande do Sul). The contract established that interested family farmers would carry out the planting and afforestation of herbs, with seedlings of native species, financed by MAESA.

In this project, 148 hectares of this agroforestry system were implemented, on 85 small family properties, from 2000 to 2007. This work also led to the establishment of a new progeny of yerba mate, developed within the scope of Apromate, which was named CAMBONA -4, which has higher productivity than common grass, in addition to a milder flavor. The twenty-one species used in afforestation were acquired from regional nurseries, being selected by the farmers themselves, therefore there is great variation in the biodiversity of each agroforestry system.

Studies on the behavior of tree species and yerba mate focus on two properties, where the intercropping systems have different compositions. Annual measurements are being carried out to monitor the development of each species (wood production). During the harvest, the production of all herbs under the influence of the tree canopy is weighed individually, noting their positions relative to the tree trunks, such as distances and geographical direction. On the other hand, the export of nutrients from the system is monitored, due to the removal of green biomass, and variations suffered by the soil over time.

Through a new project, also financed by the Machadinho consortium, two meteorological stations were acquired to evaluate the influence of afforestation on the local microclimate, compared to monocultured grasslands, starting this summer. Furthermore, studies will be initiated on nutrient cycling, provided by each species used in afforestation, through the continuous collection of deciduous material.

Although the experimental results are still preliminary, with only nine years of monitoring, taking into account the longevity of the production system, which is 30 – 40 years, until the reform of the herb, they point to a prospect of success, in relation to system profitability, environmental and social gains.

Amilton Baggio

Forestry Engineer, Master and Doctor in Agroforestry and Researcher at Embrapa Florestas