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Agronomy

Land without fire

In Pará, instead of burning, the stubble is ground up and becomes a fertilizer

EMBRAPAChopped material on the ground and the plantationEMBRAPA

Starting from a series of experiments carried out during a decade in one of the oldest areas of agricultural use in the state of Pará, the Bragantina Zone, at a distance of some 120 kilometers from the city of Belém, researchers from Embrapa (Brazilian Agricultural Research Corporation)- Eastern Amazon and from the German universities of Göttingen and Bonn have developed an efficient alternative system of preparing the ground that raises productivity of family agriculture in the region without increasing the damage to the environment.

In general terms, the method proposes an alternative to the traditional and pernicious practice of the burning of the capoeira , a popular name given to the secondary vegetation which grows spontaneously in a deforested area, and the adoption of two measures. The first recommends that instead of burning the stubble, it be ground up with the help of a special machine linked onto a tractor and to use this shredded vegetation (richer in nutrients than its burned ashes) for the building of a dead vegetable cover, called mulch, above the ground to be planted.

This practice becomes even more efficient if there is an enrichment of the native underbrush through the growing of accelerated growth trees, capable of developing faster than the original species of the region. Thus, a secondary reinforced vegetation grows in less time, which, if adequately chopped, is going to generate a dead vegetable cover with even more nutrients.

Six agricultural communities in the municipality of Igarapé Açu, of the total of fifty communities in the region, are testing the new method on properties of, at the maximum, 25 hectares. The results look good. By the conventional system, the farmers could only use a parcel of their property for corn and manioc growing, the main crops of the region, every three years. They used to plant one year and leave the ground “to rest” during three or four years, the necessary time for the undergrowth to grow and reach a minimum biomass that would justify the adoption of a “preparatory” burning of the soil for the next harvest.

Productive efficiency
Quitting burning as an agricultural practice and the combined use of mechanized grinding of the enriched undergrowth reduced the fallow time of the ground to two years. Or, in other words, the tenant farmer is adopting cleaner behavior from the environmental point of view and still attains greater economic efficiency in his property. “This is good for nature and for the farmer’s pocket which, with more productive land, does not feel the pressure to leave the land and migrate to the town”, says the agronomist Tatiana de Abreu Sá, of Embrapa, one of the coordinators of the Shift- Capoeira Project, a joint initiative of research centers in Brazil and Germany.

“We now need to find ways through which the small farmer has access to this technology.” Embrapa, along with the Germans, have developed prototypes of chopping machines, such as the Tritucap, which can carry out the work of cutting and grinding of the brush. However, the machine is expensive to be widely purchased: cost of R$ 20,000 to R$ 30,000. For the farmers, the solution would be to form cooperatives to buy the machine or to rent it from some institution that have acquired the tractor.

The adoption of the new method would be worth. Data from Embrapa shows that the technique brings advantages to the small farmer. Besides reducing the fallow period, it ensures that farmers’ income does not suffer lots of oscillations during the harvest years. The burning provoked the loss of more than half of the nutrients stocked up in the vegetation, especially nitrogen, and wrongly seems good practice for agriculture because of the increase in the short time of the productivity of the soil. This occurs because a small quantity of the nutrients of the burned undergrowth is stocked in the ashes that cover the area to be planted. But this small part of the nutrients is eaten up faster by the land, which, afterwards, drops considerably in yield.

“By preparing the land with the ground up vegetal cover, the nutrients, besides being more abundant, remain available for a longer time in the location chosen for planting”, says Tatiana. Another advantage is to give the farmer more flexibility in the choice of the ideal moment to prepare the land. By the old method, this could only be done in the dry months, generally between July and September, when the burnings reign in the Amazon.

Atmosphere trapping
From the environmental point of view, the rewards are also tangible. The abandoning of rudimentary techniques of burning, helps to diminish the emission of smoke and of gases, above all carbon dioxide, which contributes to the exaggerated warming of the temperature of the earth’s atmosphere. There is another benefit: the enriching of the undergrowth with fast growing species , such as acacias (Acacia auriculiformis and Acacia mangium) originally from Central America, increases the quantity of oxygen in the atmosphere, creating a double effect of cleaning the earth’s air.

This occurs because an area with secondary vegetation in clear development removes more carbon dioxide from the atmosphere than a non-enriched undergrowth. For now, there is no indication that the introduction of new species of fast growing trees in the middle of the secondary vegetation of the region has significantly altered the ecosystem.

Similar experiences are under test in other tropical countries. In Costa Rica, for example, there is research going on into the beneficial effects of abandoning of burning and of the use of chopped up undergrowth as a dead vegetal covering on cultivated land. In Africa and Asia, the enriching of the native undergrowth for future use as a ground up vegetal cover is also the target of similar studies. “The difference is that the undergrowth of the Amazon is much richer in terms of its biodiversity than these other locations”, compares Tatiana.

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