AGRICULTURA OU PASTAGEM? PAPEL DAS COBERTURAS PEDOLÓGICAS NA DIFERENCIAÇÃO E NA TRANSFORMAÇÃO DE SISTEMAS AGRÁRIOS PIONEIROS NO BRASIL

Resumo

O objetivo deste estudo é mostrar como a natureza da cobertura pedológica orienta as modalidades de manejo agrícola desde o início do processo de desmatamento. Numa zona de dinâmica antiga do Paraná, é mostrado como os agricultores, aproximadamente 40 anos após terem destruído completamente a floresta, foram obrigados a remodelar totalmente a paisagem para a construção de estruturas anti-erosivas, e como o controle da erosão, não sendo eficiente, os obrigou a mudar seus sistemas de cultura de acordo com os solos explorados, optando também pela associação agricultura/pastagem. Paralelamente, observa-se o mesmo processo em curso numa zona de dinâmica atual da Amazônia. Esses dois exemplos fornecem elementos para projetar formas racionais de manejo para a Amazônia, considerando as características do agricultor e dos solos, antes do seu total desmatamento.

Termos para indexação: agricultura sustentável, manejo do solo, sistema pedológico, sistema agrário, degradação dos solos, fronteira agrícola.

CROP CULTIVATION OR LIVESTOCK? ROLE OF SOIL QUALITY
IN THE DIFFERENTIATION AND TRANSFORMATION OF
PIONEER AGRARIAN SYSTEMS IN BRAZIL
ABSTRACT

Brazil's land long belonged to pioneers who went along mining soil fertility: after eroding it where they settled, they would move on ahead to continue farming on previously uncultivated soils. Hence naturally forested areas have almost disappeared except for Amazônia. Since this trend can no longer continue, a more useful goal is to settle the areas for agricultural activities and ensure their sustainability. With this in mind, we studied 2 examples of frontiers: the first, opened 70 years ago in North Paraná, ended with destruction of the forest, and the second continues in eastern Amazônia. In both cases, we focused on the role of the soil quality in the differentiation and transformation of farming systems after forest clearing and found that soil plays no part at all in the decision to clear forestland. After that, however, once the fertility inherited from the forest has been worn out, farming activity appears to depend on the type of soil, regardless of the farmers' characteristics (geographical origin, culture, technical and biological knowledge, capital, etc.). With no external constraints on farmers' activities, when soil type differs greatly, agriculture is practised on the best soils (that is, those with the best physical, chemical and biological properties) whereas livestock are raised on those with less clay, since their sensitivity to erosion can be better controlled in pastureland than cultivated fields. This can be observed in North Paraná as well as in a few places in Amazônia. Paraná is famous for its extended basaltic areas, and on their most fertile plots, successful cultivation of soy and wheat rapidly developed\; but now, 70 years after the forest was almost entirely cleared, farmers require advice to sustain their soils. Amazônia is well known for its widespread areas of acid rock, where cattle breeding is today developing. Despite governmental administrative and financial aid, there are very few alternatives. Farmers there too need technical support to practice sustainable agriculture.

Index terms: farming systems, territory agricultural land, agricultural and food production policy.

AGRICULTURE OU ÉLEVAGE? RÔLE DES COUVERTURES PÉDOLOGIQUES
DANS LA DIFFÉRENCIATION ET LA TRANSFORMATION DE SYSTÈMES AGRAIRES PIONNIERS AU BRÉSIL
RÉSUMÉ

L'objectif de cette étude est de montrer comment la nature de la couverture pédologique oriente les modes de mise en valeur agricole dès après les premiers stades de défrichement. Dans une zone de dynamique ancienne (Paraná), on montre, dans le cas d'une exploitation majoritairement minière de la fertilité, comment les agriculteurs, moins de 40 ans après avoir entièrement défriché, sont contraints à un remodelage total du paysage, pour la construction de talus antiérosifs; et comment, la lutte antiérosive n'étant pas probante, ils sont ensuite contraints à raisonner leurs systèmes de culture en fonction des sols, voire même l'association agriculture/élevage. Dans une zone de dynamique actuelle (Amazonie), on montre que des processus équivalents sont à l'œuvre. La mise en perspective de ces deux exemples donne des éléments pour réfléchir à des scénarios d'aménagements possibles pour l'Amazonie tenant compte de la diversité des hommes et des sols, avant son déboisement total.

Termes d'indexation: systèmes agraires, territoire, foncier, politique agricole et alimentaire, ressources naturelles et environnement.