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Abstract(s)
O olival transmontano representa 75000 ha e envolve 36000 produtores. Apresenta, por isso, elevada importância económica e
social. As áreas médias de olival por exploração são baixas e as explorações compostas por um elevado número de microparcelas.
Mais de 95% da área de olival encontra-se em sequeiro e sem qualquer perspetiva de poder vir a ser convertida em
regadio. Os olivais centenários situam-se em zonas depressionárias, em solos de razoável fertilidade. Nas últimas décadas a
generalização dos adubos comerciais permitiu instalar olival em parcelas de menor fertilidade natural, designadamente em
solos de encosta e meia encosta, no passado, cultivados com cereais em rotações que incluíam pousios de longa duração.
Estes solos são muito pobres, com espessura efetiva reduzida, devido ao processo continuado de erosão. O olival tradicional
tem estado sob forte pressão de abandono, sobretudo devido às baixas produtividades, estagnação do preço do azeite nos
mercados e aumento constante do preço dos fatores de produção. A resiliência tem estado suportada numa estrutura de
custos reduzida e em mão-de-obra familiar cujos encargos não são considerados nas contas de cultura. Por outro lado, grande
parte dos olivicultores, sobretudo os de menores áreas de olival, têm outras atividades económicas e desenvolvem a
olivicultura como atividade complementar de fim-de-semana, para melhorar a economia familiar. Assim, a maior ameaça efetiva
à sustentabilidade é a perda progressiva da fertilidade do solo, sobretudo dos olivais jovens, devido ao declive das parcelas e
às mobilizações frequentes que aceleram o processo de erosão e conduzem a níveis de matéria orgânica no solo muito baixos.
Foi neste contexto que, aproximadamente, há 18 anos se iniciaram trabalhos de investigação em olival tradicional de sequeiro,
com vista a demonstrar vantagens de outros sistemas de gestão do solo relativamente às mobilizações convencionais. Foram
desenvolvidos diversos projetos de investigação (PAMAF, AGRO, FCT, PRODER)e, publicados mais de três dezenas de
artigos em revistas científicas internacionais e nacionais. Os resultados obtidos mostraram que a aplicação primaveril de
herbicidas não seletivos é uma solução que protege o solo da erosão e incrementa a produtividade das árvores. Cobertos de
vegetação natural deficientemente controlada podem originar perda de produtividade ainda que apresentem bons indicadores
de fertilidade biológica dos solos. Em olival de sequeiro mostraram vantagem os cobertos de leguminosas anuais de ciclo
curto. Esta solução melhorou a fertilidade do solo, favorecsu o estado nutricional das árvores e aumentou a produção de
azeitona.
In NE Portugal, olive growing covers 75, 000 ha and involves approximately 36, 000 producers. The sector hás therefore high economic and social importance. The individual orchards are small and each farm is composed of a high number of micro-plots scattered throughout the landscape. Over 95% of the acreage is rainfed managed and without any prospect of being able to be converted into irrigation. Centennial olive graves are located in lowland áreas in reasonably fertile soils. In recent decades the generalization of commercial fertilizers allowed to install the olive graves in sloping terrains of lower natural fertility with a long history of cultivation with cereais in rotations that included a long-term fallow. These are unfertile shallow soils, due to the continuous process of erosion. The traditional olive sector hás been under strong pressure of abandonment, mainly due to low productivity, the olive oil price stagnation in the markets and steady increase in the price of production factors. The resilience of the sector hás been supported in a low cost strategy regarding production factors and family labour which is not considered in operating costs. On the other hand, most of the farmers, especially those growing small áreas, havs other economic activities. They cultivate their lands as a complementary weekend activity to improve the family income. Currently, the most criticai threat to sustainability is the progressive loss of soil fertility, especially in young olive graves, due to the land slope, and frequent tillage operations, which accelerate the soil erosion processes and reduce the leveis of the organic matter in the soil. It was in this context that approximately 18 years ago began research on traditional rainfed olive graves to demonstrate the advantages of other sói] management systems over conventional tillage. Several research projects were developed (PAMAF, AGRO, FCT, PRODER) and more than three dozen of papers published in international and national journals. The results showed that the application of nonselective herbicides in spring is able to protect the soil from erosion and increased the olive yields. Covers of natural vegetation poorly controlled can reduce crop productivity though showing good indicators of biological soil fertility. In rainfed olive orchards, covers of early-maturing annual legumes showed great advantages since they improved soil fertility, enhanced the tree N nutritional status and increased olive yield
In NE Portugal, olive growing covers 75, 000 ha and involves approximately 36, 000 producers. The sector hás therefore high economic and social importance. The individual orchards are small and each farm is composed of a high number of micro-plots scattered throughout the landscape. Over 95% of the acreage is rainfed managed and without any prospect of being able to be converted into irrigation. Centennial olive graves are located in lowland áreas in reasonably fertile soils. In recent decades the generalization of commercial fertilizers allowed to install the olive graves in sloping terrains of lower natural fertility with a long history of cultivation with cereais in rotations that included a long-term fallow. These are unfertile shallow soils, due to the continuous process of erosion. The traditional olive sector hás been under strong pressure of abandonment, mainly due to low productivity, the olive oil price stagnation in the markets and steady increase in the price of production factors. The resilience of the sector hás been supported in a low cost strategy regarding production factors and family labour which is not considered in operating costs. On the other hand, most of the farmers, especially those growing small áreas, havs other economic activities. They cultivate their lands as a complementary weekend activity to improve the family income. Currently, the most criticai threat to sustainability is the progressive loss of soil fertility, especially in young olive graves, due to the land slope, and frequent tillage operations, which accelerate the soil erosion processes and reduce the leveis of the organic matter in the soil. It was in this context that approximately 18 years ago began research on traditional rainfed olive graves to demonstrate the advantages of other sói] management systems over conventional tillage. Several research projects were developed (PAMAF, AGRO, FCT, PRODER) and more than three dozen of papers published in international and national journals. The results showed that the application of nonselective herbicides in spring is able to protect the soil from erosion and increased the olive yields. Covers of natural vegetation poorly controlled can reduce crop productivity though showing good indicators of biological soil fertility. In rainfed olive orchards, covers of early-maturing annual legumes showed great advantages since they improved soil fertility, enhanced the tree N nutritional status and increased olive yield
Description
Keywords
Cobertos vegetais Olival tradicional de sequeiro Gestão do solo Mobilizações Herbicidas Cobertos vegetais
Citation
Rodrigues, M.A.; Arrobas, Margarida (2015). Dezoito anos de investigação sobre cobertos vegetais em olival. In Simpósio O Solo na Investigação Científica em Portugal. Lisboa. p. 145-148. ISBN 978-972-8669-65-2