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Evolução temporal das propriedades químicas dos Calcisols do perímetro de rega do Caia
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Abstract(s)
A presente dissertação teve como principal objetivo avaliar as consequências da
intensificação agrícola nos Calcisols localizados no perímetro de rega do Caia, num
contexto de clima Mediterrânico semiárido. Para tal, analisou-se a evolução de três
parâmetros químicos do solo — matéria orgânica (MO), pH e condutividade elétrica
(CE) — ao longo de um período de dez anos (2001/2002 a 2011/2012), comparando
áreas de cultivo em regime de sequeiro e de regadio. A metodologia adotada incluiu a
recolha de amostras georreferenciadas, com posterior análise em laboratório e
subsequente análise estatística para determinar variações significativas. Os resultados
evidenciaram que os solos de regadio apresentaram uma redução significativa da MO
de 1,76% para 1,62%, reflexo do aumento da mineralização provocada pela humidade e
arejamento do solo, combinados com a ausência de técnicas culturais sustentáveis de
reposição do carbono orgânico do solo. Por outro lado, os solos de sequeiro
demonstraram maior estabilidade nos teores de MO ao longo do tempo (variaram de
1,51% para 1,47%). Relativamente ao pH, verificou-se uma tendência de aumento,
particularmente nos solos de regadio, de 7,79 para 7,91, justificada pela presença de
bicarbonatos na água de rega e pela alcalinidade inerente aos Calcisols. A CE também
aumentou de forma significativa nos solos irrigados, de 0,10 dS.m-1
para 0,16 dS.m-1
,
sugerindo uma acumulação gradual de sais, embora os valores se mantivessem dentro
de limites não salinos. Conclui-se que a intensificação agrícola, através da adoção do
regadio, provoca alterações relevantes nas propriedades químicas dos Calcisols. A sua
viabilidade a longo prazo dependerá da implementação de práticas culturais
sustentáveis, nomeadamente o incremento de matéria orgânica, a monitorização da
salinidade e o controlo periódico do solo. Este estudo contribui para um melhor
entendimento da resposta dos Calcisols à intensificação agrícola e reforça a
importância de estratégias que conciliem produtividade e sustentabilidade.
The main objective of this dissertation was to assess the consequences of agricultural intensification on Calcisols located within the Caia irrigation perimeter, under a Mediterranean semi-arid climate context. To this end, the evolution of three key soil chemical parameters — organic matter (OM), pH, and electrical conductivity (EC) — was analyzed over a ten-year period (2001/2002 to 2011/2012), comparing areas cultivated under rainfed and irrigated systems. The adopted methodology included the collection of georeferenced soil samples, followed by laboratory analysis and subsequent statistical evaluation to identify significant variations. The results showed a significant reduction in OM content in irrigated soils, from 1,76% to 1,62%, reflecting increased mineralization driven by higher soil moisture and aeration, combined with the lack of sustainable cultural practices to replenish soil organic carbon. Conversely, rainfed soils demonstrated greater stability in OM levels over time (ranging from 1,51% to 1,47%). Regarding pH, an increasing trend was observed, particularly in irrigated soils, from 7,79 to 7,91, justified by the presence of bicarbonates in the irrigation water and the inherent alkalinity of Calcisols. EC also increased significantly in irrigated soils, from 0,10 dS.m-1 to 0,16 dS.m-1 , suggesting a gradual accumulation of salts, although values remained within non-saline thresholds. It is concluded that agricultural intensification, through the adoption of irrigation, induces relevant changes in the chemical properties of Calcisols. The long-term viability of this practice will depend on the implementation of sustainable soil management strategies, namely the enhancement of organic matter, salinity monitoring, and regular soil assessment. This study contributes to a better understanding of the response of Calcisols to agricultural intensification and reinforces the importance of strategies that balance productivity with sustainability.
The main objective of this dissertation was to assess the consequences of agricultural intensification on Calcisols located within the Caia irrigation perimeter, under a Mediterranean semi-arid climate context. To this end, the evolution of three key soil chemical parameters — organic matter (OM), pH, and electrical conductivity (EC) — was analyzed over a ten-year period (2001/2002 to 2011/2012), comparing areas cultivated under rainfed and irrigated systems. The adopted methodology included the collection of georeferenced soil samples, followed by laboratory analysis and subsequent statistical evaluation to identify significant variations. The results showed a significant reduction in OM content in irrigated soils, from 1,76% to 1,62%, reflecting increased mineralization driven by higher soil moisture and aeration, combined with the lack of sustainable cultural practices to replenish soil organic carbon. Conversely, rainfed soils demonstrated greater stability in OM levels over time (ranging from 1,51% to 1,47%). Regarding pH, an increasing trend was observed, particularly in irrigated soils, from 7,79 to 7,91, justified by the presence of bicarbonates in the irrigation water and the inherent alkalinity of Calcisols. EC also increased significantly in irrigated soils, from 0,10 dS.m-1 to 0,16 dS.m-1 , suggesting a gradual accumulation of salts, although values remained within non-saline thresholds. It is concluded that agricultural intensification, through the adoption of irrigation, induces relevant changes in the chemical properties of Calcisols. The long-term viability of this practice will depend on the implementation of sustainable soil management strategies, namely the enhancement of organic matter, salinity monitoring, and regular soil assessment. This study contributes to a better understanding of the response of Calcisols to agricultural intensification and reinforces the importance of strategies that balance productivity with sustainability.
Description
Keywords
Calcisols condutividade elétrica matéria orgânica PH Electrical conductivity Organic mater