Enhancing Soil Organic Carbon and Soil Quality through Double-Cropping, Conservation Tillage, and Optimized Nitrogen Management under Mediterranean Conditions
Jesús Fernández-Ortega*, Jorge Álvaro-Fuentes and Carlos Cantero- Martínez
ABSTRACT
In Mediterranean agroecosystems, conventional agricultural practices have historically led to a marked depletion of soil organic carbon (SOC), compromising soil health and sustainability. This study aimed to assess the combined effects of legume-maize double-cropping (DC), tillage systems, and mineral nitrogen (N) fertilization rates on SOC and its fractions—particulate organic matter carbon (POM-C), mineral-associated organic matter carbon (Min-C), and permanganate-oxidizable carbon (POxC)—as well as on soil enzymatic activities related to the carbon cycle. A field experiment was conducted comparing monocropped maize (MC) with legume-maize DC across two tillage systems (conventional tillage, CT; and no-tillage, NT) and three N fertilization regimes (0, medium, and high). The legumes used included pea for grain (2019), vetch for green manure (2020), and vetch for forage (2021).
Results showed that DC increased SOC compared to MC, primarily through the accumulation of POM-C. DC maintained SOC levels over time, while MC led to a decline relative to initial values. NT significantly enhanced SOC, POM-C, and Min-C in the topsoil (0–10 cm), whereas CT resulted in SOC depletion. Although N fertilization initially increased SOC and its fractions, high N inputs ultimately caused a decline in SOC by the end of the study. Furthermore, DC and NT practices stimulated key soil enzymatic activities, particularly dehydrogenase and β-glucosidase, indicating improved biological functioning.
These findings underscore the potential of legume-maize double-cropping, conservation tillage, and reduced N fertilization as synergistic strategies to preserve SOC and enhance soil biological quality in irrigated Mediterranean cropping systems.
