Abstract
The agricultural soils in the Mediterranean are characterized by low stocks of soil organic matter (SOM) because of the intensive management practices and constraints on litter inputs to the soil imposed by environmental conditions (low precipitation, high evapotranspiration). To date, several studies have provided evidence for a low potential of Mediterranean agroecosystems, especially on its southern part, to store C, even under soil conservation practices (e.g., non-tillage), questioning the capacity of commonly applied practices to restore soil health, mitigate climate change and improve resilience of agroecosystems to climate extremes. Using paired orchards of avocado and olive trees, we show that soils in the South Mediterranean have a high potential for C storage that depends strongly on crop type and soil properties. Soils planted with avocado trees showed higher SOM contents compared to olive trees mainly in the upper soil layer (0–10 cm) which were linked to higher inputs and litter chemistry. Our findings enable us to re-define achievable thresholds of SOC (≈8%) in Southern Mediterranean soils to store C, to quantify the effect of different cropping systems, and the period required to reach this potential and how this potential is affected by soil properties. Thus, the findings have profound implications for the design of soil conservation practices compatible with Mediterranean conditions and developing initiatives describing achievable targets of SOM restoration depending on soil properties and cropping systems.
Highlights
Soil organic matter (SOM) is a strong determinant of soil health status [1], and there has been a growing concern in recent years for the development of effective soil health restoration practices to improve soil productivity, increase crop yield, and enhance the resilience of agroecosystems to climate change [2,3]
We investigated the effect of crop type on SOM sequestration at fields planted with olive trees, the dominant crop in the South Mediterranean, and in avocado orchards, an increasingly adopted crop in the Mediterranean
Soil texture analysis confirmed the affinity between the paired fields except in Site 1, where the avocado field had slightly greater clay content (Table 2)
Summary
Soil organic matter (SOM) is a strong determinant of soil health status [1], and there has been a growing concern in recent years for the development of effective soil health restoration practices to improve soil productivity, increase crop yield, and enhance the resilience of agroecosystems to climate change [2,3]. Soil properties, cropping systems, and agronomical practices and their interactive effects are recognized as important controls of SOM dynamics [11,12,13,14,15]. The current paradigm of SOM formation is that microbially-processed plant-derived organic-C is preferentially associated with mineral surfaces to form SOM [8,9].
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