Resilience of humification process to evaluate soil recovery in a semiarid agroecosystem of central Argentina .


Resilience has become a key concept in agricultural management for sustaining soil quality and preventing soil degradation. Land use is a factor that affects soil organic matter (SOM) concentration, distribution and dynamics. In consequence, several recovery practices have been proposed in order to maintain or enhance SOM contents in agroecosystems, such as zero soil disruption (no-till), farm enclosures and crop rotation. We evaluated the efficiency of recovery practices (after a 5-yr period) in reversing SOM losses in a Typic Haplustoll of the central semiarid region of Argentina. A comparative assessment of the resilience of SOM synthesis (humification process) was performed between the recently adopted restorative management and traditional systems (45 years of plow-tillage) using a native woodland as a baseline. In soil samples (0-20 cm), total SOM, its fractions (non-humic substances, humic substances, humic acids, and fulvic acids), and structure (humification index and polymerization index) were analyzed. Degradation rates, recovery rates and soil resilience classes were calculated. Results showed that in our semiarid environment, plowing has significantly affected the resilience of the humification parameters by high degradation rates, whereas the adoption of recovery practices did not reverse ongoing degradative processes. All the analyzed land uses were included in the same resilience class, suggesting that soils have established a new equilibrium (at low values) with high resistance in front of short-term changes. However, a small tendency of minor degradation rates in the farm enclosure site may indicate the beginning of recovery processes.
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