Soil degradation is a global problem. A third of the planet’s land is already severely degraded, and soil is being degraded at a speed that threatens the health of the planet and the civilizations that depend on it (Whitmee et al. 2015). Depletion of soil organic carbon (SOC) resulting from extractive agriculture is a key driver of soil degradation (Lal et al. 2015). Much of this SOC has been released to the atmosphere as carbon dioxide (CO2), a potent greenhouse gas contributing to ongoing climate change, including extreme weather events. Soil degradation also diminishes water infiltration and retention, biodiversity, watershed functions, and the nutritional value of food. Reversing soil degradation is a top global priority (UNCCD 2017).
Yields of major crops have increased substantially in the last century, primarily through intensive chemical fertilization. However, the greater aboveground plant biomass production resulting from chemical fertilization has usually not led to proportional gains in plant inputs to soil and soil organic matter (SOM) accrual (Khan et al. 2007; Man et al. 2021). Instead, these practices, in concert with other intensive agricultural practices such as intensive tillage, monoculture, application of pesticides, and bare fallows, have caused declines in SOM, increases in greenhouse gas emissions, and pollution of waterways (Loisel et al. 2019). However, adopting regenerative agricultural practices, such as substituting chemical with organic fertilizers like compost or manure, reducing tillage, intensifying and diversifying crop rotations, and cover cropping, often increase SOM (McClelland et al. 2021). The mechanisms underlying the positive effects of regenerative agricultural practices on SOM, however, are not well understood. Elucidating these mechanisms would advance our capacity to design agricultural strategies to reliably enhance agroecosystem SOM content, which would assist in reversing soil degradation and enhancing soil quality, food security, and climate change mitigation globally (Amelung et al. 2020).
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