Governments and industries are increasingly interested in storing more organic carbon in soil to combat climate change, especially on agricultural lands where it has been depleted. We can rebuild these soil organic carbon (SOC) stocks in two main ways: 'land sparing' (restoring natural vegetation) or 'land sharing' (improving how we manage farming, like using regenerative agriculture). Our research estimates SOC storage potential by looking at the 'photosynthesis gap'—the difference between how much carbon plants currently capture and how much they could capture if we maximized photosynthesis. This gap is largely due to the limited growing seasons of cash crops. Using a SOC model, we simulated what would happen to stocks under both scenarios. Our initial findings show that restoring natural vegetation (land sparing) offers greater potential for increasing SOC storage in tropical and cool regions compared to improving farming practices like regenerative agriculture (land sharing). Further analysis will pinpoint global hotspots for SOC restoration, helping us weigh the carbon benefits of conservation against agricultural production.