Managing for climate and production goals on crop-lands.

The assumption that crop-land natural climate solutions (NCS) have benefits for both climate change mitigation and crop production remains largely untested. Here we model GHG emissions and crop yields from crop-land NCS through the end of the century. We find that favourable (win-win) outcomes were the exception not the norm; grass cover crops with no tillage lead to cumulative global GHG mitigation of 32.6 Pg CO equivalent, 95% confidence interval (29.5, 35.7), by 2050 but reduce cumulative crop yields by 4.8 Pg, 95% confidence interval (4.0, 5.7). Legume cover crops with no tillage result in favourable outcomes through 2050 but increase GHG emissions for some regions by 2100. Crop-lands with low soil nitrogen and high clay are more likely to have favourable outcomes. Avoiding crop losses, we find modest GHG mitigation benefits from crop-land NCS, 4.4 Pg CO equivalent, 95% confidence interval (4.2, 4.6) by 2050, indicating crop-land soil will constitute a fraction of food system decarbonization.