Against a backdrop of renewed fertiliser supply disruption in 2026, the international “4 per 1000” Initiative convened a scientific webinar that put soil organic carbon at the centre of a conversation. The message delivered by two leading researchers Prof. Stuart Grandy and Dr. Matt Wellenstein was clear: soil carbon is not only a climate asset. It is a nitrogen reserve, a financial buffer, and a form of farm insurance whose value has been systematically overlooked by the markets, lenders and policy frameworks that shape how farmers manage their land.
Fertiliser supply disruptions are often treated as temporary market events. Prices rise, farmers reduce inputs, yields fall, supply chains adjust, and after a period of instability the market is expected to return to normal. Yet this way of looking at fertiliser shocks is incomplete. It overlooks what happens in the soil.
When nitrogen fertiliser prices rise sharply, farmers often apply less nitrogen. Lower nitrogen inputs reduce crop growth and yields. Lower yields mean less crop residue returns to the soil. This matters because crop residues, roots and organic inputs are the raw materials from which soil organisms build soil organic matter and organic nitrogen reserves. A fertiliser shock can therefore continue long after prices have stabilised, through a decline in soil organic matter and a weakening of the soil’s capacity to supply nitrogen in future seasons.
This Soil Carbon Note #7 was produced by the Scientific and Technical Committee of the international “4 per 1000” Initiative