The air we breathe is 80 per cent nitrogen, but it takes huge amounts of energy to break the atoms apart and make them available as the building blocks of the proteins vital to all life on earth. Despite its abundance, in most cases, and particularly in spring, nitrogen is also the key nutrient limiting plant growth.
Legumes (clovers, peas, beans, etc) have the almost unique ability to fix atmospheric nitrogen through a symbiotic relationship with nitrogen-fixing bacteria (rhizobia), which take up residence in nodules on their roots. The plant provides shelter and feeds the bacteria with energy in exchange for nitrogen in the form of ammonia (NH3).
In organic pastures, red and white clovers, vetches and other legumes typically grow in a mixture with grasses and herbs in a self-sustaining community, needing little or no external inputs.
Since the end of the Second World War, the highly energy-consumptive Haber-Bosch process (formally used to make explosives), has increasingly been used to make nitrogen fertiliser, mainly in the form of ammonium nitrate.
Fuelled by cheap fossil fuels, it became possible to replace the legumes with high-yielding, weak-rooting ryegrass. Our farmers, their soils and their plant communities have become addicted to cheap nitrogen and the cheap energy needed to make it. It has produced cheap food but has destroyed biodiversity above and below ground and, through the use of fossil fuels and loss of soil carbon, is a major factor in the climate catastrophe we face.
As war in Ukraine and disruption of global energy supplies led to a quadrupling in the price of ammonium nitrate, many farmers applied little or no fertiliser this spring. Turnout for housed cattle in our area is traditionally around 1st April but in some cases has been delayed by up to a month; without the nitrogen, the soils suffer a cold turkey shock, having lost the legumes that cannot compete when nitrogen is applied.
On our organic farmland, with the help of our legumes and active healthy soils, our cows were out on time. Conversion to organic farming can be a painful process; depending on the level of degradation, it takes up to five years for soils to recover and adjust to life without nitrogen fertiliser. Converting the mindset of a farmer raised on agrochemicals can take even longer.