I always like big pictures - the ones that can reveal a whole story from its beginnings. With Nitrogen now such a major input on most farms, spending ten minutes on the Nitrogen big picture seems a worthwhile exercise.

In its pure form, Nitrogen is a colourless, odourless, tasteless gas. More than three quarters of our air is Nitrogen and about one sixth of the protein that builds animal and human bodies is Nitrogen. Its symbol is N and it is important stuff.

I think it was Einstein who commented on Nature's strange sense of humour and certainly the fact that we are made of N, but cannot get our N directly from the air around us is a bit of a joke. Plants also need N, but again they have no direct means of accessing their need from the abundance in the air. In fact, nature only gave certain tiny N fixing microbes the tools to take their N needs directly from air.

Thus, from the start, life had to rely on indirect means such as the N that gets dissolved in rain or snow water after a lightning storm, or the "hit and miss" presence of N fixing microbes in the soil. Some plants such as clovers, have adapted to secure their N needs by creating nice places to host N fixers in nodules on their roots. However the main human food supply has come from cereals and grass that don't have that adaptation. For thousands of years, these precarious pathways put a cap on levels of plant growth and thus indirectly capped the populations of animals and humans that could survive on the planet. In fact N supply and plant and animal/human population are directly linked. The current population of 7 billion would not be around if it wasn't for the story that follows.

About 200 years ago the first additional N became available. It was Guano, the centuries old, accumulated droppings of South American sea-birds. Its arrival in Ireland coincided with the arrival of the potato and was thus jointly responsible for the doubling of the Irish population in the decades leading up to the famine. In fact, DNA testing now suggests that new potato varieties imported alongside Peruvian seabird guano in 1842 may have carried the virulent strain of potato blight that caused the Famine.

Then, about 150 years ago another South American source of N was discovered in the form of Saltpetre (Potassium Nitrate) mined from the Atacama desert of Peru. Interestingly, as well as use as fertiliser, N is also the key component of gunpowder and explosives without which mass warfare could never have happened - Maybe nature was wise to limit our access to N.

Finally, about 100 years ago, in the build up to World War 1, a German chemist called Fritz Haber, developed a method for extracting N directly from the air using fossil fuel. Without this, Germany could not have fought the war because Britain had control of supplies of Saltpetre. Today the Haber process continues to be the source of all our N fertilisers and explosives, linking their cost of the supplies of fossil fuels and munitions and thus to conflict and war.

Is it a vicious circle to continue using fossil fuel, to make more N, to feed more humans, to make more humans? Is it wrong to think that we might find a better way? To be wiser in respect to natures boundaries and to work harder to optimise the use of clovers in our farming? The next leap of history may well be to get plants of the grass family to directly host N fixing microbes. Scientists have been working on this miracle for decades but so far without success. Will it happen? No one can say!

In the meantime, Some of us farmers take a deliberate decision to work with clover. That's not necessarily easy. N fixing microbes need warm soil and I feel that the low night temperatures this year have hindered my clovers ability to fix N, making my grass supplies tighter than I would like. However, while depending on clover has its concerns, there is nevertheless, a real satisfaction in working with it. Clovers are very happy to grow alongside most plants and to share their excess N with their neighbours for mutual benefit. On the other hand, the addition of chemical N does poison such relationships. For all of us, the win-win possibilities that brought N fixing microbes and plants to form lifelong partnerships, might well be a life lesson worth the learning. In fact I think the whole BIG picture story of N is well worth a few thoughts now and again.