Nitrogen may be a tasteless, odourless and colourless gas – but as 78 per cent of the earth’s atmosphere, it’s mostly what we inhale with every breath we take.

There are also vast amounts of nitrogen in the earth’s crust and in soil organic matter.

Nitrogen compounds are found everywhere, and we use them in so many ways.

We use them to extend the shelf life of our foods; to manufacture acid, nylon, dyes, and explosives; and to freeze blood and destroy diseased tissues for example. And of course, we make fertiliser from them to grow our food.

Why we need N

All living organisms contain nitrogen. It forms the amino acids that make proteins, and it’s even in our DNA.

Plants also need nitrogen to make the chlorophyll they use for photosynthesis.

So, it’s not surprising that nitrogen is the nutrient in most demand by plants – especially in the early stages of their growth.

Deficiencies and excesses

A plant deficient in nitrogen will be badly stunted and suffer from chlorosis, or yellowing of the leaves.

Examples of deficiency can be seen in pasture where there is strong growth in the urine patches only.

A plant suffering an excess of nitrogen will have lush growth and stem weakness.

Nitrogen excess can be a problem for animals and humans, and we are well versed in the negative consequences of too much nitrogen fertiliser in the environment.

So although nitrogen is vital for life, and a shortage is detrimental, we need to be responsible about how we apply it.

How plants get N

While nitrogen is plentiful in the atmosphere (as N2) and the soil, it’s not always available in the forms like ammonium (NH4+) and nitrate (NO3-) that plants need.

So how do plants get their nitrogen? It’s all down to biology and microbial activity in the soil.

A major source of plant-available nitrogen is produced by legumes like clover, which form symbiotic relationships with Rhizobium trifolii bacteria.

The bacteria invade the legume roots to create nodules where they ‘fix’ N2 gas from the atmosphere into plant available nitrogen. In return, the legume provides carbohydrates as energy for the bacteria.

Other plants get the nitrogen that the legumes fix when the legume roots and nodules are naturally sloughed off or when the legumes are broken up during cultivation.

The best source of N

The very best source of nitrogen for your pasture and crops then, is that which you grow yourself by planting legumes like clover. Unfortunately, biology and microbial action can’t always provide enough nitrogen to meet food production demands.

That’s where nitrogen fertiliser comes to the rescue.

The next best option

A 2009 study estimates nitrogen fertiliser is responsible for 40-60 per cent of the world’s food production. So, there is no denying that it is necessary.

However, it’s also clear that responsible use is important.

The 4R Nutrient Stewardship Framework developed by the fertiliser industry worldwide suggests how this can be achieved.

The framework is simple: apply the right product, at the right rate, at the right time, in the right place.

Following these principles, a nitrogen fertiliser that supports plant growth throughout the growing season with reduced wastage is a good start.

Polymer-coated granular nitrogen products like Fertco’s 44Magnum and N-durance are two such products.

The coating imbibes water and swells.

The nitrogen moves slowly through the semi-permeable membrane by osmosis, so the nutrients are available at a more controlled rate for longer.

Being granular, the products can be applied more accurately, and because they don’t get converted to plant-available nitrogen as soon as they hit the soil like urea does, there is no sudden excess.

Wastage to the environment – and to your pocket – is greatly reduced.

But perhaps the best advantage for time-poor farmers in spring is these products can be applied in the late-autumn/early-winter period. So, they’re a ‘one and done’ product.