In contrast to the lack of awareness of the importance of plant nutrients such as boron, silicon and sulphur, it is probably safe to say, that every farmer is well-aware of the role of nitrogen in plant growth.  The issues with nitrogen are different.  Nitrogen is a chemical element with the symbol N and the atomic number 7.  In its elemental form, it is an abundant gas throughout the universe.  Nitrogen occurs in all living organisms, mostly in amino acids, and therefore proteins, but also in the nucleic acids of every living cell.  It is essential to all life on Earth.

There are three main sources of Nitrogen: Atmosphere, Organic Protein Decay and Fertilizers.

In its elemental form, in the atmosphere, nitrogen cannot be used by plants and animals.  It has to be converted into a fixed state, such as a nitrate, before it can be assimilated by a plant.  Nitrogen in various forms may be present in soil due to natural mineral deposits, animal waste or as a product of organic digestion. Specific bacteria, such as Rhizobium bacteria can also fix atmospheric nitrogen in the soil; these bacteria exist in a symbiotic relationship in the root nodules of legumes.

Of course, when it comes to soils that are conventionally farmed, the presence of nitrates in the soil is due to the use of cheap synthetic fertilisers such as ammonium nitrate (NO₃⁻) and ammonium sulphate (NH₄⁺) fertilisers, and this is where the issues with nitrogen arise. (We will deal with each one of these elements in later posts)

I would also like to put the use of chemical nitrogen into perspective, this only started to occur after the second world war and the major reason for this is that after the war the world sat with a huge stock pile of explosives which of course are derivatives of N and it was here that we started to experiment with it in agronomy. Before this we did not have chemical nitrogen and we had to rely on the natural system.

NO₃⁻ fertilisers are negatively charged, very acidic and nitrates have a high salt index (100) that results in dehydration their surroundings.  They are also powerful oxidisers that literally burn up the organic matter and micro-life in the soil.  Excess NO₃⁻ nitrates in the soil react with boron and lime causing high acidity and a deficiency of sulphur.  Ammonium Nitrogen is positively charged nitrogen in the soil; it works really well with phosphorous to drive the fruiting process and is a great source. However it is volatile and converts to NO₃⁻ very quickly especially if the conditions in the soil are incorrect which is almost always the case in conventional situations.

The use of these synthetic fertilisers has caused major water pollution issues throughout the world due to the run-off from agricultural land into water systems that kills aquatic plant and animal life. Excessive nitrates are carcinogenic to life, if you look at the increase of usage of synthetic fertilizers in production and you plot it on a graph next to the occurrence of major human health diseases you will see over the last 6 decades that the graphs mirror each other. You don’t need to be a scientist to see the connection!

Nitrogen is exceptionally important to plants; there is no growth without it, and you certainly need enough of it in its natural form.  Nitrate Nitrogen specifically supports green growth and lush leaves and in vineyards this can be a huge issue when it comes to phenolic ripeness.  The use of synthetic nitrogen fertilisers in the vineyard results in excessive green growth, lots of trimming and leaf breakage. This in turn results in green tannins in the grapes which mean at harvest time and forces wine makers and agronomists to let there grapes hang for longer resulting in higher sugars and therefore higher alcohol.  You also lose the grape flavours and experience an over-ripe taste which is most definitely not what we are after!  Therefore, the choices that a wine farmer makes when it comes to nitrogen impact on everything from the general health of the ecosystem to the specific quality of the wine.

Incorrect sources and handling of “Organic” nitrogen sources such as manures can be as bigger issue form a pollution perspective, negative impact on soil life as well as excessive NO₃⁻ in one’s soil.

It is for these reasons that Avondale avoids the use of synthetic sources of nitrogen, any manure and relies instead on the organic chemistry of our vineyard ecosystem where the micro-life in the soil binds all the nitrogen our vines might need for healthy growth.  This is why Avondale’s BioLOGIC® approach has a keen focus on a cover cropping system that always includes a variety of legumes that support the life of nitrogen-fixing bacteria. We also have an extensive program that promotes the diversity of soil life and especially free living nitrogen fixers. The key to all of this is to build the organic matter and humus in the soil, not burn it up!