What is… Nitrogen
England and all civilised nations stand in deadly peril of not having enough to eat. As mouths multiply, food resources dwindle. Land is a limited quantity, and the land that will grow wheat is absolutely dependent on difficult and capricious natural phenomena... I hope to point a way out of the colossal dilemma. It is the chemist who must come to the rescue of the threatened communities. It is through the laboratory that starvation may ultimately be turned into plenty... The fixation of atmospheric nitrogen is one of the great discoveries, awaiting the genius of chemists.
Sir William Crookes – 1898
The “genius of chemists”, was the German Fritz Haber, who discovered how to artificially fix Nitrogen (N) along with the industrial engineer Carl Bosch who scaled up the process so it could be accomplished on an industrial scale. The process came to be known as the Haber-Bosch process, this process produces over half a billion tons of artificial manure every year, requiring a huge 5% of the world’s natural gas to do so. The Haber-Bosch process sustains more than a third of the worlds food production, so it transpired that Sir William Crookes was absolutely right in his prediction on the importance of Nitrogen fixation in the agriculture industry.
The 7th element of the periodic table, it is an odourless, colourless, and mostly inert gas, and continues to be colourless and odourless at a liquid state. Nitrogen makes up around 78% of the air you breathe and is present in all living things, including the human body and plants.
The importance of Nitrogen
Nitrogen is found in both organic and inorganic forms in the plant. It combines with Carbon, Hydrogen and Oxygen (sometimes with Sulphur) to form amino acids, amino enzymes, nucleic acids, chlorophyll, alkaloids and purine bases. To emphasise the importance here, amino acids are the structural building blocks of proteins, so without Nitrogen there are no amino acids and no amino acids means no life. Furthermore, Nitrogen has an essential role as a base element for nucleotide molecules, the building blocks of DNA and RNA, which are the blueprints and translators of the genetic code respectively. Lastly, without the 4 Nitrogen atoms in the chlorophyll molecule (C55H72MgN4O5), there would be no photosynthesis. This also helps to explain why a Nitrogen deficient plant turns yellow, due to the lack of chlorophyll’s green pigment… Nitrogen is kind of important when growing plants.
Nitrogen and metabolism
Plants absorb Nitrogen as either NO3- (Nitrate) or NH4+ (Ammonium) ions. Both of these ions supply Nitrogen to the plant, but they will have big differences within the plants metabolic pathways. Nitrate for example is absorbed by the plant slowly and as we mentioned before provides the materials needed for the production of amino acids and other structures. In comparison, ammonia is absorbed rapidly and can cause problems such as toxicity if present in high concentrations.
The uptake of NO3- stimulates the uptake of cations (Positively charged ions), however chloride (Cl-) and hydroxyl (OH-) anions (Negatively charged ions) restrict NO3- anion uptake. This could be an explanation for why some cultivators choose to let their water stand for 24 hours before watering, which allows the chlorine to evaporate off. This practice has not been scientifically proven to give the cultivator any apparent benefits other than the water reaching room temperature to reduce shock from cold/hot watering.
Spotting Nitrogen deficiency and over fertilisation
A typical Nitrogen deficiency will manifest itself within the plant as a pale green coloring on the lower leaves, moving upwards through the plant as the deficiency becomes worse, eventually turning brown and dying. Plant growth is slow and maturation occurs earlier than normal with possible stunted growth. Nitrogen is a highly mobile element within a plant, therefore when a deficiency does occur, Nitrogen can translocate to the parts of the plant that require it the most, i.e. the new shoots and younger parts of the plant. This explains why yellowing occurs from the bottom upwards.
It should be worth noting that overwatering can also look like Nitrogen deficiency to an un-trained eye, as it also manifests itself as a yellowing of the plant, the cause of this is a lack of oxygen at the root system.
Nitrogen excess makes the leaves a very dark green colour, any new growth will be succulent and the plant is very susceptible to disease, insect infestation and drought stress. Lodging, blossom end rot (BER) and lack of fruit set can often occur as well.
The importance of Nitrogen cannot be understated, it is a fundamental part of the growth and an important part of the flowering stages in a plants life cycle. However, with a good nutrient formulation and sound cultivation practice, it should be a very rare occurrence that a Nitrogen deficiency or excess occurs in the grow room.
Thanks for reading the second installment of ‘What is…’, hopefully I’ve added a little insight into the 5th most abundant element in the universe.