By Graeme Sait, Author of ‘Nutrition Rules!’, Consultant, CEO Nutri-Tech Solutions (NTS)
In the first part of this article, we discussed the nuances of nitrogen, the most misused of all minerals. In this installment, I will continue with our six strategies to master this important mineral.
2) Discover the Sweet Spot
Nitrogen is the ‘Goldilocks mineral’, in that it is very important to get levels “just right” in your crop. Many profits have been decimated with too much, or too little N. There is a sweet spot for every cropping situation and it will vary during the vegetative and reproductive stages. If you can master this, you will most certainly be a happy camper at season’s end.
A nitrogen meter is an essential tool to achieve the required precision. You will need to determine the “just right” level in your crops, and in your conditions. Visual observation will help, but you can also correlate with other meters – i.e., when the sap pH is 6.4, the brix levels are high, vigour is good, and pest pressure is low, you have found your ideal nitrogen level. There is always more nitrogen involved before flowering, but from thereon in, potassium dominates and N requirements will be less.
3) Dramatically Increase N Efficiency with Foliar Urea
This may well prove one of your most effective strategies. When urea is applied to the soil, it is rapidly transformed from an amine into ammonium-nitrogen. Nitrifying bacteria then convert the weakly-bound ammonium N into nitrate-nitrogen, and this N form floods the plant, dilutes the mineral content and creates a calling card for insects.
The conversion of these nitrates into protein in the leaf is critically important, because plant immunity is protein-driven. The first stage of a three-part process is remarkably energy intensive. In fact, it can account for up to 20% of photosynthates to drive this initial step. This sugar-sucking, yield-sapping first stage involves the creation of a driver called the nitrate reductase enzyme. This molybdenum-based enzyme converts the nitrate nitrogen into the first stage of protein, called an amine. Ironically, this is exactly how your urea started out in the soil.
What would happen if we delivered that amine directly into the leaf, 12 times more effectively? Would that create more efficient, less energy intensive protein production? The answer is a resounding YES! It is also far more cost effective. There is no groundwater and atmospheric contamination and the associated nitrates do not dilute nutrient density in the plant.
10 – 15 kg of urea, foliar applied with humic acid, can provide an N response equivalent to an 80 kg urea side dress – and it is in a much more plant-supportive form.
4) Understand the Crop Cycle Link
Nitrate nitrogen is predominantly a vegetative mineral and, as such, it is best suited to the first half of the season. Ammonium nitrogen is strongly reproductive. In fact, aqua ammonia is an invaluable tool to switch a crop from vegetative to reproductive. Ammonium sulfate is the preferred form of nitrogen, if nitrogen is required during the last half of the season. Sulfur is also a reproductive mineral, so this combination offers a double whammy. Conversely, calcium nitrate and potassium nitrate both offer a double-barreled vegetative push, and they are best suited for that purpose.
5) Utilise the Perfect Biological Partners
If you can establish Mycorrhizal fungi and Azotobacter together in the root zone, you have achieved a highly productive partnership that will seriously reward your efforts. Azotobacter require a constant source of soluble phosphorus to create ATP, the battery of life, that fuels the nitrogen-fixing, enzymatic reaction. Mycorrhizal fungi provide that ongoing P source, through acid exudates that release locked-up phosphorus. In turn, the Azotobacter provide the AMF with a nitrogen source to build the protein required for their substantial, tag-on root extension.
6) Stabilise all N Inputs and Slow Nitrification
Nitrate N leaches and volatilises, (gases off), while ammonium N can be rapidly converted to the nitrate form by nitrifying bacteria. The solution is to stabilise both forms, to increase their longevity and performance. It can also be productive to select more sustainable strategies to slow nitrification and hold the N in the more stable ammonium form for longer. Slow-release urea is often based upon toxic substances like formaldehyde. These chemicals can certainly kill the nitrifying bacteria, but there is no consideration of collateral damage in the soil foodweb. There are several more sustainable stabilising options including:
a) Zeolite – The unique, honeycomb structure of this mined material features pores the exact size of the ammonium ion. The mineral slots into this framework, like a hand into a glove, and this reduces the surface area available to the nitrifying organisms. Hence, the conversion is seriously slowed. Zeolite has a second smaller group of pores that are the exact size of potassium, so this leachable mineral can also be held longer in your soil.
b) Humic acid – This powerhouse, natural substance binds with urea to form a stable, urea humate. It does the same with ammonium nitrogen and forms an ammonium humate. In both cases, it also increases uptake of nitrogen via a phenomenon called cell sensitisation. Here, the humic acid renders the cell membrane more permeable, allowing 30% more N to be absorbed.
Nitrogen is a multi-faceted mineral with multiple roles. This most abundant mineral in the plant is a major player in photosynthesis and is the building block for the protein that creates enzymes, amino acids and a great deal of the plant’s immune response. When undersupplied, the plant is forced to cannibalise enzymes in search of N. The wheels fall off shortly thereafter, as enzymes are responsible for the protective capacity of the plant. In this manner, nitrogen shortage is a major driver of plant disease.
Conversely, when we oversupply this important mineral, we create even more problems. In fact, the nitrogen component of the greenhouse blanket is a key player in the greatest challenge we have ever faced. The good news is that when we address nitrogen mismanagement, there can be a profound win/win outcome for the soil, the farming enterprise, the consumer and the planet.
This article first appeared on the Nutri-Tech Solutions (NTS) website. For over 23 years, NTS have been world leaders in discovering a viable alternative to extractive, chemical agriculture. Follow them on Twitter @ntsaustralia