ENTEC and how it works
ENTEC was introduced to cane growers and advisers in 2014.
It’s now widely used to protect against nitrogen losses and give cane crops greater potential for higher yields when the season allows.
WHAT IS ENTEC?
ENTEC is a liquid chemical (3,4 dimethylpyrazole phosphate) that is sprayed on to conventional nitrogen fertilisers at pre-determined rates.
ENTEC is described as an ammonium stabiliser or a nitrification inhibitor, but it doesn’t do anything to the nitrogen directly.
The active ingredient targets the Nitrosomonas group of bacteria, which are attracted to the ammonium from the fertiliser.
It is the Nitrosomonas bacteria that convert ammonium to nitrate in soils.
The Nitrosomonas population builds up quickly when an ammonium food source appears in the soil.
Their numbers can double every eight hours.
ENTEC works by binding to a copper atom in the ammonia mono-oxygenase enzyme in the Nitrosomonas bacteria.
This blocks the enzyme’s activity and stops the Nitrosomonas bacteria from converting ammonium to nitrite.
The result is more ammonium nitrogen in the soil and less nitrate nitrogen, which reduces the potential for leaching, denitrification and runoff losses.
It is only nitrate that denitrifies, and nitrate is also prone to leaching and run-off.
ENTEC is active until it is broken down by other soil microbes.
ENTEC can be used in all agricultural soils with a pH(w) of more than 4.5.
Below this level, the Nitrosomonas bacteria do not thrive so there will be no effect.
APPLYING NITROGEN IN CANE
ENTEC fertilisers are applied in ratoon cane using stool-splitters or double disc openers, with the fertilisers applied in the centre of the hill or side dressed either side of the plant row into the hill.
ENTEC fertilisers can also be side dressed in plant cane where a significant amount of nitrogen is needed and there is a risk of leaching, denitrification or run off.
The best-practice use of ENTEC urea blends in cane soils involves applying the fertiliser into the soil with at least 10cm of compacted soil cover.
ENTEC does not protect nitrogen from volatilisation losses, so effective incorporation into the soil is essential.
In recent times, the StoolZippa has been useful in helping cane growers to ensure adequate compacted cover over their fertiliser bands and reduce the potential for volatilisation losses.
WHAT HAPPENS WHEN NITROGEN IS APPLIED?
Different nitrogen fertilisers behave in different ways in the soil after application, regardless of whether ENTEC is used.
For example, when urea is applied to the soil and is exposed to moisture, it converts to ammonium in the presence of a naturally occurring enzyme called urease.
The process of dissolving urea creates a localised alkaline reaction which drives the conversion of that ammonium to ammonia.
A band of ammonia is likely to be present in the soil within 24 hours of applying urea or ENTEC urea and concentrations of ammonia may continue to increase over the following week or two.
This has its own unique protection against nitrifying bacteria.
At a boiling point of -33.4C, the interior of the fertiliser band is toxic to all life.
This ‘soil state’ significantly slows the conversion to nitrate nitrogen. PROTECTING CROP NITROGEN SUPPLIES
Where ENTEC has been applied with the fertiliser, it blocks the activity of the Nitrosomonas bacteria, allowing the nitrogen to remain in the ammonium form for extended durations.
Whether this affects the total availability of nitrogen and the performance of the cane crop will depend on seasonal conditions.
For example, if there is a storm or even a few days of heavy rain while there is a large pool of nitrate nitrogen in the soil, this nitrogen may be lost through leaching, denitrification or run-off.
This reduction in the overall supply of nitrogen to the crop may impact on crop growth and yield.
Because ammonium is positively charged and sticks to the soil rather than moving with water flows, it is not subject to leaching.
Ammonium is not subject to any denitrification losses either.
HOW LONG WILL IT BE EFFECTIVE?
Every ENTEC application is unique, so how long ENTEC is active in the soil is likely to be different each time it is used.
The soil will have different chemical, oxygen and bacterial compositions each time. It will be wet and dry and warm and cool at different times and for different durations.