Nitrogen is one of the most important inputs in productive agriculture — and increasingly one of the most scrutinised.
For New Zealand farmers and growers, the challenge isn't simply about using less nitrogen. It's about getting more value from every kilogram of nitrogen applied while maintaining crop and pasture performance.
This is where biological inputs may have an important role to play.
At EMNZ, our focus is not on replacing conventional fertiliser with biology. Instead, we are investigating how biological products can work alongside existing nutrient programmes to improve nutrient cycling, root development and ultimately nutrient-use efficiency.
Recent New Zealand field trials are providing some encouraging results.
It's Not Just About How Much Nitrogen You Apply
When nitrogen fertiliser is applied to a crop or pasture, not all of it ultimately ends up in the plant.
Its efficiency is influenced by a wide range of factors including soil conditions, microbial activity, root development, moisture, temperature, timing and the form in which nutrients are present.
This means two crops receiving similar amounts of nitrogen can use that nitrogen very differently.
A biologically active rhizosphere — the zone of soil immediately surrounding plant roots — can play an important role in nutrient cycling and availability.
Microorganisms break down organic material, transform nutrients between different forms and interact directly with plant roots. At the same time, a larger and more active root system gives the plant greater access to both nutrients and moisture.
Rather than looking at biology as another source of nitrogen, we believe the more useful question is:
Can biology help the plant make better use of the nutrients already available to it?
A New Zealand Maize Trial Provides an Interesting Example
An independent maize trial conducted in Hawke's Bay provides a good example of this approach.
The trial investigated EMNZ biological treatments alongside nitrogen applications under commercial growing conditions.
One treatment combining Plant-Stim with 40 kg N/ha produced:
29.45 tonnes DM/ha
compared with:
23.94 tonnes DM/ha in the control.
That represented approximately a 23% increase in dry matter production.
Importantly, the result wasn't achieved by simply increasing nitrogen inputs. It demonstrated the potential for a biological programme to complement a reduced nitrogen input while maintaining — and in this case increasing — crop productivity.
As with any individual field trial, the result should not be interpreted as proof that nitrogen can automatically be reduced by a particular percentage on every farm.
Soils, seasons, crops and management systems vary enormously.
But it does raise an important question worth investigating further:
Could improving biological function allow farmers to achieve more production from each unit of applied nitrogen?
How Could Biology Improve Nitrogen-Use Efficiency?
There probably isn't one single mechanism.
Plants, microorganisms, roots, organic matter and nutrients operate as an interconnected system. Biological inputs may influence several parts of that system at the same time.
1. Supporting nutrient cycling
Soil microorganisms are central to the decomposition and transformation of organic material.
Through these processes, nutrients held in crop residues, organic matter and other soil pools can be converted into forms that plants can access.
A more active biological system may therefore help maintain nutrient movement through the soil rather than viewing fertility solely in terms of what is applied from the fertiliser spreader.
2. Developing a larger root system
The efficiency of nutrient uptake also depends on the plant's ability to find nutrients.
More roots mean a greater volume of soil can potentially be explored for nitrogen, phosphorus, potassium, trace elements and water.
This is an area where we have seen interesting results in our own work.
In an EMNZ pasture trial, measured root mass increased from 149 g in the untreated control to 211 g with Plant-Stim.
That's approximately a 42% increase in measured root mass.
While root development alone doesn't prove improved nitrogen-use efficiency, it provides a logical mechanism through which plants may improve their ability to capture available nutrients.
3. Biological metabolites and plant response
Plant-Stim is not simply a microbial inoculant.
It is produced through fermentation of plant materials using EM microbial cultures. During fermentation, microorganisms transform the raw materials and produce a complex mixture of microbial and plant-derived metabolites.
These compounds can influence plant and root responses without necessarily acting as conventional fertiliser nutrients themselves.
This is one reason we increasingly think the term biostimulant is useful when discussing products such as Plant-Stim.
The objective isn't necessarily to supply more nutrition.
It's to help the plant use its growing environment more effectively.
We're Seeing Similar Signals in Other Crops
The Hawke's Bay trial isn't the only result that has encouraged us to investigate nutrient efficiency further.
In an independent Waikato maize trial, a Fert Enhance treatment produced approximately 34.2 tonnes DM/ha, compared with 30.0 tonnes DM/ha in the untreated control — an increase of around 14%.
In a replicated Canterbury wheat trial, Fert Enhance increased yield from 7.22 t/ha in the control to 9.08 t/ha, an increase of approximately 26%. The Fert Enhance versus control comparison was statistically significant.
Across pasture and lucerne work we have also recorded improvements in dry matter production, root development and plant performance following biological treatments.
Different products and trials shouldn't simply be grouped together as proof of one mechanism.
What they do provide, however, is enough of a pattern to justify asking better questions about the interaction between biology, roots, nutrition and productivity.
Biology Doesn't Mean Abandoning Fertiliser
This is an important distinction.
We don't believe New Zealand farmers should view biological products and conventional fertilisers as opposing systems.
Nitrogen, phosphorus, potassium, sulphur and trace elements remain fundamental to productive agriculture.
The opportunity is potentially in combining sound nutrition with improved biological function.
Instead of asking:
"Can biology replace my fertiliser?"
a more useful question may be:
"Can biology help me get more from the fertiliser I'm already using?"
That change in thinking is important.
If biological programmes can improve nutrient-use efficiency, even relatively small improvements could have significant implications across large farming systems.
Putting This to the Test on New Zealand Farms
This spring, EMNZ is continuing to investigate this question under commercial farming conditions.
Our current dairy field programmes include treatments where conventional nitrogen inputs are being progressively reduced alongside biological programmes incorporating products such as Plant-Stim and EM Balance.
Rather than simply measuring whether the grass looks greener, the objective is to look at production under different nutrient strategies and determine whether biological inputs can help maintain performance as conventional nitrogen inputs are reduced.
This is exactly the type of work we believe is needed.
Biological agriculture needs to move beyond broad claims about "soil health" and demonstrate where biological products create measurable value within real farming systems.
Where Does This Leave Nitrogen?
Nitrogen will remain one of agriculture's most important nutrients.
But the future conversation may increasingly be about nitrogen efficiency rather than nitrogen quantity.
That means considering the entire system:
soil biology → roots → nutrient availability → plant uptake → production.
The encouraging results we have seen in maize, wheat, pasture and other crops suggest biology has the potential to play a meaningful role within that system.
There is still plenty to learn, and results will vary between soils, seasons and farming systems.
But after more than 30 years working with biological agriculture in New Zealand, we believe this is one of the most important areas for the industry to investigate.
The goal isn't simply to use less fertiliser.
It's to get more from every nutrient we apply.
Want to explore biological nutrient efficiency on your farm?
EMNZ develops and manufactures biological products in Christchurch for New Zealand agriculture and horticulture. Our programmes are designed to complement existing fertility systems by supporting soil biology, root development and plant performance.
Talk to the EMNZ team about incorporating biology into your crop or pasture nutrition programme.
