What can a middle aged Englishman from the late 1600s teach us about nitrogen mitigation in the 21^st century?

 

Here’s a clue: For every action, there is an equal but opposite reaction.

 

The Englishman was Sir Isaac Newton, and this is his Third Law, published in 1687 in a book that changed science forever.

 

He wasn’t talking about farming. But this principle holds true for the millions of cows across New Zealand. The more water we put into them, the more comes out.

 

And this points us towards a novel, much improved approach to nitrogen leaching that’s already right under our feet.

 

Watered down

Imagine diluting a can of paint. The paint becomes thinner; its properties are weakened. You can cover a bigger area with it, but each brush stroke contains less pigment than before.

 

Dilution rarely makes for a great paint job. But as studies have repeatedly shown, it’s very good for lowering the amount of nitrogen left on the ground every time a cow urinates.

 

That’s the key reason plantain has become the poster child for nitrogen mitigation. It contains more water than diploid perennial ryegrass, dilutes cow urine and thus reduces the concentration of nitrogen deposited on the ground.

 

So too, however, do many other common forages!

 

As soon as we start looking at pasture species in terms of water content, it’s clear we have multiple potential options for diluting cow urine, not just one. Many dairy farmers are already using these – just not being rewarded for their associated benefits.    

But first, data

Take three different pastures: Diploid perennial ryegrass, tetraploid hybrid ryegrass, and diploid perennial ryegrass with 30% plantain dry matter.

 

Put them in a replicated trial system, and measure each for grazeable water content. Which one will come out on top?

 

No-one’s really sought to answer this question before, so we spent three years gathering data to quantify the difference.

 

The result? Of those three pastures, tetraploid hybrid ryegrass contains the most water. If diluting cow urine is a key way to mitigating nitrogen leaching on NZ farms, as research indicates, this data points us in a promising new direction.

 

Not least because farmers like you are already highly adept at using tetraploid hybrid ryegrass in your systems, and it is easier to grow and manage than plantain.

Stack the odds

Ranked on grazeable water content, diploid perennial ryegrass has the least. Chicory has the most. Plantain is second to chicory; tetraploid hybrid ryegrass is second to plantain.  

 

We know chicory makes cows urinate more than any other species listed above. So that’s one option to mitigate nitrogen leaching. But while chicory contains a lot of water, it is typically short-lived, and winter dormant.

 

To make a real difference, you need something that grows year-round, for more than one or two years. The longer it lasts, the more sustainable and cost-effective it is.

 

It should also be profitable to farm, easy to grow and manage, nutritious and palatable.

There’s just one other thing that really matters...

Scale up   

To get more water out of cows, more water must go in.

 

In itself, tetraploid hybrid ryegrass may not contain as much grazeable water as chicory or plantain. But in practical terms, that matters less than how much of it we can successfully incorporate into the cow’s diet.

 

Thousands of hectares of tetraploid hybrid ryegrass are sown every year on New Zealand farms. Our cows are already eating tonnes more of it, year round, than plantain as a minor component of a diploid ryegrass pasture.

 

True, they’re not getting as much water with each mouthful of tetraploid hybrid ryegrass as each mouthful of plantain. But they’re getting many, many more mouthfuls.

 

Wouldn’t it be exciting if we were in fact already achieving meaningful urinary dilution, at scale, using a tool that can enhance farm finances as well, through better animal performance and increased efficiency? Only more research can reveal the answer.

Big picture

You’ve probably noticed we haven’t yet talked about where tetraploid perennial ryegrass might fit into this thesis.

 

It also contains more water than diploid perennial ryegrass, not as much as tetraploid hybrid ryegrass, but arguably enough to tip the scales in favour of urine dilution.

 

Again, this is a pasture many of you have successfully deployed at scale, across thousands of hectares, with all the associated benefits of ease of management, relative persistence, palatability and nutrition.

 

What’s emerging here is a suite of potential pasture options for nitrogen mitigation, rather than the current focus on plantain.

The last word

Amid this debate, and others about future farm systems, certain fundamentals always prevail.

 

Efficient farms are better than inefficient farms for the environment, animals and those whose livelihoods depend on them.

 

Healthy, well-managed, well-grazed pasture – made up of plants that suit your conditions and nourish your animals – is inherently less wasteful and more efficient than pasture which do not fit your system.

 

New technology to measure and model collective inputs and outputs from pasture systems holds the promise of accelerating our efforts to breed efficient, productive, profitable pastures with enhanced environmental features.

 

Meantime, however, we pursue every opportunity to continue doing what we’ve always done – creating pastures that help farmers thrive. And we’re always available to support you. Book your free Pasture Health Check today.