Agroforestry Systems Can Reduce Nitrate Leaching By 50%

Following on from Mike Barton's presentation to Beef + Lamb NZ, about farming under a nitrate cap. I thought I'd look at some less conventional ways farmers can reduce nitrate leaching.

Today I want to discuss Stephen Briggs Nuffield report into Agroforestry.

The report shows how an agroforestry system can dramatically reduce the amount of nitrate leached from a farming system.

It's a pretty radical change, but maybe the pasture based dairy farm of the future will include 100 trees/ha as well as cows.

Transcription:

Glen Herud here again and I'm blogging from my van today because I'm struggling to find time to blog. I still want to blog, but the only time I have to myself is when I'm stuck in Christchurch rush-hour traffic for 30 minutes every morning. 

So, I know I'm a bit weird.

I posted a video of Mike Barton last week about how he farms under a nitrogen cap. Heres the link to the full video on the Beef + Lamb NZ website. I recommend you watch it. 

But this is what he had to say:

"We leach 93% of the manageable nitrogen that's going into the lake. We wanted it to be all the batches and the septic tanks and the town and whatever else you could hope for. It wasn't. It was us."

You know, I think it's just a matter of time before all farmers will have to farm under a nitrogen cap. And whether that's right or wrong, I don't know. I just sense that the movement is towards that. 

When you look at the changes on the Horizons District Council, what's happened in Taupo. Canterbury is talking about it. Southland is talking about it. You know, I just get the sense in 10 to 15 years time, that's where we'll be.

And I don't think farmers are really thinking radical enough about how we could change our farming systems. I'm sure farmers understand how big the effect will be on their farming businesses. They understand that. But I think we need to really think about how we're going to farm under that, rather than spend all our energy on fighting it. Because I think it will happen, as Mike Barton said.

Now, one radical system, I'm going to cover a few radical ways that we could farm cows over the next couple of weeks. 

Agroforestry

And I want to talk about agroforestry. The reason is that agroforestry has been shown to reduce nitrate leaching by up to 50% over a monoculture system. Now, Stephen Briggs is a Nuffield scholar from the U.K. and he released a report on agroforestry last year. And I'll put a link to it, it's really good.

But, what you do is you really combine trees with agriculture. So, they could be nut trees, fruit trees, timber trees and they could be cropping. Could be dairy, whatever. And what you do is you plant them in lines, you have about 100 trees per hectare. And you farm within the alleyways.

Now, the reason it reduces nitrate so much is that the tree roots will grow down deeper. And they go in underneath the alley crop and they join up in the middle. That creates a kind of a safety net. So, any nitrate that drops out the bottom of the agricultural system gets absorbed by those trees. Therefore, you have a much lower rate of nitrate leaching.

So, there's a lot of other advantages. For instance, shelter. Also, agroforestry systems have shown to have 30% reduction of evapotranspiration rates. So that means that you're losing less water out to the atmosphere. Which is probably pretty good for Canterbury farmers that particularly, when you think about our howling nor'westers in the summer. But it's not all plain sailing. Shading is an issue and Stephen talks about how to overcome shading and the research done on that.

I know Lincoln has done some research into agroforestry and they showed that, after 15 years, their pine trees have totally shaded out their alley crop. So, we don't want that to happen. There needs to be a bit more research done into it. But, you know, it's a radical way of doing things. I mean, imagine if your average dairy farm sort of looks like this and imagine just planting that full of trees. Planting thousands of trees in your most productive land. That's a pretty radical thing to do.

Now, these are the sort of things I think we need to start thinking about if we're going to have a dramatic effect on our rate of nitrate leaching. And of course, many people, many farmers, don't think we need to. 

But as Mike Barton says in his presentation, 'If farmers don't come up with the solutions, some bureaucrat in Wellington probably will.' And it's much better that farmers come up with solutions than someone else. 

So, I'm just going to throw out some real wacky, way-out sort of things that maybe we need to consider to reduce our environmental impact.