Squeezing out the nitrogen

Farming in an area where cutting nitrogen leaching losses is already a major goal gives added impetus for a team in Mid-Canterbury. Anne Lee reports.

Matt and Amanda Ward’s expansive 2140-cow dairy operation in Mid-Canterbury is among hundreds of Canterbury farms looking hard at options to drag the final few kilograms of nitrogen fertiliser out of the system so it can meet the Government’s new nitrogen cap by next year.

The 571-hectare Coringa Park, 14km south west of Ashburton, is in the Hinds water zone – where farmers have already been working hard on strategies to hit the arguably more meaningful goals of cutting nitrogen leaching losses.

In the Hinds area, farms - other than those covered by irrigation schemes such as MHV Water - must slash annual potential nitrogen leaching losses by more than a third (36%) by 2035. Within the next five years those losses must be down by 15%. Coringa Park draws water from both MHV Water and a groundwater consent.

Matt and Amanda don’t shy away from the need to cut nitrogen losses.

“We know nitrate levels in the ground water around the district are too high. There’s no question we all have to be doing what we can to fix that,” Matt says.

It’s their water and their community too, he says.

That’s why they’ve joined in DairyNZ’s Meeting a Sustainable Future project where more than 40 farmers are working with DairyNZ and consultants to identify what they can do to reduce nitrate leaching and limit environmental impacts and then share their experiences.

Coringa Park was converted eight years ago from dairy support with Matt and Amanda joining with Matt’s parents Rod and Jo, from Te Awamutu, to form an equity partnership.

Matt and Amanda had previously been equity managers of another large-herd property near Rakaia.

It was there, in 2009, just five years after he graduated from Lincoln University with a Bachelor of Agricultural Commerce, that Matt won the Canterbury Dairy Industry Awards farm manager of the year title. Matt’s continued as a high performer with Coringa Park easily sitting among the top 10% of Canterbury farms across a range of metrics.

The ability of the operation to turn feed – home-grown and bought-in – into milk makes it highly efficient and profitable but over the past three seasons they’ve also added an environmental lens to how they view success.

Matt Ward addresses a field day as part of DairyNZ’s Meeting a Sustainable Future project to identify what the 40 farmers involved can do to reduce nitrate leaching and limit environmental impacts.

Last season their operating profit was $7189/ha compared with the Canterbury owner operator average in DairyBase of $4014/ha.

At $3.95/kg milksolids (MS), operating costs are almost $1/kg MS under the DairyBase average of $4.91/kg MS.

Like many Canterbury conversions, Coringa Park - at 320kg nitrogen (N)/ha/ year (prior to 2018) - had been a relatively high user of nitrogen fertiliser.

Good response rates make it a highly cost-effective way to boost feed.

“But I think when you get on a fast round and you’re following the cows with reasonably solid rates of nitrogen then all of a sudden you’re applying a lot,” Matt says.

In the 2018/19 season they embarked on a concerted effort to reduce nitrogen fertiliser use and limit opportunities for nitrogen to leach down through the soil profile without impacting production.

They took a closer look at when and at what rate the nitrogen was being applied and managed to drop an immediate 84kgN/ ha/year less.

“We didn’t really see a noticeable drop in pasture production at any particular time through that season.

“It wasn’t something we picked up in our measurements and we didn’t see any changes in (pasture) quality or production,” he says.

That indicated they were likely wasting a chunk of the nitrogen they were putting on, he suggests.

“When we were putting on nitrogen in the high 200 rates, each application was going on at around 80kg N/ha – now that’s back to 50kg.”

Last season their total nitrogen use lifted slightly again because Covid-19 meant it was difficult getting culls off and extra feed was required.

This season they’re aiming for fertiliser nitrogen use of 220kg N/ha and have sat down with their fertiliser rep and drawn up a set plan.

“We’ve made some changes in August and September. Where we might have put N on to paddocks with low cover before we graze them – we haven’t done that this season.

As a highly profitable unit, Coringa Park easily sits among the top 10% of Canterbury farms across a range of metrics. Now the team are working towards being highly nitrogen efficient.

“We’re looking at dropping out a summer application too and at this stage we’re thinking that any paddocks we graze twice over that month won’t get any N after the second grazing.”

DairyNZ environmental change specialist Katherine McCusker has been working with Matt as part of the Meeting a Sustainable Future project to investigate different management options for reducing their environmental footprint.

“Cutting out an application over the hot summer months when you’re really not

going to get a good response can give you a significant cut without hurting production. “It’s also when clover is active and can be fixing nitrogen.”

Matt’s paddock records show both fertiliser applications and pasture production and Katherine says these can help show where the best responses are coming.

“We can see some paddocks are getting up around 300kg N/ha and others are getting under 200kg N/ha but with the 190kg N/ha rule that flexibility will be lost,” she says.

The farm puts effluent out through it’s pivots and with it spread so widely and thinly there’s no real opportunity to cut nitrogen rates on effluent areas.

To counteract any reductions in pasture growth from reducing nitrogen inputs, Katherine says farmers should be looking at other areas within the system that might not be operating efficiently or effectively.

Meeting a Sustainable Future project farmers are learning from each other.

Matt’s made some relatively simple fixes in the irrigation system to get good gains for pasture production.

He says large pivots, such as their 800m pivot, are known to be less efficient at applying water on the outer ring.

“That’s compounded if the pressure isn’t correct because it doesn’t push the water right out (to the end).

The simple bucket test revealed they weren’t getting the amount of water they should have been on the outside ring.

“We were probably letting the pressure get a bit low in our mainline so we put some strategies in place so when the pressure dropped below a certain level, we could isolate that part of the mainline and use our pumps to make sure the pressure stayed up so the pivot operated correctly.”

They also put more emphasis on managing irrigation scheduling based on the soil moisture probes.

MHV Water farmers are all subject to audit of their farm environment plans by the scheme’s independent auditors.

Coringa Park earns a “solid A grade” audit.

Matt says the bucket tests required as part of the audit are worthwhile.

“It’s another tool or piece in the puzzle. It does show up any deficiencies in your system but you still need to be doing other things like regularly looking right along the pivot for any blocked nozzles or ones that aren’t spinning and keeping an eye out for any dry rings starting to appear in the paddock.”

The MHV Water irrigation water arrives at the gate in a pipe under pressure now that the formerly open race gravity fed system, that’s part of the larger Rangitata Diversion Race (RDR) scheme is piped.

“It’s in our best interests to use that water first rather than pumping it 100m up to the surface from the groundwater and paying that electricity.

“We keep that in mind when we’re scheduling so after a rainfall event we might start earlier with the pressurised water and not use the ground water so we’re leaving that in the ground.

“It’s a bit like managed aquifer recharge except instead of putting water into the groundwater we’re just not taking it out.”

Matt says the farm is tight for water with consents to pump 180litres/second from MHV Water and 80l/sec from groundwater.

They also have an onfarm storage pond they fill during the shoulders of the irrigation season and add to during any wet weather periods.

They can pump from that at 100l/sec and if that’s continuous will give them water for 30 days.

The farm’s watered by four pivots but they only have one Aquaflex soil moisture monitoring unit.

“You could argue we should have more and it’s something we may look into but we’re pretty lucky here in that the soil type is all the same – Lismore 2a.”

The soil moisture is constantly monitored with the aim to keep it between field capacity and refill point so that plants have enough for growth but it doesn’t get wet enough for drainage to occur because that’s when there’s a heightened risk of nutrients being lost to groundwater.

So, there’s two parts to why managing irrigation is important in managing nitrogen loss reductions – one is to ensure the system’s working well so that pasture growth isn’t limited and the other is to ensure it’s managed well so water isn’t draining down into groundwater.

PURCHASED N SURPLUS

Katherine says the “purchased N surplus” metric is a good indicator of how efficiently nitrogen is being used.

“It takes into account all of the nitrogen you’re bringing into the system – both fertiliser nitrogen and nitrogen in boughtin supplement and then subtracts the amount going out as milk, meat and any feed that goes off the farm.”

The number can be calculated using Overseer information and Fonterra farmers are receiving it on the Environmental Report.

Coringa Park has 55kg N/ha coming in as supplement and in 2018/19 had 219kg/ ha coming in as fertiliser.

Last season fertiliser N coming in rose to 245kg N/ha because of the increased feed demand from culls held.

“But Coringa Park doesn’t have a high purchased N surplus at either 154 kg N/ha in 2018/19 or 168 last season because it has high production.

“A lot of Coringa Park’s bought-in nitrogen is going out the gate in the tanker and that pulls the N surplus number down and shows it’s an efficient user of nitrogen.”

The amount of nitrogen going out in product was 133kg N/ha last season with a lot of Canterbury farms sitting about 100- 110kg N/ha/year, Katherine says.

Pasture and crop eaten is 16.8 tonnes drymatter (DM)/ha with imported supplement about 950kg DM/cow of barley, contracted through a long-term relationship with a local grower and pit silage, bought as standing grass.

Efficiency comes from a strong focus on pasture management and turning as much feed, both grown and bought-in, into milk.

Farm managers Josh Wardell and Louise Spowart run a farm team of 10 people across the four-herd system and measuring, monitoring and measuring again is the name of the game.

The pair are originally from Dunfermline in Scotland and arrived on the farm six years ago as backpackers with little knowledge of Kiwi pastoral dairying. They’re clearly fast learners. Pre-graze covers and post-graze residuals are watched closely and the rising plate meter has been an indispensable tool of trade.

“We get quite particular about residuals,” Josh says.

If a herd hasn’t cleaned out the paddock to the required 1550kg DM/ha residual it will go back in after milking with cows doing the job rather than the mower. The farm is a mix of diploids and tetraploids and over the past few years they’ve been sowing Viscount tetraploid ryegrass, white clover and plantain.

Plantain could offer further nitrogen loss reductions.

“Last year’s N loss here was 74. If there was 10% plantain in paddocks that would take it to 68 and if it was 20% it would take it to 62,” Katherine says.

While it is a straight line interaction – the more plantain the less nitrogen is lost – getting populations up and keeping them up still appears to be challenging.

But for Matt and Amanda and the team at Coringa Park that and other challenges are in their sights.

“We still have a way to go – we’re not crushing everything so I’m by no means the pin up man for awesome environmental stuff,” Matt says modestly.

But staying open to new knowledge and doing their best to implement, measure and monitor best practice is their modus operandi.