While some councils make the information available, others have the background, the infrastructure and the systems in place to take the guesswork for farmers out of deciding when to spread effluent. Anne Hardie reports.

Rain, soil deficit and the rate of transpiration are all part of the equation when farmers are deciding whether they can spread effluent, but it’s often guesswork.

Yet councils around the country have that information across their region and dairy effluent consultant Logan Bowler says there’s an opportunity to make it more readily available to farmers as another tool in their decision making.

Environment Southland already has that information online and farmers can view 19 locations that are monitored for aspects such as soil moisture, with different colours used for each site to show whether the soil is safe to irrigate, or not – or somewhere in between.

Other councils could do the same, Logan says, and though it might not have 100% accuracy for every farm, it would be considerably better than guesswork.

‘Farmers have to try and make a decision around
whether to irrigate without a lot of understanding
of the drivers behind that decision.’

“It’s way better than what we have now, which is absolutely nothing. Farmers have to try and make a decision around whether to irrigate without a lot of understanding of the drivers behind that decision.”

Farmers who irrigate through the dry and especially those with soil probes probably have a better understanding, but he suspects the majority of farmers don’t have tools to measure the soil water deficit or a good understanding of the calculation required to find out if they can irrigate effluent or not onto the soil and how much they can irrigate.

“It’s relatively simple, but you need to know the science behind it. What is the soil deficit and what is the evapotranspiration (ET) today and how much rain have I had? That’s all part of the equation.”

Logan says the evapotranspiration remains reasonably consistent with day lengths – the more daylight you have, the more hours in a day for grass to be doing photosynthesis and growing which is drying the soil out.

For example, as long as it isn’t raining, October this year will have the same ET as October last year because the daylight hours are the same. Rainfall isn’t consistent, but ET is.

He says farmers shouldn’t need to try and do those calculations, though, when councils have the equipment and are measuring those factors and could add more sites to provide information which would benefit farmers and also the environment.

“They have the background, the infrastructure and the systems in place. What I don’t want to see is 10 farmers down a road all having to pay for soil monitoring equipment when in my opinion, district wide (measurement) is good enough as an indicator.

“It comes back to Joe Bloggs farmer having to decide whether today is a good irrigation day, or not.”

When farmers aren’t spreading dairy effluent, they are storing it and calculating just how much storage is needed can be done with a lot more accuracy using the improved Dairy Effluent Storage Calculator (DESC).

The former Massey University version was more than a decade old and written in code no longer used for software, so DairyNZ took up the task of rewriting it and making it web-based so it can be accessed wherever there is access to the internet.

Logan helped DairyNZ develop the now-released online version and continues with activities for greater refinement of the tool.

He also milks 250 cows on a dairy farm in Manawatu and runs his own dairy effluent business, Agblution Solutions, which gives him a practical background for the multiple factors needed on each farm for the calculations.

He says the upgraded model better reflects the science, especially on low-risk soils. Now there’s the ability to enter multiple irrigation depths and associated pump rates.

The end result is it reduces storage requirements on low-risk soils at application depths less than 10mm and increases it at application depths greater than 10mm.

Multiple dates or periods can now be selected for milking days, stormwater diversions such as the yard or feedpad, and also non-irrigation days.

Many default values have been removed forcing those using the DESC to calculate or estimate inputs making the result farm-specific.

Bladders are now an option under storage options. Plus, the files can be shared online or assigned to another user and company logos can be added to reports.

Logan points out the importance of entering accurate information into the calculator to achieve an accurate result and recommends final calculations should be done by a qualified person such as dairy effluent warrant of fitness assessors or accredited effluent system designers.

Much of the dairy effluent work in the industry has focused on infrastructure, but there’s still a lot of work to do around effluent management.

Things can go wrong even with the most sophisticated system and good management. That’s when it’s good to know when it happens as soon as possible, or better still, before it happens. One of the companies supplying the technology to do that is Halo Systems which has a monitoring and control system designed to shut down the pump and send out an alert message when there’s a problem with the flow or pressure in the effluent line or pump, or any movement.

Sales marketing manager Blake Lattin describes it as an interface with the company’s hardware that has already been installed on farms. Several hundred farmers have added the technology which varies in cost between $4,000 and beyond $20,000 to purchase, depending on what it is set up to do. Then a monthly fee of $60.

“We try to help them prevent what they don’t want to happen.”

If there is a high flow and low pressure, or vice versa, something is wrong. Too much pressure may indicate a blockage and cause a pipe to burst or permanent equipment damage.

A sudden drop in pressure may mean a pipe has burst. Either way, the system shuts the pump down and sends out an alert to the farmer. Likewise, if the irrigator stops moving unexpectedly.

It was created five years ago and Lattin says they continue to add to its functionality. The latest addition measures nitrogen levels in the effluent being irrigated on to pasture. And geofencing provides an electronic barrier to stop the system irrigating wet or other sensitive areas in a paddock. If the neighbour’s house is on the paddock boundary or there’s a stream through the paddock, geofencing can place a protective barrier around those areas so they don’t get effluent near them.

Through the GPS in irrigators, the system records where effluent has been spread and how much has been spread which ensures farmers are compliant and also has that history as proof.

The monitoring system collects data outside the dairy such as weather and soil moisture, and Lattin says as more data is collected, farmers want more features added. He says every farm and every effluent system is different, so a monitoring system needs to be robust but also flexible.

A Golden Bay dairy effluent contractor, Alan Williams who runs Dairy Solutions, is an advocate for low-maintenance systems where there is less to maintain and less potential for things to go wrong. The way to achieve that, he says, is by using the smallest number of moving components possible in an effluent system and where possible, using gravity. That way, if something does go wrong, the effluent can still flow to the pond or tank and be spread. He realises that is not an option on all farms.

Though many farmers have upgraded their dairy effluent systems in recent years, he says there are still many waiting to see what systems work well and which ones are high maintenance, before making a decision and spending the money.

In the meantime, he has seen more farmers choose bladders for storing their effluent because they are cheaper and don’t need resource consent.

They provide another storage choice in high-rainfall areas like Golden Bay where rainfall can quickly fill a storage facility. Plus there’s the option of selling it down the track if circumstances change or farmers are waiting on environmental rules and more research before deciding on a long-term effluent solution.

Logan is not so sure about bladders though. Small bladders can be cost-efficient, but he wonders about the long-term effect of effluent in them.

Will they fill up with solids over time when you don’t have the option of stirring the effluent as you do in a pond or tank? Plus, he says, the lack of oxygen in a bladder creates an anaerobic process which won’t help the odour when irrigated on to paddocks.

Williams expects more farmers to use direct drilling as a method of effluent disposal, especially in higher rainfall areas.

He also expects more farmer interest in turning effluent methane into electricity to power the dairy, which is being done on a Southland dairy farm, though it’s still early days.