Barrie Ridler
Finding environmental solutions on a dairy farm is often associated with less production and less profit, but a new predictive model provides options to alter the farming system for a good environmental outcome and often more profit.
The Enviro-Economic Model (E2M) analyses a farm’s system and by adding many options, it can recalculate the figures to provide the optimal economic solution and the outcome such as profit, nitrogen (N) leaching and greenhouse gas (GHG) emissions.
E2M has been developed by agricultural analyst Barrie Riddler and is used on the Lincoln University Dairy Farm. Now there have been case studies conducted on farms in conjunction with NZ Landcare Trust, Fonterra and DairyNZ.
NZ Landcare Trust coordinator for the Top of the South, Annette Litherland, says it is all about optimising a farm’s system. Farmers can decide they want to retain aspects of their farm system, such as cow numbers or adding a certain feed into the cows’ diet, then the model provides scenarios for the best outcome. It does that by assessing the change in profit from each additional individual input such as kilogram of drymatter, kilogram of N or bought-in feeds.
“This is a tool a farmer could use to interact with his or her farm system and come up with the optimal farm system for the changes that are facing us with the environment. E2M can do this much faster than other modelling tools currently available.”
For the Rosser farm in Golden Bay used as a case study, the data supplied for the model came from a Farmax simulation for the farm using DairyBase information as well as farming details from the family. The E2M model then came up with four alternative farm systems that reduced N use, used different pasture mixed to reduce reliance on irrigation and the use of the runoff block versus a self-contained system.
The amount of inputs such as bought-in feed, supplements harvested, areas of summer crops, cow stocking rate and per cow production level were varied by the model based on the energy feed supply and economic optimisation.
Annette, who has a background in agricultural science, says feedlots overseas use models all the time, but New Zealand farmers have been reluctant in the past because they can’t see how a model could predict what happens on a farm. Yet she says modelling is powerful and this particular model is a way for farmers to bounce their ideas around to find economic solutions to meet nitrate leaching and GHG reduction targets.
Whenever a scenario changes in farming, such as milk price, farmers usually have goals and change their system to cater for it, such as dropping inputs for a lower milk price, she says. Now they need to look at changing farm systems for better environmental outcomes and she says that requires some left field solutions such as modelling.
“Can you achieve what you need to do and still make the same profit or more? This gives you a system to examine many situations.”
As Annette explains, the model assumes cows are going to eat grass, produce milk and get in calf, so if an extra kilogram of feed was added into the system one way or another, the marginal economic result of that extra kilogram can be calculated, or any other factors in the farming system.
In the Golden Bay case study, Annette says the Rossers wanted to carry on feeding supplements in the shed, so the model could reduce it but not drop it completely. They also retained the production per cow and irrigation area, but allowed the model to change cow numbers.
“We allowed it to reduce cows by up to 60 and it said it would reduce cow numbers by 60 because it was more profitable. And it didn’t have to reduce N so much because it had reduced cow numbers.
“So then we looked at reducing cow numbers by up to 90 and it bought in less feed and had extra grass which meant more silage and so more feed and we could keep more stock at home and less grazing.”
At about $3000 to use the model, she says it is not cost-prohibitive for farmers to get modelling done on their own farm system. All they need is figures from Dairy Base and/or their farm accounts, plus other factors such as pasture growth, to look at various options for their farm. It’s particularly easy for those farmers set up in Farmax. Annette says it is really important that the farmer works with the modeler to try practical options that they think might work for them and then let the model optimise those options.
“This is a tool a farmer could use to interact with his or her farm system and come up with the optimal farm system for the changes that are facing us with the environment.
“You don’t need to change your whole system overnight. You’d make some changes the first year and step it through and see how close it’s coming to the model.”
In time, the model is expected to be expanded to include aspects such as soil and forestry get it to work out N leaching as well which is now being worked out through Overseer. But first it needs more funding and to achieve that it needs more farmers on board, she says.
The farm has a mix of rivers flats and pakihi hill, with forestry on the steeper country.
The full reports can be viewed on https://www.landcare.org.nz/current-project-item/farm-systems-project.
