Southern Dairy Hub Research

The Southern Dairy Hub (SDH) grew out of the need for a large-scale research facility that focused on improving dairy management systems under the unique environmental conditions of Southland and West Otago. It was set up to replace a small demonstration farm, which was started by local farmers in 2007, when notice was given that the lease of that property was to end in 2016. Farmers wanted research to continue so that they would have sound information relevant to the southernmost region on which to base management decisions. The size of the SDH means that it can be used for longer-term farm system comparisons at scale as well as shorter more targeted research projects.  DairyNZ and AgResearch each have projects they are responsible for and also oversee some PhD and honours projects.

The farm is divided into four farmlets, each with its own 165-195-cow herd. In 2017 farmers identified that having systems with reduced nutrient loss was important for the region, and the current design allows for exploration of the various factors involved.  Dr Dawn Dalley, senior scientist with DairyNZ, says the research is taking risks and pushing boundaries so that farmers don’t have to. “Sometimes, as is currently happening at the Hub, we may push the boundaries too far. Being a research farm, we can’t change the protocols part way through an experiment to address negative impacts without compromising the research outcomes,” she says. “So, we follow the process through and record all the farm systems impacts including profit, animal performance and environment. Our learnings and associated discussion mean farmers can use our research as a starting point for system change and can focus on the refinements required to re-stabilise a system.”

Farmers said they wanted to understand two issues that were of particular interest/importance to them. The first addressed appropriate management of winter forage crops and the second examined what systems look like that have reduced environmental losses. A farm system comparison was therefore designed comparing two crop types and two levels of system intensity.

The current four-year system comparison is exploring the effects of de-intensification by reducing fertiliser nitrogen input from 200kg/ha to 50kg/ha per annum and reducing nitrogen imported in feed, with associated adjustments in stocking rate in systems based on either kale or fodder beet as a winter crop. The comparison, which still has about 18 months left to run, provides a platform for additional short and longer-term studies. Currently, there are some short-term studies of animal behaviour when grazing winter crops, and a longer-term project to find out whether there are any impacts of what the cows eat over winter on their offspring – this involves measuring calves as they are growing and recording their performance when they eventually enter the herd and are lactating. 

Dawn says that it’s important to make sure the ratio of crop to supplement is correct to minimise any nutritional deficiencies. “What drives the low nitrogen leaching with grazing fodder beet is that the bulb, which makes up about 80% of the plant, is very low in nitrogen – great from an environmental perspective but if a cow’s diet is too low in nitrogen that can affect her performance.”

Some of the findings so far include:

• Reducing N fertiliser input increases the amount of clover in the pastures in summer
• Cows wintered on fodder beet put on condition more easily than those on kale
• Phosphorus supplementation is necessary but tricky when grazing fodder beet in winter
• There is considerably less nitrogen loss to water from the fodder beet systems, but the lower plant protein that drives this outcome creates challenges in ensuring animals are offered sufficient protein to meet their requirements 
• The fodder beet systems produce smaller calves at birth but the lifetime impact of this is still under investigation
• To date we have been unable to maintain the profitability of the fodder beet system with the lowest environmental footprint because of reduced milk solids production and increased costs of fodder beet wintering

“The strength of what we are doing is that we are looking at the whole farm system over multiple years, the physical performance and financial performance as well as the environmental impact.” 

AgResearch has been involved with measuring nitrogen losses under the different farmlet cropping regimes, particularly the wintering systems. Science team leader Dr Ross Monaghan says that the main question they have been addressing is how much nitrate leaching takes place from the different uses of forage crops, particularly the ones they winter on. “The question we’ve asked is ‘are the losses from wintering under a fodder beet feeding system any different to those if you winter on kale instead?’ To answer this we have put quite a lot of money and energy into installing soil solution samplers, which are little ceramic cups, underneath the root zone at 60cm depth,” he says. “We extract the soil water on occasions when we know the soil to be draining and we measure how much nitrogen is in that water, and that gives us a very good estimate of nitrogen loss. We have been measuring nitrate losses under kale and fodder beet. There were questions about how beneficial fodder beet is as a winter crop, and are there any downsides to feeding fodder beet compared with kale? 

“We also were trying to get some data on what sort of losses you could expect if you use fodder beet in autumn as supplementary feed for cows. Often cows receive supplement, including fodder beet, during autumn when pasture growth slows, so we measured losses under that type of system – just a short grazing to give them a small amount of fodder beet before they go back onto grass. We’ve also simulated lifting the fodder beet and taking it away for feeding elsewhere and seeing whether that would help to reduce losses because of lower urine returns but it didn’t show much benefit, probably because of the longer time the soil remained bare before being re-sown in spring.”

With the three-year study almost at an end some important new findings have emerged, which will be used to ensure that nutrient loss models are working properly. Wintering on fodder beet results in considerably less nitrate leaching losses than wintering on kale. The main reason is that fodder beet is a low protein crop and so animals excrete less urinary N. However, it means that an appropriate supplementary feed is required to top up protein and  minerals such as P. 

Feeding fodder beet in late autumn will likely result in significant N leaching because the soil remains bare for longer, and Ross says they are going to have to figure out ways of making soils less leaky. Cover crops are problematic to establish so close to winter.

In contrast, N losses from pasture paddocks on the Hub farm are low, probably between one third and one fifth of what is being lost under the crops. To put that in perspective Ross says that the reason for the focus on the cropping part of the farm system is because those crops are potentially quite leaky.

“However, they represent maybe only 15% of the dairy system area, and the fodder beet crop would probably contribute only a third of the total system nitrogen loss whereas with kale it could be up to half.  So this work is giving us more data and confidence in being able to describe just how leaky these cropping systems are.”

Showdown Productions Ltd.   Rural Delivery Series 16 2021