Drought is an inevitable part of farming in Australia, but outcomes from the Improved drought resilience through optimal management of soils and available water project are equipping farmers with a host of additional strategies with which they can prepare.
Since 2017, numerous small-scale field trials across southern NSW have shown that early sowing of slower maturing crops, diverse legume rotations and nitrogen banking can all increase profitability and productivity by increasing soil moisture availability and preventing carbon and nutrient loss under drought conditions. Proving these practices are profitable and deliver co-benefits on a paddock scale is key to ensuring grower adoption.
“In this project we have taken outcomes from 4 years of small-plot research, and rolled out 12 demonstration sites across southern NSW, to allows farmers across different geographies and constraints to assess what long-term nitrogen management strategies could work at farm scale in their systems,” said Dr John Kirkegaard, CSIRO, who leads the ongoing parent project in collaboration with NSW Department of Primary Industries and funding from the Grains Research & Development Corporation (GRDC).
“Maintaining robust N supply is not only important to hit yield potential in above average years when most money is made, but to ensure soil organic matter is not mined to supply crops with N leading to significant soil carbon loss. Nitrogen mined from organic matter when fertiliser N is insufficient leads directly to soil C loss and can outweigh the embedded emissions related to the fertiliser.”
Three different nitrogen management strategies were used across 12 paddock-scale demonstrations, these were:
Each of these strategies (diversity, early sowing, N-banking) have previously shown in small-scale NSW field trials to increase profitability and productivity by increasing soil moisture and the prevention of carbon and nutrient loss under drought conditions.
It can be challenging for farmers and agronomists to adopt new strategies, especially those that take long term planning or longer to pay-off, without having seen the outcomes at paddock-scale and the impact that it has on in-season logistics and performance across different system constraints.
“Whether it was building diversity into rotations, early sowing, or N-banking, understanding how these strategies worked for local farmers was an important piece of validation and gives other farmers and agronomists confidence to implement or recommend these strategies more broadly,” said Pip Grant, CEO of Riverine Plains who led the project in collaboration with Central West Farming Systems, Charles Sturt University, CSIRO, FarmLink, NSW DPI, and Southern Growers.
“It was great to be able to take pressure-tested results from smaller scale trials and see how they actually worked in the paddock under real conditions and seasonal pressures. The insights from the farmers were incredibly value, and really expanded on the positive results seen in the earlier research.”
There was different farming systems and constraints across the demonstration sites, delivering a valuable suite of case studies to support farmer’s decisions to invest in long-term nitrogen management.
Integrating legumes into cropping or pasture rotations come with many co-benefits, including increasing soil organic carbon, nitrogen, and soil water holding capacity.
Roger and Fabian Todd’s property, 75kms northwest of Condobolin, NSW, consists of 3500 hectares of controlled traffic continuous cropping and a further 3000ha of mixed farming, with a rotation of 2-3 years of grazing wheat before sowing lucerne and grazing paddocks with their own stock (sheep and cattle) or stock on agistment.
“As far as legumes go, we’ve tried them all! We used to grow chickpeas, but we were finding that while they gave us great chemical and marketing options, we weren’t getting a lot of nitrogen banked in the soil for subsequent crops,” Roger said.
“We really like the early sowing option vetch offers our system in addition to the amount of biomass it can grow. It gives us the hay option for feed or to sell for income, as well as grass weed control for emerging herbicide resistance issues with wild oats and annual ryegrass — it’s an effective way for us to tidy up paddocks ready for canola the following year,” Roger said.
The Todds have been working with local agronomist Chris Baker, Baker Ag Advantage, for about 16 years, to develop and maintain a low-risk sustainable grain-growing enterprise.
As part of the Improved drought resilience through optimal management of soils and available water project, Roger was looking to validate how early sowing with a pulse crop (e.g. vetch) could benefit his grain-growing operation.
“What’s surprised me is the versatility vetch gives us in our farming system — it can be brown manured, taken through to grain or run through as a hay crop — and with the increasing fluctuations in seasons, this is key to our profitability and production,” Roger said.
“In regard to early sowing, by incorporating vetch we can start our sowing program during March. With the size of our cropping program and only having the one seeder this means we can keep the seeder going starting with sowing vetch and get the wheat in within the desired sowing window.”
Chris agreed saying, “Early sowing is a big tick for vetch — it’s in and it’s out of the way.”
“And when considering nitrogen banking, another strategy the overarching project is also looking at, where canola tends to follow the vetch, we are reducing the nitrogen risk in low- rainfall areas. But if the season is favourable, we can load up the canola with more nitrogen without the risk of burning the canola crop off and banking the nitrogen in the soil profile for the subsequent wheat crop,” Chris explained.
“Knowing the inclusion of a pulse — vetch — in our rotation can help to bank nitrogen in the soil profile for subsequent crops, and also give us good weed control options for herbicide-resistant wild oats and annual ryegrass, also gives us peace of mind,” Roger said.
Image: Roger Todd
Early-sowing of longer season varieties can provide multiple benefits depending on the weather and type of enterprise.
Eurongilly farmer James Brady says early sowing dual-purpose crops — wheat and canola — provides valuable winter feed for their composite ewe flock, on top of substantial grain yields, adding resilience to their mixed farming business.
James sows around 400 hectares of early sown canola and 400ha of early sown wheat annually, with the remaining 600ha sown to pasture (lucerne and subclover mix) on his property located at Eurongilly, NSW.
Dual-purpose grazing crops have been a key component of James’ system for the past 20 years, but around 8-9 years ago he made the shift to 100% dual-purpose grazing varieties to fill the winter feed gap and meet the nutritional requirements of his composite ewes during lambing. Additionally, this approach also allows James to finish lambs ready for sale by October – November.
“We’ve been growing grazing crops such as wheat and oats for a long time now so it’s nothing new,” James said.
“But with breeding improvements over the years, we are now spoilt for choice with dual-purpose varieties producing higher grain yields and delivering more grazing options for our mixed farming operation.”
Winter feed is a high priority for James and the shifting rainfall patterns mean he cannot guarantee the pastures will have sufficient moisture to germinate and grow enough feed for his lambing ewes.
“We need winter feed to sustain our 6500 ewes and the best way we can do this is to get in early with dual-purpose wheat and canola,” James said.
The move to early sowing with a single variety each of wheat and canola has significantly reduced the complexity of the Brady’s operations, without any negative implications.
“We’re fortunate with our rainfall and longer season compared with much of the cropping zone. They might see larger differences in grain yields, but ours are very similar, so we’ll stick with one variety and keep sowing as long as there is moisture in the ground,” James said.
“We generally start sowing mid-late February — as soon it rains, we are on the tractor sowing — and depending on soil moisture we continue sowing until the crop is all in; usually by mid-March.”
Nitrogen is key.
The research led by CSIRO researcher John Kirkegaard shows that around 150kg/ha of nitrogen, a combination of soil banked nitrogen and fertiliser, is required at sowing for optimal forage potential from dual-purpose crops.
To ensure high soil nitrogen, James plants early sown canola into paddocks coming out of a seven-year pasture phase or paddocks where soil tests show a high residual soil nitrogen level — aligning with CSIRO research outcomes.
CSIRO research also shows that canola roots can draw moisture from a depth of more than four metres. While James does not have moisture probes to confirm moisture levels at depth, he said they are seeing the clear benefits of early sown canola roots accessing moisture from the profile at depth.
“We’re seeing the benefits of the deeper root system of our grazing canola crops that we sow in early-mid February, around three to four weeks earlier than our grazing wheat,” said James.
“And with John Kirkegaard’s research showing that canola roots can suck moisture from the soil profile down to three to four metres, I believe our crops are benefiting from these deeper root systems.”
Image: Eurongilly farmer James Brady
Despite challenging seasonal conditions and inconclusive yield results, a two-year paddock-scale investigation has given the Trevethan Family Farms, Howlong NSW, the confidence to continue incorporating a legume into his cropping rotation.
On the back of escalating fertiliser prices and a desire to reduce nitrogen inputs to the system, it was a ‘no brainer’ for Tim Trevethan to partake in the Improved drought resilience through optimal management of soils and available water project.
The Trevethans typically employ a wheat-canola rotation, followed by a maize crop over summer, on their irrigated property between Howlong and Corowa, NSW. They also run a sheep enterprise on their dryland block about 10km north of Howlong.
“We’re not set on any particular rotation, we’re just trying to find what makes us money and to be honest, we are still trying to work out the best rotations to do this,” said Tim.
Tim saw the project as an opportunity to test a different cropping system and explore the impact of incorporating a legume crop on nitrogen levels and soil water.
“At the end of the day, we want to reduce our nitrogen spend in-crop and lower our cost base,” Tim said.
“We also want to understand how much the nitrogen fertiliser input for the following crop might be reduced and whether we can grow high-yielding crops using organic nitrogen instead of applying large amounts of fertiliser.”
Deep nitrogen analysis and farmer observations show that a legume history can provide more nitrogen than a cereal history for the Trevethans. Replacing wheat with faba beans in their traditional wheat/canola rotation reduced his in-crop nitrogen requirements for the canola phase by 58kgN/ha. At $700/t and an application cost of $7.50/ha this equates to a saving of $95.70/ha.
Image: Tim Trevethan, Howlong
This project is supported through funding from the Australian Government’s Future Drought Fund – Drought Resilient Soils and Landscapes Grants Program, and a co-investment of the Grains Research and Development Corporation (GRDC).
This project was led by Riverine Plains in collaboration with Central West Farming Systems, Charles Sturt University, CSIRO, FarmLink, NSW DPI, Southern Growers and the Southern NSW Drought Resilience Adoption and Innovation Hub.
Media Contact
Pip Grant, CEO, Riverine Plains
E ceo@riverineplains.org.au
M 0499 998 138