Research funded by the Grains Research and Development Corporation (GRDC) shows that when break phases are incorporated, increased profitability of up to $100 per hectare per year can be achieved over a four-year period compared with cropping continuous wheat.

Mallee Sustainable Farming (MSF) agronomist Michael Moodie, who has been a coordinator of the Low Rainfall Crop Sequencing Project, says two-year break phases are a reliable management tool for increasing the yields of subsequent wheat crops in paddocks where agronomic constraints are affecting yields of continuous cereals.

“Wheat yield benefits of one to two tonnes/ha commonly accumulate over two or three seasons following the break phase,” said Mr Moodie.

The Low Rainfall Crop Sequencing Project, a collaboration between the South Australian Research and Development Institute and five farming systems groups – MSF, Eyre Peninsula Agricultural Research Foundation, Upper North Farming Systems, Birchip Cropping Group and Central West Farming Systems – was established in 2011 at five trial sites across the low rainfall zone (LRZ) of south eastern Australia.

The trial sites were at Minnipa and Appila in SA, Mildura and Chinkapook in Victoria, and Condobolin in New South Wales.

The GRDC funded the research, on behalf of growers and the Australian Government, to quantify the yield benefits that break phases provide to subsequent cereal crops and to quantify the impact of break phases on profitability of the long-term rotation.

“The aim of the project was to test if a one or two-year well managed break phase in low rainfall crop sequences could successfully address agronomic constraints, increase the productivity of subsequent cereal crops and most importantly, improve the profitability of the crop sequence when compared to continuous wheat,” Mr Moodie said.

Mr Moodie, who has spoken about the project at recent GRDC Grains Research Updates, said that over the past 15-20 years, the intensity of cereal crops in LRZ paddock rotations had increased dramatically and it was not uncommon for farmers within the region to have implemented cropping sequences that included five to 10 consecutive cereal grain crops.

Mr Moodie said that when the project started, intensive cereal cropping sequences in the LRZ were declining in productivity due to constraints such as grass weeds, declining soil nitrogen fertility and crop diseases.

The project involved the establishment of replicated trials in paddocks with a long history of intensive cereal cropping and a prevalence of agronomic constraints. Each trial consisted of up to 19 unique crop sequences which included both one and two-year break phases in 2011 and/or 2012, followed by wheat in 2013 and 2014.

Each trial also maintained a continuous wheat treatment for the four years of the project as a benchmark to assess the impact of the other crop sequences.

Mr Moodie said the inclusion of break phases was most profitable at the Mildura and Appila sites where more than half of the rotations with break phases were more profitable than continuous wheat.

At Mildura, the top five rotations increased gross margin by an average of $230/ha over the four years, while at Appila, the five most profitable sequences delivered an average of $370/ha additional profit over four years.

Mr Moodie said trials had demonstrated that the type of break phase appeared to have little effect on subsequent wheat production as long as the break phase successfully addressed the agronomic constraints present.

At Mildura, rotations that included break crops grown for grain such as field pea, canola and chickpea tended to be the most profitable, however, at Appila where frost was an issue, improved pasture and hay treatments were best. For example, medic-pasture-wheat-wheat, and a mix of oats, vetch and medic for two consecutive years, followed by two years of wheat, recorded gross margin advantages of more than $400/ha over the four years, compared with continuous wheat.

To address the perceived risk of growing broadleaf break crops in the LRZ, pulse crop comparison trials were implemented at the crop sequencing site near Mildura in 2013 and 2014, involving field pea, chickpea, lupins, faba bean and lentils.

In 2015, a new project funded by the SA Grain Industry Trust (SAGIT) was set up to compare broadleaf break crop performance across four soil types in the northern SA Mallee.

These two trials have highlighted the potential for grain legume crops to be productive and profitable in the northern Victorian and SA Mallee, according to Mr Moodie. “Field peas, chickpeas and lentils have produced acceptable yields and gross margins in this region over three consecutive seasons.”


Caption: MSF agronomist Michael Moodie, pictured in foreground, speaking at one of the break crop comparison trial sites at Karoonda in SA. Photo: MSF.
Caption: MSF agronomist Michael Moodie, pictured in foreground, speaking at one of the break crop comparison trial sites at Karoonda in SA. Photo: MSF.