Leaving paddocks fallow is a crucial moisture management tool for low-rainfall growers Mark and John Flannagan. The Flannagans farm at Mullewa, in the northern WA wheatbelt, where the average annual rainfall is 250 to 300 millimetres a year. But there are years when it is significantly less. Opting to fallow as part of wheat-dominant rotations helps build the soil’s capacity to retain moisture while also keeping on top of weeds. However, if rainfall is favourable, canola or lupins may be considered or wheat-on-wheat planted.
John says in every decade there will be four years when there is not sufficient rainfall for a viable crop. But if paddocks are left to fallow, a profitable wheat crop can be grown the following year.
However, last year (2024), they received all their annual rainfall in an unusually short period: “We had rain from the first week of June through to mid-August and then it stopped. We received 350mm in two months.”
John says they ended up with a decent, although still disappointing, yield. “Germination was pretty poor. We were disappointed with the way it came up.” Some areas yielded less than two tonnes per hectare. John says waterlogging also led to burst seed. “Usually we don't have enough rain, but too much rain also brings its own problems.”
He says that in years with less than 200mm, it would only take an extra 40 to 50mm to make a difference, so retaining soil moisture is important. “Fallow can lift a couple of those poorer seasons into a good season the next year and keep you going forward.”
Record yields
The third-generation growers operate a 22,000ha family farm, with up to another 22,000ha on lease. Depending on the season, they are continually looking for ways to improve yield and make the most of the drier years. Their decision to use fallow is one that many growers in the low-rainfall areas across the state opt for.
Research agronomist Michael Lamond from SLR says that in most years about 300,000ha is fallowed. In 2023, however, there was more fallow than normal – closer to one million hectares. His 2024 Crop Report, published by the Grains Industry Association of WA, says this factor certainly influenced grain production. “2024 was a defining moment for grain production in WA. The amount of grain produced from the rain that did fall could be the third-largest harvest on record.”
While there was “no single factor influencing the incredible quantity of grain harvested on very little rainfall”, less-stressed crops played a part and “the large area of crop in the low-rainfall regions on fallow” in 2023 helped this.
Weed break
Fallow years also lend themselves to cleaning the paddocks of weeds. Fallow spraying usually starts in August through to September for the cooler climate weeds, then again in November to December for the summer weeds. Clean-up weed spraying will continue as needed through this period. Typical weeds include roly-poly tumbleweeds, tar vine, button grass and melons. The fallow also allows chemical rotation to minimise the risk of herbicide resistance or crop damage.
As variable-rate technology pioneers, the Flannagans have accumulated much data on their enterprise. However, John says one of the biggest impacts on the farm in the past 20 years has been the introduction of robotics. Using WEED-IT optical spot sprayers for weed control on fallow ground has been quite effective, but the recent introduction of SwarmBots has taken it to new levels.
