STUBBLE retention is a critical soil management tool for growers in the northern Wheatbelt to protect against erosion from wind events, with the practice also providing other benefits.
In May 2020, farmers east of Geraldton were hit with a super wind storm which lasted eight hours, consisted of average winds above 80 kilometres per hour and shifted countless tonnes of sandy soil.
In that event, any soil that was slightly bare and didn't have cover was moved - there were examples of the wind blowing so much sand that it buried fences and roadways.
Agrarian Management agronomist Craig Topham said in a severe event like that one, there was always a lot of learning.
"The main lesson from this was that stubble cover and standing stubble significantly reduced wind erosion," Mr Topham said.
"Simple things like the height of the stubble, the orientation of the working and the amount of disturbance the seeding machinery had caused all had significant effects on reducing the amount of soil that moved."
While last year's wind event was particularly nasty, growers in that northern sandplain part of the Wheatbelt are used to wind erosion and have found ways to reduce erosion and soil moisture loss.
Soil amelioration is always risky and even more so on lighter sandplain soil types, but it's a risk growers in the northern area have to take as the yield increases are significant.
How the soil is left after the amelioration process and how much stubble was there beforehand both have an impact on the amount of damage that is caused by severe wind events.
Mr Topham said the timing of amelioration processes and where they were implemented in the rotation were both critical.
"The more stubble and the taller it is above the ground before amelioration techniques - such as deep ripping, spading or mouldboard ploughing - are implemented, the less erosion that will likely be caused," he said.
"In May 2020, we were coming off the back of severe drought affected season, there was very light stubble cover because of the decile one rainfall the year before, so we were already going into with poor soil cover before amelioration processes were implemented.
"If the soil is very bare, it's more risky, but the responses to deep ripping are significant on our sand plain soils - we have to have that ripping in the rotation somewhere but we have to be slightly flexible to avoid ripping paddocks that have very poor stubble cover."
While getting as much stubble cover as possible sounds simple, there are seasons such as 2019 with very poor winter rainfall results in poor stubble cover.
The traditional practice used to be harvesting at beer can-height, but now growers are increasing the amount of soil amelioration and trying to cut the stubble as tall as possible at harvest.
"It all comes back to keeping as much cover on the soil for as long as possible in all stages of the rotation, but in doing that, we need to change the way we look at herbicides, tillage and machinery practices," Mr Topham said.
"We're starting to look at how we adjust our machines to handle a greater amount of stubble, or trash on the soil surface, at seeding time.
"We also have to look closely at the herbicide techniques that we implement - more stubble cover means less pre-emergent herbicide hits the ground, so there are other implications we need to consider."
While retaining stubble does require a change to many traditional farming practices, it does also have other benefits, apart from just protecting from wind erosion.
If all of the stubble is standing above the soil, there is less wind and sunlight hitting the soil surface which reduces evaporation, which means more moisture can be retained closer to the surface of the soil.
"In the northern region of WA, rainfall patterns are changing so we are getting less rainfall in May and June, more summer rain and less heavy rainfall events," Mr Topham said.
"With that in mind, anything we can do to retain more moisture close to the surface can help with establishing crops on less rainfall events.
"If we can get a crop out of the ground two or three weeks earlier on a small rainfall event because of the way we've managed our soil, that could be a substantial yield increase."
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