Clay-renovated soils arrest productivity decline

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A man standing beside farm equipment

John Wallace, grain grower north-east of Esperance, with his clay delver.

PHOTO: Evan Collis

When John and Stewart Wallace could clearly see their crops and pastures were failing to reach their yield potential, the brothers decided to take action to change the soil structure that was holding back production on their Neridup property north-east of Esperance.

Seventy per cent of their 4000-hectare farm comprises, to varying degrees, non-wetting sands. In an average year, John says this can mean non-wetting parts of the paddock yield just one tonne per hectare of wheat, while the rest of the paddock might yield 3t/ha.

Another frustrating aspect of the problem, John says, is that non-wetting soil makes weed management doubly hard. Some weeds will germinate early in the season, while other weeds germinate later.

Two chaff carts were bought 15 years ago and are never taken off the harvesters in a bid to capture any weeds that escape in-season sprays, but the most painstaking effort has been an earthworks program.

Eight years ago, the brothers started clay spreading – aiming to ameliorate 100ha per year – to increase the water-holding capacity of their duplex sands.

Although initially a contractor was hired, John and Stewart eventually bought their own clay scraper and a clay-delving machine to reduce costs.

John says they were motivated to fix their soils after seeing positive results from Department of Agriculture and Food, Western Australia, trials on neighbouring properties.

“We looked at what they had done and could see it was having a positive impact,” he says. “Hopefully by the time we’ve finished our farm, we will also better understand the pitfalls.”

Recently, John and Stewart removed a tagasaste plantation where crops would not grow, and are looking at renovating the soil with clay before planting the area to lucerne or serradella for five years.

After building up the soil with clay and organic matter, they hope to crop the area as much as every second year, or more, depending on the first year’s results.

John says he is pleased with how well lucerne responds to added clay. Previously, their lucerne would only survive for up to three years on unclayed soils, but after claying, the lucerne has remained productive for up to seven years.

The brothers like to incorporate pastures within their crop rotation and have found that canola planted onto paddocks previously sown to lucerne yields as much as 1t/ha better than after barley or wheat.

With input costs increasing daily, John says having productive serradella or lucerne pastures in the rotation for grazing makes financial sense.


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