Low pH soils are ripe for more research

29 Mar, 2018 04:00 AM
Evergreen Farming representative Phil Barrett-Lennard talking about the positives of perennials in acidic soils.
Evergreen Farming representative Phil Barrett-Lennard talking about the positives of perennials in acidic soils.

EXTENSIVE soil sampling and trials over the past decade have shown low phosphorus (pH) levels are a major issue in WA agriculture.

And Evergreen Farming representative Phil Barrett-Lennard is calling for more research into the tolerance of perennial pastures with low pH levels.

Mr Barrett-Lennard said the amount of C4 grasses being grown in sandy soils in the western part of the northern agricultural region is increasing every year.

“The grasses are very good for stopping erosion and for livestock production and there has been a lot of soil testing done on cropping soils but not so much done on pasture land,” he said.

The Department of Primary Industries and Regional Development (DPIRD) report found 70 per cent of the State’s top soils, up to 10 centimetres deep, were on average below 5.5pH and 50pc of the subsurface pH was below 4.8.

Mr Barrett-Lennard said an Evergreen Farming trial on 20 farms between Gingin and Geraldton found similar pH levels on perennial farms.

“There are lots of types of subsoil acidity happening on that perennial pastoral country in the west of the Dalwallinu region,” he said.

After looking extensively into the data of plants sensitivity to acidity, Mr Barrett-Lennard said plants such as pulses and lucerne had a low tolerance of acidity so they need higher pH soils to reach their potential.

He said barley was more sensitive to acidity than wheat and canola is similar to wheat with a moderate sensitivity.

“We know that some crops are quite tolerant, such as triticale, cereal rye and lupins, and also some pasture species, such as yellow serradella, rye-grass, couch and kikuyu,” he said.

Perennials being grown include panic and Rhodes grass which are similar to couch and kikuyu, giving Mr Barrett-Lennard the assumption that they too are relatively tolerant to acidity.

Mr Barrett-Lennard said there were many questions to be asked when they could get substantial data on acidity, pH and the connection to perennial pastures.

“Can the perennial pastures tolerate the acid soils?

Is the acid soil holding them back?

Are there other limitations to soils that we might need to address?” he said.

Mr Barrett-Lennard has also seen a decrease in subclover due to pH levels decreasing, although he said there isn’t enough trial data on the issue.

He said perennials had deep roots that could go down to about three metres, so they needed to get more trial data on the pH levels below the 50cm mark and how they can incorporate pH that deep.

More trials and monitoring will need to take place to give him all the answers, but Mr Barrett-Lennard will continue to ask the questions on the impact of soil acidity on different pasture species.



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