The influence of transient salinity on sodic soils could be severely constraining some Western Australian grain crop yields in dry landscapes.
Sodic soils are often associated with yield limitation, due to the soil type’s increased susceptibility to waterlogging.
Recent research by the Department of Primary Industries and Regional Development and the CSIRO has found grain yields on sodic soils can be lowered by transient salinity in dry years.
Department principal research officer Ed Barrett-Lennard told the recent World Soil Day forum in Perth that growers may not be aware of the extent of the impact of transient salinity on crop yields.
“Clayey soils in semi-arid environments, like the eastern and northern Grainbelt, can become dispersive because of sodicity and alkalinity,” Dr Barrett-Lennard said.
“These soils subsequently lose their porosity and become dense, causing salt from the rain to accumulate over hundreds of years in the root zone.
“In dry years, the salt concentration in the soil solution becomes higher, as there is not as much water in the soil to dilute the salt, which restricts plant growth and crop performance.”
The department has reviewed nine years of the Grains Research and Development Corporation’s National Variety Trials for wheat, barley and field peas conducted across the southern States and found the interaction between salt and rainfall to be very strong.
Dr Barrett-Lennard said while the effect of transient salinity on sodic soils was consistent, its severity depended on the crop type.
“Cereals are more salt tolerant so the impact is not as great compared with field peas, which are more susceptible,” he said.
To counteract the risk of transient salinity in dry years the department has been exploring improved water harvesting techniques.
Dr Barrett Lennard said the department and the CSIRO have examined methods to encourage surface water movement via tailored mounds and furrows, such as plastic sheeting and polymer treatments.
“In a trial at Bonnie Rock with barley in 2017, we doubled crop yields on a sodic soil using plastic sheeting over the mounds to direct more rainfall into the furrow to the plant roots,” he said.
“Obviously, using plastic sheeting is not a practical field solution. Trials are now required to determine if what we achieved with the plastic can be replicated with spray-on polymers.”
For more information about the science and management of dispersive and sodic soils click here.
Jodie Thomson/Megan Broad, media liaison
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