THE yield benefits from surface applications of lime can be augmented by incorporating it into the soil using strategic deep tillage - particularly on compacted acidic soils.
That is one of the key findings from 35 years of research by the Department of Primary Industries and Regional Development (DPIRD) to be discussed at the Grains Research and Development Corporation's (GRDC) Grains Research Updates, in Perth, today and tomorrow.
Much of the research was undertaken with co-investment from the GRDC and the support of grower groups, like the Liebe Group, Merredin Farm Improvement Group and the Mingenew Irwin Group and growers, including the Nixon family at Kalannie.
DPIRD research scientist Gaus Azam said the department had amassed a vast amount of knowledge over more than a quarter of a century researching liming strategies to assist growers to overcome multiple soil constraints and optimise yields.
"Field, glasshouse and laboratory experiments across the grainbelt demonstrated that lime applications increased yields and net profitability, one to seven years after amelioration," Dr Azam said.
"In most trials, surface application of at least two tonnes per hectare of lime increased yields, however, applying more than that resulted in higher subsoil pH and lower extractable aluminium.
"The extra lime applied is not wasted, as it will continue to treat ongoing acidification and maintain crop yield potential."
Dr Azam said the trials also showed that incorporating lime using deep tillage practices to a depth of 25 to 45 centimetres achieved greater yields than tillage alone or surface applications of lime.
"However, lime incorporation using shallow tillage to a depth of less than 20cm did not improve crop yields compared to surface applications."
The research has also found a high correlation between soil pH and extractable aluminium, providing useful advice on measuring the risk of low pH and aluminium toxicity.
"Aluminium toxicity occurs in soils that contain aluminium and are strongly acidic," Dr Azam said.
"Aluminium levels are higher at lower soil pH and both soil parameters strongly affect plant root growth in acidic soil, suggesting the most readily available and cheapest test of either parameter can be used to diagnose subsoil acidity."
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