Lifting fertility in saline soils

Treating yield limiting factors in agricultural crops is no different.

Researchers at the University of Queensland (UQ) and Western Sydney University have taken this philosophy to the next level in a discovery that could change the way Australian farmers deal with growing crops in salty soils.

Their research has identified a hormone produced by stressed plants which could combat damage caused by salty soils and considerably increase plant growth.

This naturally-occurring chemical in plants - known as 1-aminocyclopropane-1-carboxylate, or ACC - has been found to reduce the symptoms of salt stress when applied to soil.

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Dr Hongwei Liu, who conducted the research during his Doctor of Philosophy work at UQ, said he was excited to strike a blow against salinity, which affected more than 220 million hectares of irrigated farming and food-production land worldwide.

"Scientists have long tried to find ways to breed salt-tolerance or remove salt and this new research is promising," he said.

Professor Peer Schenk from the School of Agriculture and Food Sciences at UQ said traditionally, salinity has been treated using a range of long-term and slow-acting materials such as gypsum, manures, tillage and other methods to reduce the exposure of plants to the salts in soils.

"But these are costly, frequently ineffective and work to limited benefit over years or decades," he said.

ACC in essence is an -amino acid and is a precursor for the plant hormone ethylene.

Dr Liu said applying ACC to crops planted in salty soils prevented the formation of compounds causing plant damage under salty conditions, increasing beneficial soil enzyme and microbial activity.

This enabled the plants to cope with the salt.

The research looked at lettuce under growing conditions in the lab and growth chamber. The soils used for the research were silty clay loam.

The team also used plant modeling with Arabidopsis thaliana to test the effects of ACC. Arabidopsis thaliana is a small flowering plant that is widely used as a model organism in plant biology

"In this study, we increased the salinity to a level (8 dS m1) that can lead to more than 50 per cent yield loss for most crops worldwide," explained Professor Brajesh Singh of Western Sydney University.

The experiments indicated an increasing growth in lettuces by nearly five-times and in plant models by more than 30 times, growing in extremely salty soil under lab conditions.

THE future is bright for a naturally-occurring chemical in plants - 1-aminocyclopropane-1-carboxylate, or ACC - to reduce the symptoms of salt stress, but there's still more research to be done.

Dr Hongwei Liu, a postdoctoral fellow in Soil Biology and Genomics at the Hawkesbury Institute for the Environment at Western Sydney University said researchers still need to see if the method works for different soil types and crops under different climatic conditions, as well as testing any potential environmental impact.

"Our study contributes to a better understanding of plant-microbe interactions, opening the door to commercial use of ACC in agriculture, improving fertility of salty soils," Dr Liu sai d.

He said ACC treatments could be much more cost-effective as it was naturally produced by plant roots, and contributed to long-term soil health, plant-microbe relationships and carbon storage.

"ACC treatments won't be able to remove salt from soil, but it can improve the soil microbial properties of the saline soils," he said.

"The soil microbial communities drive the carbon turnover in soils and facilitate plant in stress defence.

"Any improvement in soil microbial diversity and activity can improve plant growth in soils. ACC does the job in this way, for a short term fix."

Dr Lui said the next research step was to study the mechanisms underlying the beneficial effects of ACC.

"I've run out of funding, but would like further funding and collaborations to continue this research" he said.