Root zone salinity, a silent time bomb for permanent horticulture in the Riverland and Sunraysia areas, is being tackled in a new tri-state salinity project, funded by Land and Water Australia.

"Despite the use of improved irrigation practices over the years, there is a risk emerging of a salinity build-up in the root zone, threatening the sustainability of this region," says NSW DPI’s Graeme Sanderson, a member of the project team.

Irrigated horticulture in the region contributed a farm gate value of about $2.5 billion a year to the national economy.

Salinity in irrigation water from the River Murray introduces salt into the root zone of irrigated crops.

"A preliminary field survey at 23 sites, carried out by the tri-state research team, show that the upper range of average soil salinity in both Sunraysia and the Riverland are well above the threshold for salinity damage to vines and citrus,” said Mr Sanderson, based at Dareton.

“We need to understand why the extra water beyond what the crops normally need to remove this salt is not decreasing salinity in the root zone."

"If we have to put on more water than we thought to do the leaching, then this will limit how efficient our irrigation can be in applying what the crop needs."

The project is testing the hypothesis that a depressed leaching efficiency has been raising the root zone salinity and that any improved water use efficiency may have an upper limit determined by a paddock's leaching efficiency.

This story appears in Agriculture Today.