Acidity

Complete

Andrew Harding and Brian Hughes

Australian Government’s National Landcare Program – Smart Farms Small Grants

PIRSA

The Coorong and Tatiara District Council’s covers a combined area of 1.54 million hectares. This is a productive agricultural area with a total value of agricultural production of $490 million annually. Due to more productive and intensive farming practices, soil acidity is becoming an emerging and significant problem throughout the area, particularly on the sandy and sandy loam soils. The area currently acidic or likely to become acidic in the next 5 – 10 years is approximately 334,515 hectares or 35.9% of the agricultural area, with an estimated annual production loss of $5.8 million.

It is estimated that a further 375,114 hectares of agricultural land has the potential to become acidic in the next few decades assuming that that current farming practices continue, and that soils are not adequately treated by liming or other soil modifications; a further annual production loss of $6.1 million is
anticipated.

When the soil pH falls below pH 5.5 (CaCl2) productivity of crops and pastures starts to fall; nutrients such as phosphorus, magnesium, calcium and molybdenum become less available to the plants; microbial activity begins to decline (including Rhizobia); and toxic levels of aluminium can impair root and plant growth. Lime and / or soil modification techniques such a ripping, spading, delving or clay spreading are options for the treatment of acid soils provided that the underlying clay is neutral to alkaline.