Recently we went on a trip to the South East of South Australia, ending up in the Mt Gambier region in soil pits in pivots planted to carrots, rich volcanic soils over deep limestone and 80% organic matter wet peat soils. The diversity of soils and production is broad in the south east of SA, with viticulture, horticulture, broadacre cropping, livestock and dairy systems all intertwined well within a defined radius of each other.
The South East is a higher rainfall zone with rainfall around the 750mm plus. The soils also provide large volumes of underground water that is readily utilized across extensive irrigation regimes.
Potatoes, carrots, broccoli and other horticultural crops have high irrigation water usage and have capacity to gain high value returns in production over the summer months with water being readily available.
Dairy is another high water user in the area with pasture production being in high demand all year round. Management of pasture, especially for dairy systems, is closely monitored due to the direct impact pasture quality has on milk production every single day.
The irrigation water however is not with out its issues that do impose other constraints on the system. The underground water consists of high electrical conductivity (EC) which can, in turn, create water stresses on plant production especially when water is limiting in the soil before follow up irrigation cycles. The high EC is being constructed by the high levels of carbonate and bicarbonate in the water. This results in the pH of the water being high and the water is considered to be ‘hard’ water. This water, although having many positives for agricultural production, does also lead to soil issues that can result in poor nutrient use efficiency and poor soil structure.
Read the next article on carbonates and bicarbonates to learn more!