Ground Cover Supplement : GC Supplement - Wheat pre-breeding
10 Issue 127 | March – April 2017 | GRDC GROUNDCOVERTM SUPPLEMENT: WHEAT PRE-BREEDING GROUNDCOVER SOIL SALINITY Paddock-ready traits for troublesome soils Various soil constraints limit the grain yield of wheat and barley, often without obvious crop symptoms. Improving the technical capacity to map plant responses to soil constraints is an integral part of developing paddock-ready salt-tolerance traits By Dr Stuart Roy, University of Adelaide n Saline soils affect crop growth in two ways: osmotic stress, which results in an immediate reduction in shoot growth; and ionic stress from the build- up of sodium and chloride ions, which interfere with metabolic processes. Cereal crop yields in Australia are significantly limited by a long list of soil constraints including salinity, sodicity, low or high boron concentrations, low concentrations of macronutrients (nitrogen, phosphorus and potassium) and micronutrients (zinc, copper, manganese, iron and molybdenum), acidity or alkalinity, and water availability. Crops are often affected by several of these constraints within a growing season. Of particular interest to our research groups at the University of Adelaide are soils affected by salinity and sodicity. Soils are considered saline if the electrical conductivity of the soil- FAST FACT n Salinity is a major abiotic stress, with 51 per cent of Western Australian farms now affected in some way by saline soils. saturated paste extract is greater than 4 deciSiemens per metre (dS/m). Soils are considered sodic if the exchangeable sodium percentage is greater than six per cent. The level to which plant growth and, ultimately, yield are affected by these two soil constraints depends on several factors including plant species and variety, plant age, soil type, soil water availability and weather. About 67 per cent of Australian agricultural areas are affected by so-called ‘transient’ salinity (including sodicity, alkalinity and toxicity due to high aluminum, boron, carbonate and bicarbonates). Seepage (or dryland) salinity affects 16 per cent of the agricultural area in Australia. Soil salinity reduces plant growth and high levels of sodium (Na+) and chloride (Cl-) in leaves increase premature leaf senescence (yellowing). Salt-stressed plants grow slower and die faster than non-salt-stressed plants. While certain growing regions show visible symptoms of saline-affected soils, such as areas of salt burn, salt crust and/ or crops with significant yellowing of leaves, there are also many paddocks with levels of salinity high enough to reduce growth and yield without displaying any of these telltale signs. Our research has focused on improving the salinity tolerance of bread wheat and barley. Both wheat and barley are grown in areas where salinity occurs and, because of its higher salinity tolerance, barley is often the crop of choice in paddocks with known salinity issues. However, the yields of both are significantly reduced by salinity. This is one of the reasons why average bread wheat yields in Australia are about two tonnes per hectare compared with countries with minimal soil constraints and ample water and nutrient supply, which can achieve 8 to 9t/ha. There have been many studies looking PHOTO: STUART ROY Field trial site for salt tolerance research at Whitwarta, South Australia.
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GC Supplement - Weeds