Shallow storage irrigation for sorghum production in north-west Queensland

Abstract

The Mitchell grass plains of North West Queensland are used almost exclusively for extensive grazing by sheep and cattle. However, the nutritive value of pastures is frequently poor and thus strategic use of grain and forage supplements to boost wool and beef production has been considered by many graziers in the region. Therefore, opportunities for crop production in this tropical, semi-arid area need to be evaluated.
The gently undulating topography and fertile, cracking clay soils of the Mitchell grass plains are well suited to agriculture but rainfall, which is highly variable and strongly seasonal (summer dominant), is only sufficient for dry and forage cropping in about twenty percent of years. The region's mean annual rainfall is 400 mm. The land system is also well suited to storage of ephemeral run-off in shallow but expansive farm dams, and use of such dams for irrigation of crops is termed 'shallow storage Irrigation'. Distinctive features of shallow storage irrigation are: rapid use of water for irrigation before evaporation losses become too great, and agricultural use of the bed of the dam. This latter feature is termed 'ponded-area' cropping and is practised by planting successive strips of crop around the edges of the dam as irrigation and evaporation cause the dam's water line to recede.
This study evaluates the biophysical and economic potential of irrigated grain sorghum and ponded-area forage sorghum production from shallow storage irrigation systems on the Mitchell grass plains of north west Queensland.