Soil Management for Australian Irrigated Agriculture
Australian soil structure deteriorates rapidly under irrigation with current management practices, resulting in inefficient water use and low yields. These soils lack the mineral montmorillonite present in those overseas soils which maintain porosity and stability under irrigation. This project aims to overcome this deficiency, developing new preparation and management practices enabling large inputs of stable soil organic matter.
Preliminary trials indicate this is feasible through incorporation of stable soil sheaths (rhizosheaths) formed on ryegrass roots. Physical, chemical and biological factors enhancing rhizosheath formation will be investigated to best harness rhizosheath development to improve water use efficiency and irrigated crop yields.
To develop a new system of soil management for irrigated orchards, row crops and pastures that increases yields two to three times current (Table 2. System 5) and at the same time improves the soil resource. Is cheap and simple to set up and manage. Is applicable to all Australian irrigation including row crops and the dairying industry. Is equal in productivity to the very best of the best soils overseas e.g. In California and Yangtze delta, that we call ”super soils”.
The benefits of the project will be increased yields, cheaper and simpler orchard and row crop soil management. Reduced water use per tonne of plant product. Improved soil. High carbon sequestration – soil organic carbon increase from 1% to 4%. Improved knowledge on soil management.
Irrigated agriculture in Australia performs poorly in the dollars it generates. This is because the yields of nearly all crops and fodder are low compared with potential; but also because of low cost, low return (per ha and per Ml) grazing industries. Examples of Australian average and best overseas yields include maize 10t/ha v 40 (dry wt.), Tomatoes 45t/ha v 160 and pears 35 v 180. To consider potential productivity we should not only compare our results with what others can achieve; the ultimate limitation to plant productivity is the available solar radiation.
This is expressed as the conversion of incoming energy to plant dry matter: 6% conversion is possible on farm, 12% has been achieved. A 4% conversion in southern Australian irrigation areas to plant dry matter would give 64t/ha which is 5 times the current yield of, for example, perennial pasture. Cockroft and Mason (1987) discuss this and give examples of a range of crops.
ProgramNational Program for Sustainable Irrigation
- Irrigation (442)