Ground Cover Supplement : GC Supplement - Soil health
GROUND COVER HEALTHY SOILS 8 SOIL KNOWLEDGE Right rate and place for best results from lime The I'Ansons crop 1250 hectares in South Australia's mid-north. This productive country produces annual average wheat yields of four tonnes a hectare across the heavy red clay, shallow grey shale and deep black soils. Yet acidity and sodicity were found to limit productivity on a large proportion of the I'Anson's properties. However, soil type variation within paddocks meant that across the farm 90 per cent of land needed lime, but only 70 per cent required gypsum. In response to this finding, Kym and Katie I'Anson developed a simple but intensive program of mapping and soil testing to establish the appropriate rate of lime and/or gypsum. Since 2003, the I'Anson's have manually mapped the soil types in each paddock. By zoning soil types, a variable rate spreading program was developed saving $22/ha, compared to the use of a blanket application rate of lime and gypsum across the farm. A free nitrogen fix Peter O'Brien considered intensive cereal cropping as the way forward for sustainable farming. The fragile soils in the Mallee are highly vulnerable to wind erosion and the traditional systems of stubble burning, cultivation and fallow resulted in poor and unreliable returns. By incorporating stubble, reducing cultivation and not burning, Peter aimed to reduce the threat to soil erosion. As much of the soil's readily available nutrients are in the topsoil, reducing soil erosion was anticipated to have positive knock-on benefits for productivity. Peter has continuously cropped since 1998. He uses soil testing to assess fertiliser requirements at seeding and a single-pass no-till seeding system. At least one cultivation in summer, to a depth of between 5 and 10 centimetres, is conducted each year, which incorporates some stubble. These cultivations are carried out when the summer weeds are small and soil moisture is usually high. To date no in-crop urea has been needed to achieve targeted yields on the Mallee Monitor paddock. This is in line with local research, which has established that free-living, nitrogen-fixing bacteria can contribute up to 40 kilograms of nitrogen per hectare annually in intensive cereal rotations in the Victorian Mallee. Growing cover protects soil and saves water Peter Schramm and his family, who farm at North Star, New South Wales, changed to single skip-row sorghum (one metre) in 2001. This change made them concerned about soil erosion on their light soils on sloping ground. The simple solution was to replace the long fallow with a short-term cover crop. However, the purpose of the long fallow is to conserve soil moisture and provide a disease break against crown rot. So they needed a cover crop that did not use too much stored moisture or host crown rot. The Schramms have planted white French millet on their long fallow since 2004. They have found this establishes well in their light soil types and provides a good level of soil cover and consequently erosion protection. Comprehensive case studies Here are extracts from three of the farmer case studies that will be available on the Soil Health Knowledge Bank website (www.soilhealthknowledge.com.au), which will be live from 23 June 2009. Each case study is preceded by details of the farm's location, soil types, rainfall and production enterprises. At the end there is a resource section providing links and details of further information sources for each topic. In addition to the farm-based information, each case study presents the latest research on each issue and how these findings may be of relevance to farmers in different districts, regions or production sectors to provide a comprehensive information resource. Ryegrass, acidity and sodicity were the primary challenges for Kym and Katie I'Anson. Since creating detailed soil maps and strategic applications of gypsum and lime, the challenge of matching nutrition to crop need and available moisture is now their priority.
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