Ground Cover North : Ground Cover 051 August-September 2004 - North
Researchers Graeme Schwenke, Ian Daniells and Bill Manning from the NSW Department of Primary Industries in Tamworth, are also finding that subsoils are playing a far greater role in crop performance than previously considered. These 'subsoil constraints' can include salinity, sodicity, alkalinity, acidity, nutrient deficiency, nutrient toxicity or high physical strength. Dr Schwenke says the key to managing subsoil constraints lies in correctly identifying the particular problem and understanding how it is affecting the crop. This generally requires much deeper soil samples -- down to a depth of one to two metres -- and over several sites because most farmers usually only have a problem with a couple of paddocks. Dr Schwenke says options for managing subsoil constraints will vary depending on the problem. "The physical location of subsoil constraints makes them hard to access and therefore hard to fix. Lime (for acidity), gypsum (for sodicity) and fertiliser (for deficiencies or imbalances) are well-known additives for surface soil problems, but getting them to the subsoil can be difficult and may not be cost effective," he says. No one solution fits all and sometimes the problem cannot adequately be fixed, so it becomes a matter of deciding how best to manage the problem. "This involves choosing the correct crop species and varieties to better cope with soil conditions as well as revising management practices, such as matching fertiliser application to yield expectations," he says. Researchers are now investigating a range of strategies to deal with subsoil constraints. These include comparing different crop species and varieties for tolerance to various constraints, looking at the usefulness of deep-placed 'amendments', and increasing topsoil nutrition to give plants more vigour in dealing with nutrient imbalances. GRDC RESEARCH CODE Program 4 Sustainability Farming Systems (SIP08) DNR 00004 (Subsoil Constraints) DAQ 00050 (Eastern Farming Systems II) For more information: Dr Graeme Schwenke, NSW DPI, Tamworth, NSW, 02 6763 1100, email@example.com FEATURE / NEWS 29 AUGUST 2004 SUBSOIL RESEARCH By DAVID HORWOOD Most crops rely on the topsoil for water and nutrients. Until recently that's where research and farmer interest were focused -- the zone most easily influenced. Yet subsoil moisture reserves and nutrients are potentially valuable. For many cereal crops, the growing season can end swiftly as the topsoil dries out. The aim of subsoil modification is to make that zone more root-friendly, expanding the water and nutrient supply available. David Davenport, Land Management Consultant with Rural Solutions in Port Lincoln, and Mark Modra, who owns a property at Greenpatch on Eyre Peninsula, have reported increasing recognition that the subsoils of most agricultural land in South Australia have major impacts on plant growth and production. On Lower Eyre Peninsula, soils with significant subsoil constraints to production are mainly: n sand-over-clay soils -- these usually comprise a grey sand/loamy sand topsoil over a bleached sand layer sitting on an impervious, often sodic clay; n ironstone soils -- sandy loams over poorly structured clays with ironstone ('buckshot') gravels; and . n soils with shallow sodic layers -- these have hard, sodic barriers at various depths under sandy loam to clay loam surfaces. Yield responses to subsoil modification have been obtained on these soils, with responses ranging from 12 to 47 percent, depending on treatment and soil type. As one example, Davenport and Modra presented results from a barley trial of deep fertiliser placement (20 centmetres) on a sand- over-clay soil at Edillilie. They recorded a residual benefit in 2002, the season after the treatment in 2001. The authors say deep nutrition on these soils is worth considering, particularly where deep placement and sowing can be achieved in the one pass. At present this requires customisation of conventional sowing machinery. In a canola trial on Mark Modra's property, the authors used deep ripping (to 40cm at one metre spacing) and a range of fertiliser treatments. Increased crop height along the rip lines produced a distinctive 'wave' effect, but visual differences between treatments were hard to see. Yields told a different story -- humic acid dropped behind the tine during ripping boosted yields by 39 percent compared with no ripping. Are subsoil treatments economical? Answers to this complex question depend on soil issues and the treatment required, the cost of treatment, and the residual benefit. On all these points, Davenport and Modra say more research is required. So far, too little is understood about modification of the structural and nutritional status of subsoils, and the long-term crop responses. Although there appears to be considerable potential to increase yields, much of the work has not provided enough information to explain what is happening with nutrition and physical structure in the subsoils. This situation may change as more results come in. However, the complexity of the issues and the range of soil types involved may require more detailed research than is currently being considered. GRDC RESEARCH CODE UA 457, program 4 For more information: David Davenport, 08 8688 3404, firstname.lastname@example.org, Ann McNeill, 08 8303 7879, email@example.com SEEING THE BENEFITS Treatment (2001) Yield (t/ha) Yield benefit (t/ha) Treatment cost ($/ha)* Benefit ($/ha)** N, P normal sowing 1.518 0 0 0 N,P@20cm 1.96 + 0.442 0 110.94 N,P,Cu,Zn,Mn@20cm 2.24 + 0.722 35.52 181.22 Key is to identify the problem Attention to subsoil can yield positive results 'The physical location of subsoil constraints makes them hard to access and therefore hard to fix.' Western chickpeas feel the cold By BERNIE REPPEL Research that aims to explain disappointing chickpea yields in south-west Queensland and north-west New South Wales will focus on planting dates, row spacings, crop maturity and local temperature differences this winter season. Goondiwindi consultant Michael Castor and Associates and scientists from CSIRO/APSRU are collaborating on the GRDC-supported project 'refinement of best management practices for chickpea and mungbean in north-western farming systems'. Results of the three-year project -- one of the first in the northern grains region to be led by private sector consultants -- are to form the basis of revised advice on Best Management Practice, and accredited courses for agronomists, agribusiness and farmers. Project leader Paul Castor sums up the problem when he says chickpea growers in these western areas often struggle to convert impressive, bushy crops into grain in the bin. "Excessive early leaf growth appears to be leaving insufficient soil moisture reserves for grain filling," Mr Castor says. "Under moisture-stress late in the season, chickpea crops fail to fill their top pods and grain size is reduced in lower pods. Low soil-moisture levels at planting, poor in-crop rain and subsoil constraints can all have impacts on moisture supply to the crop. "We are keen to explore our ability to manage vegetative growth, to increase the supply of soil water for grain filling." Mr Castor says the project team believes the biggest factor involved is temperature, as warm conditions around planting time can promote vigorous early growth. Then later in the season, cold nights can cause pod and flower losses, further encouraging vegetative growth. "We are also interested in the interaction of planting date and row spacing with this temperature effect." Mr Castor says delaying planting until late May and early June is likely to better manage temperature effects on chickpea development. "Later planting than that, however, increases the risks of short plants, poor harvestability and yields reduced by rising spring temperatures. "Last season's trials indicated that as the team delayed planting, it needed to reduce row widths to 50 centimetres or less. We will repeat these trials this season." GRDC RESEARCH CODE MCP 00002, program 2 For more information: Paul Castor, 07 4671 2045 * Treatment costs include only the extra cost of additional fertiliser (trace elements). ** Based on a cash price for barley of $251.00/t.
Ground Cover 052 October-November 2004 - North
Ground Cover 050 June-July 2004 - North