Ground Cover South : Ground Cover 057 August-September 2005 - South
Soils 13 AUGUST/SEPTEMBER 2005 GROUND COVER Beds raise new challenges Renick Peries, research scientist with the Department of Primary Industries in Victoria, reports on work that is tackling hostile subsoils in southern Australia the soil structure at depth under beds is improving, there sometimes appears to be a problem zone under the bed surface that occurs around the furrow depth. Initially, following the tillage undertaken when the beds were formed, aeration and conductivity increased at this depth. However, if water sits at this depth in the furrow for extended periods, some of the initial benefits appear to reverse. The saturation of this band of soil can lead to anaerobic conditions, which slow biological activity. The problem is further exacerbated in dispersive soils and it can lead to a decline in macro-porosity. It can also lead to fewer of the large pores that move water rapidly and provide oxygen for root respiration. In our current work, we are concentrating on achieving the connectivity between the topsoil and subsoil that is crucial to enhancing the soil structure. The incorporation of organic matter, or any other material that could improve and maintain the porosity at that depth, could contribute to this enhancement. In 2003, SFS conducted trials at Gnarwarre on slotting the soil with poultry manure and wool scour waste. The operation also makes it possible to use other ameliorants at depth, such as gypsum and straight fertiliser phosphorus, where sodicity or lack of root proliferation were issues. The results were encouraging, with most treatments giving better yields than the control. In 2004, we also followed a mechanical approach where we attempted to use a slurry of poultry manure in a slot that was created behind the tine of a deep ripper. These treatments clearly showed the qualitative differences brought about in the proliferation of roots and increased biological activity in the subsoil. As yet there have been no significant yield responses, and this is thought to be the result of sub-optimal rainfall conditions in the last three years. In 2005 we plan to use two soils to further test our hypothesis and also to test the modified deep ripper on two different subsoils. Both soils are marginally sodic at depth. However, the soils are different in the amount of clay in the profile. The heavy clay vertosol (Mt Pollock) is just coming out of a lucerne phase and its subsoil structure is very different to the 'Moorabool Viaduct' soil (Inverleigh), which is very low in clay in the top 50 centimetres. We are concentrating mainly on the connectivity between topsoil and the subsoil (10 to 30cm below the surface of beds) and believe that our approach will throw some light on soil specific management options for these problem subsoils. ∆GRDC Research Code SFS00007 For more information: Dr Renick Peries, 03 5226 4827, email@example.com Renick Peries: advancing the understanding of what happens to soil under raised beds. PHOTO: BRAD COLLIS n Work by Southern Farming Systems (SFS) in the past five years has advanced our understanding of what happens to soil under raised beds. Raised beds alleviate waterlogging and reduce compaction through controlled traffic. When crops or pastures are grown on beds, the soil in the beds is rapidly re-aerated after heavy rainfall events. These repeated events of wetting and drying, together with biological activity in the root zone, appear to help build aggregates in the soil resulting in reduced soil bulk density, improved porosity and consequently the storage of increased amounts of plant-available water (PAW). Our work on vertosols (cracking clay soils) has also shown that following the installation of raised beds, the porosity of the soil can improve even below the depth of the initial tillage. Consequently there appears to be an improvement in hydraulic (water) conductivity at depths that would favour movement and storage of PAW. However, we are yet to successfully address the issue of low harvest indices of crops, which is most likely a result of inadequate PAW during grain-fill to meet the higher demand of bigger crops produced on raised beds. It has also been observed that although MANY SNAILS HAVE SHELLS THAT ARE EQUAL IN SIZE TO GRAINS OF WHEAT OR BARLEY OR CANOLA AND THEY CAN BE DIFFICULT TO REMOVE. SNAILS: FARMERS AND SCIENTISTS JOIN FORCES n A comprehensive series of management guidelines for the control of snails has been developed through some innovative research and help from farmers. Scientist Megan Leyson, of the South Australian Research and Development Institute (SARDI), has focused on four snail species: common white snails, white Italian snails, conical snails and small conical snails. They are all exotic species from the Mediterranean region, most of them having been introduced to Australia in the 1920s on imported farm machinery. These hermaphroditic creatures can lay up to 400 eggs a year. While these snails can eat a good crop and ruin it, the main problem with them is contamination of harvested grain. The smaller snail species have shells that are equal in size to grains of wheat or barley or canola and they can be difficult to remove. Ms Leyson says the project began by contacting farmers across South Australia and testing in the laboratory and in trials their methods for managing snails. One of the farmer-driven solutions is particularly simple and effective: snails like stubble because it gives them something to climb to get away from the soil as it starts to heat up in the warmer months -- a 36°C day results in a 55°C ground temperature, which is enough to kill a snail. The answer is to knock them off the stubble onto the ground to literally stew in their own juices. Farmers in the upper south-east of SA came up with the idea of stringing a steel cable between two tractors and dragging it across a paddock. Two runs across the paddock in the morning and the afternoon is usually all that is needed. Other stubble management solutions for snails include slashing and using stone rollers to crush them. The project has also resulted in a shift in baiting strategy. Previously farmers in southern Australia put out bait in September. Ms Leyson says it is now recommended that baiting occur at the break of the season in autumn. When the rain comes, the snails mate. Baiting at the break hits them before the eggs are laid. On the Yorke Peninsula, biological control has been shown to be effective. Ms Leyson says an earlier project looked for a natural predator of snails in the Mediterranean area and found a parasitic fly (Sarcophoga penicillata) that targets the conical snail throughout its life cycle. It places a single larva in the snail shell, which feeds on the snail and kills it. It then pupates in the shell and emerges a couple of weeks later as an adult fly. These flies were first released in 2000 as part of the current project and are slowly establishing themselves on the peninsula. These and other management guidelines are outlined in a new 40-page booklet, Bash 'Em', Burn 'Em, Bait 'Em, available from Ground Cover Direct on freecall 1800 11 00 44, at $20 per copy plus postage and handling. ∆GRDC Research Code DAS300 For more information: Megan Leyson, 08 8303 9670 Left and bottom left: A slurry of poultry manure is slotted into the soil behind the tine of a deep ripper. Below: Improved root proliferation in the subsoil where poultry manure has been slotted.
Ground Cover 058 October-November 2005 - South
Ground Cover 056 June-July 2005 - South