Completion Date: June 2016
- Investigating Different Approaches to Manage Soil Acidification in the WA Wheatbelt
- Mouldboard Plough on Wodjil Soil Demonstration
- Evaluation of Spading with Lime Incorporation in Low pH, Non-Wetting Sand
The short term effects of different cultivation methods are well understood however, little is known about the mid-long term. The practice is relatively new for the Liebe Group region, with these demonstrations being one of the first implemented in the area. This project aims to show the mid-long term effects of deep cultivation for management of water repellence and subsoil acidity. By utilising demonstrations previously established, it is possible to see the mid-long term impact of such a major soil renovation event. The project also aims to educate farmers on the mid-long term effects of amelioration techniques to incorporate liming products in order to reduce acidity caused by unused nitrogen in the system and highlight what the different techniques used in the area have on crop productivity. Over time growers have experienced decreasing margins and increased risk which makes it imperative that they can apply knowledge from this type of research. Specifically, spading and mouldboarding to incorporate lime and the affect this has on soil acidity and gross margins.
Liebe Group members have shown a continuing interest and investment in soil health, particularly soil acidity. Adoption of liming in the Liebe Group area is 100% (Liebe Group Technical Audit, 2012) however, soil acidity remains an ongoing problem. Growers want to determine how to gain the most economical and effective response to manage subsoil acidity. Understanding of the long term effect of liming is essential to show farmers that whilst lime does not always give an immediate return there are long term benefits to the gross margins.
This innovation was originally chosen because the host farmers were facing two issues; non-wetting soils and acidity. We wish to revisit these sites as this early adoption now provides insight into the mid-long term effects on soil sustainability. Research to date has also shown us that the quickest response to liming comes from incorporation throughout the profile.
The outcome of the demonstrations will be an improved understanding of the mid-long term impacts that different amelioration techniques have on soil health. The demonstrations will be monitored, analysed and reported on at the end of the season. It is expected to highlight the importance of balancing lime costs in the budget even in poor seasons and that an improved liming approach is possible through better understanding innovative management decisions in the Wheatbelt.
Demonstration 1 is located on the Hunt Partners Farm in Marchagee, a non-wetting deep yellow sand. The site was established in 2010 to assess the impact of a one-off deep soil cultivation using a rotary spader to dilute water repellent soils and ameliorate subsurface acidity through the incorporation of lime. The applications, rates and amelioration techniques were chosen so that growers could see the differences between current practice in the area and what innovations could be utilised on their farms to improve this practice and ensure that they are farming sustainably and maintaining their soil health. It was implemented using farmer machinery with plots sizes being 22.5m x 2000m (Figure 1). Having the demonstration on such a large scale is a great advantage as it shows the effect over a large area, taking into consideration paddock variation.
The site was spaded in May 2010 to a depth of 30cm. It is estimated that the rotary spader buries at least two-thirds of the nutrient rich but non-wetting topsoil, leaving one-third on the surface. In 2011 the rest of the paddock was spaded to a depth of 34cm and lime and dolomite was incorporated giving us a side by side comparison of incorporation to depth. The site yield results of the spading only plot have reverted back to control levels while the spading + liming treatment continues to outperform.
Demonstration 2 was established in 2012 to try and overcome the wodjil soils in the area. The trial is located on Colin Cail’s farm east of Wubin. It was implemented using farmer machinery with plot sizes being 17m by 318m (Figure 2).The host farmer, along with many growers in the area, has a problem with wodjil soils. Wodjil soils are typically yellow deep sands which are inherently strongly acidic, particularly in the subsoil. The low subsoil pH results in high aluminium concentrations that create a hostile environment for root growth and therefore reduces yields.
The site received 1.5 t/ha of lime in 2006 in an effort to increase pH. However, research has shown that surface applied lime usually takes four to seven years to treat subsurface acidity. Mechanical incorporation is one of the methods being used to speed up the process. To gain weed control and lime incorporation in one pass the farmer wanted to determine the effect of mouldboard ploughing. The mouldboard ploughing does a great job at getting lime to depth however; the spreading of lime on the topsoil does not ameliorate to depth. Therefore the host farmer wanted to determine which is more effective; offset discs repairing just the top 10cm or offsets following mouldboard ploughing to create a better soil profile to depth.
The trial was mouldboard ploughed on the 12th June 2012 using a 3 board Kvernerland plough which was 1m wide. The site received 63mm of rain in the previous 7 days, allowing the soil profile to wet down to at least 30cm the required depth for an effective inversion.
Mouldboard ploughing inverts the soil by burying the topsoil and brings the subsoil to the surface. On soils with acidity at depth this creates an acidic topsoil. In an effort to overcome this, the grower added another 1.5 t/ha of lime and 0.5 t/ha of dolomite which was then incorporated with offset discs in 2015. The offset discs ensured the lime was incorporated through the top soil.
Figure 3: Implementing demonstration 1 at the Hunt property 2010.
Figure 4: Demonstration site 2 on the Hunt property November 2014 (spaded plot).
Figure 5: Implementing demonstration 2 on the Cail property 2012.
Figure 6: Demonstration site 2 on the Cail property in 2015 (ouldboard plots are not germinated).
This project is supported by the Liebe Group and the Northern Agricultural Catchments Council, through funding from the Australian Government’s National Landcare Programme.