Clayton Butterly1, Peter Sale1 and Caixian Tang1.
1Department of Animal, Plant & Soil Sciences, La Trobe University, Melbourne, 3086, C.Butterly@latrobe.edu.au
The incorporation of crop residues into acidic subsoils via deep ripping could be an effective approach to ameliorate the effects of acidity of crop growth. The utilisation of on-farm residues is thought to be more cost effective than other materials, such as litters and manures, which are expensive and difficult to transport. Brown manuring could providing a source of residue while also facilitating the control of herbicide-resistant weeds. Crop residues generate alkalinity during decomposition. In addition, using NO3– as the form of N can facilitate alkalinisation of the rhizosphere due to the excess uptake of anions over cations by plant roots. A pot experiment was conducted in a glasshouse to evaluate the effectiveness of 4 commonly used brown manures, field pea, oats, vetch and wheat in combination with two Ca(NO3)2 levels (64 and 191 mg N/kg) in improving wheat growth in two contrasting acid soils. Residues were added at 16 g/kg soil to a Sodosol (pH 3.9) with an extractable Al of 9 mg/kg soil and low pH buffer capacity (pHBC) of 23 mmolc/kg soil/pH. An experimental soil (pH 3.9) consisting of a 60/40 mix of Ferrosol/Dermosol with high extractable Al (38 mg/kg) and pHBC (86 mmolc/kg soil/pH). All treatments increased plant growth and soil pH, and decreased Al concentration, with legume residues (field pea and vetch) being more effective than cereal residues (oat and wheat). Higher rates of Ca(NO3)2 further increased pH except when combined with legume residues in the Sodosol. Improvements in ES8 wheat biomass were not always associated with greater reductions in Al in the Sodosol, since most treatments had reduced Al concentrations to below toxic levels.