Site-specific doses best use of lime and money
GroundCover™ Issue: 104 | Author: Catherine Norwood
An extensive liming program has helped Rex Glass and his son Corey rescue the productivity of the soils on their Wongan Hills property, providing a return on investment within three years.
The Glass family added the Wongan Hills property to their holdings in 2004, only to discover that in some areas the soils were so acidic they were toxic. Taking soil samples from 0 to 100 millimetres, 100 to 200mm and 200 to 300mm, Rex found the subsoil pHCaCl was as low as 3.7 at some sites; 4.5 is the point at which soils become toxic to most crops.
It has taken an extensive liming program over eight years to restore the balance and productivity of these soils, applying as much as six tonnes per hectare on the worst-affected areas. At least 2t/ha of this was incorporated at depth by deep ripping to distribute the lime as quickly as possible. The pH of the treated soils is now holding steady at about 5.7 or better, and yields from the most acidic area have increased by about 40 per cent.
Soil samples have been collected annually by Precision SoilTech and analysed for both pH and nutrients. The consultancy’s research officer Joel Andrew says the strategies Rex and Corey have been using are now recognised as best practice – soil testing to a depth of 300mm, site-specific liming applications taking account of subsoil requirements and a long-term approach.
A three-year research project, funded through the Australian Government’s Caring for Our Country Program, has been encouraging more growers to take a deeper look at their soils. Precision SoilTech has been involved in this project, along with the Department of Agriculture and Food, Western Australia (DAFWA), collecting and assessing samples for more than 350 growers.
Joel says 150 growers participated in 2012, the first year of sampling, with an additional 200 taking part in 2013. Growers fund the testing and analysis for the first 0 to 100mm soil sample and the project funds two deeper samples. Participating growers are provided with a suggested 10-year liming program to address any soil acidity issues identified. Lead DAFWA researcher Chris Gazey says the program has highlighted the importance of addressing acidity in the subsoil as well as the topsoil. It has also highlighted the value of site-specific application rates, to make the best use of lime and money.
Analysis has provided a clearer picture of the pH status of different soil types across the wheatbelt regions, which will be incorporated into new soil maps for the state, and has identified the extent of both surface and subsurface acidity.