Developing a lime program
One of the best ways to manage soil acidity is through application of lime. Carbonate ions from lime neutralise excess hydrogen ions in the acid soil to generate carbon dioxide and water released into the soil air and soil water.
The liming materials most commonly used are lime sand or lime stone (calcium carbonate) and dolomite (calcium/magnesium oxide). Burnt lime or quick lime (calcium oxide) is not recommended for use as an agricultural lime as storage and handling of these products is difficult.
To develop a lime program, we need to know what our soils are, what sort of lime we can manage to use and to get down lime in the right place. “Three Checks” should be taken into account to do this right.
Check 1: Soil test
Checking soil regularly will help detecting any changes in soil pH and allow liming rates to be adjusted accordingly. This way the lime will be applied where it is needed most.
Check 2: Lime quality and total cost
Before purchasing lime, check on the quality of lime that’s available and the costs associated with transport and spreading. The key indicators of agricultural lime quality are neutralising value and particle size, regardless of the source.
Neutralising value (NV): The carbonate content of lime sand, lime stone and dolomitic lime determines the capacity of the lime to neutralise acidity. Neutralising value (NV) indicates the capacity of lime to neutralise soil acidity relative to pure calcium carbonate (100%).
Particle size: The size of the lime particle determines how quickly the lime can neutralise acid. The finer the particle of lime the faster they react with soil.
Total cost to be considered should include the purchase cost at pit, transport cost to paddock and spreading cost. As lime quality varies from pit to pit, it can actually be more cost-effective to transport a higher quality product further.
A useful tool for calculating and comparing the cost effectiveness of agricultural lime, Lime comparison calculator is available at the Soil Quality Website.
Check 3: Latest product information
Once you decide which lime to apply, it is recommended that you read your supplier’s latest product information sheet. You can find out the laboratory results which include information on neutralising value and particle size. As lime is a natural product there will be variability within each pit. It is important to check the pit range which shows how consistent the product is. Lime WA suppliers present the latest information with a range based on the approved laboratory test.
Sourcing lime on the South Coast
The best lime is the one which can be sourced and spread for the cheapest price when quality has been taken into account (Gazey et al., 2014).
There are numerous considerations in sourcing lime on the South Coast. Because of its geological history, the South Coast Region has much fewer and lesser quality lime supplies, than the west coast. Nevertheless the economics of applying more South Coast lime versus transporting lime from the west coast has to be carefully considered.
SCNRM is currently working on economic review of lime crushing on the south coast versus transporting lime from the west coast.
On-farm lime extraction
An option for industry and growers on the South Coast is if lime can be found on private land where extraction is acceptable based on environmental and amenity values and competitive in an economic sense to sourcing lime off-farm. On-Farm Extraction is considered in the following sections. It is strongly recommended that all on-farm lime extraction projects begin with identifying what you want to achieve during the life of the pit and the results you seek when the pit is expired. Considerations include successful approvals, extraction, sound financial management, sound natural resource management and successful site rehabilitation, restoration and also social consideration.