Long-hand lime comparisons
The calculations performed by the lime comparison calculator (Figure 2) can be calculated by hand. Here we use are using values for lime X from Figure 2:
1. Calculate the overall percent efficiency of the lime (EP)
Lime EP = Sum all individual particle size EP
EP for the particle size = % of lime × neutralising value (NV) × particle size discount factor
Lime EP for lime X = 86.9 (see Table 1)
| Paticle size (mm) | Particle size discount factor | % of lime | NV | % efficency (EP) |
|---|---|---|---|---|
| 0-0.125 | 1 | 5 | 90 | (5 ÷ 100) × 90.0 x 1 = 4.5 |
| 0.125-0.25 | 1 | 48 | 90.5 | (48 ÷ 100) × 90.5 × 1 = 43.4 |
| 0.25-0.5 | 1 | 38 | 94.8 | (38 ÷ 100) × 94.8 × 1 = 36.0 |
| 0.5-1 | 0.5 | 8 | 72.1 | (8 ÷ 100) × 72.1 × 0.5 = 2.9 |
| >1 | 0.2 | 1 | 62.5 | (1 ÷ 100) × 62.5 × 0.2 = 0.1 |
| - | - | - | - | Overall EP = sum of particle size EP = 86.9 |
2. Calculate the costs
In this example, the lime costs $10 per tonne (t) and needs to be transported 250km to the farm at a cost of 10 cents/km. It can be spread for $8/t.
Costs = lime cost + transport cost + spreading cost
Costs for lime X = $43/t (Table 2)
| Item | Cost/tonne ($) |
|---|---|
| Lime | 10 |
| Transport (at 10c/km/t for 250km) | 25 |
| Spreading | 8 |
| Sum of costs | 43 |
3. Calculate the effective cost of lime on paddock
Effective cost = (100 ÷ EP) × costs
Effective cost for lime X = (100 ÷ 86.9) × 43 = $49.48
For a lime with 100% efficiency, the effective cost would be the same as the actual cost. For a lime with an overall percentage efficiency of 50, the effective cost would be twice the actual cost.
Western Australian lime suppliers
The further lime needs to be transported, the more critical high neutralising value becomes.
Approximately 35 agricultural lime suppliers currently service the WA wheatbelt. A 2008 Department of Agriculture and Food, Western Australia survey found abundant high quality lime sources along the west coast between Perth and Geraldton. The number of sources diminishes moving south of Perth and east across the south coast to Esperance. Limited numbers of inland sources of varying quality are also available.
Many lime suppliers are members of the Lime WA Incorporated group of independent lime suppliers and operate under the association’s Agricultural Lime Industry Code of Practice. Members of Lime WA Inc provide standard product information sheets with detailed product information and independent lime quality test results (downloadable from Lime WA), which can be used with the lime comparison calculator, which is available online on the Soil Quality website.