Soil Quality
Lime Benefit Calculator
How to use this calculator
Some base assumptions have been set up on the calculator. These are for guidance only and should be adapted for your own situation.
- Enter your base yield. A good starting point is your long term average for the area in question. This calculator is base on cereals, so using wheat yield is suggested.
- Enter a grain price – Use the long term net on farm values, say a five year average. Do not use current prices as these are likely to be misleading.
- Enter a cost of sowing the crop. This should include all costs you include in your gross margin calculations (i.e. all direct costs)
- This will leave you with a gross margin for the crop in question.
- Enter the cost of lime landed on your farm and the rate at which you intend to apply the lime.
- Enter your cost of funds. (if you are borrowing money then this should be at the cost of your overdraft. If you have credit funds in the bank this should be at the rate of interest you are being paid, or the rate of return you will get from investing the funds elsewhere)
- Enter the expected change in yields from liming and the timing at which they are likely to occur. This is very subjective and will depend on the condition of the soil prior and the rate of lime applied.
- The model also allows for break crop/pasture/fallow where little or no income is received from the area. Enter a “p” into the no profit column.
The outcome is in 2 forms, an internal rate of return which reflects the effective annual rate of interest you will receive on the funds invested in the liming process. The second measure is the Net present value (in today’s $) of the income stream to you after considering the initial cost.
Background
This calculator, like all on the Soil Quality website has been simplified to provide guidance to the relative benefit of liming. Please note this calculator will only be as good as you assumptions – You will make better assumptions by soil testing through the profile.
Please also remember that the management of acidity and the responses expected are the result of many interacting components including, soil type and starting soil pH profile, expected potential crop/variety yields, seasonal rainfall distribution and many others. This calculator relies on you being able to make reasonably accurate judgements on the impact of these for your property and your liming program.
For a more detailed assessment models such as “Optlime” are available.
In many soil profiles, continuing current practices without liming will be detrimental, with pH continuing to decrease. As a result the unlimed yield will not remain the same over a 10 year period. Be aware that if yield potential in a paddock is decreasing without treatment, a positive response from a liming treatment may be maintaining your current yield.
Please also note that while the responses to lime have been recorded from nil (usually where pH through the profile is not limiting – or there are other limiting factors), up to responses of 300%. The larger responses are usually from low base yields (i.e. not 2.2t/ha) where low pH is significantly limiting yield.
The aim of this tool is to allow you to conduct “what if analysis” of a rate of return and a likely response.
Biological
General
