How much lime to correct soil acidity? - Ask Extension
Hello.
I have an entire garden of raised beds with soil that is ridiculously acidic, and a large unit of new soil delivered that is even worse. I ha...
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How much lime to correct soil acidity? #896772
Asked April 08, 2025, 8:27 PM EDT
Hello.
I have an entire garden of raised beds with soil that is ridiculously acidic, and a large unit of new soil delivered that is even worse. I have applied pileated lime, but so far in some areas the Ph has risen for an inch or two, but not going deeper. For the new raised beds - quite large - how do I apply lime (or something else) to bring up the Ph (currently anywhere from -3.5 to 5.5. How much and what type? Appreciate some help, as I now know why my garden did not thrive last year with soil from the same source, and have more waiting! Thanks!
Yamhill County Oregon
Expert Response
Suze Ridley:
Can you clarify pileated lime - it's not a term I'm familiar with.
You are correct, with soil pH at that level, plants are going to struggle to take up nutrients.
Agricultural lime is the amendment that increases soil pH. And your observation is correct - lime moves very slowly in soil. For best results, it should be tilled in. I say that even though I've personally given up on tilling my vegetable garden. So if you've been applying lime on the surface of the soil, likely there hasn't been much pH increase in the rooting zone. Dolomitic lime (contains calcium and magnesium) should only be applied on the advice of a soil test interpretation.
Without a soil test, it's just not possible to tell you how much lime to apply. Some soils are very resistant to pH change, and require far more lime than others. Generally, I recommend that home gardeners have their soil tested in the fall. That way, if lime is required, it can be incorporated into the soil and have all winter to react and increase pH.
Soil pH changes on an annual cycle, and you can't really track changes in pH unless you sample for testing in about the same 2-week window every year. Nevertheless, it sounds like you have a situation that requires action now. It may be that your best bet is to grow a much smaller group of vegetables in containers (my rule of thumb is that tomatoes require a minimum of 5 gallons of soil).
Be sure to choose a lab that will provide you with an agronomic interpretation of the test results - that way, you'll know just how much of which amendments to apply for a more successful garden.
See this page for extension publications that tell you how to sample soil, which tests are valid for Oregon soils, and how to talk to the lab so you get the most useful information for your testing dollar.
I'm sorry I can't give you an easier answer. But it will be worth it to
WAIT WAIT - how do you know the pH ranges of these soils? Are you using a soil pH meter? Has it been appropriately calibrated? Are you following the directions to the T?
Please write back if you have questions about any of the above.
Can you clarify pileated lime - it's not a term I'm familiar with.
You are correct, with soil pH at that level, plants are going to struggle to take up nutrients.
Agricultural lime is the amendment that increases soil pH. And your observation is correct - lime moves very slowly in soil. For best results, it should be tilled in. I say that even though I've personally given up on tilling my vegetable garden. So if you've been applying lime on the surface of the soil, likely there hasn't been much pH increase in the rooting zone. Dolomitic lime (contains calcium and magnesium) should only be applied on the advice of a soil test interpretation.
Without a soil test, it's just not possible to tell you how much lime to apply. Some soils are very resistant to pH change, and require far more lime than others. Generally, I recommend that home gardeners have their soil tested in the fall. That way, if lime is required, it can be incorporated into the soil and have all winter to react and increase pH.
Soil pH changes on an annual cycle, and you can't really track changes in pH unless you sample for testing in about the same 2-week window every year. Nevertheless, it sounds like you have a situation that requires action now. It may be that your best bet is to grow a much smaller group of vegetables in containers (my rule of thumb is that tomatoes require a minimum of 5 gallons of soil).
Be sure to choose a lab that will provide you with an agronomic interpretation of the test results - that way, you'll know just how much of which amendments to apply for a more successful garden.
See this page for extension publications that tell you how to sample soil, which tests are valid for Oregon soils, and how to talk to the lab so you get the most useful information for your testing dollar.
I'm sorry I can't give you an easier answer. But it will be worth it to
WAIT WAIT - how do you know the pH ranges of these soils? Are you using a soil pH meter? Has it been appropriately calibrated? Are you following the directions to the T?
Please write back if you have questions about any of the above.
Thank you. I am
Likely spelling it wrong but it is pelletized lime rather than fine powder.
I have a device I bought that measures light, soil wetness, and Ph. No - never been calibrated. I had never used it before now. Also - I have just had new planting mix delivered and that appears to to be the problem - same source as last year. It has dairy manure, compost, and “sandy loam”. According to to my little tester that soil is really low Ph. Of course that is what I used in my new raised beds A and some from same
Source last year to supplement my old ones.
I will take some of that soil to get tested asap. Thanks for your detailed response.
Suzanne
Suzanne,
Those pH meters only give accurate readings if you follow the directions precisely. And that includes the calibration schedule.
I recommend that you pull out the literature that came with the meter (very likely you can also find it online) and read it carefully.
ljb
Those pH meters only give accurate readings if you follow the directions precisely. And that includes the calibration schedule.
I recommend that you pull out the literature that came with the meter (very likely you can also find it online) and read it carefully.
ljb
Thank you for the clarification.
I took a soil sample to local Extension office this morning per your suggestion. My sampler is a very low tech model and no way to calibrate it. Thanks so much. I hope my tester is wrong!!
Thank you for the clarification.
Well, this situation has a solution, whether the meter is correct or not. Pelletized lime :) much easier to spread, and you have less dust exposure. Always be careful when handling soil amendments - many can be harmful if inhaled (like lime). The binding agent that holds the pellets together dissolves readily in soil, but does not speed the lime reaction.
ljb
ljb
