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Bob, the purpose of adding lime is to neutralize the acidic levels in the soil. Soil ph is listed by a number on a soil test. The number 7.0 is neutral... neither acidic, nor alkaline. I have been told that corn likes a ph level of about 6.7 to 6.9, soybeans like a level of 7.0 The only way to know a ph level is to do a soil test. I soil test every field every year. The purpose of adding lime is to bring the soil ph "UP" to the proper levels. In southern Illinois clay and timber soil will have a ph level of about 5.4 to 6.1 if lime has never been added to the field (that is VERY acidic). I am not sure of what the acid levels do "chemically" to the nutrients... (I believe it has something to do with bonding the N,P,K molecules electrically to the soil, so that the plant cannot use them), but I do know that crops will not utilize the fertilizers at these low ph levels. As the levels approach the 6.9ph level the corn will utilize the nutrients (N=nitrates, P=phosphates and K=potassium) at the maximum levels, and will grow the most efficiently! However... if lime is continually added at the 6.9ph to 7.0ph level then the soil will become too alkaline (higher than 7.0ph) and will then not break down the nutrients to be utilized by the plants... in otherwords, it then ties up the nutrients. So then, "over-liming" is a waste of money and will hurt you financially, in both having to pay for something you don't need, and then tying up nutrients and lowering the yields. There are usually 2 types of lime that can be applied (atleast here) one type of "dolamet"(sp?) lime has a higher magnesium content (costs more) and is a better lime for these soils. But, if your soils aren't deficient in Mag., then you can save money and put on just a regular lime. I was told by a certified plant expert that magnesium is required to change P2 (a type of phosphate that a plant cannot use) to P1 (a type of phosphate that a plant CAN use). A good soil test will tell P1 and P2 levels. Also there is something called a "buffer" ph level. Applying lime to soil does not immediately change the soil to a more alkiline level. Lime has to be broken down over a period of years. If you are considering liming.... FIRST, soil test!!! Then ask a certified crop expert to analyze the results. You will be money ahead!
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