When done right there is no wrong time to apply lime

By Doug Carter, Rankin County Extension Agent

At the Rankin County Extension Office, we handle many soil samples each year. Soil samples involve forages, row crops, food plots, yards, gardens, and pastures. One question I frequently receive is “When is the right time to put out lime”. I probably get this question more often from folks planting food plots. Really, there is not a bad time to put out lime, as long as soil tests indicate the need for it.

If we lived in a perfect world, we could schedule all our tasks to be done, stay on schedule, and our lives would be much simpler. But this is not the case. We have to work with the time and conditions we have been given. Lime needs to be put out 3 months ahead of time, and for row crop farmers, fall is the preferred time to apply lime. This way, it will have the winter months to get into the soil solution and neutralize acidity, but this is not an absolute requirement.

The first consideration is to use quality lime that is finely ground so that it can quickly react with soil acids and do its job. One must also consider that the lime and the water in which it is carried must move into the soil profile, by infiltration by way of pores in the soil. It may need to be incorporated into the soil. 

Another factor that some people forget is that when lime has been applied to the surface, the application of most types of nitrogen fertilizer following it, leads to the loss of nitrogen as ammonia gas. When nitrogen must be applied following a lime application, it should be injected or incorporated in order to avoid nitrogen loss. Lime and nitrogen applications should be separated by as much time as possible and at least one good rain.  

I often get questions about poultry litter. Some people have come to believe that poultry litter is a good substitute for lime, but this is not true. Poultry litter does contain small amounts of the basic element’s calcium and magnesium. The lime value of a ton of good quality broiler litter may range from 200 to 400 pounds per ton. This is not enough to correct a low pH problem, although it may be sufficient to maintain soil pH in the preferred range after it has been corrected.  Simply put, poultry litter will not fix the problem, but it may help prevent it. Regular soil testing is necessary to monitor soil pH and other factors.

Lime is important to the availability of most plant nutrients. Soil pH levels below around 5.6 or above 7.0 may significantly reduce the availability of some of the plant nutrients including nitrogen, phosphorus, potassium, sulfur, calcium, and magnesium. Another issue in most of our soils is that when pH falls below about 5.5, aluminum and magnesium enter the soil solution and are toxic to plant growth. The take home message, is that we need to do our best to keep soil pH in the range between 6.0 and 6.5 if possible.  

Lime is important enough to apply almost anytime you can get it done, and crops will begin to gain benefits from it as soon as it begins to go into solution.  About the only time one might want to avoid liming is when the crop is nearing maturity.  

Good soil pH is the foundation of a sound soil fertility program. Most of the soils that need lime will show benefits from it as quickly as from fertilizers. If a soil test recommends lime, get started and apply as near to the recommended amount as possible. If you can’t handle the entire amount, go with as much as you can, retest after about a year, and apply more as the soil test recommends.