It is fall; so like many you are probably going to apply lime – but do you know why?
The function of limestone is to reduce the acidity of the soil and change the pH (potential Hydrogen). Liming provides three potential benefits important to growing healthy turf; improves soil chemistry, encourages beneficial soil biology, and improves soil structure.
Improve Soil Chemistry. Soils range from 0 being very acidic to 14 being very alkaline with a pH value of 7.0 as neutral. Because of how pH is measured what appears to be a small change can mean a lot: a pH of 6 is 10 times more acid than a pH of 7.0, 5.0 is 100 times more acidic than pH of 7.0; while a pH of 4.0 is 1,000 more acidic than that of pH of 7.0. Studies show potential crop yields are reduced dramatically with soil pH <5.0. Bringing pH into optimal range can increase yield by 10-40%. Turf grass grows best in soil with a pH of 6.5 – 6.8. Soils in this range encourage root growth and make more nutrients available to the grass.
Encourage Biology. Microbial activity is affected by pH. Soils that are more acidic tend to be fungal
dominant. Soils that are in the 6.5 – 6.8 pH range tend to be more balanced between fungal and bacterial activity. Encouraging this microbial activity contributes to the availability of nitrogen, sulfur and phosphorous in the soil.
Earthworms are also affected by the pH. They need the pH to be near neutral for their sticky mucous or slime. The slime has several purposes, including allowing the earthworm to breathe through its skin. The slime also acts as a lubricant; facilitating their burrowing. The slime also helps to form soil aggregates.
Improve Soil Structure. The formation of soil aggregates helps to improve the soil’s structure. The addition of calcium through the liming process also helps improve soil structure. Calcium and magnesium stabilize soil aggregates via the formation of organic matter – clay bridges. Aggregate stability increases soil porosity and tilth. Soil must be able to breathe to grow grass.
How much and What Kind of Lime to Apply? Often, not nearly enough lime is put down to either help or hurt the soil chemistry. It is critical to soil test with a reputable laboratory for pH, buffer pH, Calcium and Magnesium to determine how much and what kind of lime to use – dolomitic vs. calcitic.
Buffer pH provides an indication of the soil’s potential acidity, resistance to change and how much lime will be necessary to cause a change in the soil’s pH. Sandy soils tend to have a high Buffer pH while rich organic soils have a lower Buffer pH. The difference can be dramatic with respect to the amount of product required even in soil with the same pH reading. Using conventional lime, soil with a pH of 6.2 and buffer pH of 6.8 would require roughly 46 lbs/1000SF, where as soils with a pH of 6.2 and buffer pH of 6.4 would require 138 lbs/1000SF.
The decision on which lime to use, calcitic or dolomitic, should be based on the Calcium to Magnesium ratio found on the soil test (ideal Ca:Mg range is 7:1 – 15:1). Dolomitic lime contains both calcium and magnesium while calcitic lime contains primarily calcium. Unless your soil needs additional magnesium, dolomite should not be used. Calcium is the most important nutrient and plays a major role in strengthening the plants physical structure, increases nutrient uptake, protects the plant from disease and improves soil structure. Without realizing it you may be raising the pH while creating an imbalance in the Calcium to Magnesium ratio which can create other problems (i.e., soils that are not in balance tend to be more prone to compaction and exhibit greater weed pressure than those that are in balance).
Due to the high labor costs associated with putting down large amounts of conventional lime products we recommend a line of high efficiency lime products ( HiCal Lime and Gypsum humates and CAL/MAG Turf Pro data sheets). Typically these products require only 1/5th the amount of their conventional counterparts. While the product costs are higher it is more than offset by lower associated labor costs for the application.
When to Apply? Lime can be applied anytime during the season and up until the ground freezes in late fall. Because it can take up to 6 months for lime to affect soil chemistry the sooner in the season it’s applied the better. It is often applied in the fall to set up for the spring growing season. Depending on the pH/Buffer pH spring and fall applications may be required over subsequent years.
A final word of caution when adjusting soil pH . . . be sensitive to other plants sharing the same space and their soil chemistry requirements (i.e. Oak Trees, Pine Trees, like a lower pH) . . . so don’t sacrifice the gorgeous old oak tree in an effort to grow grass under it.
Please contact PJC & Company at 978-432-1019 or info@pjcecological.com for more information on our lime products or if you have any questions on what liming product to use.