Back Yard Gardener: The power of lime

Hello Mid-Ohio Valley farmers and gardeners! What a change has occurred in the weather! Fall is definitely here as daytime highs are in the 60s and the nights are getting chilly. Get your pumpkins carved and ready because Halloween is just around the corner.

We have experienced a few light frosts here in the Valley as gardeners are finishing up their harvest. There are many vegetables and fruits that must be picked and dealt with almost immediately or they will lose quality, such as tomatoes, which must be eaten or processed. Warm season vegetables will not survive even a light frost because they get partially or totally frozen and decay begins almost immediately.

Crops below the surface of the soil are not affected by frosts, but they are affected by freezing. As long as the soil is damp, they do well where they grow. If the soil is wet, they could rot. Root crops like carrots, turnips, beets, rutabagas and parsnips can remain in the garden after a frost and still be removed in good condition later, but get them dug and stored before the ground freezes.

This week I want to discuss how important lime is to our soils, no matter if you are growing a garden, a lawn or field crops. I answer many phone calls about fertilizing the garden to provide nutrition for many vegetable plants. However, many gardeners should examine the pH of the soil first, then look at what fertilizer is needed.

Fall is a great time to apply agriculture lime to the soil, giving it time to react in the soil to raise the pH, provide calcium and improve the production capacity of our soils. Liming the soil will definitely pay for itself in the long run. Research at Michigan State shows lime will return $5 to $10 for each dollar invested.

Your soil pH is an important indicator of fertility because it influences the availability of essential nutrients. Most horticultural crops will grow satisfactorily in soils having a pH between 6 (slightly acid) and 7.5 (slightly alkaline). Most soil nutrients are readily available in this pH range. Low soil pH limits the release of some nutrients from soil organic matter and reduces nitrogen fixation by legumes.

The pH scale runs from 0 to 14 and is used to indicate the relative acidity (sour) or alkalinity (sweet) of the soil. A pH less than 7 is acid, while that above 7 is alkaline. A pH of 7 indicates a neutral soil. For garden soils, I would consider any pH less than 6.2 to need limed.

Most of our agricultural lime is calcitic limestone, a naturally occurring rock composed primarily of calcium carbonate. This calcitic or high calcium limestone usually contains 90 to 95 percent calcium carbonate and less than 5 percent magnesium carbonate.

Dolomitic limestone is a naturally occurring rock composed primarily of calcium-magnesium carbonate. Dolomitic limestone contains 15 to 45% magnesium carbonate by weight and the remaining 85 to 55% is mostly calcium carbonate.

Simply put, liming acid soils will result in improved crop yields no matter if you are growing vegetable, grass in the lawn or field crops. Raising the soil pH will improve overall nutrient availability to plants. This is why I stress the “lime before fertilize” strategy. If you fertilize low pH soils the nutrients are not available to the plant for uptake and you could be wasting money better spent on lime.

Maintaining proper soil pH maximizes the availability of several plant nutrients. Agriculture lime reduces soluble aluminum and improves microbial activity in the soil. When available in excess, aluminum and manganese are harmful to plants, inhibiting cell division in plant roots and reducing growth. Plants with aluminum toxicity may also experience calcium or magnesium deficiencies.

A major effect of liming acid soils is making phosphorus more available to plants. Acid soils causes phosphorus to form insoluble compounds with aluminum and iron. Liming soils with low pH “dissolves” these insoluble compounds, making phosphorus more available for plant uptake.

Be careful adding lime and wood ashes (which also increases soil pH) every year to the garden. Liming soil to points beyond 7.0 will cause phosphorus to form complexes with calcium or magnesium. It is recommended to maintain the soil pH between 5.5 and 6.8 to reduce these problems

I always get questions about pelletized lime. Pelletized lime consists of very fine calcitic or dolomitic limestone formed into pellets with a soluble binding agent. There is nothing special about the effectiveness of pelletized lime. It is chemically the same as traditional agricultural lime and neutralizes soil acidity the same exact way. Therefore, the application rate for pelletized lime is the same for agricultural lime to achieve the same effect.

One question I hear repeatedly is: How long will it take for lime to react with the soil? Well, that depends. High quality lime that is ground very fine will react with soils quicker than larger particles. Tilling the lime into the soil will also speed up this process.

The benefits from lime may occur within six months after application and completely with the soil in two to three years. How long the effects of lime last will depend on the type of lime used, starting soil pH, use of nitrogenous fertilizer, amount of organic matter, soil types (clay versus sand), and cropping and management systems used. A soil test three to four years after lime application will help provide the answer.

The amount of lime your soil needs will depend on your soil test. Recommendations from the WVU Soils Lab will tell you the amount of lime needed for application in tons per acre for field crops and ounces per 100 square feet for lawns and gardens.

I highly recommend using the WVU Soil Lab for soil testing. Home kits are not nearly as reliable as a source of information. The WVU Soils lab analyzes over 10,000 samples a year, so the results are much more accurate than home kits. Soil testing is a free service provided by the WVU Soils Lab.

Getting soil for the sample is not complicated. You collect a thin slice of soil from the top 4 inches of several well-spaced, representative spots in the garden. Then mix them together in a clean plastic pail and let air dry. Never dry the soil in an oven or microwave oven. Fill a zip lock with soil from the pail and mail it to the WVU Soils Lab with your soil test form.

Most farmers will use spinner type spreaders, but lime can be applied to yards and gardens by hand or with small manual or garden tractor spreaders. However when you spread the lime the main goal is to spread lime evenly. The best way to achieve uniform application at the appropriate rate is to measure the amount needed to cover the entire area, apply half while traveling with swaths oriented in one direction, and apply the other half with swaths oriented perpendicularly.

The best incorporation implement for gardeners is a heavy-duty rotary tiller that mixes the soil throughout the root zone. The most commonly used lime incorporation tool for field crops is the disk. Its main limitation is that it incorporates lime only about half as deeply as the disk blades penetrate. Contact me at the Wood County WVU Extension Office 304-424-1960 or e-mail me at jj.barrett@mail.wvu.edu with questions. Good Luck and Happy Gardening!