Lime Abuse and Neglect - A Serious Problem

I am often asked, "Does this crop need lime?" Many of you who manage nurseries or garden centers have probably been asked the same question by some of your customers. Perhaps you have also heard such statements as "I'm going to lime my yard this year because so and so down the road did his and it looks a whole lot better" or "I'm gonna throw some lime by my tomato plants this year because I've been having trouble with blossom end rot." I know you've heard these statements before and, like me, you're probably frustrated that something so basic to horticulture is so often misunderstood.

You and I know that the only way to correctly answer the questions above is to have the soil tested to determine the need for lime and/or the amount to be applied. In North Carolina, we can get our soil tested with no fee by the NCDA. Even though we have the benefit of this service, too many people don't take full advantage of it. Perhaps if people understood why we lime, what lime is and what determines the liming recommendation, then maybe they would take advantage of the soil testing service. With the following information, you and I can inform people of the importance of having their soil tested and how to use lime properly.

First of all, let's talk about why we lime soil. We apply lime to soil in order to change the soil from an acid to a near neutral condition. Lime is an alkaline material and when alkaline and acidic materials come in contact with one another, each material tries to neutralize the other. A unit of measurement called pH is used to record whether a substance is acidic, alkaline, or neutral, and also determines the strength of acidity or alkalinity. The pH scale reads from zero to fourteen with seven being neutral, zero to seven considered acidic, and seven to fourteen considered alkaline or base.

Most plants, but not all, grow best in soils with a pH range between 5.0 and 7.0. As pH levels in the soil begin to drop below 5.0, toxic elements such as aluminum and manganese become more available to plants. Essential elements such as nitrogen, potassium, phosphorus, and others become less available to plants. Beneficial biological activity is hindered as well. As pH levels rise above 7.0, elements such as phosphorus, copper, and zinc are less available.

At least five factors are used to determine the lime requirement and to make a lime recommendation. These factors include the present pH, desired pH, soil acidity, soil type, and the crop. The pH of the soil is measured and if this reading is below the desired pH level, then a lime application is recommended. The desired pH is based on the soil type and the specific crop requirements. Soils are placed into three classes, based on the amount of organic matter that is present - mineral, mineral- organic, and organic. Soils that have more organic matter tend to have lower aluminum content. Thus, for most plants, a lower pH level can be allowed. Mineral soils contain more aluminum, therefore, a higher pH is recommended to avoid aluminum toxicity. For most plants, the desired pH level in a mineral soil is 6.0, 5.5 for a mineral-organic soil, and 5.0 for organic soils. Some crops have specific pH requirements that are also taken into account when determining desired pH. Acidity is the term used to express the quantity of hydrogen and aluminum in the soil. Along with the present pH and the desired pH, the acidity is used to determine the amount of lime required to raise the pH to the desired level.

Because of heavy rainfall, North Carolina soils are highly weathered and are naturally acidic. Therefore, correcting soils with low pH levels is more common than correcting soils with high pH levels. Occasionally, a soil with a pH reading that is higher than the desired pH level will be found in North Carolina. This can happen when someone overlimes their soil and sulfur is the material recommended to bring the pH levels down to an acceptable level. Sulfur is more expensive than lime and overliming can easily happen when it is applied without knowing how much it needs, therefore, all the more reason to encourage people to have their soil tested to determine its needs. For more information about soil acidity and proper lime use, contact the Cooperative Extension Service and ask for publication number AG-439-17.

Strawberry Season is Here!

Do you want to experience the best tasting strawberries that you'll ever find? Well, now is the time to buy them. Strawberry season has arrived in Eastern North Carolina and Cumberland County. Due to the hard work of our local strawberry growers and cooperation from mother nature, we are experiencing an excellent crop. Now is the time to buy, but make sure that you are buying locally grown berries or at least berries that have been grown in North Carolina.

The quality and taste of locally grown berries are far superior to the berries that are shipped in from other states. Berries that are shipped into our area are picked while they are white (unripe). This allows them to be shipped with little damage and these berries will store longer before going bad. These berries will turn red, but the inside will remain white, and practically inedible. Because they don't have to be moved over long distances, berries that are grown for the local market are picked when they are ripe and have developed their flavor.

You may find locally grown strawberries in grocery stores and produce stands, but don't assume that all of the berries are produced in this area. Ask before you buy. To be sure that you are getting local berries, you may want to visit one of the area's "pick-your-own" strawberry farms. Some of these operations will pick for you at a slightly higher cost. Either way, you can be assured that you are getting berries at the peak of their ripeness.

You may pay more for locally grown strawberries, but they are well worth the extra cost and you can bet that none of them will go to waste. For information on pick- your-own strawberry operations in your area. contact your local Cooperative Extension Service.

The Plant Disease and Insect Clinic has received several reports of Bacterial Angular Leaf Spot in strawberries. The disease is caused by the bacterium, Xanthomonas fragariae, and has probably been introduced through the transplants. The disease can become serious if the plants are watered for frost protection.

Symptoms of the disease include the presence of black, angular leaf spots on the underside of leaves, especially the older leaves. Look carefully because the spots can be easily mistaken for soil adhering to the leaves. When the leaves are held up to the light so that they are backlighted, a distinct, pale green to yellow halo can be observed surrounding the necrotic spot. The bacterium can cause defoliation, infect fruit, and result in death of the plant.

Check your plants daily for this disease. It can be present and not show much injury, therefore, it can easily be overlooked. If the disease is positively identified, then I suggest that you implement the following control measures: spray the infected field with a copper fungicide, minimize the use of overhead irrigation, and avoid working the plants when they are wet. Early detection and prompt action is the key to controlling this disease.

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