Hello, Trumbull County.

Finally, after a long winter, we are starting to see signs of spring — daffodils are blooming, buds are starting to break on willow trees and the grass has turned from a drab brown to green.

While we still have some cooler weather to contend with over the next few weeks, the march to the growing season has begun and I’ve been getting several calls about how much fertilizer to apply to gardens, trees and lawns.

Like most OSU Extension answers, it depends.

The foundation for fertilizer recommendation is a soil test I’ve written about several times. Soil tests are a quick and inexpensive (less than $20) way to evaluate the levels of potassium (K), phosphorus (P) and pH in your soil. You can find soil test kits in many locations, including the OSU Extension office in Cortland. With baseline information from a soil test, you can tailor fertilizer applications to meet the needs of your crops.

I see hundreds of soil tests in my office each year and more than half show an excess of nutrients in the soil and a high pH (>7.0). We love our gardens, and many of the soil tests reflect that “love.” Applying more nutrients than necessary costs more money and you will not see a benefit in your garden. Once you have sufficient nutrients in your soil to promote plant growth, adding more will not increase yield or plant health. At some point, it’s like throwing a bucket of water into the ocean.

If there are more nutrients in the soil than the plants can use, you can simply stop applying that nutrient to draw the levels back down. For example, I have seen soil test reports with phosphorus levels at 2,680 pounds per acre. The recommended range for most crops is 60 to 80 pounds per acre. I could dig up the soil from that small garden and apply it as fertilizer to approximately 90 acres of corn.

The high soil pH that I see is mostly due to an overapplication of lime. The ideal pH for most vegetable crops is about 6.5-6.8. Lime is used to raise soil pH, or make it more basic.

In acidic soils (<6.0), nutrients like phosphorus and nitrogen can become tightly bound in the soil and will not be available to the plants. It doesn't matter how much fertilizer you add, if you don't correct the pH, the plants will not be able to use it efficiently. Conversely, in high pH conditions (>7.0), other nutrients like manganese and iron become unavailable. With really high pH (>8.0), phosphorus again becomes unavailable in the soil.

There is no need to apply lime every year unless you KNOW the soil pH needs to be corrected. Although most lime contains calcium, lime itself is not a fertilizer — its primary purpose for gardening is to raise the pH. Once the pH is in the correct range, it will likely stay in that range for three to four years. Even if you stop applying lime, it will take years to bring the pH back down to the ideal range and may require an addition of sulfur to the soil to bring it down faster.

Although I see overapplication of lime, phosphorus and potassium, I typically see an underapplication of nitrogen (N). Nitrogen does not stay in the soil from year to year and requires an annual application. While many fertilizers have nitrogen, many gardeners underapply.

When you are purchasing fertilizers, the numbers on the bag correspond to the percentage of nutrients (N-P-K). So, if you buy a 50-pound bag of 10-10-10 fertilizer, it will contain five pounds of each nutrient (with the remaining weight being filler).

Each crop you grow will need a different amount of nitrogen. You can find crop-specific fertilizer recommendations in the Midwest Vegetable Production guide (mwveguide.org) or you can always call our office at 330-638-6783.

Stay safe and have a productive gardening year!

Beers can be reached at beers.66@osu.edu.