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There is so much science right in your own backyard. From gardening to composting, lawn care to water management, Backyard Science walks you through the science behind the things you encounter around your home. Today, we take a look at soil preparation and how achieving proper soil balance is key to a successful garden this summer.

It’s finally that time of year again: gardening season! We are just a few weeks away from the ever-famous Midwest tradition of planting the garden over Memorial Day weekend. Sure, there are a few hardy plants that you may already have planted, or maybe you are a risk taker and planted everything over Mother’s Day. But for many, now is the time to make sure that our garden soil has the perfect balance and is ready for planting in the next few weeks.

Soil preparation can and should start in the fall, but getting outside and getting the garden ready for planting is a great spring tradition that will be sure to put a smile on your face and get you in the mood for summer. Every plant needs nutrients to grow, and vegetables need a soil that is nutrient-rich with a well-balanced pH, which refers to the acidity or alkalinity of a solution. Whether you are starting a new garden, fixing an under-producing plot, or reviving an old neglected one, we’ve got some tips to help you make sure your soil is healthy and ready for planting.

Testing the ground

Getting the soil right starts with knowing what you are working with. Soil tests will help you understand your soil’s pH, nitrogen, phosphorus, and potassium content, and sometimes more. There are several ways to get a soil test done. For example, you can buy an inexpensive soil test kit that will allow you to test it regularly, or you can send a sample to the UW Soil and Forage Lab and they will test your soil for you.

Once you get your test done, it’s time to evaluate. If you have a very high or very low soil pH, it could cause a plant nutrient deficiency or toxicity and kill your garden. We’re aiming for a slightly acidic pH range of 5.5 to 7. At this pH, microbial activity is at its best for plant growth, and a plant’s roots will be able to efficiently absorb soil nutrients. Resolve any pH issues before attempting to correct a nutrient imbalance. Your nutrient tests will indicate where your soil falls between the range of a surplus or depleted content.

Fixing the problem

If you need to bring the pH levels down like in my case, add some organic matter like decomposed leaves or compost to your soil. This will also do a great job of slowly releasing nutrients into your soil and will help promote microbial activity. If your pH is way too low, you’ll need to add some lime to the soil. Just be aware that lime will take a season to absorb into the soil, so you may instead be better off adding some soil with a lower pH to your garden to dilute the issue.

The main nutrients that are needed for a successful garden are nitrogen (N), phosphorus (P), and potassium (K). Levels of these nutrients can be raised by adding either synthetic fertilizers (inorganic) or natural additives (organic). We will be explaining the organic methods, as it is nearly impossible to apply too much organic fertilizer.

Nitrogen (N) encourages strong leaf and stem growth and gives your plants that nice dark green color, which is what we’re looking for in broccoli, greens, and herbs. To increase nitrogen levels, you can add aged manure to the soil. Alfalfa meal, blood meal or fish meal can also be used to increase nitrogen.

Phosphorus (P) assists with root and early plant growth, which is key in the Midwest. Blossoms and fruit development also depend upon phosphorus levels. This is key for veggies like zucchini, cucumbers, peppers, and tomatoes. Adding bone meal is ideal for quickly getting your garden up and running with phosphorous this spring.

Potassium (K) promotes plant root strength and resistance to drought or disease. This is also huge for flavor and is a must-do for root vegetables like potatoes, onions, carrots, radishes, and garlic. Langbeinite will help increase potassium levels.

Calcium (Ca) is considered a secondary nutrient for plants, but if you grow tomatoes or peppers, a calcium deficiency could be impeding your garden. These plants use a lot of calcium and can deplete your soil’s reserves. Throughout the summer, rinse and save all the egg shells that come through your house. To expedite the process of drying, and to kill off any bacteria that may be living on the shells, you can break them up and dry them in the oven before storing. In the fall, use a mortar and pestle to grind them into a fine powder. Once you’ve cleaned out the garden of any lingering fall plants, sprinkle the powdered egg shells on the soil before tilling.

If you are looking to increase the structural integrity of your soil, there are some things you can add for that as well. Unless you live on the lakeshore, your problem is likely too much clay in your soil. To fix, add a mixture of peat moss, coarse sand (not beach sand), and compost. If you have sandy soil, add some aged manure, peat moss, or sawdust.

Getting the garden ready

Once you’ve identified what you need to add to your soil and have gathered the necessary supplies, you are ready to get your hands dirty! First, till the garden and make sure the soil is broken up so that there are no large clumps. It helps to do this at least twice a year, in the fall and in the spring to make it easier on the back. Wet the soil lightly, to the point that when you squeeze the soil in your hands it does not drip water. Spread the ingredients evenly over the plot, starting with any nutrient additives and ending with a layer of compost, which can be added to every garden every year. Turn the compost and additives into the soil with a pitchfork or rototiller. Wet the soil and continue to till until the soil is evenly mixed and wet, making sure not to allow the soil to puddle.

And that’s all there is to it, your plot is ready for planting! You are ready for a fantastic growing season that should be full of strong and healthy plants. Check back later in the season for more tips on fruit production, weed and pest prevention, and more!

Written by Jason Kern for the Milwaukee Area Science Advocates

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