How to amend your garden soil for next season

Sara’s vegetable garden with faded squash plants on the right side. Photo by Sara Welch.

It’s not quite the end of the growing season, but it’s time to start evaluating your vegetable garden’s performance and it starts with the soil.

Over the past two years, part of my vegetable garden has consistently underperformed. The tomatoes and peppers planted there were spindly and weak two years ago. Beans planted there last year produced almost no pods. The squashes planted this year have withered and shriveled.

I thought squash would surely survive – it can grow anywhere. Unfortunately, that was not the case. Few squash and zucchini were harvested from three rows of plants.

It must be the ground. This is the only plausible explanation for why this corner of my garden refuses to let anything grow.

Test the soil

Each year, fertilizer is plowed into the garden and sprinkled when seeds and starter plants are planted. This year fertilizer was added periodically throughout the growing season and it did not change the results.

The only logical conclusion is that what the soil is missing has not been added – this is a common problem for gardeners trying to fix their soil without a soil test.

A soil test is the best method to determine what soil amendments your garden needs. A soil test is a process that measures phosphorus, potassium, calcium, magnesium, sodium, sulfur, manganese, copper, and zinc for their plant-available content in the sample. In addition to determining the amount and type of fertilizer needed to correct any nutrient deficiencies, soil tests also measure soil pH, humic matter, and exchangeable acidity. A soil test can give you a complete view of the deficiencies in your garden soil and ensure you add the correct amendments to address them.

When collecting soil for a soil test, you should take a representative sample, which means that the soil’s appearance, texture, color, slope, drainage, and pest control practices should be similar throughout. the whole area. In cases like mine, where an area of ​​the garden has been particularly struggling or the quality or characteristics of the soil are obviously different, a separate sample should be taken.

You should always label your samples and take soil when the soil is not very moist.

Your local soil and water conservation district or extension office should be able to answer questions about testing your soil and may even have soil test kits available.

Amendments to correct soil pH

An ideal soil pH for most plants is between 6.0 and 7.0, but many garden vegetables prefer more acidic soil with a pH between 5.8 and 6.5. The results of your soil test and the growing preferences of the vegetables you plan to grow next season should help you determine how to adjust the pH of your garden soil.

Amending garden soil in the fall is ideal because it allows ample time for the chemical reactions to occur that are necessary to change the pH of the soil.

Increase soil pH

If your soil is too acidic for the vegetables you want to plant next spring, you will need to raise the soil pH using agricultural limestone.

Agricultural limestone comes in two combinations. Calcitic limestone is composed of calcium carbonate and dolomitic limestone is composed of calcium and magnesium carbonate. Dolomitic limestone should be used in soils low in magnesium.

The soil test lab will recommend your lime application rate based on your target pH and the buffering capacity of the soil test sample or its tendency to resist pH change.

Lower soil pH

Growing acid-loving plants or an abundance of calcium and magnesium in your soil can justify lowering the pH. Elemental sulfur is commonly used to lower soil pH.

In this case, the lab will determine the amount of elemental sulfur needed to lower the pH of your soil based on its texture, current pH, and your target pH.

Elemental sulfur reacts slowly with the soil, so it is best applied in the fall. It should be worked into the ground to a depth of 6 inches. Soils with a sandy composition will require less elemental sulfur than those with more clay. No more than 15 pounds of elemental sulfur per 1000 square feet should be applied at one time.

Organic amendments

Adding organic matter improves soil structure, increases nutrient holding capacity, improves drainage and water holding capacity, provides nutrients to plants and increases soil biological activity. In sandy soils, organic amendments help bind the particles together and increase the soil’s ability to hold moisture and nutrients. In heavy clay soils, they bind to smaller clay particles and form larger particles that have larger air spaces between them, allowing better drainage and air circulation.

Fall is the perfect time to add manure or compost to garden soil because it has plenty of time to break down and provide plant nutrients and other soil benefits in the spring. In the case of manure, fresh applications in vegetable gardens are not recommended in the spring because feed can be contaminated with microorganisms harmful to humans, such as Salmonella and E. coli. Applying it in the fall gives these harmful microorganisms time to die off before the vegetables are planted.

Manure and compost should be applied to the surface of the soil at a rate of ½ to 3 inches, then rototilled into the top 6 inches of soil. These organic amendments should be worked into the soil when it is dry to prevent stratification.

Additionally, manures and composts contain high levels of phosphorus, so regular soil testing should be done to prevent phosphorus buildup when applied continuously.

Organic fertilizers like greensand, rock phosphate, kelp meal, bone meal, or blood meal are other organic amendments that slowly break down over several months when not applied in excess. They can be used instead of manure or compost.

cover the ground

Covering your amended garden soil with straw or leaves is a great way to insulate the soil and encourage worms and microbial activity during colder months. This will help any organic matter you added break down and improve the quality of the soil in the spring.

Cover crops

Cover crops are another way to improve soil health during the shoulder season. Much like covering your soil, cover crops create a protective barrier during colder months to encourage activity below the soil surface. They too extract nutrients from the subsoil, remove excess water, and return nitrogen and organic matter to the soil when you plow them into the ground in the spring.

For more on planting and choosing cover crops, read How to Plant a Cover Crop in Your Vegetable Garden.

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