Ask a Master Gardener: Ways to improve garden soil

Can you believe the beautiful weather we have had?

I know when you read this, it will have cooled off a little, but I will take a whole week of high 60s in November anytime.

Dhruba Dhakal, MU Extension horticulture specialist, had an excelent article on improving garden soil. Here is Part 1 of the article, Part 2 will be next week.

Soil improvement in the garden

The most important resource for garden plants is soil.

Soil is an unconsolidated material on the earth surface which is made up of inorganic (mineral) materials and organic matter. It is a living ecosystem containing a large number of microorganisms, macroorganisms (such as earthworms and insects) and plant roots.

Soil holds nutrients, air and water required for plant growth and development while also providing structural support to the plant roots. Gardeners want to make improvements to soil for better plant growth and development. There are some methods by which soil can be improved in the garden.

Test garden soil

Understanding the soil properties and nutrient status is the first step for creating an optimum soil environment.

Testing soil periodically provides information about the properties and nutrient status in soil. A soil test report provides fertilizer and soil amendment (such as lime and gypsum) recommendations for specific crops. In addition, the soil test report suggests which fertilizer nutrient(s) and amounts needed to achieve the expected yield goal.

It is recommended to test soil once every three years. However, the gardener may want to test soil more often if there is a problem.

After harvesting the crop, fall is an ideal time to collect a soil sample for testing because this provides enough time to plan fertilizer and lime applications for the spring season.

It is recommended to wait at least three months after application of fertilizer, lime, or manure before taking a soil sample. Soil sampling technique is very important to get accurate soil test results from the garden, so care must be taken to collect a representative soil sample.

Details about soil sampling in the garden, landscape and lawn is available at: https://extension.missouri.edu/programs/soil-and-plant-testing-laboratory/spl-soil-analysis/spl-garden-landscape-lawn-soil-test or a copy is available at local county extension centers.

Soil samples can be submitted to local county extension centers. Soil sample collection boxes and soil sample information forms are available at local county extension centers. The soil test results are generally available a week after soil sample submission.

Add organic matter

Organic matter is considered the heart of the soil. It is a well-decomposed product of plant and animal residues which has many benefits in the soil.

Organic matter improves physical, chemical, and biological properties of soil. It improves soil structure, increases pore space and makes soil more friable and loose. It is easy to work and till a soil containing a good amount of organic matter. It is recommended to maintain 4-6 percent organic matter in garden soils.

Organic matter improves water and nutrient holding capacity of soil. Optimum organic matter in soil allows healthy root growth of plants. Organic matter is a food source of soil microorganisms. The population and activity of microbes in soil is increased if there is good content of organic matter in it. Soil microorganisms secrete glue-like substances and other chemicals in the soil. These substances help to bind soil particles, improve soil structure, increase soil porosity and reduce soil erosion. Organic matter is a source of macronutrients such as nitrogen, phosphorous and sulfur and other essential plant nutrients including micronutrients.

Organic matter in soil can be increased by making and using compost from plant and animal residues (such as animal manure). Details about making and using compost are available at: https://extension.missouri.edu/publications/g6956.

When making compost from plant residues, some precautions need to be taken. Avoid using any plant material that is diseased or insect infested. Additionally, make sure it is free from weed seeds. Perennial weeds may also reproduce from vegetative structures. So, avoid using any perennial weed plant parts when composting. Make sure there is no herbicide residue in the plant material used for composting.

Animal manures are good resources for making compost. However, avoid using uncomposted animal manures directly on the garden, because plant injury can occur when using fresh manure. During the decomposition process, microorganisms utilize nitrogen from the soil and garden plants will suffer from temporary nitrogen deficiency. (Avoid using dog and cat manures, which may attract rodents and other animals and spread disease.)

Happy gardening!

Peter Sutter is a lifelong gardening enthusiast and a participant in the MU Extension's Master Gardener program. Gardening questions can be sent to [email protected].