By Heather Kirk-Ballard

LSU AgCenter Horticulturist

Fall is an excellent time to plant and to make improvements in your garden. One way to make a real impact is enhancing your soil in preparation for better plant growth next spring.

Any avid gardener or plant expert will agree that an investment in your soil is an investment in the health of your plants. The healthier your plants are, the better they can defend themselves against pests and disease. Consider it the plant’s immunity. This in turn reduces the amount of chemicals — such as pesticides, fungicides and other inputs — you need to use in the garden.

Autumn is a perfect time to improve the soil. Start by utilizing those fallen leaves. Leaves can provide valuable organic matter and minerals to your soil. Nutrients come from the organic matter in the soil. Decayed plant materials contain carbon (C), oxygen (O), hydrogen (H), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) as well as other nutrients in smaller amounts. All of these nutrients are key to soil fertility and plant health.

Microorganisms also are an active organic portion of soils, making up 10% to 40% of the organic matter. This is in addition to about 40% to 60% of humus, which is a stable form of organic matter.

Chop or shred leaves to make it easier for worms and other beneficial microorganisms such as fungi and bacteria to break down the leaves. Leaves can be composted first to make leaf mold, or you can work the leaf mold into the top several inches of the soil in autumn. In addition, chopped leaves also can be used as a winter mulch on top of garden beds to help retain moisture, reduce weeds and insulate roots from cold temperatures.

Another excellent source of organic matter is composted animal manures. Most composted manures contain low levels of macronutrients, nitrogen, phosphorus and potassium. Common manures used in gardens include cow, sheep, horse and chicken. Fresh or partially composted manure cannot be used in the spring garden, because it may burn plants or introduce unwanted pathogens. This is especially important to avoid in vegetable gardens where edible foods can become contaminated with soil-borne food pathogens.

You can use no-cost or low-cost amendments such as locally sourced manure, compost and compost tea, leaves, grass clippings and kitchen scraps from your own home to add organic nutrients to your soil any time of year.

Knowing your soil composition is the best place to start. If you understand the nutritional composition and condition of your soil, you will be a more successful gardener. You can learn how to send a sample to the LSU AgCenter for analysis at www.lsuagcenter.com/soillab.

As far as soil pH goes, it is an indication of the acidity or alkalinity of your soil. Plants prefer a slightly acidic soil at a pH of about 6.5. At the correct pH, your plant will have the optimum availability of soil nutrients. If your soil pH is off, plants may not be able to uptake some nutrients.

To adjust soil pH, you can use acidifying fertilizers or lime. For more information on soil pH and how to adjust it, go to LSUAgCenter.com and search for the “Louisiana Home Lawn Series: Soil pH” publication.

Soils that lack nutrients can be improved by adding organic matter, or what we commonly refer to as soil amendments. Amendments are mixed into the topsoil to improve soil texture and nutrient content.

Here is a brief list of common soil amendments that can be found at local nurseries and garden centers: compost, peat moss, mycorrhizae, topsoil, composted manure, worm castings, wood ashes, mushroom compost, biochar and many others. Just think “natural” when you are thinking of organic materials, and you cannot go wrong.

In general, soils high in organic matter will retain more moisture, have improved drainage and aeration (oxygen), resist compaction and have higher levels of nutrients that improve plant growth.

Fertilizers also can be used to improve nutrient content in the soil; however, caution should be taken when using them. When fertilizing, it is important to apply at the proper rate following the label instructions to prevent runoff into surface waters such as bayous, swamps, rivers, ponds, lakes and streams.

Enhance your soils for spring by putting in rich organic matter into your soils this fall. Make use of those leaves; avoid blowing them away or bagging them. Reduce, reuse and recycle.

Leaves are an excellent source of organic matter to add to your garden. Instead of blowing or raking and bagging, chop and incorporate them into your garden soil. Photo by Heather Kirk-Ballard/LSU AgCenter

Leaves make an excellent mulch in the fall and winter and as they break down, they add organic matter and nutrients to the soil. Photo by Heather Kirk-Ballard/LSU AgCenter

Compost can be composed of kitchen scraps, leaves, sticks and grass clippings. Photo by Heather Kirk-Ballard/LSU AgCenter

Kitchen scraps such as vegetables, egg shells, coffee grounds and fruit peelings make excellent additions to compost for organic nutrients. Photo by Heather Kirk-Ballard/LSU AgCenter