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Denton County Master Gardener Association educates and engages county residents in the implementation of research-based horticultural and environmental practices that create sustainable gardens, landscapes, and communities.

Joseph A. Carroll Building401 W. Hickory Street, Suite 112

Denton, TX 76201-9026master.gardener@dentoncounty.com

Phone: 940-349-2883 or Help Desk 940-349-2892

Preparing Garden Soil

Preparing your vegetable garden soil

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About DCMGA

How to get copies of presentations

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dcmga.com

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How to sign up for DCMGA monthly newsletter

Topics

▪ Decisions

• What kind

• Where

• How large

• How to supplement water

• Organic or not

▪ About soil

▪ Improving existing soil

▪ In-ground traditional vegetable gardens

▪ Creating a raised bed

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Deciding on the type of bed

▪ In-ground

• More space

• Lower initial cost

• Requires significant amount of prep time

▪ Raised bed

• Control over soil

• Less time required for maintenance

• Better drainage

• Higher initial cost

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Location, location, location

▪ Fruit bearing plants such as tomatoes, peppers, eggplant and squash need full sun for at least 6 to 8 hours per day

▪ Leafy vegetables can tolerate some partial shade (lettuce, spinach)

▪ If starting a traditional garden from scratch, begin prep several weeks before adding plants or seeds

▪ Before deep tilling, check on buried utility lines. Call 811 to get lines marked.

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Supplemental watering options

▪ At times during the growing season, it is necessary to water your plants. Check moisture down about 2-3 inches (plant root zone) with moisture meter or screw driver.

▪ Make sure that getting water to your plants is relatively easy.

▪ Drip systems and soaker hoses provide water slowly allowing it to percolate down to plant roots and keep water off of leaves to discourage fungal infections. Both of these options have an initial cost and drip systems require set up.

▪ Laying out your system should be done before planting to minimize soil compaction or accidently stepping on plants. Emitters for drip system can be added after planting.

▪ Overhead or wave-style sprinklers are less desirable but lower cost and require no installation.

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Organic or not

▪ This is a personal choice.

▪ Organic gardening means growing without synthetic fertilizers or pesticides.

▪ If you choose to grow organically only, consider also the source of your seeds, seedlings, compost and mulch as well as soil amendments.

▪ “Organic gardeners have realistic expectations when it comes to insects and diseases. They don’t try to eliminate them from their yard or garden. Instead they seek to keep them below damaging levels.” (North Carolina Cooperative Extension)

▪ Encourage your neighbors to grow organically also so that your crops are not impacted with pesticide drift or pollinated by non-organic plants.

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Let’s talk about soil

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About soil

▪ Soil is not dirt—Dirt is what people and pets bring into the house that needs to be cleaned up.

▪ Soil, with its organic material and microorganisms, contains EVERYTHING that plants need to grow. Soil should be treasured.

▪ Gardening soil should be loose enough that you can dig a planting hole with your hand.

▪ Old farmer’s saying: “A poor gardener grows weeds; a good gardener grows plants; a great gardener grows soil.

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Types of soil

▪ Texture

• Sand, silt or clay

• Most native soils are a combination of these three particle types

• Relative size of particles—if a particle of clay were a BB, then a particle of silt would be the size of a golf ball and a grain of sand would be the size of a chair

• Sandy soils feel gritty; silty soils feel floury and clay soils feel greasy

• Many North Texas soils are “heavy” with a high proportion of clay

▪ Clay is nutrient rich, but slow draining. Sand is quick draining, but has trouble retaining nutrients and moisture. Loam (a combination of clay, sand and humus) is generally considered to be ideal soil because it retains moisture and nutrients but doesn’t stay soggy.

▪ Clay is not bad gardening soil but it is challenging to achieve desirable structure and tilth (Factors that determine tilth include the formation and stability of aggregated soil particles, moisture content, degree of aeration, rate of water infiltration and drainage.)

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What is your soil type?

To determine your soil type, take a handful of moist (but not wet) soil from your garden and give it a firm squeeze. Then, open your hand. One of three things will happen:

• It will hold its shape but when you give it a light poke, it crumbles. Lucky you—you have loamy soil

• It will hold its shape and when poked it sits stubbornly in your hand—you have clay soil.

• It will fall apart as soon as you open your hand—you have sandy soil.

Photos courtesy of the University of California Division of Agriculture and Natural Resources14

ClayLoam Sand

Clay soil—the good, the bad, and the ugly

▪ The bad

• Difficult to work

• Dries out slowly

• Surface hard crust restricts moisture penetration

▪ The good

• Clay can hold moisture and nutrients between its thin layers

• Clay layers have “parking spaces” that can hold nutrients

• The parking spaces are negatively charged which attracts positively charged (cations) nutrients such as calcium, magnesium, potassium and ammonium nitrate and zinc

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Improving your native clay soil

▪ It is very difficult to change the texture of native soil.

▪ However, soil structure can be improved through management practices that increase pore spaces, nutrient and moisture flow and increased biologic activity.

▪ What can you do?• Add organic material—lots of it (25 to 50 percent by volume)• Grow cover crops (grains, grasses, or legumes that will grow during fall and winter and then tilled

under in the spring) such as cereal rye, hairy vetch, alfalfa, fava beans, winter peas• Reduce tillage over the long term• Use paths to reduce soil compaction caused by walking on soil• Plant vegetables with a strong tap root to penetrate the soil• Put down 3 inches of expanded shale on top of the area and tilling it in six to eight inches deep.

▪ Be patient. Transforming clay soils into well-structured growing media may require several years.

▪ If patience is lacking, consider building a raised bed!

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Benefits of adding organic material to transition your dirt into good soil

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▪ Improves the ability of the soil to accept and store water.

▪ Increases the activity and number of soil organisms.

▪ Over time, a well-amended soil will supply all of the nutrients your plants require and reduce fertilizer requirements (except nitrogen).

▪ Although you might not expect it, adding organic matter to soil also helps to protect water quality and the environment by limiting chemical runoff into watershed.

▪ How much? For vegetable gardens, add 6 inches of compost each year.

Five yards of compost

Amending your garden soil

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Soil analysis

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Macro-nutrients = N – nitrogenP – phosphorusK – potassiumCa – calciumMg – magnesiumS – sulfur

Micro-nutrients =Boron (B), Copper (Cu), Iron (Fe), Chloride (Cl), Manganese (Mn), Molybdenum (Mo) Zinc (Zn)

Ph = soil acidity Take samples from several locations in your garden or landscape bed; 4 to 6 inches deep

Mix samples

Pack samples (use double bags for safety), label and ship to lab

http://soiltesting.tamu.edu/

Understanding a soil analysis report

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Calculating how much fertilizer

Example: if a 20-lb. bag contains 12% nitrogen

To calculate the pounds of nitrogen: Multiply 20 by .12, which equals 2.4.For an 800 square foot garden: 2.4 x .8 = 1.92

So, use just about 1/2 the bag

Soil fertilizer—the big three

▪ Rock phosphate (0-3-0). Be sure to double check the phosphate levels in your report before adding more as this mineral can remain in the soil over several years. (50 pounds per 1,000 square feet)

▪ Green sand for potassium (50 to 100 pounds per 1,000 square feet).

▪ Cottonseed meal (5-2-1) adds nitrogen and helps slightly acidify the soil. (2-4 pounds per 100 square feet)

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To add fertilizer based on your soil analysis report, mix into soil or planting hole:

Organic options Non-organic options

▪ Most garden fertilizers have a ratio of nitrogen, potassium and phosphorous (NPK). These may be balanced (10-10-10) or weighted toward one element or another. (10-20-10 for example would have more phosphorous).

▪ All commercial chemical fertilizer bags have filler to help distribute the chemical evenly. The filler is usually about 70% of the total weight.

Organic soil amendments

▪ Fish meal—hydrolyzed fish fertilizer (approximately: 2-4-1) plus some proteins and minerals to feed soil microorganisms. Almost no smell (as opposed to fish emulsion)

▪ Bone meal—source for phosphorous

▪ Blood meal—source of nitrogen. Be aware this smells a bit the first few days and may attract critters.

▪ Molasses—dry from feed stores or specialty nurseries or dilute store-bought (1 to 2 tbsp. per gallon) feeds microorganisms

▪ Sea minerals or rock powders (ex: SEA-90, azomite)

▪ Animal—bat guano, gerbil, rabbit, and chicken poo and ungulate manure are okay if properly composted. Dog, cat or human not okay because even high-temperature composting may not kills all parasites

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Tips for adding mulch

▪ Because mulch is less decomposed than compost and could absorb nutrients meant for plants, it should be placed on top of the soil. It should surround the plant but not touch the stems.

▪ Over time organic mulch will decompose and can be worked into your soil to feed plants.

▪ How much? Add 3 to 4 inches of mulch on top of soil to moderate temperature, limit weeds and conserve water.

▪ Pine bark, straw, or wood chips are recommended. Hay may be used but be cautious. Not only can hay bales contain weed seeds, they may contain herbicide residue that will kill your vegetable plants. If using manure or hay, know the source. These herbicides: Aminopyralid, clopyralid, and picloram are registered for application to pasture, grain crops, residential lawns, commercial turf, …. According to North Carolina State University, these herbicides “can also remain active in the manure even after it is composted. The herbicides can also remain active in hay, straw, and grass clippings for an unusually long time.” (several years)

▪ Plastic mulch may be used. HOWEVER, it does not decompose to feed the soil and must be removed annually during bed preparation.

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In-ground or raised bed for your

vegetable garden?

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Traditional (in-ground) row vegetable garden

▪ Rows can be as long as desired or available space allows.

▪ The greater size provides larger harvests. (Try to control your enthusiasm though. What seems perfect in March can be overwhelming in July).

▪ Accommodates crops that spread out such as melons and sweet potatoes.

▪ Wide rows, raised above the surface, help with drainage.

▪ Be sure to create pathways between rows for weeding and harvesting and to reduce soil compaction.

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Soil preparation for in-ground vegetable garden

Traditional

1. Clear the area of all vegetation.

2. Till to a depth of 8 inches.

3. Layout rows and walkways (rows are 2- 3 feet wide or up to 4 feet wide for wide-row gardens). Paths are 1 foot wide.

4. Use a shovel or hoe to move soil out of the paths and up onto the rows.

5. Add organic matter to the rows.

6. Flatten the row with a rake.

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Alternative (no till method)

1. Clear the area of all vegetation. This can be done by covering with layers of newspaper, or cardboard covered with leaves and other organic materials. Or,

2. Dig up the top layer and turn it over exposing the roots of vegetation. Cut the sod into small pieces to speed decomposition.

3. Wait 4 to 8 weeks for the vegetation to die.

4. Add organic materials and work them into soil.

5. Flatten the area with a rake. Layout rows and walkways.

Be aware: Neither method is very successful in dealing with Bermuda grass. You can remove by frequent tilling, pulling or glyphosate, but it doesn't give up without a good, long fight.

The raised bed alternative

▪ Mounded soil or framed about 9 to 12 inches deep

▪ Advantages:

• Excellent drainage

• Discourages aggressive grasses

• Can be tall enough to reduce bending and stress on the lower back

• Can be just functional or an attractive landscape addition

• Less soil compaction

• Fewer soil-borne weeds

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Benefits of raised beds*

▪ Prevents soil compaction: One of the greatest advantages of raised beds comes from the protection the structure provides from foot traffic, especially from children working in a garden area.

▪ Longer growing season: Raised beds warm up more quickly in the spring and drain better (assuming the soil is properly prepared).

▪ Less weeding and maintenance: Once the soil in a raised bed has stabilized, compaction is almost non-existent so the need for seasonal tilling is minimal. Weed populations decrease over time in a raised bed that is well cared for and mulched.

▪ Better drainage: A well-prepared raised bed allows the soil to drain better than in an in-ground garden.

▪ Material conservation: Because the gardening space is concentrated, the management of water, fertilizer, mulch and soil amendments can be more carefully controlled, leading to less waste.

▪ Access for gardeners with disabilities: Raised beds, at the proper height, can improve access for wheelchairs, or for gardeners who have a hard time bending over.

28*University of Georgia Extension “Raised beds versus in-ground”

How to build a raised bed frame

▪ Construct the frame with a nontoxic building material, such as stone, cinder blocks, bricks, untreated wood or fiberglass. (Some garden centers and catalogs sell raised bed frames ready for assembly.)

▪ Make sure the frame is sturdy enough to hold together when filled with soil.

▪ If using boards, secure them at the corners with metal braces, or use screws or nails to secure the boards to a reinforcing block of wood inside the corners.

▪ Or use rebar posts to support frame. Drive posts into the ground to brace the boards at the corners and every 3–4 feet, on the outside of the box. Boards 2 – 3 inches thick will last much longer than 1-inch boards.

▪ If using concrete blocks or bricks, offset placement to provide more stability and reduce soil loss.

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Preparing raised bed for planting

▪ Place a layer of cardboard on the bottom to keep sneaky weeds and grasses with deep roots from invading your garden space. Cardboard will decompose in a few weeks.

▪ Add gardening soil and compost or potting soil. Use a soil volume calculator to determine how much soil you need.

▪ Layout watering system if using drip irrigation or soaker hoses.

▪ Add 3 to 4 inch layer of mulch.

▪ Soil test the second year. Continue yearly testing until soil tests well and then test every couple years after that.

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Raised bed construction examples

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Rebar support

Corner support

Offset for greater stability

More raised bed ideas

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Easily rolls into new location for sun or partial shade

Herbs, small vegetable plants or flowers can grow in cinder block holes

Add vertical support for peas, pole beans and cucumbers

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CongratulationsYou are ready to plant

Go for it!