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Soil Management

Most gardeners do not have the ideal sandy loam which allow vegetables to perform best, many have soils with too much sand or clay. These have to be dealt with to achieve best results. To begin, always start with a soil test.

 

Soil Testing: To perform a soil test, you need to collect soil samples from each of your unique garden areas, bring it to OSU Extension office where it will be sent to OSU Stillwater for a test. The cost is $10 per sample and the turn-around time is about 2 weeks. It is important that the soil samples to be tested are collected properly; the instructions for collecting the samples and information about interpretation are listed here:

 

 

Soil Test Instructions

 

Soil Test explanation

 

This soil test will inform you of your soils pH (acidity) along with the amounts of the major nutrients, nitrogen, phosphorus and potassium. The report will also include recommendations about correcting the pH, if needed, and which and how much fertilizer to use to correct nutrient deficiencies.

 

Soil test results of over 1000 samples submitted by Tulsa area homeowners in 2007 show some interesting findings. The results are summarized below.

 

Average Results of Soil Tests for Tulsa County Homeowners 2007

 

 Measurement

Average Value

Optimum Value

Mobility in Soil

Comment

pH (acidity)

6.6

6-7

NA

Generally no adjustment needed for this acidity level

Nitrogen

22

40

Very mobile

Most soils will need extra nitrogen added

Phosphorus

162

65

Very immobile, attaches to soil where it is placed

No addition of phosphorus, elevated concentrations may take years to return to normal

Potassium

299

250

Moderately immobile

Most soils have enough potassium, more is not needed.

 

The take home message from these test results is that a gardening area previously regularly fertilized usually has too much phosphorus and potassium. To add more is harmful to plants and can pollute our environment. Excessive phosphorus is particularly harmful when it gets into the waterways. If your veggie garden has not been fertilized before and you do not have a soil test, use a balance fertilizer containing all three nutrients—nitrogen, phosphorus and potassium, otherwise use a nitrogen only preparation.

 

Listed below are some things to do and not do for best management of your vegetable garden.

 

Do Not: Till the soil excessively or till when the soil is wet. Some tillage is needed to prepare the garden bed, but if one overdoes it, it leads to soil compaction by reducing the air and water spaces in the soil. Plants breath through their roots and compacted soils causes plant suffocation. Excessive tillage also reduces the organic material in soil.

 

Do: Incorporate organic matter to the soil as possible. The organic matter should be composted (fully decayed) if added during the growing season. Uncomposted organics will bind soil nutrients needed by plants. In fall uncomposted materials such as leaves can be tilled into the garden and should compost before spring. Some raw organics, such as wood chips and sawdust are slow to decompose and may need a year or more to decay into compost. Manures must be composted to reduce their salt content. If not the salts will "burn" plants.

 

Organic material will also loosen up clay and help sandy retain moisture and nutrients. Go to the Fertilizer page for more information on the characteristics of organic material, including their nutrient content.

 

 

Do: Keep the soil covered, either with mulch or plant material. In our area bare soils becomes very hot in the summer; mulch may reduce ground temperatures by as much as 20 degrees. Mulch also conserves water and helps control weed and disease pressure. Mulch, if added yearly, breaks down to add both organic material and major and minor nutrients to soils.

 

Do: Use only the nutrients needed. Buying and adding fertilizer components which are not needed is expensive and harms the environment.  A soil test is invaluable for directions as to which nutrients are needed.

 

Do: Where possible, such as in vegetable gardens, rotate crops. This reduces the pressure of disease, weeds and insects in a particular area. Soil disease such as fusarium wilt may be prevented in tomatoes and its kin by regular rotation.

                

Do: Practice sanitation in the garden. At the end of the growing season remove any material which may harbor insects or disease. Fungal spores such as black spot on roses and squash bugs on cucurbits over-winter in garden debris. Some insects and their eggs get through the winter in the upper level of soil, and tilling in fall will expose them to winter weather. Also remove any weeds nearby the garden, some insects over-winter in these patches.

 

 

Do: Consider raised bed gardening if you have unfavorable soils. These gardens can be very productive for vegetables. See OSU fact sheet “Raised Bed Gardening” for more information.