Questions and Answers: Soil and Fertilizer

• What is the best type of fertilizer?

  This depends entirely on the type of plant and the circumstances. The numbers on the bag (6-6-6, 10-10-10, 16-4-8, etc) represent the percent of nitrogen, phosphorous, and potash in the product. It is also recommended that the fertilizer also contain trace or micro-nutrients such as iron, manganese, sulfur, etc. These nutrients are listed on the label as secondary plant nutrients. For a "long lasting" fertilizer, select one that contains "slow-release" nutrients.

• What is the best fertilizer for spring garden plants?

  A 10-10-10 or a 5-10-5 for most spring annuals and vegetables.

• What does "100% Organic" mean?

  When the term "organic" is used on a fertilize label, it means that all or part of the nitrogen is in an organic form. This form must be identified as synthetic-organic and/or natural-organic, and the respective percentage or each must be specified (for example:70% synthetic, 30% natural). Synthetic organics are organic compounds which are chemically synthesized such as Urea Nitrogen. Synthetic organic nitrogen is identified in the guaranteed analysis as Water Soluble organic nitrogen and/or Urea Nitrogen. Natural organic nitrogen comes from natural sources such as manure, seed meal, sludge, dried blood, etc. The percent of natural organic material is listed under Water Insoluble Nitrogen. Recently, many forms of water insoluble nitrogen have been developed (sulfur-coated urea, ureaformaldehyde, Isobutylidine dilurea-IBDU, etc.). These sources act like natural forms in that the nitrogen is slowly released.

• How do I know what type of soil I have?

  Pick up a handful of moist garden soil and squeeze it. If it sticks together like cookie dough it is probably clay. If it doesn't hold together in a ball and it feels gritty, it is probably sandy soil. If it holds together in a ball but crumbles if tapped lightly it is loamy soil. Or you can bring a sample to the local Master Gardeners' Office.

• What is pH?

  pH is a measure of soil acidity (sourness) or soil alkalinity (sweetness). pH is expressed by a number on a scale from 014. A neutral reading is 7. Any reading below 7 represents an acid soil and the lower the number the more acidic the soil. Any number above 7 indicates an alkaline condition and alkalinity increases as the number on the scale increases.

• What is the best pH and why is it important?

  Optimum pH will vary from plant to plant, but a pH between 5.0 7.0 is generally accepted as the best range for most plants. The pH of the soil governs what nutrients are available to plants. If the soil pH is above or below the recommended range (5.5 - 7.0), nutrients may not be soluble (absorbable by plants) or they may be so soluble that they become phytotoxic. Therefore, a plant can show signs of nutrient deficiencies or toxicity even when the correct amount of fertilizer is applied to that plant.

• When should Lime be used?

  Lime is added to soil when a soil test determines that the soil pH is too acid. Lime reacts with water and releases calcium which neutralizes the acidity of the soil, thus raising the pH of the soil.

• Are Dolomite and Lime the same thing?

  Dolomite is a type of lime: There are various forms of lime used to increase soil pH. Standard lime contains calcium. Dolomitic lime contains calcium and magnesium. Whenever lime is recommended, dolomite is suggested since it will adjust the soil pH and also add magnesium which is usually deficient in Florida's sandy soil.

• My soil is too alkaline (sweet or basic). How can I lower the pH?

  Alkaline soils are a result of natural soil characteristics or excessive applications of lime. The pH of over-limed soils can be lowered by adding sulfur, iron sulfate, aluminum sulfate, or ammonium sulfate. Naturally alkaline or calcareous soils are common in coastal counties. It is difficult, if not impossible to lower the pH of these soils. Nutrient deficiencies in plants growing on calcareous soils should be treated by nutrient foliar sprays.

• How do I take a soil sample correctly?

  Using a trowel or shovel, dig a V-shaped hole in the soil four to six inches deep. Remove the entire soil wedge. Collect similar "wedges" from several spots in the area you wish to plant. Mix all the individual "wedges" together. One pint of this mixed sample is sufficient for testing purposes. The sample should be free of all plant debris and rocks. It is also very important for the soil to be completely dry.

• What is the best pH value for most spring garden plants?

  Between 6 and 7. Most garden plants prefer a slightly acidic soil.

• My soil test pH 4. What does this mean?

  A pH of 4 means your soil is very acidic. It is unsuitable for most gardening. Add lime to raise the pH. The amount added depends on what you want to grow there because some plants like a slightly acid soil and some do not.

• I have recently moved to a new home with an established yard. When should I fertilize?

  Your plants will benefit from two feedings per year, one in March and another in September. Remember that fertilizing equals more branches, more stems, more leaves, more roots, therefore, more maintenance cost, more cutting, more clipping and more pruning. If you are happy with the size and appearance of your plants, why encourage it to change?

• I have heavy clay soil. Will just adding sand improve it enough so I can have a garden?

  This might work in small areas, however, adding organic material would be much more beneficial.

• What makes some hydrangeas blue and some pink?

  The acidity of the soil causes the color difference. Blue is produced by acid, and pink by lime. Aluminum sulfate for blue and lime for pink.