Just like people, plants have a few basic requirements in order to thrive. Along with fresh air, sunlight and water, plants need fertilizers. The air supplies oxygen, hydrogen, and carbon. Everything else comes from the soil. Fertilizers are any material that provides any of the nutrients plants use as food. Just like us, they need a variety of foods. When nature is allowed to follow its own course, plants will only grow where nutrients are available. We want plants to grow where we want them to grow; thus we apply additional fertilizer to the soil.

How do I know if my soil needs any fertilizer and how much to add?
To get an accurate evaluation of the nutritional needs of your soil, you will need to have a sample analyzed. The University of Minnesota provides this service. Bachman's Garden Centers have the form and bags for taking soil samples. Soil testing costs around $15, and takes about 10 days. Once you have gardened for a while, you will begin to see signs your plants are hungry. Sometimes the same symptom may mean very different things. Soil samples every few years can be extremely helpful and remove a lot of the guesswork.

What is the most common mistake in fertilizing?
Over fertilizing is the most common mistake made by beginners and experienced gardeners. Just because a little is good, does not mean more is better. It is much better to err by giving a plant too little than too much.

Every package of fertilizer gives three numbers, such as 10-20-10. What exactly do these numbers mean?
These numbers indicate how much nitrogen (N), phosphorus (P) and potassium (K) is in the fertilizer. The numbers are percentages of the total package and are always listed in the same order, N-P-K. A package labeled 10-20-10 will contain 10% nitrogen, 20% phosphorus and 10% potassium by weight.

10-20-10 only adds up to 40%. What else is in there?
Nitrogen, phosphorus and potassium are all joined to at least one other element to form a molecule. Synthetic (non-organic) fertilizers are then mixed with a substance that makes it easier to spread. These substances are listed on the label as inert ingredients.

What is meant by macro-nutrients and micro-nutrients?
Primary nutrients, such as nitrogen, phosphorus, potassium, sulfur, calcium and magnesium are called macro-nutrients. Nutrients needed in much smaller amounts (such as iron, manganese, zinc, chlorine, boron, copper, nickel and molybdenum) are called micro-nutrients. Even though a plant needs less of a micro-nutrient, it doesn't mean that ingredient is less important to the health of that plant.

What are the pros and cons of inorganic fertilizer?
Inorganic fertilizers (also called non-organic and synthetic) are made up of nutrients obtained from non-living sources. They are available in higher concentrations and their nutrients are readily available to the plants. They are inexpensive but it is very easy to use too much.

What are the pluses and minuses of organic fertilizer?
Natural sources of nutrients, usually derived from living things, are referred to as organic fertilizers. Organics are slowly released and have low levels of nutrition. Organics also improve the soil's structure and ability to hold nutrients. Organic fertilizers tend to be more expensive than inorganic. It is more difficult to over use organic fertilizer.

How do I determine which organic fertilizers to use?
There does seem to be a lot to choose from, but they fall into basic groupings that make it easier. Manures and composts are good sources of organic matter and nutrients. Pulverized rocks, such as limestone or rock phosphate, are good sources of minerals but are slow to break down and become useful to the plants. Dried blood, bone meal and fish meal/emulsion are all good sources of nutrients. Please remember to check the N-P-K, as they all differ.

How is a soil amendment different than an organic fertilizer?
To be a fertilizer, the material needs to contain significant amounts of the nutrients needed by plants (such as N-P-K). Soil amendments are materials that improve the soil in some way (structure, drainage, microbes) but don't contain much nutrition. Compost and peat moss are both soil amendments. Manure, bone meal and blood meal are examples of fertilizers. Both are important to the soil and many fertilizers are also soil amendments.

Is it less expensive to use organic or inorganic fertilizer?
Organic fertilizers are more expensive to use than the inorganics, but organics have the added value of improving the soil. They are also much less likely to damage the plants.

Are dry or liquid fertilizers best?
These vary quite a bit. A dry granular fertilizer is usually the least expensive and easiest to spread over a large area. Liquid and water-soluble fertilizers are more quickly absorbed, about the same price, but take more time to apply.

What is meant by slow-release?
Fertilizer granules can be coated with something that releases the nutrients slowly over a period of weeks or months, depending on the coating. These slow-release fertilizers are very useful in indoor plants and containers, but may be too expensive for general use.

Are fertilizer spikes slow release?
Spikes release their nutrients slowly. Because they are so hard, it takes them that long to dissolve. During wet weather, they dissolve much more quickly.

What do they mean by pH, and is it important?
pH is a measurement that tells you about the soil's acidity level. It can greatly affect your plant's ability to make use of the nutrients in the soil. A neutral pH is 7.0.
Measurements below 7.0 are considered acid, and those above 7.0 are called alkaline. Most garden plants grow best when the soil is slightly acid to neutral (6.0-7.0). Very few plants require acid or alkaline soil. It is important to check the pH every year or two and make the necessary adjustment. Bachman's has an information sheet available on soil pH.

Recommended Products
Bachman's Branded Fertilizers
Bachman's Excel Gro™ and Mighty Bloom™
Drop and Rotary Spreaders
Osmocote™ Slow Release Fertilizer
Fish Emulsion and Kelp Extract

Additional Bachman's Information
Fertilizing Annuals and Perennials
Fertilizing Trees and Shrubs
Fertilizing the Lawn
Plants for Acid and Alkaline Soils

© Bachman's 2007