Essential Elements

• For successful growth, plants need 18 essential elements. Without these elements, plants will become nutrient deficient and will not grow to their full extent. The primary nutrients needed in large amounts are nitrogen, phosphorus and potassium. Secondary nutrients include calcium, sulphur and magnesium and most soils naturally have sufficient quantities of these. While most fertilizers contain various quantities of the primary elements, the secondary elements are included with other garden materials such as irrigation water or fungicides.
  
  

Chemical Fertilizers

• Chemical fertilizers contain various inorganic salts that are readily soluble and quickly absorbed by plants. A fertilizer is complete when it contains nitrogen, phosphorus and potassium. The labels on fertilizer containers show the amounts of these nutrients. Commonly used fertilizers are 10-10-10 and 20-10-5, which identify the percentages of nitrogen, phosphorus and potassium respectively. Special purpose fertilizers are available for particular plants, such as tomatoes or roses. Slow-release fertilizers provide a constant flow of nutrients to the plants, which they can absorb continuously,
  
  

Organic Fertilizers

• Organic fertilizers come from natural products, specifically the remains or by-products of a once-living organism. Cottonseed meal, blood meal and all manures are organic fertilizers. As natural products, organic fertilizers have a variable and lower nutrient composition than chemical fertilizers and some will be strong in only one primary essential element. Organisms in the soil break down the nutrients in organic fertilizer, which the soil releases over time and in unpredictable amounts. These organisms need a warm and moist environment in which to work.
  
  

Applying Fertilizer

• Fertilizing the soil provides an optimal environment in which plants will grow. An annual application of organic matter will help to maintain the soil's structure and the health of its organisms. A light application of fertilizer at the start of the growing season will prepare the soil for the months to come by balancing the nutrients. During the growing season, application of fertilizers specific to the plants in the garden and their growth stages will ensure a successful growing season. Knowing the pH and the nutrient make-up of your soil will help you select the right fertilizers.