Understanding Lawn Fertilizer and Fertilization - LawnPro


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Understanding Lawn Fertilizer and Fertilization

July 26, 2022

Beautiful lawns do not happen naturally but have to be planned and created. Lawn fertilizer is one of the most important parts of the creation process. The purpose and variety of fertilizers available can be overwhelming. In order to find the right fertilizer for your yard, you need to understand the ingredients of the products you are buying.

Choosing the right fertilizer begins by knowing what nutrients are currently in your soil, as determined by a soil test. Soil nutrients, whether placed there by you or occur naturally, work together to help grass perform one primary purpose: performing photosynthesis. Lawns that are not fertilized will have to rely completely on what is in the soil for all their nutrients. 


Lawn grasses need several micronutrients and macronutrients to stay healthy and to perform necessary plant functions. The list of micronutrients includes Boron (B), Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo), Nickel (Ni and Zinc (Zn). Most of the micronutrients, with the exception of iron, are usually not included in a bag of lawn fertilizer. The primary macronutrients are Nitrogen (N), Phosphorus (P), and Potassium (K) and represent the most commonly used ingredients in lawn fertilizer. Each nutrient plays a specific role in overall plant health: Nitrogen (N) promotes green, leafy growth. Phosphorus (P) is important for strong roots and healthy fruit and seed formation. Potassium (K) promotes vigorous growth, hardiness, heat tolerance, and disease resistance. These three nutrients are very important for plant function and are the elements most deficient in soils.


What do N, P, and K mean? What do the numbers on the bag mean? The three numbers on a fertilizer bag represent the three primary macronutrients, which are Nitrogen, Phosphorus, and Potassium, in that order. These 3 numbers on the bag represent the nutrients grass needs in the greatest amounts. More specifically, the numbers on the bag represent the percentage by weight that the bag contains each element. For example, if the bag weighs 25 lbs and the first number on the bag (Nitrogen) is 10, then the bag contains 2.5 lbs of Nitrogen. If the bag weighs 30 lbs and the first number is 20, then the bag would contain 6 lbs of Nitrogen.


Synthetic fertilizers are the most often used type and come in liquid and granular forms. Granular fertilizers are the easiest to apply and require the least expensive equipment.

Liquid Fertilizer: Liquid lawn fertilizer may require special equipment to apply. For small lawns, you can use a handheld sprayer or backpack sprayer. For larger lawns, you can purchase 10 or 20 gallon sprayers at your local farm and home store. For the most part, both liquid and dry fertilizer perform equally well.

All Mineral vs Slow Release Lawn Fertilizer: Some fertilizers are referred to as “all mineral”, which means all elements are released quickly as soon as water is applied. All mineral lawn fertilizers are usually the least expensive but often contain no instructions for storage or safe use nor any information on how much to apply. Due to the high salt content, they must be used carefully and watered in thoroughly after use to prevent any possible burning of the grass.

Slow Release Nitrogen: More expensive fertilizers will contain higher quality ingredients and often more than one form of available nitrogen. Usually, at least one form of nitrogen in the bag will be slow release. By blending different ingredients with different release rates, they can be marketed as “spring”, “summer”, and “fall” or “winterizer” fertilizers.


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