Fertilizer

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Importance of fertilizers

Fertilizers can do wonders for lawns and gardens, but can also pollute our water supplies.

Types of fertilizers

Fertilizers generally come in two varieties: chemical (also known as mineral) and organic. Chemical fertilizers are made from minerals or synthetic substances. Organic fertilizers come from decayed plant or animal material.

Chemical fertilizers

Most chemical fertilizers supply the elements nitrogen, phosphorus and potassium. Other chemical fertilizers supply other nutrients, such as sulfur.

What does 30-3-15 on a bag of fertilizer mean?

Those numbers on the bag represent the percentages (by weight) of nitrogen (in this case, 30%), phosphorus (3%) and potassium (15%) contained in the fertilizer. Thus, a one hundred pound bag of 30-3-15 fertilizer contains 30 pounds of nitrogen, 3 pounds of phosphorus and 15 pounds of potassium.

Nitrogen

Nitrogen is an essential nutrient for plant growth. Because nitrogen makes grass green, it is often used in excess of what the grass needs. Nitrogen not used by plants can leach through the soil into the groundwater, threatening drinking water supplies, or it may run off into surface water.

Do not apply more that one pound of nitrogen to 1,000 square feet of lawn for each application.

Phosphorus

Phosphorus is important for root and seed development, and for maturation of your turf. It is, however, a primary water quality concern in Michigan. Excess fertilizer on lawns, sidewalks and driveways can make its way to lakes and streams by storm sewers or over land when it rains. As phosphorus adheres to soil particles, erosion can carry it directly into area surface waters. This can cause nuisance aquatic weed growth and algae blooms, effectively choking area waters.

Please do no apply phosphorus on lawns adjacent to lakes, rivers, streams or wetlands. One pound of phosphorus can support about 750 pounds of algae.

Potassium

Potassium is important for rooting and turf resistance to wear and climatic stress. It is usually applied in a range from one-half to the full rate of nitrogen for each application and does not generally cause water quality concerns.

Other mineral fertilizers

Other types of mineral fertilizers provide other nutrients. Gypsum, for example, provides sulfur.

Organic fertilizers

Organic fertilizers are made from various plant and animal substances, such as manure, compost, sewage water and packing house waste. These fertilizers usually contain a smaller percentage of nutrients than do mineral fertilizers. Thus, they generally pose less of a threat to water than do mineral fertilizers.

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Last modified: March 02, 2005