Saturday, September 14, 2013

Saturday Short Subjects: Removing the “P” from N-P-K

The days are getting shorter and the nights cooler. 

Lawn lovers know that this is their last opportunity to seed and feed their prized bit of turf in anticipation of lush green grass in springtime. 

Everyone who buys fertilizer has seen the ratios printed on the bag or box, numbers like 10-10-10 or 6-6-18. But not everyone knows what they mean. These numbers represent the percentage of three primary nutrients contained in the box or bag of mixed fertilizer. The first represents the amount of Nitrogen (N), the second the amount of Phosphorus (P), and the third the amount of Potassium (K). For more on this subject, check out “A Homeowner’s Guide to Fertilizer,” prepared by the North Carolina Department of Agriculture. 

Each nutrient has a different purpose. Nitrogen promotes green leafy growth, phosphorous is essential for establishing strong roots and flowers, and potassium helps regulate water movement within the plant and increases the plant’s ability to withstand stress.

A soil test is the best way to determine the levels of these essential nutrients your soil contains. Many universities, including UMass and U Conn offer this service for a small fee, even if you live out of state (unless your county is subject to a quarantine for fire ants or golden nematodes). 

Your test results will indicate whether your soil is below, at, or above optimum level for these nutrients. The lab will also make recommendations about how to reach optimum levels for nutrients you may be lacking. You do NOT want to add a nutrient you already have in excess, phosphorus in particular.

A new law regulating the use of phosphorus on established lawns went into effect in Connecticut on January 1, 2013. This legislation prohibits the application of lawn fertilizers containing phosphorus on established lawns unless a soil test, done within the last two years, indicates a phosphorus deficiency and recommends that phosphorus be applied. The No Phosphorus legislation enacted by Illinois, Maine, Maryland, Michigan, New Jersey, New York, Vermont, Virginia, Washington, and Wisconsin served as models for Connecticut’s law. The law is posted here. A summary provided by the UConn Soil Nutrient Analysis Laboratory is posted here

Why is phosphorus such a problem? Phosphorus is the leading cause of declining water quality in freshwater lakes and ponds. The addition of even small amounts of phosphorus stimulates the growth of algae and other water plants. As the lush plant growth dies and decomposes, oxygen levels in the water are reduced, resulting in fish kills. The phosphorus entering the water supply comes primarily from three sources: wastewater treatment plants, failing septic systems, and fertilizer runoff. 

In May, 2013, Scott’s announced that it had “successfully removed phosphorus from all its Turf-Builder products,” creating a product for lawns needing both nitrogen and potassium. There are other alternatives if you require only one nutrient. For example, greensand (0-0-3) can be applied to supply potassium, and bloodmeal (12-0-0) can be used to supply nitrogen.

It is important for each home gardener to be aware of this problem, to abide by the new law, and to dispose of any now unwanted fertilizer in a responsible manner. Take any lawn fertilizers or chemicals you do not plan to use to your local hazardous waste collection facility for proper disposal. 

If you live in New Haven County you should take them to HazWaste Central, open on Saturday mornings from 9 to noon through October 26 this year.

Remember, in most cases you want “-0-” in the middle.

Why Saturday Short Subjects? Some readers may recall being dropped at the movie theater for the Saturday matinee — two action-packed feature films with a series of short subjects (cartoons or short movies, sometimes a serial cliffhanger) sandwiched in between. Often the short subjects were the most memorable, and enjoyable, part of the morning. That explains the name. The reason behind these particular posts is that we are all short on time. My Short Subject posts should not take me as long to write or you as long to read (or try).

No comments:

Post a Comment