In 2007, when the price of fertilizers went through the roof, fertilizer manufacturers sought a way to maintain profits in a way that did not cause sticker shock to consumers. They did this by totally removing phosphorus and drastically reducing the amount of potassium. Removing phosphorus was good because most soils in Michiana naturally contain enough for lawns, as well as being the responsible environmental thing to do. Reduced amounts of potassium in fertilizers kept profits up for manufacturers, but has resulted in lawns that range from looking okay at times to lawns having poor color, poor draught tolerance, poor disease resistance, slow recovery from insect damage, and poor spring green up.
Nitrogen, the first number on a bag of fertilizer gets the most attention, because it is the most abundant ingredient and has the quickest, most noticeable response. Phosphorus is the second number on a bag and is a “0” most often. Potassium, the last number, is the silent workhorse in a grass plant. Just as good assistants make the boss look good, soils with enough potassium make a lawn look good.
Experts say the amount of potassium that should be applied varies between one third and one half of the amount of nitrogen depending on soil type. This means the last number on a bag should be between one third and one half of the first number. If the first number is about 30, then the last number should be between 10 and 15. If you look at a bag of the most common, popular fertilizers, the last number is around 3, which means the fertilizer contains only about one third of what the plant needs! Is it any wonder that some lawns look worse and worse each year as the turf uses up the potassium in the soil?
What can you do? If you are really fussy about your lawn, have your soil tested to determine potassium levels. Send it off to a lab because quick strip tests are not accurate. Red Hen Turf Farm will send a soil testing kit to you upon request. If the results show low potassium levels, a supplement fertilizer, 0-0-60, can be added to raise levels. Then make changes in your yearly program by either changing brands or regularly adding the supplement. Read this article to learn How to Evaluate A Fertilizer Program.
If you like your current fertilizer but it needs more potassium, you can apply a supplement. 0-0-60 fertilizer can usually be bought at garden stores or Red Hen and should be applied spring and fall in addition to your other fertilizer at the rate of 1 lb. per thousand sq. ft.
If you don’t want the work of making extra applications, you can buy fertilizer that has the recommended amount of potassium. It is unlikely it will be a popular brand at a box store. You can try your local garden center or come to Red Hen Turf Farm. Our fertilizer programs are specially designed to meet the potassium needs of turfgrass.
For more details about potassium and fertilizing, see our links section and Google “potassium for turfgrass.” Look for articles that discuss the grass species you have, as they will be more appropriate.