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Posted on Mon, Mar 29, 2010 : 2 p.m.

If you fertilize, don't use phosphorus fertilizer ...

By Matthew Naud


Be the hero with a zero

Take care of the river when you take care of your lawn this summer. If you fertilize this spring, summer, or fall, don't use phosphorus fertilizer. It's that simple. Your local lawn professional or local home and garden shop can provide you with no phosphorus solutions to your lawn care needs.


The city is under a federal mandate to reduce phosphorus levels in the Huron River by 50 percent in order to meet water quality standards. Cutting back on the unnecessary and even harmful applications of phosphorus-containing lawn fertilizer is an effective way to meet that federal requirement.

The practical reason to not use phosphorus fertilizer is that most soils in Ann Arbor have plenty of phosphorus to grow grass. We looked at about 1,000 soil samples and the turf experts at MSU said 85% of the samples don’t need any more phosphorus to grow grass. The runoff from residential fertilizer is the primary source of phosphorous entering the Huron River. By limiting the unnecessary application of phosphorus to lawns by residents and commercial applicators, the city can reduce the amount of phosphorus in the river.

The scientific reason is that we have seen levels of phosphorus in the Huron River drop for the past two years. These are measurable and statistically significant changes. Visit for more information on the scientific studies showing phosphorus level drops.

The legal reason is that the City of Ann Arbor enacted an ordinance to reduce the amount of phosphorus used in manufactured lawn fertilizers, effective January 2007. You are not allowed to apply fertilizer with phosphorus unless you have a soil test that demonstrates that you need it.

Visit the city phosphorus website for links to the manufactured fertilizer ordinance and other information on phosphorus in our watershed.

Matthew Naud is the Environmental Coordinator for the city of Ann Arbor. He is a contributor to the Your World column. Visit for more information on environmental issues in the city. He can be reached at


Keith A. Paul

Fri, Apr 22, 2011 : 4:35 p.m.

Thanks for bringing this to my attention that in the City of Ann Arbor is under a mandate to reduce phosphorus loading to the Huron River in order to meet water quality standards. It is important to choose fertilizers that are in accordance to local ordnance. There are always the Green options listed here by our readers or on the Washtenaw County website. find more info here. <a href=""></a> <a href=""></a>

Matthew Naud

Tue, Mar 30, 2010 : 12:23 p.m.

While it may not appear that most of us live right on the creek or river, as soon as a drop of water leaves your lawn and hits the street, it is on a one-way trip to the nearest creek or river with no treatment in between. So any extra fertilizer gets carried along with it to the river. That goes for pet waste too but that is for another story.

Adam Jaskiewicz

Tue, Mar 30, 2010 : 11:09 a.m.

Test test test! Why would you add chemicals to your lawn or garden without knowing how much of what chemicals it needs? That's like salting food without tasting it first.

Matthew Naud

Tue, Mar 30, 2010 : 8:55 a.m.

Apologies to PittfieldTwp (the commenter, not the township which also limits phosphorus in fertilizer) if I missed the point. Thanks for clarifying the nitrogen issue - it is a very important point. We too have wondered about seeing an increase in nitrogen Your comment is important and brings out another key point. Although we are focusing on phosphorus to meet a federal requirement, the mix of nutrients that go onto our lawns can wreak havoc on watersheds when used in amounts that the system cannot handle. Folks should err on the side of not fertilizing, but, if you do, get good advice based on a soil test before just buying a bag and tossing it on. If you need compost for your gardens, visit the city compost site - - for pricing and tests. The city's cured, screened compost is tested and certified three times/year by the U.S. Composting Council.


Tue, Mar 30, 2010 : 7:22 a.m.

Mathew, There is probably enough phosphorus AND enough nitrogen in Washtenaw soil to "grow" a lawn without adding anything. The issue I was highlighting is the new blended fertilizers will add extra nitro to grass and not appropriate extra phosphorus to the grass to balance the growth. Below is an excerpt from MSU's turf care department (considered experts) regarding this issue. They also back up much of your phosphorus concern about water supply: "Phosphorus ordinances may result in confusion for homeowners...Often the only fertilizers available that satisfy the zero phosphorus requirement, are fast-release nitrogen fertilizers such as urea (46-0-0). Such fertilizers can be very effective when used properly. For homeowners, however, these products may not be the best choice....Another potential problem with applying fast-release fertilizers is that they produce excessive amounts of top growth, often at the expense of root growth. Fast-release fertilizers also have the potential for burning turfgrass when applied at high rates or at high temperatures, or when they are not watered in. For most homeowners, using fastrelease nitrogen fertilizers for lawn fertilization is not recommended."

Matthew Naud

Tue, Mar 30, 2010 : 6:28 a.m.

If you have old fertilizer - - the County Home Toxics web page is a great resource - Beginning in April 2010, the Home Toxics Collection Center will be OPEN the first three Saturdays of each month (excluding holiday weekends) from 9am - Noon. The Huron River Watershed Council has links to local places to get your soil tested here - Regarding what professionals say - here is a link to lawn care from Downtown Home and Garden - I looked at a few other local websites but I would pick one and talk to someone there. There is P free fertilizer on the Ace website. The English Garden website didn't say much about fertilizer.


Mon, Mar 29, 2010 : 10:22 p.m.

Chemicals baby...that's what gets it nice and green.


Mon, Mar 29, 2010 : 6:21 p.m.

1. What should I do with any bags I have of old fertilizers? 2. What are professionals suggesting as alternatives?

Matthew Naud

Mon, Mar 29, 2010 : 4:56 p.m.

We agree that folks should only put down fertilizer with amendments that their lawns absolutely need and we think organic is a good thing too. Please remember that our goal was to significantly limit phosphorus runoff to the river, so a no phosphorus fertilizer is what meets that goal. There are a lot of good no phosphorus choices out there. Thanks to residents, we are seeing significant drops in phosphorus in the urban creeks and river. To my knowledge, we are not seeing an increase in nitrogen. The previous comment suggests that you should buy a balanced fertilizer because you..."may not have the appropriate amount of phosphorus". Based on the science, anyone fertilizing existing turf in Washtenaw County can assume there is plenty of phosphorus to grow grass, and if anyone is unsure, they should head to the local home and garden store and have the soil tested so you only put on what you really need.


Mon, Mar 29, 2010 : 2:32 p.m.

Most of the local big box home centers now sell lopsided fertilizers (nitro, but no phosphorus.) Its easy to tell by looking at the three numbers: the first number is Nitrogen, second is phosphates or phosphorus, the third is potassium. So when you buy a bag that is labeled 24-0-2, its phosphorus free. Here's the problem...a balanced lawn needs all three in modest amounts. If you buy a heavy nitro fertilizer, the grass will be green with heavy sudden growth, but it may not have the appropriate amount of phosphorus for root and stem development to back the extra green growth. A better suggestion? Go with organic options like soybean meal, corn meal, etc. Its the equivalent of giving your lawn a "meal" instead of a high sugar snack. It lasts longer, feeds slower, and the decomposition process of soybean meal also helps get rid of thatch and clipping build up.