Does chemical fertilizer cause lawn thatch?

[Bob_Skurka]

I have often heard from the organic gardeners that Scott's Fertilizer, K-Gro, and all similar chemical based fertilizers are the CAUSE of thatch build up in lawns.

The general discussion seems to be that the chemicals keep the grass roots very close to the surface, so the roots don't dig deep into the earth. It causes a thatch build up at surface level, further a secondary issue is it makes the lawn prone to drying out during drought periods because the roots can't reach deep enough to find moisture. I had Chemlawn at my office but cancelled them this year because it seemed to cause more harm than good, didn't kill the weeds, and the lawn basically looked bad. So I am not convinced that chemicals are actually good, but I am not sure that the organics are any better.

My dad used to fertilize regularily and he did have thatch problems. I occasionally use a light dose of weed and feed, and sometimes use natural products to supress weeds or as fertilizer, but I often skip a year. My yard is a mixture of clover, grass and weeds, but I don't have any thatch build ups. I am seriously considering a full organic approach to attack the weeds and to build the grass strength.

BUT, the organic methods cost considerably more than the chemicals. Until you factor in a lawn de-thacther for the tractor, the price of one of those units will easily pay for a half a pallet of organic fertilizers and weed supressors.

My question is does anyone have any PROOF that the chemcial fertilizers cause thatch?


PS. We did have a dog almost die from chemical fertilizers and that is bascially why I am biased away from them. Our vet said she sees cases of chemical fertilizers poisoning & sometimes killing pets every year.

 

[beenthere]

Never thought about it as much as you have, but I thought thatch was cut-off 'grass', and fertilizer made the grass grow more, therefore there would naturally be more thatch. Also thought thatch to some extent kept the moisture in the soil (but too much thick thatch kept new grass from sprouting).

What are the 'natural products' you speak of that supress weeds and sometimes fertilize?

I lightly fertilize to keep healthy grass, and I use a light herbicide in Spring and Fall to keep down the clover and the weeds, such as dandelion and thistle and creeping charlie. There are others that get hit too.

I don't have any dogs other than the neighbors' that think my lawn is theres to fertilize (I'd chemical fertilize more if I really thought it would keep them off my lawn /forums/images/graemlins/grin.gif ). I don't understand people who let their dogs run on someone else's property, but then I don't profess to understand people sometimes (they are nice people!). I don't care for the dog manure smell on my lawn tractor tires. Really disgusting smell. /forums/images/graemlins/tongue.gif

I am intrigued by your question, and maybe others have some good answers. /forums/images/graemlins/wink.gif

 

[Bob_Skurka]

It is my understanding (been told by a couple different horticulturalists locally - our library has a "master gardener" series) that THATCH is actually the build up of a grass root mat, not dead grass clippings. The mass of grass roots, close to the soil surface effectively chokes everything, including continued growth of grass itself. The thought it you want the roots to go DOWN into the soil, not sit on top. Deep roots help in extreme heat and draught periods.

Again, the arguement seems to be that the chemicals artificially keep the roots at the surface, which is why the thatch seems to develop. I do know that I have virutally no thatch compared to what my dad had. That could be from my simple neglect of the yard other than regular mowing???

As for the natural items to prevent weed growth, they are all corn based products and when used spring and fall are SUPPOSED to dramatically reduce perennial and annual weed sprouting. I've occasionaly used these products, but never enough to do much good. I've also occasionally used chemical based (ortho, etc) products, but again, never really enough to call it regular use.

The one company I have dealt with is Garden's Alive. They have an all natural weed inhibitor called WOW and another called WOW Plus (natural weed & feed) that can be spread using a broadcast spreader.

What I have figured out is that Chemlawn doesn't automatically equal a healthy lawn, and in some cases seems to do a good job of destrying the lawn.

 

[bigpete]

Yes, yes, yes...and not necessarily... there's no simple answer.

Thatch is comprised primarily of dead grass leaves still attached to the grass plant, as well as other dead plant matter that is not shed by the plant. Grass clippings are good for your soil, but may not decompose at a proper rate if your thatch is too thick.

A healthy lawn will retain a light layer of thatch which is critical to retaining moisture and preventing weed seed germination. Grass varieties will present different thatch conditions for different growing cycles throughout the season.

For example, I have primarily tall fecsue on my fair-sized acerage. Tall fescue will not typically develop an unhealthy/too-thick layer of thatch under normal growing conditions throughout the year. However, this year, we have had three phases of near-full dormancy each caused by a three-week drought period. Each drought period was ended with two to three weeks of very high rain amounts. When the grass would go dormant, the top of the plant and most of the leaves would essentially wither and die while the plant roots and root crown went dormant. When the rains came, new leaves would grow and the dead leaf material would mat around the plants and soil between plants, still attached to the root crown. The bottom line is that I had to dethatch this fall even though fescue should not present a thatch problem under normal condition. I fertilized very lightly with slow-release chemical fertilizer on March 21 of this year and nothing else.

Any time a grass plant grows rapidly, then slows or goes dormant, thatch will be the result. Most grass varieties go through several cycles each year, and some varieties continually create thatch naturally with steady growth (Kentucky Blue Grass, for example). Most organic fertilizers feed more slowly and promote a slower growth cycle, which equals a more natural and manageable layer of thatch on the lawn. The real culprit is overfeeding with chemical fertilizers which unnaturally accelerates the growth cycles so the plant lays down dead leaves continuously to make way for the nitrogen inspired new growth..

I'm not an expert but seek out all kinds of advice on these topics from my local Ag Extension office rather than commercial operators. My plan includes chemical fertilizers but they are timed properly and balanced across the N-P-K ratios. In addition, the recent trend among horticulturalists is to advise the majoriity of feeding to occur in the fall and late fall seasons as grasses are processing and storing nutirents for winter survival and root growth. Because organics are slower feeding, timing is less critical.

My advice is to get a soil analysis done at your local Ag extension office and create a balanced program that you can live with economically and aesthetically. Anybody who points at one single thing as a fix-it-all doesn't really understand the science and might be trying to sell you something. I considered going organic, starting with a compost application and feeding with alfalfa and corn gluten meal, which also has some pre-emergent weed control charateristics. Unfortunately, I would have had to have sold my tractor to continue the plan for more than a couple of years. /forums/images/graemlins/shocked.gif

 

[Bob_Skurka]

Pete, thanks that really made some sense out of all the different things I've been hearing.

The price of using organic fertilizers seems to be close to the price of chemical fertilizers at the Home Depot (Malorganite versus Scotts) but the only weed inhibitors I can find that are organic are in the $45 per bag range and while that is affordable for a small suburban lawn it would be pretty darn expensive for a couple acre front lawn.

Weed inhibitors/killers that are chemical based, on the other hand, scare me because I almost lost one of my dogs (a 117# Akita) to a single dose of weed & feed. So, at least from the perspective of loving my dogs and not wanting to pay massive vet bills, the $45 per bag cost of a natural weed inhibitor sounds pretty reasonable.

I never understood why chemical fertilizers "caused" thatch, but your explination seems to be very logical.

 

[bigpete]

Bob, it is complicated, indeed. I have resigned myself to what I feel is a fairly responsible program that has a little of both the "chem" and "organic" worlds. I feel a chemical pre-emergent in the early spring with a light to medium feeding (most pre-emergents are carried with a modest N-P-K fertilizer) gets me through spring and summer with a reasonably attractive and healthy lawn. I will spot spray weeds with hand tank or two of a 2-4D mix in late June and the pre-emergent does a good job of keeping most of the crab grass out. For the last two years I have shopped a pretty good price on alfalfa pellets in late June or July, which makes a good slow feed for the hot months. I core aerate and de-thatch as need in September and October and apply two modest to medium level chem feedings in the fall. Another important factor that I would recommend to anybody who doesn't mind the little extra work is to use a good mulching kit on their deck. I have to clean it out more than most, but the finely mulched clippings feed the lawn more efficiently than normal grass clipping.

My father-in-law, who passed away early this year, farmed in southern Iowa from his youth in the Great Depression until the day he died. He always had a good sense for what it meant to return plant matter to the soil at the end of a growing season, and for the problems associated with trying to fix any imbalance with chemicals. He felt that most things fixed themselves over time and that it was the year after a particularly bad year, or the year after a paricularly good year, that he needed to pay close attention to what the soil might need or not need. He was reading about organic farming back before it had a national council, a logo, and federal funding. Maybe what he put into each of his best crop years was an application of common sense along with whatever trend the industry was trying to sell at the time. Sorry to wax sentimental....

Thought I'd also take the opportunity to show off my custom front-mount de-thatcher--pic attached. Front hydraulics and moldboard frame from my 54" snow blade. Two holes drilled in arms of JD 54" dethatcher for large JD garden tractors. Pivot points are bushings over bolts through existing holes in moldboard frame. /forums/images/graemlins/cool.gif

 

[Junkman]

Could you expand on the alfalfa pellets? I was told to put them down in late October / early November for feeding in the spring. I just purchased a bag and the local nursery said to use them for planting the mums. The dog likes them also, because I found her eating them out of the bag. A lot cheaper than dog food, but I don't think that it will sustain her for very long. /forums/images/graemlins/grin.gif

 

[bigpete]

Hey, Junkman. I have always been told that you can put down organic or feed-type fertilizers most any time except for the winter months when it would really just sit there until the warmth returned and the microbes start breaking down the vegetable matter. I know that we should not apply chemical fertilizers around here going into the hot months--late June, July and August. Grass plants apparently need to conserve energy during the heat, not spend it on growing new leaves. It's easy to burn up grass that way. Organics are fine for those months because they do not stimulate rapid growth the way chemical fertilizers do.

If you are going to use corn gluten meal as a pre-emergent, it should be applied a few weeks before weed and crabgrass seed begins to germinate.

The only other things I know about alfalfa are that it is processed into different sized pellets and sometimes processors add minerals and other supplements. The best size I have found are the smallest horse feed supplement pellet. The big horse pellets are 1"+ cubes and will never break down. Also, check the label to make certain that there are no salts or other minerals added. Small animal alfalfa pellets for guinea pigs, etc, often contain mineral supplements that your lawn doesn't need. In fact, salt is pretty bad for grass, as you know.

I've gotten into a few debates about the semantics of calling commercially bagged fertilizer "chemical" fertilizers. It is true that they do not add anything in the way of "organic materials," plant or protein matter, ot tilth into the soil. However, most bagged fertilizers are made up of urea, phosphorous, and potash which are simply concentrations of naturally occurring elements and minerals. Sometimes the granules are coated with a plastic film to slow the release of the nutrients. The true ecological problems come from too many residual and run-off nitrates which can occur with applying too many fertilizers of any type, including poultry, porcine, bovine, equine, or even canine dookie.

 

[Bob_Skurka]

<font color="red"> If you are going to use corn gluten meal as a pre-emergent, it should be applied a few weeks before weed and crabgrass seed begins to germinate.
</font>

Pete, I've been told the gluten products are best applied fall and spring and that 2 years of proper application yields substantial weed control. I'm thinking of buying about 20-25 bags of WOW+ (a weed & feed from Garden's Alive) but only if I can get a quantity discount. Do you know of other brands available and other sources?

 

[Junkman]

I found a place in Kentucky that sells it for $27.50 per 50 pound bag plus shipping. At that price, it puts it out of the question for me. I was recently reading about why many of the pre emergence products don't work successfully. The author stated that many are put down too late. When the daffodils start to break through the ground is when the first application should go down. I am going to try it next season to see if it helps. In the meantime, I will spread the alfalfa pellets and see if they do any good... can't hurt and it isn't very expensive...