What’s the big deal about core aeration?

Core Aeration is Great for the Lawn

Every fall we see a flurry of activity at the rental stores, with folks loading up core aerators. We see signs all over the place, especially those placed illegally at intersections, promoting, “Core Aeration Special–$40!” And we see the professional LCO’s running their machines on our neighbor’s lawns. So, what’s it all about, Alfie?

The vast majority of soils in St. Louis are considered to be “clay loams”. West and southwest communities have rocky clay loams! These soils are productive, but they are very fine in their texture. Our subsoils are often pure clay. Fine textured soils are considered to be “tight” in the agronomic world—which means limited water penetration/percolation and oxygen exchange. A tight soil restricts root growth, limiting absorption of water and nutrients. Roots need oxygen to grow and thrive. The more large pores, the more oxygen. The more large pores, the better the water percolation. The more large pores, the better the nutrient penetration. The more large pores, the better the root growth. The better the root growth, the healthier the plant. Healthy turf tolerates stress better and has fewer disease issues.

In addition to our tight clay loam soils, our lawn mowers and even regular foot traffic increases compaction! Areas where the kids play, or the dogs run, become heavily compacted. This further exacerbates the situation. As tough as it is to grow plants in our “regular clay loam soils,” grass trying to grow in compacted areas lack vigor, thins out, or flat out dies.

The smart folks in the crowd are wondering when I’m going to talk about how core aeration helps to decrease thatch. Am I right? Pat yourself on the back if you’ve wandered there. Indeed, another huge benefit of core aeration is that the soil plugs deposited upon the soil surface contains millions upon millions of beneficial microbes. Maybe billions, I’m not sure. As that soil core breaks down the microbes help to break down the thatch layer. The issue of thatch management is something deserving its own newsletter. But know that fescue lawns DON’T develop thatch. Grasses that spread laterally do so with rhizomes (below ground shoots) and stolons (above ground shoots), which are more resistant to decomposition than leaf tissue. Zoysiagrass is notorious for developing thick thatch layers. Bluegrass will also develop thatch. Up to 3/8-inch thatch is usually OK! More than ½ inch of thatch is not good. Thatch actually gets to a point that it repels water. If you have more than ½ inch of thatch you should consider renting a “dethatcher”, properly called a vertical rake. Don’t rely on the core aerator for thick thatch situations. Dethatch cool season lawns in September to October. Dethatch zoysiagrass in June or early July.

Jeez, I’m really rambling. The best way to increase water, nutrient and oxygen exchange, reduce compaction, decrease thatch, and increase root growth of turf is to core aerate. Sidebar here, folks:  it’s pronounced “AIR-ate”. Not “AIR-e-ate” (definitely hoosier!) A core aerator removes plugs of soil out of the ground, 3/8th inch to ½ inch in diameter. For the millennials in the crowd, the ones that NEVER helped their parents do chores (except occasionally vacuuming the crumbs off the couch in the basement) the soil plugs look like dog poop. Thousands upon thousands of dog turds! Maybe hundreds of thousands. Not chihuahua-sized, not retriever-sized, but more like Pomeranian-sized. You want those holes to be 1.5 inch to 3 inches deep. The deeper the better, but the deeper the plugs are pulled, the greater the risk of puncturing irrigation lines, piercing electric dog lines and for sure, the damn cable company lines! Call 1-800-DIG-RITE and give them a minimum of 3 days’ notice, but know that they prefer 10 days’ notice. Dig-Rite won’t mark electric dog fences—so call your vendor for that. For the dullards in the crowd, you shouldn’t waste your money aerating bone dry soil! I’ve seen neighbors pay good money to pull ½ inch to ¾ inch cores—what a waste of money!

Cores.jpg

If you’ve conducted a soil test in the past few years, it’s likely the results indicated a need for lime (calcium, to raise pH), magnesium (Mg), phosphorous (P) and potassium (K). The only nutrient in the aforementioned list that will percolate (move deeper) is potassium. But it’s still a helluva lot less mobile than nitrogen (N), which literally moves with the water. Calcium, magnesium and phosphorous are IMMOBILE nutrients, meaning if you apply them on the soil surface, it’ll take a 2-3 years to move ¼ inch deep. We want these nutrients to be available to the roots for uptake. So, here’s the answer to the $64,000 question. Or is it the $69,000 question? Where’s Yogi when you need him?  Core aeration is an essential element for adjusting our soil pH, and to provide the turf with the amount of P and K that it needs for optimum growth!

Are you a “recreational limer?” That’s what the PROS call you goof balls that lime every year, without the benefit of a soil test. The optimum soil pH for turf is 6.2 to 6.8. That’s considered to be slightly acidic. Liming atop the soil surface is moronic.  And most of you don’t know that the FILLER in the 50 lb bag of fertilizer is coarsely ground limestone—big grits. A bag of 18-0-4 fertilizer has 18% nitrogen, 4% potassium and 78% large grit limestone. It’s literally a small rock. It’s essentially useless for adjusting soil pH. Re-read that last paragraph, if you’re confused.

Most lawns benefit from annual core aeration, best done in the fall. After you do this, you MUST water because you’ve opened up tremendous surface area for the roots, making it more susceptible to drought for the first 2 to 3 weeks. WATER! Those teaser adds for the $40 aeration are for single passes, usually with old machines. And the seed those guys use is pure crap—usually called “contractor mix” meaning a lot of annual ryegrass (crap) and weeds. New machines like that used by the Turf Guys at THE Turf Plan® have at least 35% more hollow core tines than the walk behind units. That equates to more plugs per pass. It’s best to at least do a “double pass” on your trouble spots. The more passes, the better in your thin or weak areas.

Any questions?

Now get to work! Get it done by mid-October, for the highest probability of success.

Trav

 

 

Beware the bad advice–there’s lots of it!

Idiots on the Airwaves

This past Saturday morning, while running errands for the family (not just my wife, but my daughter…WTF?), I had occasion to listen to a popular talk show host on the AM airwaves. I concede that this person has a few key strengths (indoor horticulture, annuals, perennials) in the broader field of horticulture, but his understanding of the SCIENCE of pesticides, especially herbicides, is woefully inadequate. Every summer, right on cue, this goofball says, “Summer weeds have hardened off so much, you really can’tkill them with herbicides!” What a load of crap! He proclaims this for both nutsedge and the entire collection of broadleaf herbicides. He’s dead wrong!

Before I skewer him on his abject stupidity in this specialty area, I’ll try to give him the benefit of the doubt. I’m a fair guy…even-tempered…open-minded—for an Irishman (50%). Maybe he’s thinking about those huge mats of crabgrass, two feet in diameter, or a hefty clump of goosegrass (aka “silver crabgrass”)(below left). Or maybe it’s an established area of deep-rooted black medic (below right). [By the way, the photo of black medic also has some white dutch clover in the photo–both are legumes–and both are tough weeds, but black medic is tougher!] These tough weeds become quite noticeable in late summer because they love the heat and they get very large. Herbicides have their limits–they kill small seedlings easy but an established monster weed won’t be controlled. There are no “selective” POST herbicides that will kill these tough weeds with only one application, this time of year. A “selective” herbicide means it will kill weeds but not grass (if used properly). But a non-selective herbicide, glyphosate (Roundup), CAN kill all these weeds, along with the turf!. STOP HERE! It’ll take at least two applications of glyphosate to kill established black medic. It will take at least 3 applications of common retail broadleaf weed killers to kill established black medic.

Herbicides used in turfgrass work by preventing weed seeds from developing (PREEMERGENCE or “PRE”) or killing established weeds after they are emerged (POSTEMERGENCE or “POST”). Every single herbicide used in turf can injure turf if over-applied, and most herbicides can even kill turf if horribly over-applied. There are “easy-to-control” weeds and there are “tough-to-control” weeds for every product used in your lawn and landscape. For example, dandelion is an “easy” weed for the multitude of broadleaf weed herbicides, while wild violet is a tough weed (3 applications required). Crabgrass is an easy weed for PREEN to prevent but nightshade is a tough weed for this product. PRE herbicides cannot control weeds beyond the seedling germination stage and POST herbicides work best on weeds less than 4 inches tall/wide. So our talk show host is only partially right about why herbicides might disappoint when applied in late summer. THE WEEDS ARE TOO FREAKIN’ BIG! They aren’t “tougher!”

Halosulfuron, the best herbicide on the face of the earth for control of nutsedge, is sold under “at least 3 different names, such as PROSEDGE, SEDGEHAMMER, and NUTBUSTER.  It still works GREAT right now! But the host of this show will tell you otherwise. [SIDEBAR: i did 75% of the development research for this herbicide while employed by Monsanto in the mid- to late-80’s, and it was introduced as MANAGE herbicide. I know WTF I’m talking about!] The broadleaf herbicides (no fewer than half a dozen) will still control weeds 4 inches tall if you apply them now, as long as it’s an easy-to-control weed.  

In summation: this guy doesn’t know crap about herbicides and weed control.

The Value of Compost

There are two ddifferent guys on two different stations that over-promote their proprietary compost blends. Not just for turf, but for ALL lawn and landscape woes. Compost is wonderful as a topdressing in turf, or when incorporated into the native soil when you’re establishing new beds. I don’t recommend it as a mulch because it becomes very powdery when it dries out. Heavy rains or heavy irrigation can wash compost downslope quite easily.

My beef with these two hosts is that they OVER PROMOTE the nutrient content of compost, and one says you don’t need to fertilize your lawn all season long! This is just pure crap.

The vast majority of our soils in St. Louis are typically adequate in phosphorous (P) and potassium (K) thus good turf management generally comes down to proper management of nitrogen (N). Fertilizer values for these there macronutrients are provided in the order of N-P-K. Compost typically 1-1-1. Furthermore, the nitrogen in the compost is very slowly released, in YEARS. Not days, not months, but YEARS. It may take 3 years for all the nitrogen in compost to be made available for use by plants. Compost usually has about 1% phosphorous, but it is essentially unavailable for several years. Finally, compost has about 1% potassium and it is readily available.

Let’s get back to the N, because good turf is all about the N! Healthy cool season turf in the transition zone needs between 2.5 and 4 lbs of N per season, per 1,000 sq ft. By simple math there is no way a single application of compost will provide you with a decent looking sward. We always want to limit our nitrogen to only 1 lb of actual N per 1,000 sq ft in a single application. With compost having only 1% nitrogen, that’s 100 lbs of compost per 1,000 sq ft. That’s certainly “doable” but a lot of work.

There’s nothing wrong with adding compost to the lawn, especially if it’s applied as a top-dressing after heavy aeration and seeding. There are billions upon billions of beneficial microbes in compost which serve to break down thatch, improve soil structure, combat pathogenic fungi, and improve aeration.

In summation: these guys should stop over-promoting compost as an adequate source of nitrogen.

Remember folks, the month of September makes or breaks the turf studs from the turf duds. If you aspire for a great lawn, work hard now through mid-October.

Stay cool!

Trav