How to Fix Fertilizer Stripes in Your Lawn (and Never Get Them Again)

You fertilized last weekend, and now the lawn looks like a bar code. The stripes run in straight lines that match your spreader passes. First figure out what color they are. If they're dark green, you overlapped. The extra nitrogen will run out and the stripes will fade on their own. If they're yellow, brown or straw-colored, that's salt burn. Act now: sweep up loose granules, soak the area, and keep watering it for a week. Then set up your spreader and your walking pattern so it doesn't happen again.

What the stripes are and how to fix them

Stripes after fertilizing are a known problem with a known cause. UC IPM describes "stripes of green, white, or brown turf" that follow the pattern of the application and show up soon after you fertilize. The color tells you which problem you have.

Dark green stripes next to lighter ones. This one isn't damage. It's uneven coverage. The strips that got fertilizer, or got it twice, turn rich green. The strips you missed stay pale. In 20-some years running golf courses, I've seen this "zebra lawn" on fairways and in plenty of neighborhoods. There's nothing to repair. The extra nitrogen gets used up and the color evens out. Your job is to fix the spreader and the pattern before the next application.

Yellow, brown or straw-colored stripes. This is fertilizer burn. Washington State University explains that too much fertilizer raises the salt level in the soil. The salt damages roots and makes it harder for them to take up water. Nevada Extension notes that the yellow-to-brown color usually appears a day or two after fertilizing. Their fix: sweep up what you can, soak the area until the soil underneath is saturated, then give it about an inch of water a day for seven days. With that much water, they say the grass should start regrowing in about 7 to 14 days. If it doesn't come back, it's dead, and you reseed or sod.

Why stripes happen

Both kinds of stripe come from the same few mistakes.

• Overlapped passes. WSU says burn stripes usually show up where spreader passes overlapped. The overlap gets a double dose and the gap next to it gets nothing, which is how you end up with both dark and pale stripes in one yard.
• Turns and start/stop points. WSU also points to these. If the gate is open while you stand still or swing the spreader around, it keeps dropping product in one spot.
• Quick-release fertilizer that isn't watered in, or goes down in heat. WSU lists both as common causes. Quick-release nitrogen is mostly salt. Leave it sitting on hot, dry turf and it burns. WSU also says never to fertilize grass that's already stressed by heat or drought.
• Wet grass. Granules stick to wet blades and burn them in place. WSU, UC IPM and Mississippi State Extension all say to apply to dry turf. Mississippi State adds that wet turf also leaves wheel tracks.
• A spreader set by guesswork. Every product flows differently, so the setting that worked for last spring's bag can be badly off for this one.

The color tells you what happened. The list above tells you what to change.

Step-by-step repair for burn stripes

1. Act fast. Nevada Extension says to act immediately after a spill or an over-application. The sooner the salt is diluted, the less root damage you get.
2. Pick up the loose product. Sweep or lightly rake up any granules you can see in the stripe. Look hardest at the ends of rows and the spots where you turned, because that's where piles collect. Sweep any fertilizer off the driveway, sidewalk and street too, so it doesn't wash into the storm drain.
3. Soak it. Run water until the soil underneath is saturated, not just the surface. You're trying to push the salt down past the root zone.
4. Water every day for a week. Nevada's schedule is about an inch a day for seven days. It's one extension recommendation, not a universal rule, but it's a reasonable target. Set a tuna can or rain gauge in the stripe to measure it. If you've already blown out your irrigation lines for winter, drag out a hose and an oscillating sprinkler. Don't skip this step to save the system.
5. Check whether the crowns are alive. After a week or two, tug on a few plants in the worst part of the stripe. If the base is firm and still has some green or white at the crown, the grass can regrow from it even if every blade is brown. If the plant pulls out easily and the base is brown and mushy, that patch is gone.
6. Reseed what stays dead. Give the stripe several weeks. Then rake out the dead grass, loosen the soil surface, seed, and keep it moist until the seed is up. Nevada Extension says to reseed or sod if the lawn dies.

A note on fall damage: if you burned a stripe with a late-season feeding, the grass may go dormant before you can tell what lived and what died. Up north, a stripe from mid-October often doesn't show its final answer until spring green-up. Flush it with water now anyway. Then wait until spring to decide whether it needs seed.

Calibrate your spreader

The setting chart on the bag is a starting point, not the answer. UF/IFAS says to calibrate separately for each material and each operator. The University of Georgia explains why: every product has its own distribution pattern, and the rate also changes with the product's weight and density, the wind, temperature, humidity, and how fast you walk.

The weigh-and-measure method UF/IFAS describes works like this:

• Mark a test area. Use 1,000 square feet for a rotary spreader, for example 20 by 50 feet. For a drop spreader, use 100 square feet on a hard surface like the garage floor or driveway, so you can sweep the product back up.
• Load a known weight of the product you're actually going to use.
• Make your pass over the test area at your normal walking speed.
• Weigh what's left and subtract it from what you started with. The difference is what went down.
• Adjust the setting and repeat until the amount matches your target.

Here's a worked example using UF/IFAS numbers. A 20-0-10 fertilizer is 20 percent nitrogen. To put down 1 pound of nitrogen per 1,000 square feet, you need 5 pounds of product per 1,000 square feet (1 divided by 0.20). For a drop spreader on a 100-square-foot test strip, that's half a pound. Say you load 10 pounds into the rotary, walk the 1,000-square-foot area, and have 7 pounds left. You put down 3 pounds when you needed 5, so open the setting and try again.

Drop or rotary? UF/IFAS explains the tradeoff. A drop spreader only covers the space between its wheels, with a hard edge on each side. Your passes have to meet exactly or you'll see skips. It's the zebra-lawn machine if you're careless. A rotary throws a wider pattern that tapers off at the edges. That's more forgiving of skips, but it's harder to calibrate. UF/IFAS also notes that a drop spreader's agitator can break the coating on coated slow-release products, so use soluble or reacted slow-release products in a drop spreader.

Spreading technique so it never happens again

When I've seen a zebra lawn, the fix was always the same three things: the spreader setting, the overlap pattern, and walking speed. A calibrated spreader takes care of the first. Here's how to handle the other two.

• Split the rate and go two directions. UGA recommends setting the spreader for half the rate and making two passes at right angles, one north–south and one east–west. Any streak from the first direction gets crossed out by the second. Mississippi State's version also works: put down half the fertilizer, move over half a spreader width, and apply the rest.
• Do the perimeter first. UGA says to run a header strip around the edges, then fill in the interior. That gives you room to turn without dumping fertilizer.
• Walk a steady pace. UGA suggests about 3 mph, which is a brisk walk, and keeping the rotary's impeller level. If you slow down, more product goes on every foot of grass.
• Open the gate after you start walking. Close it before you stop. Shut the spreader off before every turn, and avoid sharp turns. This one habit gets rid of most of the blotches at the ends of rows.
• Mark your swath. UGA suggests flags or markers so you can see where the last pass's effective coverage ended. For a rotary, that means the width where coverage is still good, not the farthest a stray pellet flies.
• Apply to dry grass, then water it in. Mississippi State says watering right after you apply dissolves the granules and moves the nutrients into the root zone, so they're not sitting on the leaves.
• Clean up. Sweep any fertilizer on hard surfaces back onto the lawn. Rinse and dry the spreader, since fertilizer is corrosive, and do it somewhere the rinse water can't reach a storm drain.

If you get a late-fall feeding down before Thanksgiving, this is the time to run it this way: calibrate on the driveway, make your edge passes, then cross-hatch the middle. It adds about ten minutes and saves you from having to fix stripes next spring.

Sources (7)

• UC IPM: Fertilizer injury in turf
• WSU Hortsense: Fertilizer burn
• University of Maryland Extension: Fertilizer injury on lawns
• Nevada Extension (JoAnne Skelly), via Carson Now
• Mississippi State Extension: Lawn fertilizer applications
• UF/IFAS: Calibrating fertilizer spreaders (LH024)
• UGA Field Report: Spreader calibration and application