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In the picture below, you can hopefully see some lighter spots on my lawn, marked by yellow lines. Does anyone know why I have these? Do I need to fertilize more often? Is this a fungal infection? How can I restore my lawn to its green color?

Update: This is sod that was laid just this past August - J.B. Sod Oregon Premium. I fertilized 6 weeks after it was laid (Scott's terfbuilder without weed control) and again last weekend; second time with a fall fertilizer. I watered religiously.

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  • Trouble with the yellow lines is, there's the inpression there are lighter lines as well as patches, is that the case? Where are you in the world and what type of grass is it? What's been your lawn maintenance routine in the last year and how long has the grass been in situ? – Bamboo Nov 19 '17 at 11:20
  • I've updated the post with additional details. – Craig Nov 19 '17 at 16:55
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    You've got a detailed answer already,but, under magnification, its impossible to see the blades of grass clearly, but my general impression is, your mower blades might not be sharp enough,and the yellow lines may simply be over applied fertilizer in those strips, perhaps a failure of the device you used to spread it. Either that or there's something buried beneath the grass there causing lines on the surface. – Bamboo Nov 20 '17 at 10:51
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I know JB Sod. Very well. They can grow sod but they are hopeless with maintenance practices. You are mowing way too short. Keep that mower raised up to at least 3" no shorter. The Pacific Northwest and cool grasses genetically have huge root systems. To support huge root systems the plant needs at least 3" with which to do photosynthesis to FEED those roots. If the grass is too short your grass is compromised, struggling. You will get weeds while your grass crop is weak. Don't use their fertilizer. Awful. I get in trouble every time I say this but try Dr. Earth's Lawn Fertilizer. Takes more, is far more slow but my goodness I forked out the money for this fertilizer to do commercial maintenance on lawns. I had my mowers custom raised for the correct height. I had multiple blades already sharped to perfection. The blades were cleaned with alcohol in between clients. Part of my service included aeration. Not an option. I always bagged clippings forget mulching!! Those stripes look suspicious...are you using a drop spreader? I used Scott's handheld cheapie spreader for everything other than ball parks. Much easier to control where that fertilizer goes. Never use weed and feed...forget moss control. Could you have your mower deck too short on one wheel? I know the Pacific Northwest and last I knew JB Sod was in the Kirkland/Woodinville area, yes? If you live there I can turn you on to the best BEST mulch for your beds; Sawdust Supply and Gro-Co. Lucky you!

This JB Sod is in Oregon or is the seed crop from Oregon? Same organization, similar environments. And watering practices are important; water very deeply and allow to dry out before watering again. Let us know what you've been doing exactly, what your automatic irrigation is set for, this doesn't look diseased. It looks like too short grass with a wheel too low on your mower or a very bad drop fert spreader. Let's figure this out before winter or you just very well have disease problems caused by stressed out wimpy grass. What exactly did you fertilize with? Sounds fine for your timing depending on the formulations you used. Don't need to aerate this year. Definitely next year. Train your grass roots watering very very deeply then do not water until you are able to see your footprints stay down when you walk on your grass. Then water again deeply...down at least 4"...this makes for very deep strong rootsystems where you won't ever have to worry about drought and watering this way reduces your water bill...if you are on city water.

One other possibility, how close do you live to a golf course? Poa annua our annual blue grass looks very straw colored, has lots of seed heads and thrives being cut short. Birds poop out these seeds and then your cool season grass mix of JB Sod's if stressed and cut too short will allow this light colored shallow rooted grass to become part of the lawn. Especially prominent living on golf courses. Golf courses up there love the ability to mow short short short and with a monocrop of this pale green color no one notices. The lawns of those that live on the golf course usually having used JB Sod on their lawns right next to huge expanses of Poa annua crops of the golf course are able to see this grass, looks like a dog peed on their lawn burning it to almost yellow. Most just had the lawn replaced over and over again. I ripped out lawns and replaced with plant beds, gravel, pavers and flagstone landscapes. They were very happy. Got lots of clients on golf courses for maintenance and landscape renovation projects.

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  • Thanks for the detailed reply. 1. I always mow at the highest setting for my lawnmower but haven't mowed for at least a couple weeks. 2. I use Scott's Wizz handheld spreader when fertilizing. 3. I have an irrigation system and watered twice daily in the morning + early afternoon. Now it's raining nearly every day so the system is winterized. I wonder if the lines are from my mower; perhaps something got on the wheels and hurt the sod? – Craig Nov 20 '17 at 5:54
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    If those lines make some sort of a pattern, did you check lawn mower blade? Maybe it needs sharpening? – False Identity Nov 20 '17 at 7:33
  • Make sure that highest setting cuts your grass no lower than 3". This is a very big deal. I had our mowers custom lifted but now mowers have generally improved with higher settings. 3.5" is best. Your watering habits need changed for sure. You are training your grass to have shallow roots. Did you check the setting for each wheel's height? Did you overfill your oil tank or gasoline tank? Definitely looks like mechanical damage, no big deal but it would be wonderful to learn the why...you want to water deeply allow to dry out before watering deeply again. 1 inch of water per week. – stormy Nov 20 '17 at 9:23

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