# Advice for Fall Overseed



## Derek_ (May 13, 2020)

First I wanted to say thanks. I am very new to lawn care only having moved into my house last year. Since I have been working from home since March I have had a lot of time to work on the yard and want to get better at maintaining it. Reading many of the post on TLF has helped me a lot. I was planning on doing a fall overseed/seed so just got my soil fertility test results from Waypoint. My front yard is FF and PRG but I was thinking of adding some KBG to that mix since my grass appears fairly patchy in the sunnier sections (most of the front yard is in shade). The backyard is mostly TTTF with a bit of FF and I was planning on keeping that mix as it is mostly sun with some shade.

Here are my results for each section:





And here are my questions:

1) Since the frontyard is very high in P, at the time of seeding should I avoid adding additional P? I was considering either a 19-26-6 or a 23-0-20. Based on the results I was thinking I should go with the latter but wasn't sure it I should still put down some P since I am planting new seed.

2) Since I was thinking of adding KBG to my front yard should I target higher N 2 - 3 lb/1000 sq ft or should I stick to lower levels (1 - 2) since fine fescue will be the dominant species. I know the latter is in contradiction to the recommendation but I'm thinking that was a recommendation for TTTF vs. FF.

3) I added some dolomitic lime in the spring based on a soil test that showed a pH of 6 and low calcium, that I got from a box store. Any recommendations on lime to use this time around? Since it appears I don't need to adjust Mg should I stick with calcitic lime? Any recommendations on brands that folks have liked?

4) I have read that root hume can improve CEC. Is that true or just marketing because I have also read CEC is very difficult to change. Any thoughts on adding root hume to my lawn plan?

5) Should I be adding sulfur and boron to my front yard? If yes, should I be looking to add those individually or as part of a fertilizer that includes micronutrients?

6) I have been using chelated iron (Fiesta) to treat white clover in my lawn. Could that be driving up my iron levels? I read Fe2+ is more readily available to the lawn then Fe3+. I was planning one more Fiesta application for white clover and moss before I seed but can skip it and use other means if that would be too much iron. Based on the label advice I could still do one more app.

7) I was planning to top dress with compost should I also add additional compost before I seed to the front yard to increase OM%?

8) Should I care about K/Mg and Ca/Mg ratio?

I am likely overthinking this but that is what I tend to do so I would appreciate any advice I can get. I also have some questions about weed control and seeding in general that I will ask in the other discussions.


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## Derek_ (May 13, 2020)

I think I have settled on using a standard 16-4-8 with Humic Acid on the front yard for seeding and more traditional starter fertilizer in the back yard. I was thinking about getting straight potash to help boost P levels and doing multiple applications in the fall. Thoughts?


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## g-man (Jun 15, 2017)

You need to do the lime to raise your pH, but there is a risk with changing the soil profile less than a month from seeding. Use calcitic lime.

You P levels are fine in the front and ok in the back. You can boost your reserves in the back.

Potassium levels are ok but can use a boost to build up reserves. If you can find SOP, it will also boost the sulfur in your soil.

You soil CEC is on the low side. This means it can hold on to nutrients too good. Increasing Organic Matter in the front can help. Consider using half the monthly rate every 2 weeks instead of a single monthly application.

Iron, boron and the other stuff is all fine.

Check the soil remediation guide for more details of products/rates.


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## Derek_ (May 13, 2020)

Thanks @g-man what is the danger with liming now?


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## g-man (Jun 15, 2017)

Lime is changing the soil pH, but it moves slow thru the soil. The top layer of the soil might have a higher pH than the rest while it moves. In a young grass with short young roots, it might affect them. Therefore, YMMV.


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## Ridgerunner (May 16, 2017)

> 4) I have read that root hume can improve CEC. Is that true or just marketing because I have also read CEC is very difficult to change. Any thoughts on adding root hume to my lawn plan?


If root hume is humate:
Yes to both.
Humate (HA and FA) has a CEC of about 400-500 meq per 100 grams.
An acre of soil weighs about 2,000,000 lbs.
If my math is correct, adding 10 lbs/M of humate (humic/fulvic acid) could raise CEC by 0.5 CEC.

That was just FYI, not to be taken as a recommendation.


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## Virginiagal (Apr 24, 2017)

I think g-man meant to say a low CEC means the soil CANNOT hold into nutrients too well. You can manage this by applying lower amounts of fertilizer more frequently. That's what g-man meant about just half rates every two weeks. Waypoint is giving you recommendations for TTTF, not fine fescue, and those are yearly totals. So if you are doing 2 lb of nitrogen a year (a compromise between the 1-2 for FF and 2-3 for KBG), you could aim for 1.5 N in the fall and .05 in the spring. Maybe you could do three applications of 0.5N every two weeks after your new grass comes up. I'd skip the fertilizer at seeding so your existing grass won't grow too fast while the seed is germinating. By the way, it is difficult to overseed KBG into an existing lawn.

I suggest applying lime is late fall (like November). Your pH is not especially low anyway. If you go with a fast acting lime, follow the directions on the package. If you can find a regular calcitic lime (not fast acting), you can apply it all at once and not have to make more applications.

Compost is a lot of work to spread and is not going to significantly increase your organic matter. Of course, it's a fine material for top dressing. As to whether to use it both under and over the seed, my inclination would be to use it just on top so the seed starts its roots in the soil it will make its home in. Don't cover the seed too much. Aim for 1/4 inch. People have also used it the other way (under the seed) and it worked fine. The pro in that is you won't cover the seed too much accidentally. To increase organic matter, mulch mow your leaves in the fall, leaving them chopped up on the lawn. It makes its own compost and you don't have to spread it! The roots from your grass go through growth cycles and the dead roots add to organic matter. So roots in the ground (any type of roots) are good for organic matter.


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## g-man (Jun 15, 2017)

Yes, cannot hold to nutrients too good. Typo.


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## Derek_ (May 13, 2020)

@g-man, @Ridgerunner, and @virginiasabres thanks for the info. I will wait to apply calcitic lime after seeding. I am going to avoid the fast acting stuff this time around so I can hopefully just put the right amount down in one shot.

Yes, root hume is a HA and FA liquid concentrate. I will apply some of that before seeding unless you have advice on a different type and time to apply.

I can rent a compost spreader so that was my plan because I know it is a lot of work. My local soil company has a topdressing that I was going to put down first which is a mix of native soil, black sand, and compost. I was then going to use their compost for actually topdressing which is Canadian peat moss, straw, hay, corn cobs, cocoa bean hulls, cotton seed meal, and poultry litter mix. I am a bit worried about weed seeds though especially in the front yard where I can't use tenacity.


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## Ridgerunner (May 16, 2017)

> Yes, root hume is a HA and FA liquid concentrate. I will apply some of that before seeding unless you have advice on a different type and time to apply.


I wouldn't put it down around seeding nor until the new grass has matured. Liquid HA has a very high pH and will have the same effect as lime.


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