# Starter fertilizer on new grass



## Bkell101 (Jun 25, 2018)

Hi all,

I realize that some folks do not use starter fert at all when overseeing, however my question is: will applying starter fert to recently overseeded lawn (3 weeks) hurt the new grass?

I ask because, let's say you overseed early and now want to overseed again due to some bare spots. Will adding starter fert harm the new grasses that did come up?


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## GJOtown (Sep 14, 2018)

I would recommend not adding additional Starter Fert-even when patching after an overseed. I made the mistake last year and the spots where I dropped additional Fert developed Pythium blight or other mold-which required an anti fungal app. I would do one application as recommended, go back and fix bare spots but don't push the Starter Fert. I have also heard of people burning the lawn as a result of too much Starter Fert. Hope that helps!


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## g-man (Jun 15, 2017)

If you want to apply fertilizer, limit it to no more than 0.25lb of N/ksqft/weekly.


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## Bkell101 (Jun 25, 2018)

GJOtown said:


> I would recommend not adding additional Starter Fert-even when patching after an overseed. I made the mistake last year and the spots where I dropped additional Fert developed Pythium blight or other mold-which required an anti fungal app. I would do one application as recommended, go back and fix bare spots but don't push the Starter Fert. I have also heard of people burning the lawn as a result of too much Starter Fert. Hope that helps!


Why would the starter fert contribute to pythum blight (totally new at this)...I've only learned about pm watering and heat and humidity leading to fungus


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## Bkell101 (Jun 25, 2018)

g-man said:


> If you want to apply fertilizer, limit it to no more than 0.25lb of N/ksqft/weekly.


Let's say you do the calculations and shoot for .25lb of N using a starter fert with higher P and K as opposed to ones that are higher in N relative to P and K, would that still be safe? In essence, will P and K hurt 2-3 week old grass?

(Also I love your Purdue pdf topics you keep posting, great reads.)


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## g-man (Jun 15, 2017)

I really don't know. I just have not tried this or research it.


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## ken-n-nancy (Jul 25, 2017)

Bkell101 said:


> g-man said:
> 
> 
> > If you want to apply fertilizer, limit it to no more than 0.25lb of N/ksqft/weekly.
> ...


No, the higher rates of P and K will not hurt the new grass, presuming that the rates are no greater than the rate on N and that the N is being kept to a manageable amount per application and per month. The N is the one most likely to damage the grass.

That said, for environmental impact reasons, restrictions on P application exist in many states or locales, so be sure you're remaining both environmentally polite and within the constraints of the law.


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## MichiganGreen (Aug 7, 2018)

Well, I just did some patching approx 2.5 weeks after overseed and applied starter in those areas. So I'll find out soon enough!


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## Harts (May 14, 2018)

@MichiganGreen How did you apply the fert to those patches?


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## g-man (Jun 15, 2017)

ken-n-nancy said:


> No, the higher rates of P and K will not hurt the new grass, presuming that the rates are no greater than the rate on N and that the N is being kept to a manageable amount per application and per month. The N is the one most likely to damage the grass.


K&N, I'm not sure about the localized effect of adding P or K. Some P sources do have an acidic effect to them. When the product is applied and watered in, the first 1/2in to 1in will see an effect. Long term over established lawns with 6in roots, I don't see a problem. I just not sure with young grass with 1in roots. The effect will be different for sandy vs clay soils

There is a risk/benefit analysis to be done around applying the product.


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## MichiganGreen (Aug 7, 2018)

Harts said:


> @MichiganGreen How did you apply the fert to those patches?


Granular, mixed the seed in with new soil at the same time and watered. I also mowed (mid-high) and bagged just on top of the little area so they would get sun


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## ken-n-nancy (Jul 25, 2017)

g-man said:


> ken-n-nancy said:
> 
> 
> > No, the higher rates of P and K will not hurt the new grass, presuming that the rates are no greater than the rate on N and that the N is being kept to a manageable amount per application and per month. The N is the one most likely to damage the grass.
> ...


That's a good point. I was focused upon the effect to the grass of the P and the K themselves, which should be beneficial, presuming reasonable application levels. I wasn't considering the effect that the source of P or K may have if it is an acidifying source. It's been a long time since I've used chemical phosphorus fertilizers on our lawn - between the mulching of lots of leaves, mulch mowing clippings, and applying Bay State fertilizer as a nitrogen source, I don't need to make any phosphorus applications, so I didn't remember the acidifying effect of phosphate sources such as monoammonium phosphate (MAP), single superphosphate (SSP), or triple superphosphate (TSP).



ken-n-nancy said:


> There is a risk/benefit analysis to be done around applying the product.


 Basically, it seems that's just about always the case. There's hardly anything to be applied to the lawn for which more is always better! (Is there anything that falls into that category? Maybe sun on Bermuda grass?)


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## Harts (May 14, 2018)

MichiganGreen said:


> Harts said:
> 
> 
> > @MichiganGreen How did you apply the fert to those patches?
> ...


The only thing I'd be concerned with is the concentration of nitrogen on those patches. Depending how big they were and how much fert you mixed, putting a high concentration of N on a small patch would possibly case burning.


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