Soil Remediation Guidelines

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Soil Remediation Guidelines

Post by g-man »

Soil Remediation Guidelines
You got your soil tested. They gave you some high level recommendations that you need to increase X or Y, but how do we do that? This article will try to address the techniques or approach to remediation based on your soil test and soil needs.


General

For most cases, don't try to remediate the soil during the winter if your soil freezes. Products applied to frozen soils might not travel deeper into the soil and get washed away. Try to focus in the months the grass is actively growing. Also avoid applications in the peak of summer under drought conditions since it might lead to more plant stress. This is a marathon and unless you are deficient (rare) most of the amendment we do is to get the soil to an ideal condition.

The recommendations are for soil modifications to be applied monthly. Do not use these rates for foliar applications unless you immediately run the irrigation to wash the product off the leaves into the soil.

pH
We need to start with the pH. Most of the recommendations depend on your soil pH. As previously discussed, a pH around 6.0-7.0 is in the sweet spot.

If pH is less than 6.0, then it will need lime. Your soil test should tell you how much lime to apply per ksqft. The guideline is no more than 50lb/ksqft every 6 months, unless you are using a fast acting lime. For a fast acting lime, follow the bag recommendations. There are 2 types of lime, dolomitic and calcitic. Dolomitic limestone is a mix of calcium and magnesium; while calcitic is mostly calcium. Most soils do not need magnesium, too much can cause the soil to become too hard and it cannot be removed from the soil. Unless the recommendation was to also increase the magnesium in your soil, use calcitic to increase your pH. For nitrogen, a low pH soil will benefit from using ammonium nitrate (34-0-0) at no more than 3lb/ksqft/month. Avoid applying other products for 2 weeks.

If soil pH is above 7.0, then the best way to reduce it is with elemental sulfur at 5lb/ksqft per hot weather season (once a year in northern states vs twice in Houston, TX). Why? Elemental sulfur needs a microbial breakdown to convert it to sulfuric acid and release the hydrogen which is what reduces the soil pH (more info in this Ohio State article). Too much elemental sulfur without the microbial activity can lead to accumulation and too much being released at once (hurt your lawn). There are other ways to reduce soil pH and this Purdue article describes it and this Iowa State article.

But (there is always a but), lowering pH in the soil might not be possible/cost effective. If the soil has enough calcium carbonate, the quantities needed of elemental sulfur are too much. This article describes a study that tilted 240lb/ksqft of elemental sulfur. It dropped the pH by 0.5, but it increased over the years. Continuous application might keep it there (but at 5-10lb/year?) and using other techniques (citric acid) will help.


High pH techniques
Having a high pH is not the end of the world. You can have a nice lawn with a high pH, as many of us do. It just needs some adjustments. The main issue with high pH is that iron is not as available via the soil. When iron is not available, then chlorosis starts (yellow lawn) due to the lack of chlorophyll. We work around it using foliar application of iron (FAS) so it is absorbed by the leaves (bypass the soil). The other option is to use a chelated source of iron. It is more expensive and might not work too well in the really high pH. Using Ammonium Sulfate (21-0-0) at no more than 4.7lb/ksqft/month as the nitrogen source will also help due to a slight acidifying effect.


Phosphorous
If your phosphorus is low, then you can use:

Triple superphosphate (TSP) 0-46-0 - Apply at 2lb/ksqft every month the soil is growing

For low pH soils you can use:
Diammonium phosphate (DAP) 18-46-0 Apply at 2lb/kqft but account for the nitrogen being applied 0.36lb N/ksqft. It will slightly increase the pH.

For high pH soils you can use:
Monoammonium phosphate (MAP) 11-52-0 - Apply at 2lb/ksqft, but account for the nitrogen being applied at 0.22lb/ksqft. It will slightly decrease the pH.

Another option is to use biosolids (eg. Milorganite). They will take longer to break down and be part of the soil, but they do work.

Last option is to use a fertilizer called "starter fertilizer". These normally have a higher percent of P than N and can be used to increase the P levels without too much nitrogen feeding.

Potassium
For potassium there are two main options:

Sulfate of Potash (SOP) 0-0-50. Apply at 2lb/kqft/monthly. This will also provide some sulfate sulfur the plant needs too. It can be hard to find. Go to the hometown folders in the forum to ask someone local to your state for sources.

Muriate of Potash (MOP) 0-0-60. Apply at 1.6lb/ksqft/monthly. MOP can be harsh into the soil(chloride), but it is widely used by most fertilizer blends (eg. Scotts). Try to find the SOP since it is better, but don't sweat it.

Potassium Nitrate 13-0-44. Apply at 0.5lb/ksqft. The nitrogen is in the nitrate form, so it moves fast and leaches thru the soil. It is applied in liquid form and needs irrigation after to avoid foliar (4oz/ksqft foliar max). Thanks Greendoc for the info.


Iron
Once the soil pH goes above 7.0, iron is not as available. Soil applications of iron are just a waste of money. As explained above, use FAS or chelated irons for the high pH soils.

For soils below 7.0, you can also use FAS. You can also use any other source of iron per the bag rate. Avoid applications with moist/wet lawn, since it can be absorbed via the leaves and cause a black lawn. After sweeping the concrete, run your irrigation after application to clean the leaves if the lawn was moist.

This article from Harrells is a great read on soil iron in general. The irony in iron

Warning
Iron stains. It will stain your concrete driveway, patio, etc. Be careful how you apply it and where you mix it. Chelated sources of iron stain less or not at all.


Sulfur
Sulfur in the form of sulfate is an essential nutrient the plant needs. If you need to increase it, then Sulfate of Potash or Ammonium Sulfate will be good options. Elemental sulfur can also be good, if your soil pH can handle it.

Gypsum
Sometimes there is a desire to adjust the calcium without impacting the pH. We use gypsum for this. You can put down 20-30 lbs/M of gypsum every 60 days. Keep the applications of P and K apart. Gypsum is 21% Ca by weight.


Micros
Research on micros is very limited. Even research on how low Phosphorus levels can be an issue is currently on going. Most of the micros ranges were extrapolated from the ag side (eg. corn). I normally recommend to leave them alone, unless you are seeing a lawn problem (eg. yellow lawn) and all of your other soil items are in range.


Balanced fertilizer
Sometimes we refer to a balanced fertilizer. This means that the ratio of Nitrogen, Phosphorus and Potassium is equal. It is a mix of the products listed here (check the label) and ready to be applied from a bag. These products are easy to find in most stores.

Applications rates (maximum per month)
10-10-10 - 10lb/ksqft
12-12-12 - 8.3lb/ksqft
13-13-13 - 7.7lb/ksqft
16-16-16 - 6.25lb/ksqft
20-20-20 - 5lb/ksqft
Last edited by g-man on Thu Feb 20, 2020 6:38 pm, edited 2 times in total.

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Re: Soil Remediation Guidelines

Post by SNOWBOB11 »

Excellent write up @g-man.

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Re: Soil Remediation Guidelines

Post by npompei »

Wow thanks @g-man I was just looking up my results from this past Fall and stumbled onto this new post. Timely!

So to clarify a few things:
1. I have low P & K and I read above what items to put down - but if I am going to put those ingredients down this coming Spring, would it be smart to just use a balanced Fert with Nitrogen? I remember reading on here that using Nitrogen during the Spring green up may be a bit excessive. Is that true? And if so, can I put down the P & K at the same time?

2. My lawn is new, just did reno/new construction this past Fall. So maybe adding some Nitrogen in the spring and going with the balanced fert may not be a bad idea?

3. And when is the best time to get fert down? I have my game plan for getting Prodiamine down in late March early April but curious how the fert timing matters when using a PreM?

You guys rock, thanks

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Re: Soil Remediation Guidelines

Post by g-man »

Spring nitrogen can cause excessive grow and sacrifice root carbohydrates. The idea is to maintain a healthy grow (clip yield). A balance fert is an easy way to apply NPK. But it might force too much grow on an established lawn.

You have a young lawn. It doesn't have a robust root system yet and it is trying to grow and the established. It will need nitrogen, so don't shy away from spring nitrogen.

Prem should go down when the soil temps/GDD/ forsythia blooms. Apply nitrogen when the grass greens up and start to grow. A fast acting 0.20lbN/ksqft weekly is in the ideal frequency to avoid surge grow with a monthly application on a new lawn.

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Re: Soil Remediation Guidelines

Post by cr0ntab »

This is treat, thanks so much!

Can we get this added to the top Sticky?

viewtopic.php?f=24&t=3124

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Re: Soil Remediation Guidelines

Post by krusej23 »

Great job!

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Re: Soil Remediation Guidelines

Post by Greendoc »

@g-man 2,2 lb of Potassium Nitrate per K is a lot at once. My usual application rate is 0.5 lb per k applied through the growing season. Nitrate N is way different in how it reacts vs the other sources. 0.3 lb Nitrate N can cause the grass to grow extremely fast. Showing effects within 3 days. I use Potassium Nitrate only because it dissolves in small amounts of water and contains no chlorides. SOP is far less soluble and safe to spread to apply a full pound ok K.

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Re: Soil Remediation Guidelines

Post by sean_h »

Not sure I can trust a post that includes a link to an Ohio State article...
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Re: Soil Remediation Guidelines

Post by g-man »

@Greendoc are you referring to a foliar application or a soil one (washing the leave off with irrigation)?

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Re: Soil Remediation Guidelines

Post by Greendoc »

A soil application. 1 lb per K is the most I have applied at once to the soil. 4 oz is my maximum as a strictly foliar application.

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Re: Soil Remediation Guidelines

Post by Scagfreedom48z+ »

Gman fantastic write up. Do you know any websites selling reasonably priced potassium and phosphorus fert? I have 30m to cover. I have a spreadermate so I’m thinking that spraying would be the best way.

I tried out spoon feedings throughout the spring and fall last year to slowly increase it. I’m going to get another soil test once I can get out and get samples.
Last edited by Scagfreedom48z+ on Thu Feb 20, 2020 5:23 pm, edited 1 time in total.

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Re: Soil Remediation Guidelines

Post by g-man »

@ScaginMass I don't know of online sources at good prices. Look for a Helena or at site one or a place that sells to golf courses for liquid fertilizers. You likely will need irrigation if you want to spray the liquid fertilizers.

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Re: Soil Remediation Guidelines

Post by Scagfreedom48z+ »

Sweet thanks

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Re: Soil Remediation Guidelines

Post by TN Hawkeye »

@g-man This totally going to sound like a stupid question but if your soil is high in a macro (potassium) is the best way to lower it to simply not apply fertilizer that contains it? Over time will the level decrease naturally?
I may not have the best lawn and I may not have a clue what I’m doing but that’s pretty much all I have to say.

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Re: Soil Remediation Guidelines

Post by g-man »

It depends. Some elements are so tightly bound (chemical bond) that they won't leave (eg. Mg). Others move thru the soil and go deeper with water (eg. Potassium). Other can be removed when you bag your clippings and throw them away (eg. Phosphorus).

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Re: Soil Remediation Guidelines

Post by Harley »

Very nice write up. I thank you for taking the time. You mention very high PH, what do you consider very high PH? Just got my test results and my front yard is 8.2 and my back yard 7.5. My thought is that these are slightly to moderately high. Thanks again

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Re: Soil Remediation Guidelines

Post by g-man »

8.2 is high. pH is an log scale. The difference between 7 and 8 is that 8 is 10 times more alkaline.

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Re: Soil Remediation Guidelines

Post by B-Rad »

Bookmarked...You the man @g-man!

Thank you for taking your time to write something like this out.

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Re: Soil Remediation Guidelines

Post by ShaneQi »

@g-man

I was looking for Sulfate of Potash (SOP) 0-0-50 you mentioned, and I found this (in MQ's Liquid Lawn Fertilizing Plan):

https://www.greenwaybiotech.com/collect ... 4459785537

Is this 'Potassium Sulfate' the same as 'Sulfate of Potash'?
If so, the website says 'Soil: Apply 2 pounds per 100 sq.ft.'. Is that a typo? Because that's a LOT of stuff.

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Re: Soil Remediation Guidelines

Post by g-man »

@ShaneQi it is the same thing and that's a typo. But this product online is extremely expensive and a powder. Others tried it and it is hard to apply.

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