# First Soil Analysis - Potassium and Phosphorus Deficient



## DannyBoy2k (May 25, 2019)

Just did my first ever soil test since moving in a decade ago. Loooong overdue, but the lawn didn't become a priority until my children started to become a little more self entertaining. Only really got serious about it last year and only really delved into the science behind it this year. Here are the reports for my front yard and back. I primarily used Milorganite last year. This year, I'm hoping to switch to primarily liquids as they are easier to apply around the obstacles and narrow strips I have in my ~7,200 sq. ft. lawn (~3k in front and ~4k in back).

Not really understanding the balance of N-P-K until this year, I was expecting my potassium levels to be low, but I was surprised how low my phosphorus levels were too. I've been deficient for a while it seems. The iron is also super high. I did apply some 7-0-0 GreeneEffect at the beginning of the month, so maybe those readings are a little superficially elevated? I took my cores to 5 inches using a soil probe and discarded the first 1/2" to 1" of the core depending on the roots.

I'd like to stay liquid if I can. I've found some TKO Phosphite 0-29-26 as well as some Forumla 3-18-18 that I thought maybe I could use as a early summer fert to help correct the deficiency a little bit before it gets too hot. Am I on a fools errand trying to stay liquid? Should I just correct with a granular?

Any thoughts welcome.

~Dan


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## Ridgerunner (May 16, 2017)

Foliar fertilization takes equipment, practice and a fair bit of commitment to do regularly timed application, but plenty of people have mastered it.
With your P and K levels, if you solely use foliar, you'll be living on the razor's edge as the soil has so little in reserve to make up for any foliar app shortages. Suggest you use granular to raise soil reserves of P and K to at least above MLSN minimums in addition to foliar fertilization.


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## DannyBoy2k (May 25, 2019)

Thanks for the feedback, @Ridgerunner .

Just for my education, when applying foliar products, does anything that washes into the soil get integrated? Or does it just leach away and not increase the reserves? I was wondering if using something like TKO Phosphite 0-29-26 at a 14 day interval, which should put ~0.25 lb of P/K every month, would build up an reserves or not. I'm only putting ~1/3 lb of N on at a time using GreenePunch and don't plan to put much if any N on during the summer as I don't have irrigation.

~Dan


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## g-man (Jun 15, 2017)

If you want to apply in liquid and immediately run the irrigation, then that will work for the soil. Target 1lb of P205/ksqft per month. You are really deficient in P.

The second soil needs lime. Use calcitic lime.


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## Ridgerunner (May 16, 2017)

Yes, anything that washed off the plant or hit the soil directly could become available to the roots or become part of the reserve. To build a decent soil reserve (27 to 38 ppm), will take about 2-3 lbs/M of P2O5. Even at .25lbs (at max rate I think it would be closer to .28 lbs) of P2O5 per month, that's going to take a while especially considering that the turf is going to use about .3 lbs/M for every 1 lb of N that it uses. I'm not very familiar with phosphite other than care should be used as it can be phytotoxic. I wouldn't exceed label rates unless advised by a reputable source. @Greendoc or @osuturfman


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## DannyBoy2k (May 25, 2019)

@Ridgerunner , that's actually the confusing part of that product. If you look at the label:
https://www.pestrong.com/file/3305-TKO_Phosphite_0-29-26_Label

In one section, they say "Apply desired rate of phosphorus" and seem to indicate to use X oz to get X lb of P and Y lb of K. And then, they have "Foliar Spray Recommendations" where they suggest 3-5 fl. oz. per M. I don't necessarily need it to be a foliar application. I was thinking I'd use my Blue Mule hose end sprayer to get a lot of water down to get it down to the soil and go with an 18 oz rate every 2-4 weeks.

~Dan


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## ScottW (Sep 16, 2019)

You are big time deficient in P and K and correcting those with liquids seems like a lot of wasting time and money IMO.
You need to be putting down 1 lb per month of each until you hit the recommendations. The sooner you get on it, the better.

If it were me I'd be loading up the spreader and slinging it out in 20-30 minutes once a month.
Any obstacles you have in the yard that you have to maneuver around would have to be walked around with a sprayer, so spraying saves no time there. For narrow areas you can just grab granules a fistful at a time and shake it out. I don't precisely meter out the granular stuff onto my 24" wide hell strips and they're among the nicest areas of grass I've got, probably because they get dosed a smidgen higher.
How long is it going to take you to cover 7500 sqft with a hose end sprayer? And doing that twice a month? Heck no.

Then there's the cost. You will need about 26 pounds of actual K to cover the recommendations (7.5K lawn times an avg of 3.5 lbs per 1000; didn't bother factoring in proportions of front & back yards). A single 50-lb bag of 0-0-50 SOP will get you 95% to target at a cost of $40 or less. That phosphite liquid looks like about $40 a gallon and you'd need how many gallons to get 26 pounds of K?

One other thing that caught my eye was that you used primarily Milorganite last year. That's usually about 6-4-0, a decent proportion of P relative to N, so I'm wondering how P is so low unless you were going really light with the N. It's possible that, because P is poorly mobile in soil, some of the P could have been in the top inch or so of your soil cores that you discarded before sending in the sample. If you're bagging and removing your clippings, consider mulch mowing instead to retain more of the P and K.


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## DannyBoy2k (May 25, 2019)

Once again, appreciate all the feedback. Doing more reading on the phosphite stuff, it's not even clear that it readily turns into available phosphorus. One article said it can take months to years for soil bacteria break it down.

So, going to go the sane route and order some triple super phosphate and SOP to solve my deficiencies.

~Dan


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## Ridgerunner (May 16, 2017)

Good decision.
There is no evidence that plants can use phosphite PO3, but as you've read, bacteria and natural/chemical processes will eventually oxidize PO3 to PO4, which plants do use.


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## Guest (May 29, 2020)

I was low on P and used a 0-45-0 granular. I was okay on my K but I also used a 0-0-50 granular. I use liquid N and FE now.

I agree for the P & K I would not use liquid to bring those up.

I have not found a 0-45-0 or 0-0-50 at a big box store. See if you can find a local Feed and Seed store.


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## osuturfman (Aug 12, 2017)

MKP is your friend, find some soon.

Phosphite will not supply plant-available P but, it's a good tank-mix partner in your climate.


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## DannyBoy2k (May 25, 2019)

Thanks, @osuturfman . That's the product I was hoping to find when I started searching for products I could spray out. As I've already ordered the SOP and triple superphosphate, I'll save the information for my arsenal of other products I could use.

As regards the phosphite, if I'm not going to be applying it for it's P value, do you have a rate recommendation per M? Is it just something I could throw into a fungicide mix if I'm going to be spraying anyway? Someone (i.e. me), in their haste to get something to correct his soil problems, may have already ordered some phosphite before being (correctly) talked into getting SOP and triple superphosphate, so it would be nice to have a use for this phosphite other than to sit on the shelf and wait to be recycled through the town's hazardous waste program.

Is my super high iron going to be an issue going forward? I noticed that most complete fertilizers include a percentage of iron in the mix. It would appear I don't need any more. Anyone think I should avoid complete fertilizers and go with applying separate N, P, and K?

~Dan


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