[sam]

Hi Everyone,

Newbie here, but I've already learned a lot from browsing the forum - thank you!

I have a couple specific questions below, but also appreciate any other advice you might have for me (soil tests below from U Delaware: the first one is front yard, second one is back yard)

Questions:
1) I need phosphorus in the front. Is there any way to add phosphorus alone without nitrogen?
2) Is it a bad idea to add phosphorus in spring? My front yard is pretty deficient
3) soil test says Mg and Ca excessive - does that matter?

Thanks!

Background:
Transition zone (Maryland)
Turf type tall fescue (+ clover + misc!)
Don''t use herbicides / pesticides. Only irrigate on exceptional basis (e.g. seeding / fert /etc)
Front is south facing with direct sun most of day. Back gets a mix of sun/shade

 

[g-man]

Sam, welcome to TLF. Does the results pages have some info about what they mean by index? Magnesium higher than calcium is not ideal, but I don't know if the reported value is in ppm. Did you follow their lime recommendations?

To apply only phosphorus, you will need Diammonium phosphate (DAP) Triple Super Phosphate. It is not likely that you will find it at home Depot, Lowe's,... You will need to find a co-op or maybe a landscape company.

Another option is to look at starter fertilizer with the middle number (P) being high relative to the first (N). This will not be a nitrogen free option.

 

[Ridgerunner]

Welcome to TLF

 

[Ridgerunner]

Questions:
1) I need phosphorus in the front. Is there any way to add phosphorus alone without nitrogen?

Triple Super Phosphate is the only non-N phosphorous product of which I am aware. I believe both MAP and DAP have some N. scroll down to chart: http://www.extension.umn.edu/agriculture/nutrient-management/phosphorus/understanding-phosphorus-fertilizers/

2) Is it a bad idea to add phosphorus in spring? My front yard is pretty deficient

No, in fact some studies indicate that it can promote root growth which is highest at spring soil temperatures. each 1#/M of phosphorous (P) fertilizer will theoretically raise soil levels 9 ppm (or in the case of the UDel Index units= will raise9 units). However, P never met another nutrient it wouldn't hook up with, so it can reduce availability of other nutrients as well its own availability. That shouldn't be a problem unless you go excessive.

3) soil test says Mg and Ca excessive - does that matter?

No. I'll try to get back tomorrow and explain the Index system and define "excessive."

 

[g-man]

@Ridgerunner thanks for correcting my screw up. Thou shall not post after being 24hr awake in flights to get back home.

 

[Ridgerunner]

@g-man Pffft. I make mistakes all the time unfortunately and I don't have any valid excuse.
DAP or MAP would be the better alternative to starter fertilizer (as more P and less N would be applied) or a better alternative to triple super P If @sam didn't winterize last year.
On the topic of Indexes. Indexes are just a convenient method for scaling amounts of something relative to a "set" base value/number - usually 100. It allows dissimilar items to be scaled on a single chart/graph rather than employing separate charts/graphs, in addition, 100 also translates as a percentile.
UofDel's FIV (Fertility Index Value) is based on 100 and M3 extracted phosphorous ppm. An index value of 100 = a soil test value for phosphorous of 100 ppm. It is 1:1 and represents the 100th percentile (100%), but they could have elected to have a FIV of 100 equal 50 ppm or 35ppm etc. if they had determined based on studies for a particular regional soil that more than 50 or 35 ppm of P was excessive. However UofDel has determined that optimum is 50-100 and over 100 ppm of P is excessive. (Which is actually quite high IMO.) For comparison see the P, K, Ca and Mg ppm values from this Waypoint soil test https://thelawnforum.com/viewtopic.php?f=2&t=1896 and where they fall within Waypoint's determinations for optimum and excessive as compared to the UofDel determination for optimum and excessive ranges (based on ppm values).
Anyway, the UofDel's FIV of 100 for potassium is 182 ppm K via M3.
UofDel's FIV of 100 for Calcium is 1000 ppm Ca via M3.
UofDel's FIV of 100 for Magnesium is 131 ppm Mg via M3.
So that creates the following multiplier factors:
UofDel's FIV reported value for P X 1 = ppm of P.
UofDel's FIV reported value for K X 1.82 = ppm of K.
UofDel's FIV reported value for Ca X 10 = ppm of Ca.
UofDel's FIV reported value for Mg X 1.31 = ppm of Mg.
To finally conclude, @sam Your Ca and Mg levels are fine and not a detrimental issue. See the recommended M3 values in this link https://thelawnforum.com/viewtopic.php?f=22&t=1088

 

[g-man]

Anyway, the UofDel's FIV of 100 for potassium is 182 ppm K via M3.
UofDel's FIV of 100 for Calcium is 1000 ppm Ca via M3.
UofDel's FIV of 100 for Magnesium is 131 ppm Mg via M3.

How are you getting these conversions? I went to their website and I could not see them there.

 

[sam]

Thanks you so much guys. Amazing answers and information.

 

[Ridgerunner]

Anyway, the UofDel's FIV of 100 for potassium is 182 ppm K via M3.
UofDel's FIV of 100 for Calcium is 1000 ppm Ca via M3.
UofDel's FIV of 100 for Magnesium is 131 ppm Mg via M3.

How are you getting these conversions? I went to their website and I could not see them there.

They are/were from this link, but the link is now 404:
Appendix 12 from Cooperative Bulletin No. 59 - The Nutrient Management Handbook https://extension.udel.edu/dstp/UDNMH/Appendix-5.pdf
In 2016 I e-mailed the Del Lab for information on their soil test index and they responded with the above description and two pdf files of the pertinent information in Appendix 12. I tried to link them here but couldn't, so I just wrote the relevant information into the post.
Let me know if you are able to find the Bulletin No. 59 somewhere on their site.

 

[crunk]

Anyway, the UofDel's FIV of 100 for potassium is 182 ppm K via M3.
UofDel's FIV of 100 for Calcium is 1000 ppm Ca via M3.
UofDel's FIV of 100 for Magnesium is 131 ppm Mg via M3.

How are you getting these conversions? I went to their website and I could not see them there.

They are/were from this link, but the link is now 404:
Appendix 12 from Cooperative Bulletin No. 59 - The Nutrient Management Handbook https://extension.udel.edu/dstp/UDNMH/Appendix-5.pdf
In 2016 I e-mailed the Del Lab for information on their soil test index and they responded with the above description and two pdf files of the pertinent information in Appendix 12. I tried to link them here but couldn't, so I just wrote the relevant information into the post.
Let me know if you are able to find the Bulletin No. 59 somewhere on their site.

I think this is the pdf link: https://cdn.extension.udel.edu/wp-content/uploads/2018/03/02042319/Appendix-5.pdf
here's info on interpreting UD's tests: http://extension.udel.edu/factsheets/interpreting-soil-phosphorus-and-potassium-tests/

 

[Ridgerunner]

That's it. Thank you.
You computer savvy people amaze me.
How did you find it?

 

[crunk]

That's it. Thank you.
You computer savvy people amaze me.
How did you find it?

I just got my results back from them and I think I Googled " FIV soil test explanation UD".
Here are my results:

 

[sam]

each 1#/M of phosphorous (P) fertilizer will theoretically raise soil levels 9 ppm (or in the case of the UDel Index units= will raise9 units). However, P never met another nutrient it wouldn't hook up with, so it can reduce availability of other nutrients as well its own availability. That shouldn't be a problem unless you go excessive.

Thanks again guys. I'd like to double check how much P-containing fert I should put down.

According to the above, it looks like to get from 12ppm (soil test) to say 40ppm would take 3 lbs of "P" per k. For a 0-50-0 that'd be 6 lbs of overall product per k (not all at once, mind you!)

Am I doing my math right?
I read in ridgerunner's soil test thread that the NPK rating is actually telling us P2O5 not P - do I need to correct for that too? When I use the formula in the thread it seems to come out the same - maybe because he has already corrected for that factor here in this quote above

Any other guidelines about how to implement this in practice - I wouldn't throw it all down at once because it sounds like quite a lot. Any guidelines on how much is too much to put down? 1) in any particular app and 2) over the whole spring season?

Thanks again!

PS - I have super triple phosphate at 0-46-0 and MAP at 11-52-0

 

[g-man]

According to the above, it looks like to get from 12ppm (soil test) to say 40ppm would take 3 lbs of "P" per k. For a 0-50-0 that'd be 6 lbs of overall product per k (not all at once, mind you!)

Am I doing my math right?
I read in ridgerunner's soil test thread that the NPK rating is actually telling us P2O5 not P - do I need to correct for that too? When I use the formula in the thread it seems to come out the same - maybe because he has already corrected for that factor here in this quote above

Any other guidelines about how to implement this in practice - I wouldn't throw it all down at once because it sounds like quite a lot. Any guidelines on how much is too much to put down? 1) in any particular app and 2) over the whole spring season?

Thanks again!

PS - I have super triple phosphate at 0-46-0 and MAP at 11-52-0

You do need to correct for P2O5 and for the depth of soil you want to correct (ie. 6 inches).

You want apply 1lb of P2O5 / k / month in the months that the grass is growing (spring/fall). It will take some time to correct the phosphorous.

 

[Suburban Jungle Life]

FYI. If you are located in MD, it is illegal to apply more than 0.5 lbs of P / M in 1 year and more than 0.25 lbs of P per application. Technically, they don't want homeowners to apply P at all but these are the limits for a licensed applicator which I think would be fine to follow. Make sure to measure your lawn accurately so you don't over apply.

Violators are subject to civil penalties of up to $1,000 for the first violation and $2,000 for each subsequent violation. If you don't follow these guidelines, I wouldn't post your usage or tell anyone...

Main page:
http://mda.maryland.gov/Pages/fertilizer.aspx

Fert Law:
http://mda.maryland.gov/resource_conservation/Documents/fertilizerwebpage.pdf

Max N rates:
http://extension.umd.edu/hgic/umd-extension-lawn-fertilizer-schedule-home-lawns

MD has strict limits on N and P. No limits on K. Too much over application by homeowners and ag has damaged the bay so now there are strict limits. BTW, my grass is green and thick and my P is even lower than yours. You don't need much P to have a thick and green lawn... If you would like some clarification, @thegrassfactor can provide the science behind it! To reduce runoff, a core aeration and watering after wouldn't be a bad idea.

 

[Suburban Jungle Life]

Due to these restrictions, I have created a spreadsheet to calculate N and P and add it up so you can ensure you don't exceed the max rates per year. It makes it hard when you use organics which have some P throughout the year and you want to use more P during fall seeding but also have to calculate the amount of N per year. If you use separate N and P products which don't have any overlap, that would be the easiest. This is why I don't use Milo. At 4% P, that adds up fast. If you read the bags sold in MD, they list a much larger coverage area due to the max rate of .5 lbs of P per year. Same thing in FL. Hope this helps. Sorry, didn't mean to ramble.

 

[g-man]

I went thru the rabbit hole trying to find the fertilizer info. I gave up. The .gov sites says to go to the U of Maryland, but then I cant find it in the linked website.

Venting - I just dont see how this is enforceable. ie. Not to exceed 0.9lb of N/M in an application. So if I apply today at 0.5 and tomorrow at 0.5, when I'm ok? Is there someone that goes around houses and measures the amount of nitrogen being applied? I think farm fields contributes more to waterway pollution than the average homeowner.

@@sam do follow your local laws.

 

[Suburban Jungle Life]

I'm sure no one checks but posting it online or making a video about doing it might be making it a little too obvious to the public. I have a spreadsheet I use which breaks it all down to specific quantities. Let me know your grass type/lawn size (you can break it down for front and back if you want) what fertilizers you want to use and I'll fill out the spreadsheet for you and post it. I need a source for N/P/K, all synthetic or both organic and synthetic unless you use an organic without any P (not common or expensive). I assume you will over seed every fall so I'll keep that in mind.

At the easiest end of the scale, all the fert they sell in MD is labeled and mixed with app rates of .9 lbs N and .7 lbs quick release. So just stopping by Lowes or Home Depot and picking up some fert and following the label to do 3 apps per year is following the law. You just won't have any P and very little K.

 

[sam]

FYI. If you are located in MD, it is illegal to apply more than 0.5 lbs of P / M in 1 year and more than 0.25 lbs of P per application. Technically, they don't want homeowners to apply P at all but these are the limits for a licensed applicator which I think would be fine to follow. Make sure to measure your lawn accurately so you don't over apply.

Thanks Suburban. Are you in MD? I definitely obey the rules as well as good practices. And when I do fertilize, I use normally use Ringer which is organic 10-0-6

As I read it, the laws say essentially "Phosphorus may only be applied when a soil test indicates that it is needed or when a lawn is being established, patched or renovated" - which definitely applies to me. I don't see anything on rates that applies to my situation. Regardless I want to follow good practice.

I did find the numbers you mention under the heading "For professionals only". But I think that is part of a clause that is actually giving pros special permission to continue applying organic ferts which contain phosphorus. i.e. They are giving extra permission to pros, with a limitation. I don't think this applies to this situation "Professional applicators may continue to apply natural organic or organic products containing phosphorus, but beginning October 1, 2013, each application may not exceed 0.25 pounds of phosphorus per 1,000 square feet with an annual maximum of 0.5 pounds of phosphorus per 1,000 square feet. These products may not be applied when soils test at "optimum to excessive" for phosphorus levels"

 

[Ridgerunner]

@sam
Sorry, I'm regularly cited for making things complicated and producing head-aches, but like I&T's Proud Mary, I don't know how to do things nice and easy. Well, I guess I could just say: You're SOL and be done with it.
Your calculations are correct. The conversion/correction factor is included. 1 lbs of P2O5/M will add the equivalent of 9.45 ppm. Applying 1 lb?M of elemental phosphorous would be the equivalent of adding 21.75 ppm. However, that is not necessarily be reflected on a subsequent soil report, due to soil chemistry/dynamics, erosion/runoff, the extraction test method used etc. It is a starting point from which adjustments can be made based on the results from the next soil test. Really, the same principle pretty much also applies to factoring for depth, unless you are attempting a one-off; although, factoring for depth will help guard against over applying.
The objective of the Md law is well intentioned and meant to serve an important concern, but like many laws, poorly written. I won't advise to circumvent it.
@g-man
http://mda.maryland.gov/resource_conservation/Documents/Fertilizer_Law.pdf
http://mda.maryland.gov/resource_conservation/Documents/consultant_information/2003%20I-E1%20p1-8%20s5.pdf
Per the Maryland Nutrient Management Manual I-E1 and I-E2, you are only authorized to apply a maximum of 3 lbs/M of N for fescue grass. The turf's use of 3 lbs/M of N over the growing season could result in the turf using as much as .75 lbs/M of P over the growing season. .75 lbs/M of P is equal to 1.725 lbs/M of P2O5. Per the Maryland Nutrient Management Manual I-E1 and I-E2, if you have a soil test done within the last three years that rates the P level low or medium, you may apply 2 lbs of P2O5 annually. The 2 lbs applied less the 1.725 lbs the turf may use, results in a yearly gain of .275 lbs of P2O5 added to the soil "bank." Or an increase of 2.6 ppm. (9.45 ppm times .275 = 2.6 ppm). Oh, well, slow but steady. Besides, in most cases it wouldn't have been advisable to add much more than 3 lbs/M of P in one season anyway. In addition, these are just calculations and somewhat theoretical approximations. The true proof will be reflected in the next soil test.