# Calculating N Rates Synthetic vs Organic



## drummereef (Oct 15, 2018)

I apologize for the noob question here... &#128584; I was looking back in my journal calculating total N rates for the year. I applied both synthetics and organics throughout the year.

Can we accurately calculate organic N rates since they are primarily microbe / temperature dependant?

I can wrap my head around synthetics as they are fairly straightforward minus some expected loss. But organic uptake could vary drastically in length and availability due to soil conditions, temperature, microbe activity etc... We know "pounds on the ground", but do we really know what's being used?

So... Do you include your organic N rates in total along with your synthetic applications? &#129300;


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## osuturfman (Aug 12, 2017)

The true answer is, we don't know. There are some decent predictive models of N mineralization in soil but, nothing that would be considered scientifically reliable. Dr. Bruce Branham at the University of Illinois is the preeminent expert on the subject of N use by grass, soil N banking, and mineralization. Here's a good podcast with him on this subject.

https://www.turfnet.com/podcasts/rossi/branham/


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## drummereef (Oct 15, 2018)

osuturfman said:


> The true answer is, we don't know. There are some decent predictive models of N mineralization in soil but, nothing that would be considered scientifically reliable. Dr. Bruce Branham at the University of Illinois is the preeminent expert on the subject of N use by grass, soil N banking, and mineralization. Here's a good podcast with him on this subject.
> 
> https://www.turfnet.com/podcasts/rossi/branham/


Thanks osuturfman. I've listened to that episode before - that was a great one. 👍 I guess where it's most confusing is the argument between soil N banking and what the plant is actually using (tissue sample). I definitely don't want to get flippant with yearly N - I don't want to risk damage or burning obviously. But considering you can dump loads of Milorganite on a lawn without collateral NaCl damage it's starting to look more like a soil conditioner to me versus actual nutrient (synthetic). Maybe that's dangerous...?! 😬


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## Ridgerunner (May 16, 2017)

> But considering you can dump loads of Milorganite on a lawn without collateral NaCl damage


@drummereef May I ask what the basis is for this relationship between Milorganite (or any fertilizer?) and NaCl damgae?


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## drummereef (Oct 15, 2018)

Ridgerunner said:


> > But considering you can dump loads of Milorganite on a lawn without collateral NaCl damage
> 
> 
> @drummereef May I ask what the basis is for this relationship between Milorganite (or any fertilizer?) and NaCl damgae?


I guess I don't have a correlation other than fear!! :lol: In regards to yearly N application there seems to be a significant range of advice from the de facto standard University Extensions, to the Nitrogen Blitz guys, to a more conservative N rate like John Perry's recommendations. I just brought up NaCl as I've known that to be one of the factors to cause dyhdration/burning damage from synthetic fertilizers. I'm likely confusing NaCl and the fertilizer salt indexes wrongly!  If you have a link to explain the difference I'd love to read into it! :thumbup:

Mostly what I'm asking is... For my _winterizer_ application, if I'm at 4lb/K of N for the year AFTER applying the winterizer will I be at risk for any damage to the lawn? (TTTF). I didn't follow the nitrogen blitz because I did heavy renovation on the yard this year.


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## Ridgerunner (May 16, 2017)

> I'm likely confusing NaCl and the fertilizer salt indexes wrongly!


 :thumbup: 
Nearly all soil amendments/fertilizers are a salt (a combination of an acid and a base). You already appear familiar with the dehydrating/osmotic affect of salts and the salt index as an indicator of the relative affects between different amendments/fertilizers against a standard set at a value of 100. Monitoring soil electrical conductivity through (EC) testing is an effective method for determining detrimental levels/accumulation and avoiding them.
I thought I had bookmarked a pretty comprehensive explanation, but it's now a dead link. This one is pretty cursory: https://www.slideshare.net/aquasoilss/salt-index-liquid-vs-granular and https://www.spectrumanalytic.com/support/library/ff/salt_index_calculation.htm


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## drummereef (Oct 15, 2018)

Ridgerunner said:


> > I'm likely confusing NaCl and the fertilizer salt indexes wrongly!
> 
> 
> :thumbup:
> ...


Awesome, I will read through the link! Is there a relatively inexpensive way (meter) to monitor soil conductivity at home? Or is that something that has to be done through our yearly lab soil tests? Thanks Ridgerunner! :thumbup:


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## Ridgerunner (May 16, 2017)

This one has a very simple explanation of the affect of salt on osmosis/dehydration
https://www.precisionlab.com/resources/wuxal_understanding_salt_index.pdf


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## Ridgerunner (May 16, 2017)

I'd strongly suggest you use a lab. One of the pros might be familiar with an accurate DIY method, I'm not.


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## drummereef (Oct 15, 2018)

Ridgerunner said:


> I'd strongly suggest you use a lab. One of the pros might be familiar with an accurate DIY method, I'm not.


Got it. And thanks for the 2nd link as well! :thumbup:


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## viva_oldtrafford (Apr 4, 2018)

IIRC, TF has a higher salt tolerance than hybrbid berumda. In other words, if I can hybrid bermuda maintain tee boxes and fairways without ever considering the impact of tss, your TF is good to go.

E: https://docs.wixstatic.com/ugd/af168c_c39d0d6e7a674ad0b4fece4d961b24ec.pdf


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## drummereef (Oct 15, 2018)

viva_oldtrafford said:


> IIRC, TF has a higher salt tolerance than hybrbid berumda. In other words, if I can hybrid bermuda maintain tee boxes and fairways without ever considering the impact of tss, your TF is good to go.
> 
> E: https://docs.wixstatic.com/ugd/af168c_c39d0d6e7a674ad0b4fece4d961b24ec.pdf


Thanks Viva. 👍 Based upon the salt index, is there a maximum allowable level of accumulated salts in the soil before risking burn?


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## Ridgerunner (May 16, 2017)

> Based upon the salt index, is there a maximum allowable level of accumulated salts in the soil before risking burn?


No, not based on the salt index. As per prior discussion the salt index reflects the relative resultant change in osmotic pressure of different fertilizers/amendments compared to an equal quantity of NaNO3. EC is the method to determine the amount of "salt" present in a particular soil and EC measurment results can broadly be used to determine detrimental levels. Nearly any soil test lab offers the EC test, some include it in their standard package, some offer it as an add-on at an additional fee. Some Labs call it an EC test, some call it a Soil Salinity test and some might call it a Soluble Salt test, etc.
From my thread:

_*Soil Salinity (The EC (Electrical Conductivity) Test)*
High soil salt content can detrimentally affect osmotic pressure. In other words, the turf plant will suffer the effects of dehydration due to the inability to take up water. As increased salt content in water increases, the electrical conductivity of water also increases, Soil salt content is determined by measuring the electrical conductivity (EC) of the soil solution. A saturated paste solution is commonly used as the standard for EC measurement. However, be aware, some labs use a different proportion of water to soil solution for their tests and their EC results must be adjusted to a different standard. EC is measured in units of dS/m (decisiemens per meter) or mmhos/cm. Using the saturated paste test, a result of <4 dS/m or mmhos/cm is considered satisfactory for most plants. A reading of <2 is preferable for salt sensitive turf grass like KBG. Bermuda grass is much less sensitive and can withstand salinity levels up to a dS/m level of 6.9._

Take those threshold values with a grain of salt  :lol: Agronomist/Soil/Turf specialists disagree slightly among their recommended thresholds. In addition different cultivars of the same type of turf grasses can vary in their sensitivity and the climate (temps) and irrigation regiment can influence the effect.

I think we're straying off from your original inquiry regarding N. Sorry about that.


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## drummereef (Oct 15, 2018)

Ridgerunner said:


> > Based upon the salt index, is there a maximum allowable level of accumulated salts in the soil before risking burn?
> 
> 
> No, not based on the salt index. As per prior discussion the salt index reflects the relative resultant change in osmotic pressure of different fertilizers/amendments compared to an equal quantity of NaNO3. EC is the method to determine the amount of "salt" present in a particular soil and EC measurment results can broadly be used to determine detrimental levels. Nearly any soil test lab offers the EC test, some include it in their standard package, some offer it as an add-on at an additional fee. Some Labs call it an EC test, some call it a Soil Salinity test and some might call it a Soluble Salt test, etc.
> ...


No apologies necessary! Fantastic discussion. 👍 It's slowly starting to make sense. 😁 This spring I plan on getting a Ward Labs S-5 test. My Soil Savvy test came back Na=14.40ppm this past year but I'm taking that with a grain of salt (pun intended) as I am the other nutrient results. 😉


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## viva_oldtrafford (Apr 4, 2018)

drummereef said:


> Ridgerunner said:
> 
> 
> > > Based upon the salt index, is there a maximum allowable level of accumulated salts in the soil before risking burn?
> ...


Are you seeing high Na numbers and equating them with "salts"? Na (sodicity) is not the same as salinity. Look into articles that outline sodicity and salinity if this is the case. Excessive Na on the exchange sites do pose an issue, but are cured with Gypsum (monovalent vs divalent cations blah blah blah)....saline soils have no remedy other than flushing with good irrigation water.


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## drummereef (Oct 15, 2018)

viva_oldtrafford said:


> Are you seeing high Na numbers and equating them with "salts"? Na (sodicity) is not the same as salinity. Look into articles that outline sodicity and salinity if this is the case. Excessive Na on the exchange sites do pose an issue, but are cured with Gypsum (monovalent vs divalent cations blah blah blah)....saline soils have no remedy other than flushing with good irrigation water.


OK, yes I think based upon this Soil Savvy test I was. I didn't realize their test was for sodicity (Na) which does make sense now. Thanks for the clarification and I'm reading into the differences now. 👍


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