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Smallaxe
12-10-2011, 11:18 AM
The following article contains some interesting ideas...

http://aggie-horticulture.tamu.edu/archives/parsons/turf/publications/fertiliz.html

"The "peaks" and "valleys" in growth rate observed between applications of soluble nitrogen fertilizers may not be obvious on frequently mowed turf areas, but they can have a detrimental effect on the grass. Short bursts of growth after fertilizer application followed by a period of slow growth can deplete carbohydrate reserves in the grass, reduce root development and eventually thin a turf. These effects are not readily apparent by observing growth rate and color responses to fertilization. Long term observations and responses to stress would more accurately establish the effect of soluble nitrogen sources on turf."

The interestting thing about this statement that it kind of explains how/why carb reserves get used up with early Spring N apps, among other things... :)

Smallaxe
12-10-2011, 11:20 AM
Same article:
"Slow-release nitrogen sources build up "residual" soil nitrogen that is made available to the grass at varying rates. The rate at which "residual" nitrogen is made available (released) may vary with nitrogen source, temperature, moisture, pH, particle size and time of application. Knowledge of a particular nitrogen source and of conditions favorable for nitrogen release is necessary for a turf manager to determine the timing and rates of application of slow-release fertilizers."

Smallaxe
12-10-2011, 11:25 AM
Residual build up of N in the soil that is released when adequate water is present and extreme temps are avoided would be a great plus for even tempered healthy growth...

Would this be an adequate reason to use organic fertilizers during the summer? ...In that an additional expense would be justified at the beginning of summer, but may possibly be compensated by 'skipping' the next app and holding off until Fall, as the 'residuals' from slow release and organic ferts get used up??

CHARLES CUE
12-10-2011, 08:51 PM
Nice article but it also states that organic sources should not be concerted a slow release fert and not a good winter fert.



lNevertheless, organic nitrogen sources can be effectively used in most turf maintenance programs. Nitrogen release from organic sources is dependent on microorganisms; thus, factors that favor microbial activity increase the rate of nitrogen release from these materials. Organic materials are not considered good nitrogen sources for winter months because of the low activity of microbes. During other seasons organic sources are very effective.

Charles Cue

Smallaxe
12-11-2011, 09:14 AM
Nice article but it also states that organic sources should not be concerted a slow release fert and not a good winter fert.



lNevertheless, organic nitrogen sources can be effectively used in most turf maintenance programs. Nitrogen release from organic sources is dependent on microorganisms; thus, factors that favor microbial activity increase the rate of nitrogen release from these materials. Organic materials are not considered good nitrogen sources for winter months because of the low activity of microbes. During other seasons organic sources are very effective.

Charles Cue

And that does make sense to me... Where I'm looking for a healthier turf is in the heat of summer when the color fades and growth sometimes stops and some plant go into dormancy. With Orgferts being reliant on microbes for N release, it would makes sense that the only time N was released would be when conditions are correct for both roots and microbes. Whereas synferts would more easily volitize or leach during short infrequent events of heavy downpours, and therest of the time is hot and dry...

If we follow the following bit of logic, it would seem that our winterizer, below 50 degree soil temp almost always have to be synthetic...

... "Fertilizer applications should be timed to coincide with favorable temperatures for growth of turfgrasses. Also, nitrogen sources should be selected based on their availability to grasses under expected temperature conditions. For example, organic nitrogen sources and ureaformaldehyde do not release nitrogen at sufficient rates for turf growth when soil temperatures are below 50ºF. ..."

The other point with organic fertilizers for the summer is that they'll help build a structure that is conducive to healthy root growth and provide CE sites that ferts can hang onto longer... Does that seem worth it?

Smallaxe
12-11-2011, 09:29 AM
"Potassium is often present in large quantities in soils, but very small amounts may be in the available form (K+). Potassium is a constituent of many soil minerals and is held very strongly by clay particles. For potassium to be taken up by the grass it must be in the solution in the potassium ion (K+) form. An equilibrium exists between the K+ in solution and that held by clay particles (see illustration). As the grass root takes up the K+ from the soil solution, additional K+ is released from the soil solution to the clay particles. Clay particles, thus, serve as a reservoir for K+ and help to reduce the amount of K+ lost by leaching."

This brings up an iteresting point that is never discussed as a possible issue in fert programs. Just like P it appears that K is likely to be available in a 'fertile' soil... In this case a fertile soil would likely just have clay particles in...

Can soil tests measure how much K is being held by the clay particles? or do they only measure how much K is available at any given time w/out regard to the 'K resevoir'?

Kiril
12-11-2011, 09:55 AM
"Potassium is often present in large quantities in soils, but very small amounts may be in the available form (K+). Potassium is a constituent of many soil minerals and is held very strongly by clay particles. For potassium to be taken up by the grass it must be in the solution in the potassium ion (K+) form. An equilibrium exists between the K+ in solution and that held by clay particles (see illustration). As the grass root takes up the K+ from the soil solution, additional K+ is released from the soil solution to the clay particles. Clay particles, thus, serve as a reservoir for K+ and help to reduce the amount of K+ lost by leaching."

This brings up an iteresting point that is never discussed as a possible issue in fert programs. Just like P it appears that K is likely to be available in a 'fertile' soil... In this case a fertile soil would likely just have clay particles in...

Can soil tests measure how much K is being held by the clay particles? or do they only measure how much K is available at any given time w/out regard to the 'K resevoir'?

P and K are not comparable, and soils tests give you semi-quanitative numbers on the labile K pool (exchangeable & solution K). Some testing methodologies will only give you numbers on exchangeable K.

Smallaxe
12-11-2011, 10:13 AM
P and K are not comparable, ...

I only meant that the idea of "Available" P changes on an 'as neede' basis with the presence of AMF, as this article claimed that "Available" K changes as on an 'as needed' basis with the presence of clay particles...

The question now becomes: How do we know if there is enough 'reserve K' in the clay for there to be a healthy amount available to the turf as needed?

Kiril
12-11-2011, 10:27 AM
The question now becomes: How do we know if there is enough 'reserve K' in the clay for there to be a healthy amount available to the turf as needed?

Already answered that.

Smallaxe
12-11-2011, 10:58 AM
Already answered that.

You mean by this statement? "...semi-quanitative numbers on the labile K pool (exchangeable & solution K). ..."

If I take a soil sample down to the testing lab, Which test would I ask for? (by name)

and how would I know that the K is being release at an adequate pace to provide the necessary amounts on a timely basis? (is the amount adequate to assume the rate?)

It would be good to be able to take a soil test to a client and show that he needn't apply any K for his winterizer... :)

Smallaxe
12-11-2011, 11:06 AM
Another issue with the soil test would relate to this concept as well. Wouldn't it?
If we are in the habit of dumping on too much N wouldn't we be shooting down whatever understanding we may have about "available" K?
It seems the following would be warning us of that possibility...

[color="blue"]"Nutrient uptake is a function of nutrient levels and interactions between nutrients. The level of one nutrient can affect the uptake of another nutrient. For example a high concentration of NH+ can reduce the uptake of K+ by the grass. Also where NO3- levels are deficient, K+ uptake will be restircted even though high levels of K+ may be present. These interactions between nitrogen and potassium can have a significant influence on the growth of turfgrasses."[color]

Kiril
12-11-2011, 11:30 AM
You mean by this statement? "...semi-quanitative numbers on the labile K pool (exchangeable & solution K). ..."

If I take a soil sample down to the testing lab, Which test would I ask for? (by name)

There are many different methodologies used depending on the lab, what you are looking for, soils types typically seen by the lab, and other soil related properties. Generally speaking, Morgan, Modified Morgan, Mehlich-1 and Mehlich-3 are used. My lab uses modified morgan for Extractable K, Na, Ca, Mg and SO4.

If you are more concerned with solution concentrations (i.e. salinity), then a saturated paste extract is typical, but not generally included in your basic testing packages given the information is really only useful when dealing with saline/sodic soils.

and how would I know that the K is being release at an adequate pace to provide the necessary amounts on a timely basis? (is the amount adequate to assume the rate?)

Plant tissue analysis

Kiril
12-11-2011, 11:40 AM
Another issue with the soil test would relate to this concept as well. Wouldn't it?
If we are in the habit of dumping on too much N wouldn't we be shooting down whatever understanding we may have about "available" K?

That is what the soil test is for. Knowledge of soil chemistry and potential interactions between ions as it relates to soil availability and plant uptake is required. You then combine that with knowledge of the site, management practices, plant monitoring, plant tissue analysis, etc.... to make an informed management decision.

Smallaxe
12-11-2011, 06:46 PM
There are many different methodologies used depending on the lab, what you are looking for, soils types typically seen by the lab, and other soil related properties. Generally speaking, Morgan, Modified Morgan, Mehlich-1 and Mehlich-3 are used. My lab uses modified morgan for Extractable K, Na, Ca, Mg and SO4.

If you are more concerned with solution concentrations (i.e. salinity), then a saturated paste extract is typical, but not generally included in your basic testing packages given the information is really only useful when dealing with saline/sodic soils.



Plant tissue analysis

That's what I figured... Plant Tissue Analysis...

It really is the only to know if the grass is getting all the nutrients needed, rather than 'predicting' what might be available from the soil...

But , I do like the idea of the modified morgan if it is able to analyse "Extractable" K, Ca, Mg and SO4...

Thanks, that makes things a little clearer... :)

Smallaxe
12-11-2011, 07:08 PM
That is what the soil test is for. Knowledge of soil chemistry and potential interactions between ions as it relates to soil availability and plant uptake is required. You then combine that with knowledge of the site, management practices, plant monitoring, plant tissue analysis, etc.... to make an informed management decision.

What I have been trying to wrap my head around for years is the connection between the soil analysis and the physical management of a particular site...

The biggest disconnect for me has always been the analysis and advise, from the lab, that doesn't relate to moisture, soil texture, structure and relevant cultural practices that gives a site its 'individual' personality... :)

Skipster
12-12-2011, 11:57 AM
That's what I figured... Plant Tissue Analysis...

It really is the only to know if the grass is getting all the nutrients needed, rather than 'predicting' what might be available from the soil...

But , I do like the idea of the modified morgan if it is able to analyse "Extractable" K, Ca, Mg and SO4...

Thanks, that makes things a little clearer... :)

It's important to remember that the "extractable" means what the solvent you're using can extract, NOT what plants can extract.

Soil tests aren't the end-all-be-all of what is in the soil. If your test shows 50#/A of P, that doesn't mean that you only have 50#/A P and no more. It only means that the test was able to detect an amount equivalent to 50#/A. Soil tests are an index value. The absolute number isn't important -- what's important is the distance between values.

Smallaxe
12-12-2011, 04:18 PM
It's important to remember that the "extractable" means what the solvent you're using can extract, NOT what plants can extract.

Soil tests aren't the end-all-be-all of what is in the soil. If your test shows 50#/A of P, that doesn't mean that you only have 50#/A P and no more. It only means that the test was able to detect an amount equivalent to 50#/A. Soil tests are an index value. The absolute number isn't important -- what's important is the distance between values.

So can the modified Morgan give an idea of how much K is being held, in reserve, by clay particles or not???

Skipster
12-12-2011, 05:13 PM
So can the modified Morgan give an idea of how much K is being held, in reserve, by clay particles or not???

All soil tests will give you and idea of how much K is held on exchange sites, but that number doesn't mean much. Different extractants will give you a different value, but that doesn't mean that one is necessarily better than another or that you have more K in one sapmle over another just because you used a different extractant.

What *is* meaningful is how the plant responds at different soil test levels from the SAME extractant. Knock yourself out using whatever extractant you like -- they all have +s and -s. But, you can't make a meaningful decision looking at a Morgan test one time, then a Bray P1 the next.

Remember, too, that K is relatively immobile in the soil, similar to P. Knowing how much is held on clay colloids is not particularly useful, since most of it will not be available to the plant.

Smallaxe
12-12-2011, 05:43 PM
All soil tests will give you and idea of how much K is held on exchange sites, but that number doesn't mean much. Different extractants will give you a different value, but that doesn't mean that one is necessarily better than another or that you have more K in one sapmle over another just because you used a different extractant.

What *is* meaningful is how the plant responds at different soil test levels from the SAME extractant. Knock yourself out using whatever extractant you like -- they all have +s and -s. But, you can't make a meaningful decision looking at a Morgan test one time, then a Bray P1 the next.

Remember, too, that K is relatively immobile in the soil, similar to P. Knowing how much is held on clay colloids is not particularly useful, since most of it will not be available to the plant.

Well that has gone full circle...
It was this quote that got the current discussion started:

..."Potassium is often present in large quantities in soils, but very small amounts may be in the available form (K+). Potassium is a constituent of many soil minerals and is held very strongly by clay particles. For potassium to be taken up by the grass it must be in the solution in the potassium ion (K+) form. An equilibrium exists between the K+ in solution and that held by clay particles (see illustration). As the grass root takes up the K+ from the soil solution, additional K+ is released from the soil solution to the clay particles. Clay particles, thus, serve as a reservoir for K+ and help to reduce the amount of K+ lost by leaching."...

If this statement is true, then the only question would be... "how can we tell if there is adequate K in the clay resevior?"
Currently it appears to be the simplest thing to do is to not worry about it as long as there are adequate clay particles in the soil, since 'testing' is less than definitive... :)

Skipster
12-12-2011, 06:16 PM
Well that has gone full circle...
It was this quote that got the current discussion started:

..."Potassium is often present in large quantities in soils, but very small amounts may be in the available form (K+). Potassium is a constituent of many soil minerals and is held very strongly by clay particles. For potassium to be taken up by the grass it must be in the solution in the potassium ion (K+) form. An equilibrium exists between the K+ in solution and that held by clay particles (see illustration). As the grass root takes up the K+ from the soil solution, additional K+ is released from the soil solution to the clay particles. Clay particles, thus, serve as a reservoir for K+ and help to reduce the amount of K+ lost by leaching."...

If this statement is true, then the only question would be... "how can we tell if there is adequate K in the clay resevior?"
Currently it appears to be the simplest thing to do is to not worry about it as long as there are adequate clay particles in the soil, since 'testing' is less than definitive... :)

Remember, this article was written by my good friend Richard Duble to be easy to read for homeowners, so it omits some details that aren't necessary to understanding soil-K relations. But, a poor knowledge of soil chemistry can lead you astray here. If your dsicussion does not include non-exchangeable K, exchangeable K, soil solution K, and mineral K, you don't understand soil K interactions.

Soil K status is a flux involving mineral K (parent material), non-exchangeable K, exchangeable K, soil solution K, and plant interactions. Richard was trying to make these concepts easy to understand, but hit a snag when he said that K is released from the soil solution to the clay after plant uptake. After plant uptake, less K is in solution, which leaves space for more K to come off soil colloids and into solution and maintain charge balance. A smaller concentration of K+ ions can not move back to clay colloids simply because they are not large enough to replace the other ions on the colloids and their removal from solution would leave a charge imbalance.

Clay colloids can certainly be a reserve for soil K, but only to the point which it is exchangeable, which is measured by most soil tests. But, it is not necessary to know anything about non-exchangeable or mineral K, since they are not plant available.

Kiril
12-12-2011, 08:43 PM
All soil tests will give you and idea of how much K is held on exchange sites, but that number doesn't mean much.

I have to disagree here. That number gives you a rough approximation of what is contained in the labile pool ... i.e. what may be plant available now and/or potentially over the short term. That information is critical in determining if you need to fertilize and how much, after all the contributing factors are considered. Without the soil test you are back to playing guessing games and Russian roulette.

Just so everyone is clear, exchange sites are not limited to clay colloids. Iron and aluminum oxides as well as organic matter can also carry a charge.

Skipster
12-13-2011, 01:06 AM
Hang on, there. I'm not sayign that soil tests are unimportant. I *am* saying that we need to understand what they measure. They don't measure the labile pool and they don't give us any idea of what is plant available. Soil tests only measure the ions that are extracted from soil exchange sites (not just clay sites, but I used the terms Smallaxe wanted to use) with a particular solvent using a particular method. Correllation-calibration studies are then performed to help us make sense of the numbers. Soil test methods are constantly being revised. At the most recent annual meeting of the Soil Science Society of America (October 2011), there were 52 papers presented about changes to common soil test methods.

Different solvents give different values and different procedures (mixing in a different order, using different mix ratios, or swirling in solvent for different amounts of time) also give different values. However, none of these are meant to correspond to plant availability.

Correllation-calibration studies try to determine what soil test values tend to correspond to particular tissue concentrations and how fertilizer rates influence soil test values. This is how the fertilizer recommendations attached to your soil test report are determined. Having performed these studies and written these recommendations for several crops at three different land grant universities, I can tell you that none are geared for turfgrass -- they are all geared for row crops.

The bottom line is that soil tests don't deliver absolute values -- they are an index value. They are only a guide to fertility, not and end-all-be-all.

Smallaxe
12-13-2011, 06:56 AM
Remember, this article was written by my good friend Richard Duble to be easy to read for homeowners, so it omits some details that aren't necessary to understanding soil-K relations. But, a poor knowledge of soil chemistry can lead you astray here. If your dsicussion does not include non-exchangeable K, exchangeable K, soil solution K, and mineral K, you don't understand soil K interactions.

Soil K status is a flux involving mineral K (parent material), non-exchangeable K, exchangeable K, soil solution K, and plant interactions. Richard was trying to make these concepts easy to understand, but hit a snag when he said that K is released from the soil solution to the clay after plant uptake. After plant uptake, less K is in solution, which leaves space for more K to come off soil colloids and into solution and maintain charge balance. A smaller concentration of K+ ions can not move back to clay colloids simply because they are not large enough to replace the other ions on the colloids and their removal from solution would leave a charge imbalance.

Clay colloids can certainly be a reserve for soil K, but only to the point which it is exchangeable, which is measured by most soil tests. But, it is not necessary to know anything about non-exchangeable or mineral K, since they are not plant available.

So the question is still about the so-call "resevior" and whether the soil test is adequate to measure available K or not...

Skipster
12-13-2011, 09:59 AM
So the question is still about the so-call "resevior" and whether the soil test is adequate to measure available K or not...

This question has been answered several times already.

Soil tests DO NOT measure plant available nutrient concentrations!

Soil tests only report how much of the nutrient was extracted with the particular solvent and particular procedure. They were deceloped as a tool to help farmers know how much pre-plant fertilizer to apply to maximize profit. As I said before, the soil science community is always changing solvents and procedures to try to find the best combination, which shows us that soil testing is an inexact science.

Also, different solvents or procedures are better for different circumstances. For example, the Mehlich-1 extractant was developed to test P, K, Ca, Mg, Zn, Mn, and B in the low pH, medium-to-low CEC soils of the coastal southeastern US. But, Mehlich-1 doesn't capture all micronutrients well, including copper, which was deficient in coastal NC soils and caused significant economic problems in alfalfa, wheat, barley, oat, corn, and soybean crops. So, Dr. Mehlich (from NC Dept of Ag) modified his Mehlich-1 extractant to better detect copper, which eventually gave us Mehlich-3. Mehlich-1 and Mehlich-3 report the same values for most nutrients, but P is usually reported 50% higher for M-3 than M-1. So, why not use M-1? If your pH is above 6.5, M-1 overstates K, while understating P and several micronutrients. This is why M-3 might be used.

There is a give-and-take with soil testing. Most labs can't afford to run several tests on a single sample or the cost would be too high for customers to afford. So, one test is usually run that hits the high points for the soils in that area and recommendations are adjusted based on the before-mentioned correllation-calibration studies.

After all that background info, I guess the answer to your question may be foudn by dropping your K fert until you find deficiencies or poor turf quality. At that point, you know you need to add K.

Kiril
12-13-2011, 10:21 AM
Hang on, there. I'm not sayign that soil tests are unimportant. I *am* saying that we need to understand what they measure.

It seemed to me you have been implying the numbers are worthless. This is not true.

They don't measure the labile pool and they don't give us any idea of what is plant available.

The general extraction tests do estimate the labile pool and they do give us an idea of what may be readily plant available over the short term (i.e. growing season).

The SSSA defines the labile pool as "The sum of an element in the soil solution and the amount of that element readily solubilized or exchanged when the soil is equilibrated with a salt solution."

Generally speaking, the above is what extraction tests do (soil is equilibrated with a salt solution) and therefore are designed to estimate. Is it an absolute measure .... no, and no one has claimed it is. Are the tests perfectly reproducible .... no. The tests are designed to give the grower/manager an estimate of what may be/become plant available during the growing season.... i.e. an estimate of the labile pool.

This is the reason why knowledge of the testing methodology and how it applies to your soils is necessary to understand where potential errors in reported numbers may exist.

One thing that has not been discussed up to this point is proper sampling methodology. Your soil test results will mean nothing at all if your sampling methods are flawed.

Soil tests only measure the ions that are extracted from soil exchange sites (not just clay sites, but I used the terms Smallaxe wanted to use) with a particular solvent using a particular method.

That is not true, a point which I believe you already made. The tests will also measure solution and in some cases readily solubilized nutrients, again, within the constraints of the testing methodology. In fact, significant error can be introduced with extraction tests as a result of dissolution of compounds and/or minerals that would normally not be considered part of the labile pool.

Different solvents give different values and different procedures (mixing in a different order, using different mix ratios, or swirling in solvent for different amounts of time) also give different values. However, none of these are meant to correspond to plant availability.

I never said the nutrients were plant available, I said they "may be plant available now and/or potentially over the short term". The short term being a growing season.

Correllation-calibration studies try to determine what soil test values tend to correspond to particular tissue concentrations and how fertilizer rates influence soil test values. This is how the fertilizer recommendations attached to your soil test report are determined. Having performed these studies and written these recommendations for several crops at three different land grant universities, I can tell you that none are geared for turfgrass -- they are all geared for row crops.

Generally speaking, yes, most soil test calibration studies are done with respect to Ag, however soil test calibration studies have been done for turf.

The bottom line is that soil tests don't deliver absolute values -- they are an index value. They are only a guide to fertility, not and end-all-be-all.

A point which I have made many times, including in this thread.

Kiril
12-13-2011, 10:39 AM
After all that background info, I guess the answer to your question may be foudn by dropping your K fert until you find deficiencies or poor turf quality. At that point, you know you need to add K.

.............. Agreed.

Smallaxe
12-13-2011, 10:32 PM
This question has been answered several times already.

Soil tests DO NOT measure plant available nutrient concentrations! ....

OK , that's fine...

Tell me what a soil test is good for in the context of whether we need to add K or N or NPK to give his lawn an optimum performance ,,, with the least amount of bul*****

We must take the time to recognize that there is a real scenario in which grass grows... Soil test do what???... :)

Kiril
12-14-2011, 12:01 AM
Axe,

You need to understand what plant available, or more appropriately, readily plant available means.

Nutrients in solution that are in plant available form are readily available for plant uptake now. That however does not mean the plant will take them up, or that those nutrients will stay in solution, it just means at that moment in time they are available for uptake. Nutrients that are not in solution, but are contained on exchangers and/or are in readily solubilized forms can move into solution easily are considered part of the labile pool. The labile pool is therefore a measure of what some call the nutrient supplying power of the soil. It relates to what may be potentially available over the short term/growing season to plants/crops. This is the information a soil test provides, an estimate of that labile pool.

For example, a soil test tells you a soil has 200 lbs/acre of K. Does that mean all 200 lbs can be utilized by the plant ..... no. What is means is the soil can potentially supply that much K to plants over the short term, not that they plants will utilize all of the available K.

Now the numbers are just numbers if you don't know how to use them with respect to the site, plants, and management goals. This is why I say lab recommendations are worthless with respect to landscapes, and even Ag to some extent. There is far too much variability in the field to make an informed management decision based solely on the results of a soil test.

Note, that is just a generalized explanation, there are exceptions.

Smallaxe
12-14-2011, 10:57 AM
Axe,

You need to understand what plant available, or more appropriately, readily plant available means.

Nutrients in solution that are in plant available form are readily available for plant uptake now. That however does not mean the plant will take them up, or that those nutrients will stay in solution, it just means at that moment in time they are available for uptake. Nutrients that are not in solution, but are contained on exchangers and/or are in readily solubilized forms can move into solution easily are considered part of the labile pool. The labile pool is therefore a measure of what some call the nutrient supplying power of the soil. It relates to what may be potentially available over the short term/growing season to plants/crops. This is the information a soil test provides, an estimate of that labile pool.

For example, a soil test tells you a soil has 200 lbs/acre of K. Does that mean all 200 lbs can be utilized by the plant ..... no. What is means is the soil can potentially supply that much K to plants over the short term, not that they plants will utilize all of the available K.

Now the numbers are just numbers if you don't know how to use them with respect to the site, plants, and management goals. This is why I say lab recommendations are worthless with respect to landscapes, and even Ag to some extent. There is far too much variability in the field to make an informed management decision based solely on the results of a soil test.

Note, that is just a generalized explanation, there are exceptions.

I understand all of that... My objective is the health and vigor of the plants and the soil... with healthy plants and healthy soil the labile pool is more readily available... Is how I see it...

The thing about P and AM Fungus... Does the lab test register the P that the fungi are mining? When roots are found wrapped tightly around sandstone pebbles in the soil, are they getting nutrient from the rock?

I still say that soil tests are only as a last resort... Once the soil is right and the watering is correct then you can start adding N in varying amounts as needed... If the first app didn't seem right then I can adjust next time around...

Skipster
12-14-2011, 11:14 AM
I understand all of that... My objective is the health and vigor of the plants and the soil... with healthy plants and healthy soil the labile pool is more readily available... Is how I see it...

The thing about P and AM Fungus... Does the lab test register the P that the fungi are mining? When roots are found wrapped tightly around sandstone pebbles in the soil, are they getting nutrient from the rock?

I still say that soil tests are only as a last resort... Once the soil is right and the watering is correct then you can start adding N in varying amounts as needed... If the first app didn't seem right then I can adjust next time around...

I'm not sure what you mean by healthy soil having more readily available nutrients. Soil is what it is and different soils have different nutrient holding capacities.

Soil tests are valuable and are certainly not a last resort. They are meant to give you an idea about what's in your soil -- and they do it quite well. To answer one of your earlier questions, you can't usually pick which test is done when you send a soil sample to a lab -- they usually use whatever test they feel gives them the most useful results.

I would recommend using your state's soil lab and following the recommendations laid out for turf by your state's turf extension specialist.

Don't get overly wrapped up in mycorrhizae or roots wrapping around pebbles. At their very best, those scenarios could reduce your additional fertility needs by a fraction of an ounce/M.

Remember that growing conditions will not be equal throughout the lawn. Each little grass plant has a slightly different growing condition than the one growing next to it and you would drive yourself crazy tryign to optimize fertility for each individual plant.

The point of the soil test is to give you an idea of what is needed to support the plant you want to grow.

Kiril
12-14-2011, 11:28 AM
The thing about P and AM Fungus... Does the lab test register the P that the fungi are mining? When roots are found wrapped tightly around sandstone pebbles in the soil, are they getting nutrient from the rock?

P is a whole different issue. I also said there are exceptions. That said, the percentage of total nutrients obtained via root interception is very small.

I still say that soil tests are only as a last resort... Once the soil is right and the watering is correct then you can start adding N in varying amounts as needed... If the first app didn't seem right then I can adjust next time around...

Then you are playing guessing games and are really no better than the spray/spread and pray x-step lawn boys. A soil test is the first step any responsible land manager takes.

Smallaxe
12-14-2011, 12:42 PM
P is a whole different issue. I also said there are exceptions. That said, the percentage of total nutrients obtained via root interception is very small..

But the idea of plants being able to extract nutrients that the lab test can't measure is the same concept


Then you are playing guessing games and are really no better than the spray/spread and pray x-step lawn boys. A soil test is the first step any responsible land manager takes.

I consider responsible lawn care to consider the soil and its ability to hold the applied nutrients and to time them for optimum usage... There is no need for a soil test that doesn't accurately say how much N is needed... The color and vigor of the lawn itself tells me more than a soil test would...

Remember a while back I was considering doing a soil test on a particular patch of lawn becuz it wasn't ever holding grass, even though the rest of the sandy lawn was doing better?
Anyways, I decided to add some compost a few times and reseeded it this past fall and I think it is going to go... Call it guessing if you want, I call it experience and success... :)

Smallaxe
12-14-2011, 12:59 PM
I'm not sure what you mean by healthy soil having more readily available nutrients. Soil is what it is and different soils have different nutrient holding capacities.

Soil tests are valuable and are certainly not a last resort. They are meant to give you an idea about what's in your soil -- and they do it quite well. To answer one of your earlier questions, you can't usually pick which test is done when you send a soil sample to a lab -- they usually use whatever test they feel gives them the most useful results.

I would recommend using your state's soil lab and following the recommendations laid out for turf by your state's turf extension specialist.

Don't get overly wrapped up in mycorrhizae or roots wrapping around pebbles. At their very best, those scenarios could reduce your additional fertility needs by a fraction of an ounce/M.

Remember that growing conditions will not be equal throughout the lawn. Each little grass plant has a slightly different growing condition than the one growing next to it and you would drive yourself crazy tryign to optimize fertility for each individual plant.

The point of the soil test is to give you an idea of what is needed to support the plant you want to grow.

I think it is becoming obvious that most loamy soils will grow good grass with N and water, when both are properly applied... Soils are more than dirt and building structure in them is a management practice and not an "is what it is" situation...

Another thing to consider is that most roots create the micro-environment immediately ahead of it by exchanging carbon with certain bacteria at vatious times as they need a particular nutrient molecule... If we provide a healthy soil with adequate SOM and moisture the plants can pretty much handle the details on its own...

Again I say that management practices are much more important than worrying about the number of nutrient in the soil... Unless there is an obvious deficiency, I don't believe there is any defieciency... If there is a problem that can't be corrected any other way, then by all means get a soil test to figure out the problem... :)

Kiril
12-14-2011, 01:14 PM
But the idea of plants being able to extract nutrients that the lab test can't measure is the same concept

Maybe you should read up on root interception before you comment on it?

I consider responsible lawn care to consider the soil and its ability to hold the applied nutrients and to time them for optimum usage... There is no need for a soil test that doesn't accurately say how much N is needed... The color and vigor of the lawn itself tells me more than a soil test would...

How did we go from K to N? NO3-N, which is the form we are usually most concerned with, is better measured in the field IMO.

As far as the rest of your comment, that is just ignorant .... sorry.

Remember a while back I was considering doing a soil test on a particular patch of lawn becuz it wasn't ever holding grass, even though the rest of the sandy lawn was doing better?
Anyways, I decided to add some compost a few times and reseeded it this past fall and I think it is going to go... Call it guessing if you want, I call it experience and success... :)

Don't preach responsible land management to others (as you do) if you are not going to practice what you preach.

Personally, I prefer to reduce the number of unknowns as much as possible so I can deliver the most effective solutions.

Smallaxe
12-14-2011, 01:37 PM
Well I did find some useful information about building root mass with N and that applications of K are no more useful than P when it comes to Cool-Season grasses...

Sorry if I seem irresponsible for not having soil tested so that the lab can tell me how much P and K needs to be added to an already healthy lawn... Perhaps I need advice on putting a pound of N on a sandy lawn in March so that I bring the soil up to lab specs...

We're growing grass, yet we micro-manage unimportant things like it was hydroponic tomatoes... can't worry about SOM building or soil structure building, until we see some numbers first...

It's looking like N is the only criteria to worry about in a healthy lawn... As long as you don't throw on too much at the wrong time of year, there should be no irresponsible problems...

Is it safe to experiment with Fe or is that irresponsible w/out a soil test first?

Kiril
12-14-2011, 02:10 PM
I see we are pretty much done here given we are to the point of your typical "we don't need to collect any data" rants .... which is one post away from your usual anti-university rant. So do what you want Axe, but don't fool yourself into thinking it is responsible, or that you are acting in a professional manner.

Smallaxe
12-15-2011, 04:40 AM
I have demonstrated respect for respectable research, anti-learning/university I'm not... but 'understanding' is an important part of that data...

I really can't relate to running a business where common sense is put on hold and we have to be led around by the noses, by the 'experts' to figure out how to grow grass...

I still think of the 'tree professional' that would take years to dead limb pine trees becuz the experts convinced him that cutting dead wood caused a wound and too many wounds at one time is bad...

The definition of the words 'professional' and 'sensible' have some kind of PC meaning that carries no independant value... We must be dependant on experts to be professional, even when the 'experts' are wrong and/or unnecessary... :)

Kiril
12-15-2011, 08:31 AM
I have demonstrated respect for respectable research, anti-learning/university I'm not... but 'understanding' is an important part of that data...

Yes ... understanding the need for data and understanding how to use it.

I really can't relate to running a business where common sense is put on hold and we have to be led around by the noses, by the 'experts' to figure out how to grow grass...

I still think of the 'tree professional' that would take years to dead limb pine trees becuz the experts convinced him that cutting dead wood caused a wound and too many wounds at one time is bad...

What does this have to do with determining nutrient needs for landscapes? Common sense tells me I can't know what to do with a soil unless I know as much about that soil as is reasonably possible. A soil test is one critical tool in a my tool box that I use to do this.

The definition of the words 'professional' and 'sensible' have some kind of PC meaning that carries no independant value... We must be dependant on experts to be professional, even when the 'experts' are wrong and/or unnecessary... :)

I don't even know what this means.

Smallaxe
12-15-2011, 11:36 AM
It means that the word "Professional" has come to mean something less than it used to mean so when you say I'm not a professional becuz I don't require a soil test to deal with grass, it doesn't matter. I focus more on looking at the soil to see if the available nutrients are readily accessable, then if need be I can always get a soil test...

A 'pro' can tell many things at a glance, including whether a soil test is needed...
If you were a Doctor you'd prescribe an MRI for everything, wouldn't you... :)

Kiril
12-15-2011, 12:03 PM
It means that the word "Professional" has come to mean something less than it used to mean so when you say I'm not a professional becuz I don't require a soil test to deal with grass, it doesn't matter. I focus more on looking at the soil to see if the available nutrients are readily accessable, then if need be I can always get a soil test...

A 'pro' can tell many things at a glance, including whether a soil test is needed...
If you were a Doctor you'd prescribe an MRI for everything, wouldn't you... :)

WOW ..... OK Axe. :waving:

Smallaxe
12-15-2011, 08:19 PM
WOW ..... OK Axe. :waving:

Your Welcome... :waving:

phasthound
12-19-2011, 11:54 AM
A freind sent the following article written by Frank Rossi to me & I thought I'd post it here.


New Ideas About Late Season Nitrogen Fertility
Frank S. Rossi, Ph.D., Cornell University

Mark Twain once wrote, “There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.” Oddly this is the best way to describe how the “dogma” of late season nitrogen and fertilization has evolved in turf.
For much of the last 40 years few have questioned the value of applying high rates of nitrogen to almost dormant turf just prior to the onset of winter. There appeared to be a significant benefit, fertilizer was relatively inexpensive when compared to other inputs, and it provided an additional service opportunity to most lawn and landscape firms.
However during the last decade growing concern for the effect of nitrogen on water quality and the overall effect of global fertilizer demand on price called the question. How real is the benefit of late season applied nitrogen and if there is a benefit, how much is enough?

History of N
Nitrogen is considered the most important macronutrient for turf growth. At between three to four percent of plant tissue, nitrogen is the most abundant in the plant after carbon, hydrogen and oxygen.
While it surrounds the plants in the atmosphere and is often abundant in various forms in the soil, it is the most limiting nutrient for turf growth. Consequently it is the most common nutrient supplied by managers to maintain healthy turf systems.
When I began in the turfgrass industry in early 1970’s it was not uncommon to apply in excess of eight to ten pounds of actual nitrogen per 1000 square feet. The goal was to keep the turf areas green and growing. If you were in the mowing management business you were happy to apply all that nitrogen, as it kept the mowers running throughout the season.
Over the years as the concern for the effect of landscapes on water quality increased and fertilizer prices increased in response to rising fuel prices, nitrogen application rates slowly declined. While there is still some debate over the exact amount required for most lawns, there is agreement that there is no need to return to the old days of double-digit annual rates.
As the turfgrass industry has evolved the number of nitrogen fertilizer options has increased. The old standard for nitrogen fertilizer was water soluble/quick release sources such as ammonium nitrate, ammonium sulfate or urea. An immediate response would be observed both in color and growth and then dissipate quickly as the nitrogen was taken up or leached past the root system.
Slow release products were available mostly as organic forms that would release based on soil temperature and moisture. These products were developed by coating traditional water-soluble sources with compounds that would slow their release or react with other chemicals to create products that released the nitrogen more slowly over time.
The goal of slow release nitrogen was to minimize the number of applications required by pulsing the nitrogen to the plant in a way that might mimic soil available nitrogen. This would provide a sustained response much longer in duration than the typical water soluble sources. It is interesting to note there has been cyclical interest in coating products for a “one application per year” strategy, theoretically to meet the plants needs over the season through sophisticated coatings.
Regardless of the technological developments fertilizer costs have increased and the more technology in the bag, vis a vie, slow release formulations the more the product cost. Of course the argument for slow release is that it lowers labor costs by requiring fewer applications.
Yet with all the energy directed towards fertilizer technology very little effort has been exerted to add precision to the amount, timing and frequency of applications required to sustain healthy turf. It seems the one-pound application rate four to five times per year is still sacred. That is until the questions began to increase over the impact of lawn fertilizer on water quality.

N and Water Quality
Eutrophication is the slow, natural nutrient enrichment of streams and lakes and is responsible for the "aging" of ponds, lakes and reservoirs. Excessive amounts of nutrients, especially nitrogen and phosphorus, speed up the eutrophication process. As algae grow and then decompose they deplete the dissolved oxygen in the water. This condition usually results in fish kills, offensive odors, unsightliness, and reduced attractiveness of the water for recreation and other public uses.
Excessive nitrate in drinking water can cause human and animal health problems, particularly for small babies. The United States Public Health Service has established a specific standard of 10 milligrams of nitrate nitrogen per liter as the maximum concentration safe for human consumption. Problems in adults that drink water with excessive nitrate are essentially nonexistent and are rare in infants. Nevertheless concern over the use of nitrogen in lawn and landscapes has led to a growing number of regulations. The regulations run the gamete from local timing and rate restrictions to larger scale watershed restrictions on total loading amounts. Areas such as the Peconic Bay Estuary and the Chesapeake Bay Watershed are poised to enact large-scale restrictions on fertilizer use for lawns.
Recent research conducted under the direction of Professor Karl Guillard at the University of Connecticut has raised the question of the “sacred” one-pound per 1000 square feet application rate and interval. Professor Guillard’s work suggests that at any one time maybe about a one-half pound rate might be adequate for the desired response. This research has been ground-breaking in many ways, questioning the long held dogma of many of our current fertilizer practices.
Additionally, research investigating water quality and lawn fertilization has concluded that slow release nitrogen sources do add a level of safety but still the overall loading rates remain a concern. Furthermore, while some precision is being added to in-season application of nitrogen, either by reduced rate or extended frequencies due to the age of the lawn, few have questioned the application of nitrogen in the late season when most top growth has slowed.

Late-Season Nitrogen
Some of the oldest turfgrass research has espoused the benefits of applying nitrogen at the end of the growing season prior to the onset of winter. The agronomic benefits of enhanced rooting, reduced Spring clipping production, enhanced Spring green-up, enhanced winter hardiness, etc. have been well established.
Still as the discussion about nitrogen has evolved to include water quality, research has indicated that independent of the source of nitrogen the later in the season the application is made the more leaches into the groundwater. Clearly there is an environmental concern related to late season nitrogen use, in-spite of the well-established agronomic benefits. It then becomes a question of balancing the two needs.
Several studies have investigated sources and timing to reveal some interesting results. Oddly while most of the research was conducted with various nitrogen sources it was always applied at the “sacred” one pound of actual nitrogen per 1000 square feet rate.
More recent cool-season turfgrass research on Kentucky bluegrass and perennial ryegrass at the University of Wisconsin-Madison and here at Cornell University has begun investigating reduced rates using different nitrogen sources applied at different timings from September through December. To date it appears the agronomic benefit from late season nitrogen can be achieved by applying inexpensive forms of water-soluble urea or ammonium sulfate at 0.3 to 0.5 lbs per 1000 square feet in September or October.
These earlier application times combined with the lower application rates provide adequate agronomic benefits with reduced overall leaching problems. This is the kind of research we need to get out into the hands of practitioners and regulators to help them enact enforceable, science-based regulations. Not regulations based on conjecture.
As an industry we need to be open to the evolving ideas that science brings to enhance our precision. In the end it will lead to improved efficiencies. Heck if we get the same response with less nitrogen that was leaching anyway and the sources we use are less expensive, who’d argue with that?
Professor Guillard and colleagues in the New England states have produced an excellent publication that addresses this as well as other fertilizer and water quality issues available at www.lawntolake.org/PDFs/NE_WQ_Fert_Rec.pdf.

Of course many scientific and logistical questions remain about late season nitrogen. There are questions concerning uptake mechanisms, evapotranspiration, disease issues and further refining application strategies before a complete picture can be drawn, but for now as Twain would say, let the conjecture begin.