How nitrogen becomes available to plants -- Synthetically and Organically

Discussion in 'Organic Lawn Care' started by JDUtah, Jun 30, 2008.

  1. JDUtah

    JDUtah LawnSite Silver Member
    from UT
    Messages: 2,636

    OK, ok... so I am trying to get my mind to grasp the concept of nitrogen and the process in which it becomes available to plants. As I do I will try to state it in English? maybe. These first questions are mainly for the very well rehearsed and resourced folks. Maybe you can direct me to reading and basic understandings that will help me understand and apply the information.

    Nitrogen is only available to plants in two forms... NO3- (nitrate) and NH4+ (ammonium)

    My first study is NO3-. For those of you who have gone there before me... Are nitrates available to plants strictly as the salts? (NO3-) OR are the nitrates known as esters also available forms of nitrogen?
  2. JDUtah

    JDUtah LawnSite Silver Member
    from UT
    Messages: 2,636

    Wow guys, this is some VERY interesting stuff... At least to me ;) (Example: one of the two forms of absorb-able nitrogen can inhibit turf root growth) I am going to post it but am working on digesting it and writing it in a readable format...

    A follow up to my above question, it appears to me that NO3- is the compound absorbed by plants, not the "Ester" Nitrates. But this leads to my real question.. The NO3- bonds to + charged metals and forms different nitrate salts... sodium nitrate as an example... In this case... when the roots absorb the nitrate, is the sodium also absorbed into the plant? Or do the root cells separate the ionic bond and leave the sodium behind?

    If the sodium is absorbed, could that bond be referred to as chelated sodium?
  3. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    I like that article in that it plainly states that the 2 forms are water soluable and available quickly. It seems bacterial activation is minimal or not worth the mention in this level.

    So manure is either NH3 or NH4. NH4 is available to plants right now. Their Manure Tea experiment was actually a Compost Tea, I think, because the store doesn't sell fresh manure :) For generations around here the same was done with real manure.

    The article stated:
    "Commercial fertilizers, both dry and
    liquid, are available with various combinations of nitrate and
    ammonium ions, enabling farmers to manage their nitrogen
    application. Crop advisors monitor the crops to ensure the
    crops receive optimum amounts of nitrogen."

    I like this statement here in that it assumes that all soils, circumstances, and crops have different needs at different times and in different weather conditions and that applying in different forms in combination can produce optimum results.

    Imagine a scaper that could actually function as a 'crop advisor' - that actually understood what a starter fertilizer does, or compost does, or a winterizer does. :)
  4. Tim Wilson

    Tim Wilson LawnSite Senior Member
    Messages: 795

    JD, I posted a short essay in another thread which may relate. It is on my website in its entirety. Here is an excerpt followed by an excerpt from a review paper which is attached as a PDF. Also attached is a PDF of a related study.


    "The plant is no passive player in the natural growing game of survival but is the master conductor of this delicately balanced orchestra. The plant receives energy from above the soil in the form of light. This photosynthesis results in the plant’s internal production of carbon. It utilizes this carbon to create and reinforce tissue as it grows, so it is a very valuable commodity. As we all know the plant also requires a form of nitrogen (N) and other macro and micro-nutrients which it receives through the root system. As already stated this N must be in a form which the plant can directly uptake and use, usually a form of ammonia (N). Research has shown that when a plant needs to uptake N from the soil it sends out some of its precious carbon through it’s root system as a feed for bacteria and *archaea which live in the rhizosphere. [* Archaea are prokaryotes indiscernible from bacteria except through specialized testing; usually DNA] There are more complexities involved, such as, that certain plant types attract certain bacteria/archaea types but that is beyond the scope of this portrayal. When the bacterial/archaea population has increased in response to the carbons excreted by the roots, protozoa and bacterial feeding nematodes are attracted to the region, ‘hatch out’ from cysts and eggs respectively and in the case of protozoa multiply rapidly. Protozoa consist of flagellates, amoebae and ciliates. Some protozoa can multiply (divide) every 2 to 4 hours so their numbers can increase in short order. The protozoa and nematodes consume the bacteria/archaea and release as waste the ammonia (N) which the roots can then absorb. The multiplication rate of the bacteria/archaea increases in response to this predation and so on. This has been called the microbial loop. Protozoa are particularly good providers as their ‘digestive system’ only utilizes about 30% of the nutrients consumed meaning that roughly 70% is released as the waste which the roots crave. This factor, combined with their short generational time makes them real feeding machines. Undoubtedly there are micronutrients also processed and absorbed in this cycle. There are still many mysteries which research has yet to unfold or are not yet known to this author.
    This is not the end. The concert continues. The bacteria/archaea also consume the ammonia (N) which is now bioavailable to them, so are in competition with the plant for these nutrients. Because of this, if there are no predators or insufficient numbers to consume the bacteria/archaea they could potentially lock up the N. When the plant is growing it is in a vegetative state and requires a large load of available nitrogen (N) so it is advantageous for it to continue this release of carbon and maintain a balance of bacteria/archaea and protozoa, while uptaking just the right amounts of nutrients. Don’t get me wrong. There are other players in this orchestra, either playing subdued roles or waiting their turn to play. There are higher order animals like mites, other microarthropods and worms. There are various forms of fungi, most of which are degraders but some of which are mycorrhizal. These all have roles in breaking down organic matter into a form which can then be mineralized by the plant’s bacteria/archaea team or delivered directly to the roots.
    When the plant receives its signal from the upper world, above the soil, that it is time to switch gears and produce flowers and or fruit, its nutrient requirement changes. Although the mechanics are not well known to this author, studies indicate that the plant then increases the uptake of the ammonia (N) (bioavailable nitrogen) and reduces or stops excreting the carbon which feeds the bacteria/archaea. This effectively starves the bacteria/archaea which will react by dying or becoming dormant. This of course results in a similar reaction by the protozoa and bacterial feeding nematode population. The mycorrhizal fungi previously mentioned is then triggered into increased growth and production. Studies have indicated that the transference of bioavailable phosphorus and potassium to the roots occur mainly as a function of arbuscular mycorrhizal fungal hyphae in symbiotic relationship with the roots of the plant. The fungal hyphae (microscopic strands) grow right into the root cells and exchange nutrients. In exchange for carbon, once again released by the plant, the fungal hyphae delivers the required bioavailable nutrients to the root system. The fungal structure derives these nutrients from organic matter and food sources in the soil, some naturally processed by the other players as previously mentioned. It is my hypothesis that the form of carbon released to stimulate the mycorrhizal activity is of a varied molecular structure from that released to promote the bacteria/archaea population previously discussed, however I have no direct data to substantiate this. There are often different types of bacteria which accompany mycorrhizal fungi, adhering to the fungal hyphae in a symbiotic relationship. It is thought that these bacterial species function to exchange nutrients with the fungi as well as to protect the fungal hyphae from consumption by other microbes and even contribute to the protection of the plant from pathogenic fungi. There are other types of mycorrhizal fungi (ectomycorrhizal) which encapsulate roots rather than entering them but these are mostly associated with trees in the temperate and boreal regions.
    So you see it is quite a complex arrangement which the plant conducts or controls and there are many facets which yet remain a mystery."

    "A century ago Hiltner (1904) introduced the term ‘rhizosphere’ to describe the stimulation of biomass and activity of microorganism in soil around plant roots. However, even today it is often not fully acknowledged that all nutrients a plant absorbs from soil pass through a region of intense microbial and faunal activity.
    The stimulation of microbial activity in the rhizosphere
    results from the fact that plants secrete an array of low- and high-molecular weight molecules into the soil as exudates, which may account for up to 40% of the dry matter produced by plants (Lynch & Whipps, 1990). As free-living soil microorganisms are strongly carbon limited (Wardle, 1992), a specialised microflora, typically consisting of fast growing bacteria, is triggered into activity by the carbon pulses provided as exudates (Semenov et al., 1999). Root-derived carbon leads to strongly increased levels of microbial biomass
    and activity around roots (Alphei et al., 1996) and channels energy to subsequent microfaunal grazers, where numbers of bacterial feeding protozoa and free-living nematodes may increase up to 30-fold compared with bulk soil (Griffiths, 1990; Zwart et al., 1994).


    Attached Files:

  5. treegal1

    treegal1 LawnSite Gold Member
    Messages: 3,911

    OK that just ruined the paper i was going to post, it only had 3 paragraphs. TIM that rocks, glad you jumped in there!!
  6. ICT Bill

    ICT Bill LawnSite Platinum Member
    Messages: 4,115

    A golf super once told me "ate", the grass "ate" the nitrate. This is the form the plants prefer for their nitrogen but it not the only form of nitrogen

    Lets stop for a second.............OK so what did all of these plants worldwide do for 450,000,000 years before we invented fertilizers??? I'm not sure how they survived without our bagged NPK with micronutrients

    “The most productive systems on this planet are systems which do not have, and have not ever had, inorganic fertilizer applied”. Dr. Elaine Ingham, Compost Tea Brewing Manual

    It is important to understand how N uptake happens but it is a very small part of "Nutrient cycling" this is the question that should be asked.

    What forms of nitrogen are used/produced in nutrient cycling and why

    If we can get nutrient cycling going by all the players in the soil, then you've got something. To state it very simply, you need basically need 2 things. Organic matter and beneficial microorganisms = end result, fertile soil and happy plants
  7. JDUtah

    JDUtah LawnSite Silver Member
    from UT
    Messages: 2,636


    I also found that article very well stated and it sets up an ideal that I believe all Landscapers should be pursuing, especially organic.


    Thank you for the article. I can't wait until I can jump into the microbial aspect of nitrogen sorbtion. I am not sure if I found your page. I did not find the article on the page I looked up. Is it a different page or a link from that one?

    JD (David)
  8. JDUtah

    JDUtah LawnSite Silver Member
    from UT
    Messages: 2,636

    Last night I watched a 22 min training video my partner got from scotts years ago... It was basic, and cornie!... Any information is welcome.. please post Tree.
  9. JDUtah

    JDUtah LawnSite Silver Member
    from UT
    Messages: 2,636


    As your golf guy stated... 'Ate' the nitrate? I wonder if chewing is involved? :)

    I know the simplistic nature of organics... provide what we as humans originally robbed and let nature (who is the real master) do the rest...

    I have three problems with that though...

    -I do not find that approach intellectually challenging enough for my personality. :laugh:

    -For all those years that we did not add fertilizer, I believe there was plenty of ecosystems that plants struggled in. Especially as Primary Succession took place.

    -Landscapes in the world today contain un-native plant species, domesticated, and genetically influenced varieties of the native plants. Hence the plants have been altered from their original function and/or envormental needs. A thorough understanding of how these plants work, and what environments/nutrients/microbes/moisture/lack of bracing up/proper mulching/etc they need (or can tolerate and still please the customer) is extremely beneficial.

    I understand the real question in organics is how to establish and maintain the natural nutrient cycle. Understanding each step of that cycle in detail helps one to better see the whole. Nitrogen uptake happens to be where I started. Thanks for the input and future input.

  10. Stewards of the Land

    Stewards of the Land LawnSite Member
    Messages: 49

    Correction... You need Humus, Mycorrhizae and the other Root-Tip-Colonizing-Mutualistic microbes, and Protein!

    USDA-ARS 6-23-05
    New findings show that a beneficial soil fungus plays a large role in nitrogen uptake and utilization in most plants.

    In a recent issue of the journal Nature, ARS chemist Philip E. Pfeffer and cooperators report that beneficial arbuscular Mycorrhizal(AM) fungi transfer substancial amounts of nitrogen to their host plants. A lack of soil nitrogen often limits plant growth.

    The studies were conducted by Pfeffer and David Douds at the ARS Eastern Regional Research Center, Wyndmoor, PA.; Michigan State University scientists headed by Yair Shachar-Hill; and New Mexico State University scientists headed by Peter J. Lammers and including graduate student Manjula Govindarajulu.

    .... The results show that the symbiotic relationship between Mycorrhizal fungi and plants may have a much more significant role in the worldwide nitrogen cycle then previously believed. With this in mind, farmers may benefit from promoting the proliferation of Mycorrhizal fungi through diminished fertilizer input, thereby making more efficient use of nitrogen stores in agricultural soils.

    Attached is a pic of my lawn of which I Hydroseeded with and continually treat solely with Humus, Mycorrhizae and the other Root-Tip-Colonizing-Mutualistic microbes, and Protein! As you can see I have built about 1" of fertile soil over a year and half without using compost! This is what we call Priming of the Pedogenesis(R)

    Humus Fertility in Turf.jpg

Share This Page