Old 05-18-2009, 12:39 PM
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JDUtah JDUtah is offline
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Plants can absorb more forms of N than NO3 and NH4?


Everywhere you turn you read that plants absorb their N as either the anion Nitrate (NO3) or the cation Ammonium (NH4). In my daily study I came across a PowerPoint (attached) that suggested plants can absorb another form of N... N assembled in the amino acid Glycine. It claims that this form of N is...

– least expensive to assimilate
– but probably not as readily available in soil as NH4+ or NO3-
– ‘short-circuit’ in the N cycle (no need for microbes to mineralize)
– known to be an important source of N in arctic and alpine tundra (organic soils)
– importance in other ecosystems is not well understood

and that...

Different plants prefer different forms of N. However, when N is limiting, “preferences” typically disappear and plants take up what N they can get.
The idea that plants can absorb and assimilate more than Nitrate and Ammonium forms of N was new to me so I dug a little more and found this article. It claims...

The application of amino acids for foliar use is based on its requirement by plants in general and at critical stages of growth in particular. Plants absorb Amino Acids through Stomas and is proportionate to environment temperature.

Amino Acids are fundamental ingredients in the process of Protein Synthesis. About 20 important Amino Acids are involved in the process of each function. Studies have proved that Amino Acids can directly or indirectly influence the physiological activities of the plant.

Amino Acids are also supplied to plant by incorporating them into the soil. It helps in improving the microflora of the soil thereby facilitating the assimilation of nutrients.

Foliar Nutrition in the form of Protein Hydrolysate (Known as Amino Acids Liquid) and foliar spray provide readymade building blocks for Protein synthesis.
This suggests (and agrees with the PowerPoint) that not only can plants absorb amino acids through the stoma in their leaves (and perhaps roots), but that the amino acids help the plant save energy by helping them build proteins without first having to build the amino acids that the proteins are made out of.

This made me wonder/recall if other forms of N could be absorbed by plants. It stood to reason that any soluble form of N could/would be absorbed. So I looked up Urea and found this study. Although not grass, it did help to validate the idea. It found that...

The 15N analysis of the younger leaves of each plant shows that urea and ammonium are the two preferred forms of nitrogen absorbed, with respectively 47% and 41% of the total amount, while nitrate is only absorbed to a level of 12%... Phalaenopsis roots, probably because of the special nature of velamen, can absorb large amounts of nitrogen directly in urea form.

As I have come across this idea only this morning I have yet to apply it. Some early speculations are that providing amino acid nutrients appropriately could potentially be more effective than supplying nutrients in mineralized form (via synthetic fertilizers or mineralized organic fertilizers). The first, and most simple, way I see we could fert with amino acids is compost tea.

I have not been a promoter of compost tea to this point but this might change my mind. If one applies the right maturity compost tea (in which many amino acids and/or proteins are free floating in solution) at the right time (while the stoma are most likely to accept these nutrients) they may see a very good response from the turf.

It is my opinion that root absorption of amino acids via compost tea would take too long and thus the amino acids would be mostly incorporated into the soil micro flora before plant absorption (which isn't bad, it just wouldn't proved such a direct response)

Things that may affect/improve leaf absorption of amino acids could include applying the tea at (or shortly after) a time when protozoa have released the semi-complex nutrients as they eat other microbes. In other words apply the tea during a protozoa population spike.

Another technique to encourage stomata absorption is to apply when plant transpiration is peaking. This would be done by watering the day before application and applying the tea during optimum sunlight and temperature.

Other speculated benefits of such a nutrient application would be increased plant pest resistance (because the plant has more energy to use to defend itself) and more growth (again because the plant has more energy to spend on cell production)

Anyways I have to get to working for the day. What are your thoughts? Ideas? Opinions? Do you have any related studies, articles, publications?

Thanks in advance,
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Old 05-18-2009, 01:24 PM
ICT Bill ICT Bill is offline
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I will wait with my reply until you can confirm that you are wearing a pocket protector and/or a lab coat

Yes amino acids are an important part of building a good food for plants, the trick is knowing which ones respond better with certain plants

Corn, Rice, potatoes, broccoli and turf all have different sets that they respond to better

The base of our #3 is a slow process of building up amino acids, it takes close to a week just to build the base to then add different nutrients to. Like making beer, the right ingredients at the right time and temp.

But the caviate, (and a little off thread) you still need, as you found, a decent SOM level for the plant to respond to that. Its a yin and yang thing.

You can throw whatever source of N at a plant, in the wrong environment it just kills it
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Old 05-18-2009, 01:55 PM
Kiril Kiril is offline
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Compost Does a Soil Good!
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Old 05-18-2009, 04:17 PM
ICT Bill ICT Bill is offline
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Originally Posted by Kiril View Post
Compost Does a Soil Good!
Thanks Kiril but not the answer he had hoped for, I don't think.

It gets very complicated, so complicated that good scientists have been working on the question for a long long time.

Amino acids are also triggers for hormone production in plants, in bacteria & fungi ( and others) it triggers enzyme production, sometimes it shuts systems down and others take over. It is definately a dance on the part of root, shoot and soil. No doubt about it though amino acids are one of the main building blocks that go back to when plants began
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