Understanding Plant Nutrition series

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jerrytheplater
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Understanding Plant Nutrition series

Post by jerrytheplater »

I was searching fertilizer information today and came across this series of articles starting in 2008 published in Greenhouse Grower, a trade magazine for the horticultural industry. The series is called Understanding Plant Nutrition and ended up being 22 topics long and covers a lot of ground. Some of the last articles were on specific plants and do not apply to us. I added in a few others that were not part of the series, but apply. Each article is not long and is easy to read. Most of the Figures and Tables are not found in the articles. I don't know if that is due to me not being logged in or not. I am not a subscriber.

Particularly interesting is how media pH can be affected by the form of the nitrogen in a fertilizer, but only when it is used by the plants. The plant roots modify the media depending on the Nitrogen form they are taking up.

An Introduction: https://www.greenhousegrower.com/produc ... roduction/

Nutrient Sources: Media Cation Exchange Capacity: https://www.greenhousegrower.com/produc ... -capacity/

Limestone and pH : https://www.greenhousegrower.com/produc ... ne-and-ph/

Limestone, Calcium, & Magnesium: https://www.greenhousegrower.com/produc ... magnesium/

Irrigation Water Alkalinity and pH: https://www.greenhousegrower.com/produc ... linity-ph/

Irrigation Water as a Nutrient Source: https://www.greenhousegrower.com/produc ... nt-source/

Fertilizers and Media pH: https://www.greenhousegrower.com/produc ... -media-ph/

Addressing Media pH Problems: Alkalinity and Nitrogen Forms: https://www.greenhousegrower.com/produc ... -problems/

Fertilizer/Alkalinity Effects on Media pH: https://www.greenhousegrower.com/produc ... ng-mix-ph/

Fertilizers and Macronutrients: https://www.greenhousegrower.com/crops/ ... nutrients/

Fertilizers and Micronutrients: https://www.greenhousegrower.com/produc ... nutrients/

Controlled and Slow Release Fertilizers: https://www.greenhousegrower.com/produc ... rtilizers/

Managing Media pH: https://www.greenhousegrower.com/produc ... -media-ph/

Managing Media Electrical Conductivity (EC): https://www.greenhousegrower.com/produc ... -media-ec/

Correcting Low Media pH: https://www.greenhousegrower.com/produc ... -media-ph/

High pH Problems: https://www.greenhousegrower.com/produc ... roblems-2/

Low Media EC: https://www.greenhousegrower.com/produc ... edia-ec-2/

Common HIgh Media EC Problems: https://www.greenhousegrower.com/produc ... roblems-2/

Calcium and Boron Uptake Discussion: https://www.greenhousegrower.com/produc ... ed-plants/

Fertilizing Container Grown Plants: https://www.greenhousegrower.com/produc ... ontainers/
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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MikeInOz
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Re: Understanding Plant Nutrition series

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''Particularly interesting is how media pH can be affected by the form of the nitrogen in a fertilizer, but only when it is used by the plants.

Not quite. If you apply N as ammonium (a cation +) it gets converted to nitrate (an anion - ) which is not held by soil colloids (which are mostly negatively charged so is repelled) nearly as well as ammonium so leaches from the soil taking calcium (mainly but also Mg and K) with it leaving the mix more acid. But leaching of nitrate added as nitrate does not affect pH. This is the main reason why nurseries have acidification eventually showing up in their media. Adding N as nitrate and ammonium in a ratio of 3 to 1 prevents this. (going from memory here)
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jerrytheplater
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Re: Understanding Plant Nutrition series

Post by jerrytheplater »

MikeInOz wrote: Tue Feb 07, 2023 3:33 am ''Particularly interesting is how media pH can be affected by the form of the nitrogen in a fertilizer, but only when it is used by the plants.

Not quite. If you apply N as ammonium (a cation +) it gets converted to nitrate (an anion - ) which is not held by soil colloids (which are mostly negatively charged so is repelled) nearly as well as ammonium so leaches from the soil taking calcium (mainly but also Mg and K) with it leaving the mix more acid. But leaching of nitrate added as nitrate does not affect pH. This is the main reason why nurseries have acidification eventually showing up in their media. Adding N as nitrate and ammonium in a ratio of 3 to 1 prevents this. (going from memory here)
Mike-

This is the article I read which led me to summarize as the quote you used. It says that plants can and do take up NH4 directly and that soil bacteria can and do convert NH4 into NO3 via nitrification. Both cause the media pH to drop. https://www.greenhousegrower.com/produc ... -media-ph/

Here is a quote from the same article which confirms your memory: "Ammoniacal nitrogen is about three times stronger an acid than nitrate nitrogen is a base."

And here is why I said plant uptake of nutrients modifies media pH. The entire section is called "Other factors affect Acidity and Basicity" and here is one specimen quote "Nitrate nitrogen (NO3-N) can cause the substrate-pH to increase, but only if it is taken up by the plant. If plants are small, or stressed and not growing, nitrate has little influence on substrate pH."

With Steve's pure mineral mix, with very little to no organics, how his media could be affected by these fertilizer/root interactions is hard for me to see. The nutrients/ions left over or released from the roots would either drain out or dry on the media to be flushed at the next watering/fertilizing.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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