>> ... along with other things that AREN’T good for your plants.
I agree that we don't want to fertilize using something with perfume or hand lotion or coloring agents. But I'm not sure HOW toxic those additives are to plants, especially after being diluted another 5-10 times more dilute than they were in the household cleaning product to start with.
>> Most household ammonias can actually be toxic to plants,
>> containing aqueus ammonia instead of the helpful ammonia ions.
I don't totally agree. Toxicity from ammonia comes from adding too much ammonia. That's true with most high-N fertilizers. Nutrient or poison: the dose makes the poison.
Would you agree? Or am I missing something?
It's the same with food for humans: enough is necessary, but too much is harmful.
I take a blood thinner: enough is necessary, or I'll start throwing clots and have embolisms and leg problems. But too much, and I have to remember that the other name for "coumadin" is "warfarin" - a.k.a. "rat poison". The dose makes the poison.
Someone is developing a weeding robot that has a little needle. Once its vision system and tiny brain are fairly sure they have identified a weed that is NOT the crop plant being grown intentionally, the robot injects a little "concentrated fertilizer" into the weed's stem, which kills it promptly.
The dilution of spreading through the weed's tissue, and then diffusing into the soil as the weed decomposes, makes it NON-toxic due to dilution. My guess is that the concentrated "fertilizer/poison" is either ammonia or urea. It might be phosphoric acid in a basic-soil region. Maybe KOH (potassium hydroxide) in a very acid-soil region.
The overall pH of the soil after adding ammonia affects the ratio of those two forms, since they stay in equilibrium with each other. But toxicity comes mostly from excessive concentration, and only after that, is pH relevant as a secondary factor.
Probably neutral NH3 is somewhat less toxic to cells than ammonium ion , because it is taken up more slowly and tends to evaporate from soil and water. But I'm not sure. Neither is toxic in low doses - a little ammonia is beneficial and indeed is part of the natural Nitrogen Cycle. Both are toxic at high doses, in part because they transform back and forth freely.
I think the time for them to reach equilibrium with each other is just a few milliseconds (or microseconds if they don't have to diffuse a distance to reach each other) (whereas it may take hours or days for plants and microbes to take up all the ammonia (ionic form first)).
The pH of the soil or water you add to it does, of course, affect the ratio of neutral ammonia (NH3) and ammonium ion (NH4+). If you add it too basic, or add it to very basic soil, you will have more neutral ammonia (NH3) than you wanted, because that neutral ammonia will rapidly evaporate from the soil or water.
Plants can (I assume) only absorb the ionic form (NH4+), but pH reactions between soluble molecules like NH3 and H2O occur in milliseconds, so as plants and microbes rapidly absorb NH4+, enough of the remaining neutral NH3 will convert to NH4+ to keep the ratio at whatever point the soil pH dictates.
If you add enough diluted ammonia to actually change the pH of your soil, you should be careful to add it in basic or acid form according to which way you want to change your soil pH. However, the basic form of ammonia (NH3) does evaporate very rapidly, so stick to ag lime if you want to make soil more basic.
>> aqueus ammonia instead of the helpful ammonia ions.
Offhand I'm not sure which form of ammonia is more likely to form tight hydrogen bonds with water, but I am guessing the positively charged ion because it attracts the partial-negative-charge on the O in H2O.
NH4+ plus H20 - - > NH5O+
H H
\ /
+N - - - OH2
/ \
H H
