About $400. Most lab stores carry it... You can get them on Amazon.
They are Horiba LaquaTwin sensors.
Handheld. Can run them in the field.
Process for soil....
10cc soil disolved in 10cc of distilled water. shake vigorously for 10 seconds, then drop a sampling tissue (come with the kit) into solution. Wait 10 more seconds, drop it on the sensor... in about 3 secs it'll give you NO3 or NO3-N (however you have it set).
Process for plant tissue... cut plant, collect half a mil of sap, put it on the sensor. You're done.
On soil are you using it in the fall or in the spring closer to seeding? This is a great idea because N is often what we are interested in when taking soil tests. Do you think it has any value using it in season on soil or tissue samples? What is involved with the calibration?
We have used it on fall samples. This spring it'll get used as we pull into fields, and then during the season on cereals so we can top dress for maximum yield.
Using uptake charts, soil moisture that's available and heat units the idea is to match nutrient uptake for maximum yield (Grow grain not hay... as I've been saying lately).
I'd like to do in-season soil tests just to see how much the crop is actually taking, plus seeing how long after top dressing applications NO3-N is actually available to the roots.
Calibration is done using the included vials of known concentrate solution - one low, one high. Basically put a few drops on the sensor, hit the CAL button, wash it off, put a few drops of the other solution on the sensor, hit the CAL button, wash it off, and away you go.
What about the available ammonium (NH4)? I don't think the nitrate (NO3) test catches that (am I correct in this belief)? I have been trying to research this and am finding the info about NH4 very difficult to find. I am being led to believe that NH3 converts to NH4 which is usable by the plants directly. NO3 seems to need to be taken into the plant and then the plant uses resources to convert this to a usable form....does all this make any sense to anyone? I find the whole thing very fascinating, but back in chemistry class I was preoccupied with other things when I should have been paying attention!(when I say research, I haven't tried extremely hard, but in between I do google searches every once in a while).
NH3 bonds with water to make NH4. Then nitrification occurs in two steps: NH4+ is first converted to nitrite by nitrosomonas (NO2-), and the NO2- is then converted to NO3- for plants. It happens quickly.
But.... if there are no bacteria, no conversion, like in the fall. Both NH4 and NO3 are plant available.
Volatilization is the conversion from NH4 back to NH3 plus a freed H atom. Won't detect that either, only as a net decrease in available N.
Could be wrong, haven't looked at this stuff in a while. Nitrification and denitirification are complex and based on enviro conditions. NO3 sensors won't detect other forms, just non target ions will affect readings. (Its been a while since i worked on lab equipment)
I find this whole thing so interesting. I read in wikipedia that NOx is the generic name for NO, and NO2....(nitric oxide, and Nitrogen dioxide).....so is Nitrogen dioxide the same as Nitrite? just like water H20 can be called dihydrogen mono-oxide?
Nope, and thats where it gets a little complicated, naming conventions and charges. NO2 is in many forms,
NO is nitric oxide but also is named nitrogen monoxide
NO2 nitrous oxide but also Nitrogen dioxide
-NO2 are nitro compounds (many kinds) and some go boom - nitroglycerin
NO2+ nitryl ion or is the nitronium ion
NO2- nitrite (it has a negative charge and loves to bond as in the intermediary in the fert breakdown cycle. Its the one we as farmers need to know about)
NO3- nitrate is plant available, and is used in medicine for example vasodilators. Its made from NO2- and nitrifying bacteria. In the olden days to make gunpowder they would ferment urine (has urea in it) to produce nitrates.
Usually two names, its the ite, ous, ryl etc by naming convention but can be named using the molecular names and charge as in your example of water two (di) hydrogen and an oxygen, read it along simply. Both are correct.
N202 is dinitrogen dioxide or hyponitrite. It can also be ionic or N2O2 (2-)
The part that I'm trying to figure out is some of the nitrogen cycle pics don't show the NH4 going into the plant. Like the one in Wikipedia. But some do. Most info when talking says the NH4 and NO3 can be used by plants, then they stumble right into how the NO3 needs to go through the reductase, and almost imply that the NH3 goes to NH4, then goes NO2, then NO3 (assumes it converts the good way and not lost). But it looks to me like if the plants need N, the NH4 is taken in and goes straight to making amino acids???? NO3 always uses photosynthesis to "rductase" the NO3 to usable form. does my question make sense? This would make me believe that NH3 would be better if you can keep if from gassing off...if the plant doesn't use the NH4, it still can convert to NO3 and be used later, almost gives you more chances at hitting the plants N curve....just my thoughts????