# Explain Sweat and Bale Moisture



## VA Haymaker (Jul 1, 2014)

Assume you've got hay that's 16% moisture per a probe meter into the bale; hay that is just baled and stacked in the barn. A week later you take readings and see 20-22% moisture. After some time, the readings come back down. Through it all, no dust or mold.

Where does this additional moisture (sweat) come from?


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## r82230 (Mar 1, 2016)

My guess, from inside the stem/leaf, you are measuring moisture at the surface, takes a bit to stabilize throughout the stem/leaf. The other factor could be the critters (micro organisms, good and bad) to multiply/die.

My 1 cent (short changed ya :lol: ), this morning.

Larry


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## slowzuki (Mar 8, 2011)

Inside a plant is not uniform, there's a whole circulation system inside to move water/sugars etc around in the plant.

Water comes out of the leaves and the "piping" pretty quick but water that is locked inside the cells, that keeps the plant alive during a drought so has adapted to resist drying out. Once baled, this water is lost into the structure of the plant first then into the space in the bales.


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## slowzuki (Mar 8, 2011)

The error comes from your probe can only estimate the moisture content from its sensing method.

Think of a fresh loaf of bread out of the oven. That's a simple uniform material at least a lot more uniform than hay. Fresh out of oven feel it, it has a nice dry crust. Cut into it and it's super moist and soft. Put it in a bag (roughly equivalent to baling) and the moisture from the middle of bread comes out softens the crust and condenses on the bag. If you guessed the dryness touching the crust when it was first taken out of the oven you are assessing only on the outside. That's like a hay probe.

Methods like oven testing aren't subject to this error and would have given an accurate number in the first place.

Twist test works well too as it tells you and moisture levels in the core of the stems.

We care a lot about the surface dryness numbers a probe gives as that humidity near the leaves surfaces is what governs mold growth. The core can stay wet longer without issues because there aren't mold spores in there, they are on the plants exterior surface. If we store in way that lets moisture escape the bale faster than it escapes the core of the plants, that probe number stays low and all is good. It's like leaving the bread bag open until the bread has gone through it's sweat.


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## broadriverhay (Jun 13, 2014)

Great analogy Slowzuki!!! Well said.


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## Ox76 (Oct 22, 2018)

slowzuki - king of the layman term!

Well spoke, sir. You are a gentleman and a scholar. I don't reckon I've ever heard a better explanation and it's one we can use to explain to others if it ever comes up - most people can understand this principle.


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## r82230 (Mar 1, 2016)

Here is an article that talks about all the 'other' stuff that you harvest when putting up hay, that you don't always realize. Some of this 'other' stuff is good and some bad, some continue to grow and some don't it seems.

https://www.progressiveforage.com/forage-types/silage/are-you-harvesting-more-than-you-think

Thanks to Progressive Forage again.

Larry


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## VA Haymaker (Jul 1, 2014)

Thanks for the replies everyone.

This is an interesting bit from a Hay and Forage article I found. I kind of focused on conversation to water, which interpret humidity.

"Shewmaker explains that heat is generated in hay bales when microbial growth uses carbohydrates as an energy source. Plant and microbial respiration convert carbohydrates and oxygen into carbon dioxide, water and heat, which results in both weight loss (dry matter yield) and increased bale temperature"

And the link to the article: https://hayandforage.com/article-22-waiting-to-go-up-in-smoke.html


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## slowzuki (Mar 8, 2011)

Yup absolutely. Sugar being the plants fuel when it's not photosynthesizing - if you don't dry it out to stop much of the biological activities it will burn that fuel and co2 / water is produced just like an engine or fire.

Interestingly in a stack the heat generated helps dry out some of the other bales as the net movement is upwards pulling fresh air in the lower sides. The CO2 rising with heat in theory would somewhat slowdown decomposition or at least reduce the risk of fire. Likely why when tearing open a severely heating pile it will start burning right when opened up. CO2 vents off and let's o2 in when opened.


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## slowzuki (Mar 8, 2011)

It's been a few year since looking at this, I was trying to build a math model for hay drying starting from some other people work modelling corn/grain. Turns out despite a lot of similarities corn is pretty simple compared to hay and the math model for hay needs extra "shell" layers to show where the moisture is located.

I've always been fascinated by the way drying fronts set up in corn or hay etc and the trouble of trying to get that front moving again if the fans are shut down before it pushes through to the top surface.


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## Draft Horse Hay (May 15, 2014)

I know this is an older thread but I need to add in the old saying

"You make hay in the field, not in the barn (or stack or bale)."

Does anyone use a Koster unit to do a DM est? Pretty popular with dairies nowadays but you can do a good DM using a microwave oven and a scale. Weigh the dish with your hay sample on it. Put in the microwave for 1 min. Take out and reweigh. Keep doing that until the weight is the same 2X. The difference btwn the original and end would be the amount of moisture in the hay. Always have a cup with some water in the microwave when doing this so you don't damage the machine and be careful you don't overdo it because you can start your hay sample on fire.

Curious as to what made you retest your bales when you put them up at 16%?


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## VA Haymaker (Jul 1, 2014)

Draft Horse Hay said:


> I know this is an older thread but I need to add in the old saying
> "You make hay in the field, not in the barn (or stack or bale)."
> Does anyone use a Koster unit to do a DM est? Pretty popular with dairies nowadays but you can do a good DM using a microwave oven and a scale. Weigh the dish with your hay sample on it. Put in the microwave for 1 min. Take out and reweigh. Keep doing that until the weight is the same 2X. The difference btwn the original and end would be the amount of moisture in the hay. Always have a cup with some water in the microwave when doing this so you don't damage the machine and be careful you don't overdo it because you can start your hay sample on fire.
> Curious as to what made you retest your bales when you put them up at 16%?


I've used the microwave test, but now rely on my baler mounted moisture meter.

Retesting because the hay analysis I had done showed 20% moisture. Pretty sure when I pulled the core samples, the hay was going through a sweat. However with the test results in the hands of a customer, "20% moisture" makes them nervous. I've since pulled new core samples and submitted for testing again. Should have the results in a week.


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## mlappin (Jun 25, 2009)

Interestingly enough, I used to apply acid to all my hay that had any alfalfa in it to get it thru the sweat. After I installed the Circle C rollers I only used it if moisture was over 18%, rarely do I have issues with heating anymore. My theory is since the aftermarket rollers crack the entire length of the stem either the moisture in the plant itself is more uniform or the cracked stem allows my Harvest tec unit to actually "see" any moisture left internally in the plant.


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