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Discussion Starter · #1 ·
As I sit waiting for the rain residual from yesterday to dry off, I am wondering about the different factors in moisture loss the first day. Today is the first of 3.5-4 days of haymaking weather but will be cloudy all day. I typically cut in a 10 am to 1 pm window to maximize the moisture loss the first day. Spread hay as much as the discbine will do, often tedding at 4 or so the first day. Specifically, my question is, does anyone have empirical data on the difference in sunny vs cloudy weather on drying given the same temps, humidity, and wind? does anyone have data on the impact of humidity on moisture loss? Obviously, I know that at 65% humidity, moisture loss will be less than at 40%, but I am wondering how much less? What I am really trying to determine is if it is actually worth waiting a day to cut which also shortens the window to oncoming unsettled weather.
 
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I am guessing there are a lot of factors in the equation so it may be tough to come up with a general rule of thumb or empirical data, but I am interested in any ideas on this myself. I am curious about tedding on the first day rule of thumb too. I have been doing it the next morning while the dew is still on the hay to avoid leaf loss but to let it dry more on the first day. This is what I have been doing on my first cutting Alfalfa this year anyway and it seemed to work out. Other grass hay seems to dry faster than alfalfa, especially later cuttings that are thinner. Just had 3 days of 78 degree weather which is rare to be that cool. Had sunshine, no wind, but humidity was like 65% every day with high amount of morning dew. 3rd cutting Alfalfa so somewhat thin and it still didn't all dry in time by end of the 3rd day.

Interested in what others say about this topic.
 

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Your best bet would be to go by pan evaporation values that are published for your local area by AWIS. HayWilson had a sheet published that determines how much total PE is required to dry hay based on tonnage and % spread in the field. I've used that as a general guide but I don't know how to link it here.

Empirically in my own experiences I have found that complete sunshine has more of an effect on curing than temperature. I've had hay down in the 60's but was a full sun day. The hay felt warm on the surface and it dried pretty quickly. Next, if humidity is high (>60%), I think the efficiency of hay drying drops off precipitously (no pun intended). The next killer to humidity seems to be cloud cover, whereas I have checked fields at the end of a cloudy day that seemed to have had very little drying occur over the course of a day. Finally, winds above 8 mph aid drying, but effect is lost if humidity is high.

To build my own empirical knowledge based I would check the dryness of the hay as soon as I finished mowing (seeing how much the first stuff cut had dried down). I also check it in the evening around 5 or 6 pm to see how much more it has dried off. The varying conditions encountered through the course of doing this has let me figure out what works and what hasn't.

In Michigan 2nd cut season, our humidity is low (40-50%), ground is dry, temp in the 80's and full sun or mostly sunny, I mow around 9 am. I ted it once I'm finished mowing, and it will be ready to rake and bale by noon or 1 the following day.
 

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Gourmet Horse Hay Producer
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Discussion Starter · #5 ·
Well finished cutting at 230 and it dried pretty well on top even with the clouds and occasional breakout sun moments. Unfortunately, it remoisturized at eleven last night in a shower so well be on the Tedder this morning
 

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Somewhere in my online travels I came across this document and saved it. It may shed some light (bad pun?) on your question about the effects of sunshine on hay drying.
Really appreciate you finding and posting this document. This is very helpful for a strategy based upon conditions. I knew wind was a factor but didn't realize it was the one of the biggest factors. I have just started watching Humidity ranges this year from feedback on here. I always thought temperatures were the biggest issue but according to this study, I am wrong.
 

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I do know at one point there were some posters with lots of charts that had a lot of information about drying hay. I have no idea who made them or what year, but they used to be made.
There were a few different ones in the barn when I bought the property.
 
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