It isn't straw we chew, it's grass.
Straw is made from the stems of wheat, oats, or barley that's been cut and baled to provide bedding for animals after the grains have been harvested.
What you see farmers chewing is grass--tall, tasseled prairie grass--which is liable to be growing in yards and pastures out in the country. There isn't a specific reason why we chew it. We just do. It's kind of like Chewing Gum. Many tall prairie grasses have a sweet, refreshing taste--one of the kind I like to chew, called big blue stem, actually tastes a bit like watermelon. So if you're working outside and it's hot out and you don't have any gum, a long piece of grass not only gives you something sweet to chew on but it can also (ever so slightly) re-hydrate you. In the very least, it breaks the monotony of farm work.
They are safe to chew but not safe to eat.
Straw
Straw is the hollow stalk of a grain plant, most farmers use Oat plants.
Gum or a straw(s).
They were skilled dry farmers, and they built houses with adobe bricks which were made from mixed mud and straw.
they used straw instead of wood as they are cultral and free spirited
it means: the last staw
It depends on the use. For mulch, straw is probably better since it carries less possibility of plant disease and may carry fewer weed seeds. For feed use for organic dairy production, hay is a much higher quality feed since straw has virtually no nutritive value.
Chaff is a chopped mixture of hay and straw and it provides slightly easier chewing for older horses and the needed chew time for all horses. It can also be used to supplement a forage poor diet.
A farmer's wife costume for a child can be as easy as a plain dress with an apron. A straw hat or sunbonnet would be an acceptable accessory for this costume.
A Straw Poll
Farmers are not those that wear a straw hat and bib overalls--although some of the more true hillbilly types do--most farmers just wear jeans, shirt (can be a cotton T-shirt or a western-type shirt), jeans, work boots, and baseball cap. If the work is really dirty, then overalls are worn a lot of the time as well.