I would never consider Round Up a lesser evil....especially if you had to use it on a whole field......it's a tough one to say and I do not know how to help you on your quick fix burr problem...I just wanted to say that Round Up would be a bad thing to do in my opinion. Keep askin'

Grass spurs will disappear when fertility improves, but I don't know time factor. Round up will not disappear in years. I think most people around here use Grazon, but I bet it is no better than round up. I have been using humates with rock phos. and and other natural forms of K with a little ammonium sufate. This small amount releases locked up trace minerals. You can have lava sand, DE and other things mixed in but have to buy 1 ton at a time.
Goog luck!
Bob Bard

I don't know about A quick fix for this year,but i would rule out Round Up.If you need to or can spot spray the grass burs you can use a solution of vinegar,orange oil and liquid soap.here's the recipe from the web site:

Organic Herbicide

1 gallon full strength vinegar
1 cup orange oil
1 teaspoon Dr. Bronner’s Peppermint Soap or other mild soap

or

1 gallon full strength vinegar
1 cup orange oil
1 cup molasses
1 teaspoon Dr. Bronner’s Peppermint Soap or other mild soap

Vinegar strengths vary. 5% is regular vinegar. 10% is pickling vinegar. 20% is the strongest you should ever use and it is dangerous and needs to be handled carefully. Avoid contact with skin and breathing the fumes. Be sure to keep the mix well shaken while spraying. Avoid products that are made from glacial acetic acid.

I've used the first recipe and it works great.Corn Gluten Meal is a natural pre emergent and herbicide,but it's not the right time to use it now.I was going to use it on my grass burs but messed around and couldn't get it out during the time window.good luck...keep us posted on your results.
Mark

How did you find the hay fields and what were you paid - money , hay, grazing on some. or what? Did you pay for products or did owner?
Robert D Bard

Liquid molasses & humates will pretty much knock out your grass burr problem in a short amount of time. That's turned out to be the least expensive and easiest two products to enrich the soil and bring the level up to where they won't grow but your hay will. You can apply both these prdoucts in dry form if you haven't got a liquid spreader but the liquid seems to turn out cheapest in our part of the country. About 5 gallons per acre seems to be effective with molasses as well as humate, depending on the maker. Hope this is helpful! Check out Acres USA link and see what they have to offer too.

Kathe Kitchens is right. Molasses and humates are inexpensive and will work best. Never under ANY circumstances would I ever use round-up. It is an SU herbicide and those are the worst! It does not work, it is a waste of money, and it causes metabolic mayhem in the surrounding vegetation.
http://www.dirtdoctor.com/view_question.php?id=115#top

Bluestem-
Check out this web site, you can get excellent information on humates and you can ask about large quantities. They currently service the agricultural customer. The owners are Terry and David Williams. You can tell them I sent you if you like. Terry is in Arizona and David is in Houston. If that doesn't work, I will dig up some other sources for you (no pun intended).
Tony M http://www.humatech.com/
AG Organics

I'm a proponent of using vinegar on small clusters of weeds in a homeowner's turf, but for acreage I would discourage it. If a plant (weed) was sensitive to 5% vinegar, then maybe; but the 20% vinegar is pretty rough stuff to be around or if you get it on you. Using typical farm application equipment I'd be worried of a breeze sending the vinegar back in my face.

20% is ok on farm if you are willing to walk a little. I got rid of thisles with this. 20% in a spray bottle with liquid dish washing soap (small amount)
Walk over pastures and pull trigger. Do in pre bloom and hot day (early morning when you don 't expect rain.
Robert D Bard