That's what I thought but the seeds are very small. Unless they didn't have enough water to grow more...
Could it be Echinochloa? http://www.henriettesherbal.com/pictures/p05/pages/echinochloa-frumentacea.htm http://www.flickr.com/photos/digitplantimages/3388606393/ http://www.prairiemoon.com/images/D/Echinochloa-crusgalli-Barnyard-Grass-seed.jpg