Genetically modified (GM) soy was first introduced in 1996, principally to make soy crops resistant to herbicides. Although resisted in some regions, notably Europe, GM soy is now grown in many parts of the world. Much of the soy in Latin America is genetically modified to tolerate glyphosate herbicide; This means soy can be sprayed several times with this herbicide during the growing season and all other plants but the soy will be killed. Recently more and more weeds have become resistant to this herbicide and as a consequence new GM soy variations have been developed with multiple herbicide resistance.
A further method of herbicide application developed around 2010, involves ridding the soil of its active weed seed bank rather than just killing the weed. This can successfully treat annual plants but not perennials . Researchers at the Agricultural Research Service found that the application of herbicides to fields late in the weeds' growing season greatly reduces their seed production, and therefore fewer weeds will return the following season. Because most weeds are annuals, their seeds will only survive in soil for a year or two, so this method will be able to destroy such weeds after a few years of herbicide application.