Iowa State University researchers combined survey results and computer
modeling to study the trend in tillage intensity in theUS in recent
years. The results of the study are published in/Nature Food/.

Thousands of US farmers were surveyed about their tillage practices and
it was found that reliance on tillage decreased from 1998 to 2008.
Genetically engineeredcrops were introduced in the late 1990s, which
helped farmers not to rely on tillage as a method of weed control.
However, the survey also showed that tillage intensity started to rise
again starting in 2009, which is attributed by the researchers to the
growing numbers of weed species with resistance to glyphosate. The
results of the survey were entered into ecosystem models to determine
how tillage decisions impact soil emissions of greenhouse gases.
According to Chaoqun Lu, lead author of the study, as tillage intensity
grows, more carbon and nitrogen stored in the soil releases into the
atmosphere in the form of greenhouse gases.

Study finds relationships among herbicide-resistant weeds, tillage
practices and agricultural greenhouse gas emissions â?? News Service â??
Iowa State University (iastate.edu)
[www.news.iastate.edu]