Agriculture Reference
In-Depth Information
The main effect of HT crop adoption on herbicide use is the substitution
of glyphosate for more toxic herbicides.
Despite the mixed but relatively
minor effect HT crop adoption has had on overall herbicide usage, most
researchers agree (NRC, 2010) that the main effect of HT crop adoption is the
substitution of glyphosate for more traditional herbicides. Because glyphosate
is significantly less toxic and less persistent than traditional herbicides (WHO,
1994; NRC, 2010),
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the net impact of HT crop adoption is an improvement in
environmental quality and a reduction in the health risks associated with
herbicide use (even if there are slight increases in the total pounds of herbicide
applied).
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However, glyphosate resistance among weed populations in recent
years may have induced farmers to raise application rates. Thus, weed
resistance may be offsetting some of the economic and environmental
advantages of HT crop adoption regarding herbicide use. Moreover, herbicide
toxicity may soon be negatively affected (compared to glyphosate) by the
introduction (estimated for 2014) of crops tolerant to the herbicides dicamba
and 2,4-D.
Adoption and Conservation Tillage
Conservation tillage (including no-till, ridge-till, and mulch-till) is known
to provide environmental benefits (USDA's ERS/NRCS, 1998; NRC, 2010).
By leaving substantial amounts of crop residue (at least 30 percent) covering
the soil surface after planting, conservation tillage reduces soil erosion by
wind and water, increases water retention, and reduces soil degradation and
water/chemical runoff. In addition, conservation tillage reduces the carbon
footprint of agriculture.
Adopters of HT crops practice conservation tillage more than growers of
conventional varieties.
Since the 1980s, the adoption of conservation tillage
practices by U.S. farmers has been facilitated by the availability of post-
emergent herbicides that can be applied over a crop during the growing
season. Post-emergent herbicides are especially beneficial in no-till production
systems because these herbicides control weeds without tilling the soil. HT
crops have helped spread no-till farming further since they often allow a more
effective system than just using other post-emergent herbicides (Fernandez-
Cornejo and Caswell, 2006).
