Integrating soil conservation practices and glyphosate-resistant crops: impacts on soil.
BACKGROUND
Conservation practices often associated with glyphosate-resistant crops, e.g. limited tillage and crop cover, improve soil conditions, but only limited research has evaluated their effects on soil in combination with glyphosate-resistant crops. It is assumed that conservation practices have similar benefits to soil whether or not glyphosate-resistant crops are used. This paper reviews the impact on soil of conservation practices and glyphosate-resistant crops, and presents data from a Mississippi field trial comparing glyphosate-resistant and non-glyphosate-resistant maize (Zea mays L.) and cotton (Gossypium hirsutum L.) under limited tillage management.


RESULTS
Results from the reduced-tillage study indicate differences in soil biological and chemical properties owing to glyphosate-resistant crops. Under continuous glyphosate-resistant maize, soils maintained greater soil organic carbon and nitrogen as compared with continuous non-glyphosate-resistant maize, but no differences were measured in continuous cotton or in cotton rotated with maize. Soil microbial community structure based on total fatty acid methyl ester analysis indicated a significant effect of glyphosate-resistant crop following 5 years of continuous glyphosate-resistant crop as compared with the non-glyphosate-resistant crop system. Results from this study, as well as the literature review, indicate differences attributable to the interaction of conservation practices and glyphosate-resistant crop, but many are transient and benign for the soil ecosystem.


CONCLUSIONS
Glyphosate use may result in minor effects on soil biological/chemical properties. However, enhanced organic carbon and plant residues in surface soils under conservation practices may buffer potential effects of glyphosate. Long-term field research established under various cropping systems and ecological regions is needed for critical assessment of glyphosate-resistant crop and conservation practice interactions.
Locke
Martin A
MA
USDA-Agricultural Research Service, National Sedimentation Laboratory, Water Quality and Ecology Research Unit, Oxford, MS 38655, USA. martin.locke@ars.usda.gov
Zablotowicz
Robert M
RM
Reddy
Krishna N
KN
D000383:Agriculture / Q000379:methods; D003247:Conservation of Natural Resources; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D003368:Gossypium / Q000235:genetics; D053209:Herbicide Resistance / Q000235:genetics; D006540:Herbicides / Q000737:chemistry*; D030821:Plants, Genetically Modified; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology; D003313:Zea mays / Q000235:genetics; D000097797:Glyphosate
D005998:Glycine; D006540:Herbicides; D012987:Soil; D000097797:Glyphosate