Abstract
The proliferation of glyphosate-resistant weeds has resulted in significant losses in the productivity of crops such as corn, soybean, and cotton. As a result, new crop varieties with resistance genes from other herbicides, such as 2,4-D and dicamba, have been developed as part of alternative weed control cropping systems. However, little is known about how the application of these herbicides impacts the microorganisms that carry out nutrient cycling in the soil of these cropping systems, particularly in the rhizosphere, the soil compartment immediately adjacent to the root system which is pivotal to plant nutrient uptake. The purpose of the current study was to assess the effects of dicamba on soil enzyme activities linked to C, N, and P cycling in the rhizosphere of resistant soybean plants. While dicamba had no significant effects on the activities of enzymes linked to C or P cycling in the rhizosphere, N-acetylglucosaminidase activity was temporarily inhibited, but recovered by three days after application. These results suggest there are no long-lasting negative effects of dicamba in the rhizosphere of treated plants when applied at field rates.
Highlights
Little is known about how the application of these herbicides impacts the microorganisms that carry out nutrient cycling in the soil of these cropping systems, in the rhizosphere, the soil compartment immediately adjacent to the root system which is pivotal to plant nutrient uptake
Dicamba has a long history of use for early season weed control in corn, but its use later in the growing season has been limited before the introduction of dicamba resistant soybean and cotton, owing to its tendency for drift and volatilization, which can damage sensitive crops in neighboring fields [4]
The current study found the activities of microbially secreted exoenzymes in the rhizosphere more affected by sampling time point than herbicide treatment with dicamba according to 2-way ANOVA (p < 0.006)
Summary
Much effort has gone into the development of additional weed control options, including the creation of new crop varieties stacked with genes conferring resistance to multiple herbicides, thereby providing farmers with more herbicide options to combat resistant weeds during the growing season. Some of these new cropping systems include those engineered with resistance genes to auxin herbicides (such as 2,4-dichlorophenoxyacetic acid (2,4-D) or 3,6-dichloro-2-methoxybenzoic acid (dicamba)) in addition to glyphosate. The introduction of dicamba resistant crops has been accompanied by new formulations designed to minimize drift, including XTendiMax® (which contains a diglycolamine (DGA) salt of dicamba) and Engenia (containing an N,N-Bis-(aminopropyl) methylamine salt of dicamba) [4]
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