Effect of New Auxin Herbicide Formulations on Control of Herbicide Resistant Weeds and on Microbial Activities in the Rhizosphere

Widespread distribution of glyphosate-resistant weeds in soybean-growing areas across Mississippi has economically affected soybean planting and follow-up crop management operations. New multiple herbicide-resistant crop (including soybean) technologies with associated formulations will soon be commercialized. The objectives of this research were to determine the efficacy of new 2,4-D + glyphosate and dicamba formulations on herbicide resistant weeds, and to determine the impact of the new 2,4-D + glyphosate formulation on microbial communities in the soybean rhizosphere involved in nutrient cycling. New 2,4-D + glyphosate and dicamba formulations registered for use on 2,4-D and dicamba-resistant soybean, respectively, adequately controlled glyphosate resistant and susceptible pigweeds (Palmer amaranth and tall waterhemp) and common ragweed. The 2,4-D + glyphosate formulation did not significantly impact soil microbial activities linked to nutrient cycling in the soybean rhizosphere. These results indicate these new 2,4-D + glyphosate and dicamba formulations can be effective in controlling glyphosate resistant and other herbicide resistant weeds while not having adverse effects on the activities of beneficial soil microorganisms.

Microencapsulated chlorpyrifos: Degradation in soil and influence on soil microbial community structures

Degradation kinetics of microencapsulated chlorpyrifos （CPF-MC） in soil and its influence on soil microbial community structures were investigated by comparing with emulsifiable concentration of chlorpyrifos （CPF-EC） in laboratory. The residual periods of CPF-MC with fortification levels of 5 and 20 mg/kg reached 120 days in soil, both of the degradation curves did not fit the first-order model, and out-capsule residues of chlorpyrifos in soil were maintained at 1.76 （±0.33） and 5.92 （±1.20） mg/kg in the period between 15 and 60 days, respectively. The degradation kinetics of CPF-EC fit the first-order model, and the residual periods of 5 and 20 mg/kg treatments were 60 days. Bacterial community structures in soil treated with two concentrations of CPF-MC showed similarity to those of the control during the test period, as seen in the band number and relative intensities of the individual band on DGGE gels （p 〉 0.05）. Fungal community structures were slightly affected in the 5 mg/kg treatments and returned to the control levels after 30 days, but initially differed significantly from control in the 20 mg/kg treatments （p 〈 0.05） and did not recover to control levels until 90 days later. The CPF-EC significantly altered microbial community structures （p 〈 0.05） and effects did not disappear until 240 days later. The results indicated that the microcapsule technology prolonged the residue periods of chlorpyrifos in soil whereas it decreased its side-effects on soil microbes as compared with the emulsifiable concentration formulation.

Microbial responses towards biochar application in potentially toxic element(PTE)contaminated soil:a critical review on effects and potential mechanisms

Soil harbors a huge diversity of microorganisms and serves as the ecological and social foundation of human civilization.Hence,soil health management is of utmost and consistent importance,aligning with the United Nations Sustainable Development Goals.One of the most hazardous contaminants in soil matrix is potentially toxic elements(PTEs),which can cause stress in soil indigenous microorganisms and severely jeopardize soil health.Biochar technology has emerged as a promising means to alleviate PTE toxicity and benefit soil health management.Current literature has broadly integrated knowledge about the potential consequences of biochar-amended soil but has focused more on the physical and chemical responses of the soil system than microbiological attributes.In consideration of the indispensable roles of soil microbials,this paper first introduces PTE-induced stresses on soil microbials and then proposes the mechanisms of biochar’s effects on soil microbials.Finally,microbial responses including variations in abundance,interspecific relationships,community composition and biological functions in biochar-amended soil are critically reviewed.This review thus aims to provide a comprehensive scientific view on the effect of biochar on soil microbiological health and its management.