POST goosegrass and other grassy weed control in bermudagrass is problematic. Fewer herbicides that can control goosegrass are available due to regulatory pressure and herbicide resistance. Alternative herbicide options that offer effective control are needed. Previous research demonstrates that topramezone controls goosegrass, crabgrass, and other weed species; however, injury to bermudagrass may be unacceptable. The objective of this research was to evaluate the safening potential of topramezone combinations with different additives on bermudagrass. Field trials were conducted at Auburn University during summer and fall from 2015 to 2018 and 2017 to 2018, respectively. Treatments included topramezone mixtures and methylated seed oil applied in combination with five different additives: triclopyr, green turf pigment, green turf paint, ammonium sulfate, and chelated iron. Bermudagrass bleaching and necrosis symptoms were visually rated. Normalized-difference vegetative index measurements and clipping yield data were also collected. Topramezone plus chelated iron, as well as topramezone plus triclopyr, reduced bleaching potential the best; however, the combination of topramezone plus triclopyr resulted in necrosis that outweighed reductions in bleaching. Masking agents such as green turf paint and green turf pigment were ineffective in reducing injury when applied with topramezone. The combination of topramezone plus ammonium sulfate should be avoided because of the high level of necrosis. Topramezone-associated bleaching symptoms were transient and lasted 7 to 14 d on average. Findings from this research suggest that chelated iron added to topramezone and methylated seed oil mixtures acted as a safener on bermudagrass.

In this study, we measured nitrous oxide (N2O) emissions from plots of fall-planted hairy vetch (HV, Vicia villosa) grown as a green nitrogen (N) source for following summer forage crabgrass (Digitaria sanguinalis). Two treatments were compared: (i) HV grown solely as green manure where all biomass was incorporated by tillage, and (ii) harvesting of aboveground HV biomass prior to planting of crabgrass. Fluxes of N2O were measured with closed chamber systems on 27 dates during a 2-month growth period of crabgrass after the termination of HV in early May. At termination, the average aboveground biomass yield of HV was 4.6 Mg ha−1 with 146 kg N ha−1 content. The N2O emissions were as high as 66 g N2O-N ha−1 day−1 on day 1 after HV incorporation, but reached close to zero within a week. Emissions of N2O increased with subsequent rainfall and irrigation events from both treatments but emission peaks were not observed during the rapid growth of crabgrass. Two-month cumulative emission of N2O (mean ± s.e., n = 4) from HV incorporated plots (921 ± 120 g N2O-N ha−1) was three times (P < 0.05) of HV harvested plots (326 ± 30 g N2O-N ha−1). However, crabgrass biomass yields, N concentrations and total biomass N uptake were decreased significantly by harvesting HV. In conclusion, the results suggested that whereas removal of HV biomass for use as forage may significantly reduce N2O emissions, quantity and quality of the following recipient crops may be constrained.

The allelopathic potential of leafy spurge (Euphorbia esula L.) was investigated in the field and greenhouse. Reductions in frequency and density of quackgrass [Agropyron repens (L.) Beauv.] and common ragweed (Ambrosia artemisiifolia L.) were noted where leafy spurge had high densities in the field. Field soil samples taken from areas of moderate and high leafy spurge densities inhibited tomatoes (Lycopersicon esculentum Mill.) in the greenhouse. Growth of seedlings was inhibited up to 60% when leafy spurge leaves, roots, or litter were incorporated into soil, but surface applied leafy spurge litter had no effect. Growth inhibition was demonstrated for crabgrass [Digitaria sanguinalis (L.) Scop.] and tomato when 0.1 to 1.0% (w/w) of leafy spurge leaves or roots were added to soil. Based on these studies we postulate that leafy spurge exhibits allelopathic characteristics which may result from the incorporation of dead or decaying plant material in soil.

Two trials were conducted to evaluate the effects of herbicide and mulch on weed management and strawberry yield. Napropamide at rates of 4.50, 6.75, or 9.00 kg ai/ha; oxyfluorfen at 0.57 kg ai/ha; and napropamide plus oxyfluorfen at 4.50 plus 0.57 kg/ha were applied pretransplant on pressed beds covered with either low-density polyethylene mulch or virtually impermeable film. There was no herbicide by mulch interaction. Mulch types had no influence on weed counts and fruit yield, whereas herbicides affected both variables. The napropamide plus oxyfluorfen treatment resulted in the highest fruit number and weight, increasing yield by 20% with respect to the nontreated control. This herbicide combination provided the best weed suppression.