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- Author or Editor: Prasanta C. Bhowmik x
Amidochlor at 2.24 to 3.36 kg a.i./ha provided excellent (90% or better) seedhead suppression of ‘Baron’ Kentucky bluegrass (Poa pratensis L.) and 80% to 90% seedhead suppression for ‘Pennlawn’ red fescue (Festuca rubra L.) turf. Although amidochlor provided excellent shoot growth reduction up to 42 days after treatment (DAT), the greatest shoot growth reduction was noted during 28 DAT. In general, turfgrass injury was within acceptable limits over the entire study period except during the 28-day period when unacceptable injury (32% to 64%) was noted. Quality of amidochlor-treated turfs was unacceptable 28 DAT. Quality improved significantly over time, and the quality ratings ranged from 7.0 to 8.5. Maximum shoot growth reduction (85% to 93%) as measured by fresh clipping weight occurred during the initial 28-day period and thereafter declined, followed by a stimulation of turfgrass growth (56 DAT). Chemical name used: N-[(acetylamino)methyl]-2-chloro-N-2,6(diethylphenyl)acetamide (amidochlor).
Fenoxaprop-ethyl at rates of 0.09 to 0.28 kg·ha−1 provided effective smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl.] control with minor injury to ‘Baron’ Kentucky bluegrass (Poa pratensis L.). Optimum timing for application was the 4-leaf to 5-tiller stage of crabgrass growth. At this stage of growth, fenoxaprop-ethyl applied at 0.20, 0.28, or 0.38 kg·ha−1 provided excellent (90% or better) season-long crabgrass control. Fenoxaprop-ethyl at 0.09 kg·ha−1 was an effective crabgrass control treatment at 2 to 4 leaf stage when combined with DCPA at 11.76 kg·ha−1. Split applications of fenoxaprop-ethyl in June and July at both 0.14 + 0.14 and 0.28 + 0.28 kg·ha−1 also provided season-long crabgrass control. Chemical names used: (±)-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate (fenoxaprop-ethyl); and dimethyl tetrachlo-roterephthalate (DCPA).
The competitive effects of bunchberry Cornus canadensis L. on native stands of blueberries Vaccinium angustifolium Ait. was assessed in 1986 and 1987, and in the greenhouse in 1987 with replacement series experiments. In the field, blueberry and bunchberry fruit were harvested in August and all aboveground growth was cut, the species were separated, and dry weight was determined. The relative yield total (RYT), defined as the dry weight (DW) of the combined aboveground portions of the blueberry and bunchberry divided by their respective DW at 100% cover, was >1 and showed an increase with increasing proportion of bunchberry. Blueberry relative yield, defined as the DW of the aboveground portion divided by the DW at 100% cover, was >1, but bunchberry relative yield DW was ≤1. Regression of individual on associate DW yield indicates blueberry is as aggressive as bunchberry. Blueberry fruit count and yield decreased with increasing bunchberry density. In the greenhouse study, plant count and cover were assessed weekly, and leaf area index (LAD and DW were obtained at the end of the study. RTY > 1, and combined DW increased with increasing proportion of bunchberry. The LAI of blueberry or bunchberry was higher in mixtures than in pure stands. Blueberries are competitive with bunchberry, but in native fields, open areas among clones allow faster growing bunchberry to spread without competition.
Treatments of oxyfluorfen at 0.43 kg·ha−1 as a pretransplant (PT) treatment, followed by several sequential postemergence grass herbicides as post-over-the-top (POT) treatments, provided excellent broadleaf and grass control in transplanted cabbage (Brassica oleracia var capitata L.). These herbicides included sethoxydim, fluazifop-butyl, and haloxyfop-methyl. Oxyfluorfen treatments alone gave 86% to 89% control of grass species. Broadleaf weeds were controlled effectively with oxyfluorfen treatments. Cabbage had acceptable tolerance to oxyfluorfen at 0.43 and 0.56 kg·ha−1 when applied as a PT treatment either alone or with grass herbicides. Increased injury to cabbage was noted with the high rate of oxyfluorfen. Yield and quality of cabbages were not reduced by oxyfluorfen applied pretransplant. Yields of marketable cabbage obtained with the treatments of oxyfluorfen as PT treatment followed by sequential grass herbicides as POT treatment, ranged from 24.3 to 27.1t·ha−1 in 1983 and 35.7 to 39.0 t·ha−1 in 1985. Chemical names used: 2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); 2-[l-(ethoxyi-mino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-l-one (sethoxydim); (±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid (fluazifop-butyl); and 2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy] propanoic acid (haloxyfop-methyl).
The role of the antioxidant response system in association with the proline-associated pentose phosphate pathway for cold adaptation was investigated in three cool-season turfgrasses during a cold acclimation period. As phenolic biosynthesis and antioxidant stimulation is proposed to be linked to the proline-associated pentose phosphate pathway, this study was aimed to determine the active role of proline in metabolic regulation and its relationship with the cold stress tolerance mechanism of cool-season turfgrasses. In this study, significant accumulation of total soluble phenolics and higher total antioxidant activity was observed in creeping bentgrass (Agrostis stolonifera L.), kentucky bluegrass (Poa pratensis L.), and perennial ryegrass (Lolium perenne L.) during cold acclimation, confirming the direct and indirect role of phenolics to counter low temperature-induced oxidative stress. A positive correlation between high phenolic content and the proline-associated pentose phosphate pathway was also found in investigated turfgrass species during a cold acclimation period. Low succinate dehydrogenase activity along with the high glucose-6-phosphate dehydrogenase activity in cold-acclimated turfgrass species suggested a probable shift of carbon flux from the energy-consuming tricarboxylic cycle to the alternative energy-efficient proline-associated pentose phosphate pathway to induce a better cold stress tolerance mechanism in these cool-season turfgrasses. Higher proline accumulation in cold-acclimated turfgrass species also supported the above findings and a probable proline oxidation to support mitochondrial oxidative phosphorylation was observed in acclimated kentucky bluegrass based on the activity of proline dehydrogenase, which likely supports the active metabolic role of proline in stress-induced situations. Through this study, a significant variation in cold stress tolerance mechanisms was observed among three investigated cool-season turfgrass species during cold acclimation. Furthermore, a high cold stress tolerance characteristic was observed in kentucky bluegrass by adapting a more efficient pathway for an antioxidant response linked to proline accumulation.
Cassava production in Amazonas state deserves to be highlighted due to its great historical, social, and economic importance. Weed competition severely constrains cassava production in Amazonas. The use of cover crops is safe and very efficient at eliminating weeds while keeping the soil covered. The objective of this study was to evaluate physical properties of soil and glyphosate residues in storage roots as a function of the weed management in cassava. The experiment was carried out in a randomized complete block design with five treatments and five repetitions. The treatments were biological control with two species of cover plants (Brachiaria ruziziensis and Mucuna pruriens), chemical control, mechanical control, and treatment with no weed control. The cover crops characteristics evaluated were dry weight, the percentage of cover, and rate of decomposition of plant residues. In the soil, the bulk density and total porosity were determined. The contamination of the storage roots was evaluated based on the analysis of glyphosate residue. Brachiaria ruziziensis presented more dry weight and higher percentage of cover compared with M. pruriens, and both cover crops showed very similar decomposition rates. The physical properties of soil were unaffected by any treatment evaluated. There was no detection of glyphosate and its metabolite, aminomethylphosphonic acid (AMPA), in any treatment evaluated. Chemical control with glyphosate is not able to contaminate cassava storage roots.