Bio-jarosite,an iron mineral synthesized biologically using bacteria,is a substitute for iron catalysts in the Fenton oxidation of organic pollutants.Iron nanocatalysts have been widely used as Fenton catalysts becaus...Bio-jarosite,an iron mineral synthesized biologically using bacteria,is a substitute for iron catalysts in the Fenton oxidation of organic pollutants.Iron nanocatalysts have been widely used as Fenton catalysts because they have a larger surface area than ordinary catalysts,are highly recyclable,and can be treated efficiently.This study aimed to explore the catalytic properties of bio-jarosite iron nanoparticles syn-thesized with green methods using two distinct plant species:Azadirachta indica and Eucalyptus gunni.The focus was on the degradation of dicamba via Fenton oxidation.The synthesized nanoparticles exhibited different particle size,shape,surface area,and chemical composition characteristics.Both particles were effective in removing dicamba,with removal efficiencies of 96.8%for A.indica bio-jarosite iron nano-particles(ABFeNPs)and 93.0%for E.gunni bio-jarosite iron nanoparticles(EBFeNPs)within 120 min of treatment.Increasing the catalyst dosage by 0.1 g/L resulted in 7.6%and 43.0%increases in the dicamba removal efficiency for EBFeNPs and ABFeNPs with rate constants of 0.025 min^(-1) and 0.023 min^(-1),respectively,confrming their catalytic roles.Additionally,the high efficiency of both catalysts was demonstrated through five consecutive cycles of linear pseudo-first-order Fenton oxidation reactions.展开更多
Waterhemp is a small-seeded, dioecious, broadleaf weed that emerges throughout the growing season. If left uncontrolled, waterhemp interference can reduce soybean yield up to 73%. Glyphosate-resistant (GR) waterhemp w...Waterhemp is a small-seeded, dioecious, broadleaf weed that emerges throughout the growing season. If left uncontrolled, waterhemp interference can reduce soybean yield up to 73%. Glyphosate-resistant (GR) waterhemp was first discovered in one county in Ontario in 2014;as of 2017, it has been found in two other counties. Glyphosate/dicamba-resistant soybean can be sprayed with glyphosate and/or dicamba preplant (PP), preemergence (PRE) and/or postemergence (POST). The objective of this study was to determine the control of GR waterhemp in glyphosate/dicamba-resistant soybean with PRE residual herbicides, glyphosate/dicamba applied POST or a two-pass program of a PRE residual herbicide followed by glyphosate/dicamba applied POST. At 8 weeks after application (WAA), pyroxasulfone (150 g ai ha-1), S-metolachlor/metribuzin (1943 g ai ha-1), pyroxasulfone/sulfentrazone (300 g ai ha-1) and flumioxazin/pyroxasulfone (240 g ai ha-1), applied PRE, resulted in 71%, 85%, 82% and 90% GR waterhemp control, respectively. The same PRE herbicides, followed by glyphosate/dicamba (1800 g ae ha-1) POST, improved control to greater than 96%. This study concludes that a two-pass program of an effective soil applied residual herbicide followed by glyphosate/dicamba POST controlled GR waterhemp in glyphosate/dicamba-resistant soybean.展开更多
Palmer amaranth, sicklepod and pitted morningglory are the three most common and troublesome weeds in soybean in South Carolina. They exhibit very aggressive growth capabilities and if left uncontrolled in fields will...Palmer amaranth, sicklepod and pitted morningglory are the three most common and troublesome weeds in soybean in South Carolina. They exhibit very aggressive growth capabilities and if left uncontrolled in fields will cause significant reductions in soybean yields. Dicamba and 2,4-D herbicides are currently having a resurgence in usage due to the recent commercialization of soybean trait technologies with tolerance to these herbicides. Dicamba and 2,4-D when tank mixed with glufosinate and glyphosate may offer additional weed control to resistant weeds through the process of herbicide synergism. Greenhouse experiments were conducted in 2013 at Edisto Research and Education Center near Blackville, SC to evaluate the efficacy of glyphosate, glufosinate, dicamba and 2,4-D treatments alone and in combination on Palmer amaranth, sicklepod, and pitted morningglory at selected heights. Results suggested that glufosinate alone provided the overall best control for all 3 weed species. Glyphosate alone provided the lowest control of all 3 species at all heights. Synergism or improved sicklepod control was observed when glufosinate was tank mixed with dicamba. However, as sicklepod increased in height, glufosinate + 2,4-D or dicamba combination offered the best control compared to glufosinate alone (90% versus 86% in 20 cm plants and 87% versus 85% in 30 cm plant). In the 5 cm Palmer amaranth, decreased control was observed when glyphosate or glufosinate was tank mixed with 2,4-D. These experiments showed that glufosinate alone and/or in combination with 2,4-D or dicamba was the overall best treatment on the three broadleaf weed species.展开更多
Palmer amaranth and pitted morningglory are difficult to manage weeds present in South Carolina soybean production fields. Glyphosate and ALS-resistant Palmer amaranth biotypes have spread rapidly throughout South Car...Palmer amaranth and pitted morningglory are difficult to manage weeds present in South Carolina soybean production fields. Glyphosate and ALS-resistant Palmer amaranth biotypes have spread rapidly throughout South Carolina making the control of these weeds more difficult. Recently, soybean varieties with tolerance to dicamba have been introduced along with several new ultra-low volatility formulations of dicamba to help with the problem. Field experiments were conducted near Blackville, SC in 2012 and 2013 to evaluate dicamba herbicide programs for broadleaf weed management in dicamba tolerant soybean. At 2 weeks after POST1 (2 WAP1), Palmer amaranth control ranged from 93% to 100% across the PRE followed by POST treatments in 2012 and 2013. By 2 weeks after POST2 (2 WAP2), control was 95% or better. Treatments containing two or three herbicide applications (PRE, POST1 and POST2) offered good to excellent (92% - 100%) pitted morningglory control. No differences in weed control were observed among treatments with 3 application times compared to those applied twice. In general, all treatments with a PRE followed by at least one POST application provided good to excellent control of Palmer amaranth and pitted morningglory. Overall, a PRE (either dicamba or flumioxazin) followed by a dicamba or a non-dicamba containing POST treatment provided good to excellent control of Palmer amaranth and pitted morningglory when applied at the correct growth stage.展开更多
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 herbi...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 </span><span style="font-family:Verdana;">resistant soybean plants. While dicamba had no significant effects on the ac</span><span style="font-family:Verdana;">tivities 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.展开更多
Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotype...Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize （Zea mays L.） genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent ofgenotype when young immature embryos, 12 days after pollination （DAP） were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction ofembryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines.展开更多
[目的]研究麦草畏对烟草生长的影响及其致害临界值,为其合理使用和除草剂药害的预防及治理提供理论参考依据。[方法]以‘贵烟一号’为研究材料,采用盆栽试验方法,模拟麦草畏土壤残留环境,其含量分别为36、72、144、720 g a.i./hm^2,烟...[目的]研究麦草畏对烟草生长的影响及其致害临界值,为其合理使用和除草剂药害的预防及治理提供理论参考依据。[方法]以‘贵烟一号’为研究材料,采用盆栽试验方法,模拟麦草畏土壤残留环境,其含量分别为36、72、144、720 g a.i./hm^2,烟苗移栽40 d后,观测麦草畏土壤残留致烟草药害症状,测定其致害烟株农艺性状和部分生理生化指标,同时对其烟叶化学成分进行评价。[结果]低剂量麦草畏对烟株生长有促进作用,而高浓度则导致烟株畸形生长,其致害临界值为144 ga.i./hm^2。烟苗移栽40 d后,较未施麦草畏处理,土壤麦草畏剂量为144 ga.i./hm^2时,分别显著提高和降低了致害烟叶POD酶活性、MDA、叶绿素和蛋白质含量(P<0.05,下同);当土壤麦草畏剂量为72 ga.i./hm^2时,致害烟叶总糖、还原糖、钾和氯离子含量均下降,而烟碱含量、POD酶活性和MDA均提高,且差异性显著,说明低浓度麦草畏虽可促进烟株生长,但已对烟株产生内在毒害效应。[结论]麦草畏易对后茬烟草产生药害,且症状不易恢复,建议前茬烟田应谨慎使用麦草畏,以防造成损失。展开更多
文摘Bio-jarosite,an iron mineral synthesized biologically using bacteria,is a substitute for iron catalysts in the Fenton oxidation of organic pollutants.Iron nanocatalysts have been widely used as Fenton catalysts because they have a larger surface area than ordinary catalysts,are highly recyclable,and can be treated efficiently.This study aimed to explore the catalytic properties of bio-jarosite iron nanoparticles syn-thesized with green methods using two distinct plant species:Azadirachta indica and Eucalyptus gunni.The focus was on the degradation of dicamba via Fenton oxidation.The synthesized nanoparticles exhibited different particle size,shape,surface area,and chemical composition characteristics.Both particles were effective in removing dicamba,with removal efficiencies of 96.8%for A.indica bio-jarosite iron nano-particles(ABFeNPs)and 93.0%for E.gunni bio-jarosite iron nanoparticles(EBFeNPs)within 120 min of treatment.Increasing the catalyst dosage by 0.1 g/L resulted in 7.6%and 43.0%increases in the dicamba removal efficiency for EBFeNPs and ABFeNPs with rate constants of 0.025 min^(-1) and 0.023 min^(-1),respectively,confrming their catalytic roles.Additionally,the high efficiency of both catalysts was demonstrated through five consecutive cycles of linear pseudo-first-order Fenton oxidation reactions.
文摘Waterhemp is a small-seeded, dioecious, broadleaf weed that emerges throughout the growing season. If left uncontrolled, waterhemp interference can reduce soybean yield up to 73%. Glyphosate-resistant (GR) waterhemp was first discovered in one county in Ontario in 2014;as of 2017, it has been found in two other counties. Glyphosate/dicamba-resistant soybean can be sprayed with glyphosate and/or dicamba preplant (PP), preemergence (PRE) and/or postemergence (POST). The objective of this study was to determine the control of GR waterhemp in glyphosate/dicamba-resistant soybean with PRE residual herbicides, glyphosate/dicamba applied POST or a two-pass program of a PRE residual herbicide followed by glyphosate/dicamba applied POST. At 8 weeks after application (WAA), pyroxasulfone (150 g ai ha-1), S-metolachlor/metribuzin (1943 g ai ha-1), pyroxasulfone/sulfentrazone (300 g ai ha-1) and flumioxazin/pyroxasulfone (240 g ai ha-1), applied PRE, resulted in 71%, 85%, 82% and 90% GR waterhemp control, respectively. The same PRE herbicides, followed by glyphosate/dicamba (1800 g ae ha-1) POST, improved control to greater than 96%. This study concludes that a two-pass program of an effective soil applied residual herbicide followed by glyphosate/dicamba POST controlled GR waterhemp in glyphosate/dicamba-resistant soybean.
文摘Palmer amaranth, sicklepod and pitted morningglory are the three most common and troublesome weeds in soybean in South Carolina. They exhibit very aggressive growth capabilities and if left uncontrolled in fields will cause significant reductions in soybean yields. Dicamba and 2,4-D herbicides are currently having a resurgence in usage due to the recent commercialization of soybean trait technologies with tolerance to these herbicides. Dicamba and 2,4-D when tank mixed with glufosinate and glyphosate may offer additional weed control to resistant weeds through the process of herbicide synergism. Greenhouse experiments were conducted in 2013 at Edisto Research and Education Center near Blackville, SC to evaluate the efficacy of glyphosate, glufosinate, dicamba and 2,4-D treatments alone and in combination on Palmer amaranth, sicklepod, and pitted morningglory at selected heights. Results suggested that glufosinate alone provided the overall best control for all 3 weed species. Glyphosate alone provided the lowest control of all 3 species at all heights. Synergism or improved sicklepod control was observed when glufosinate was tank mixed with dicamba. However, as sicklepod increased in height, glufosinate + 2,4-D or dicamba combination offered the best control compared to glufosinate alone (90% versus 86% in 20 cm plants and 87% versus 85% in 30 cm plant). In the 5 cm Palmer amaranth, decreased control was observed when glyphosate or glufosinate was tank mixed with 2,4-D. These experiments showed that glufosinate alone and/or in combination with 2,4-D or dicamba was the overall best treatment on the three broadleaf weed species.
文摘Palmer amaranth and pitted morningglory are difficult to manage weeds present in South Carolina soybean production fields. Glyphosate and ALS-resistant Palmer amaranth biotypes have spread rapidly throughout South Carolina making the control of these weeds more difficult. Recently, soybean varieties with tolerance to dicamba have been introduced along with several new ultra-low volatility formulations of dicamba to help with the problem. Field experiments were conducted near Blackville, SC in 2012 and 2013 to evaluate dicamba herbicide programs for broadleaf weed management in dicamba tolerant soybean. At 2 weeks after POST1 (2 WAP1), Palmer amaranth control ranged from 93% to 100% across the PRE followed by POST treatments in 2012 and 2013. By 2 weeks after POST2 (2 WAP2), control was 95% or better. Treatments containing two or three herbicide applications (PRE, POST1 and POST2) offered good to excellent (92% - 100%) pitted morningglory control. No differences in weed control were observed among treatments with 3 application times compared to those applied twice. In general, all treatments with a PRE followed by at least one POST application provided good to excellent control of Palmer amaranth and pitted morningglory. Overall, a PRE (either dicamba or flumioxazin) followed by a dicamba or a non-dicamba containing POST treatment provided good to excellent control of Palmer amaranth and pitted morningglory when applied at the correct growth stage.
文摘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 </span><span style="font-family:Verdana;">resistant soybean plants. While dicamba had no significant effects on the ac</span><span style="font-family:Verdana;">tivities 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.
文摘Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize （Zea mays L.） genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent ofgenotype when young immature embryos, 12 days after pollination （DAP） were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction ofembryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines.
