Low Carryover Risk of Corn and Soybean Herbicides Across Soil Management Practices and Environments

Herbicides with soil-residual activity have the potential for carryover into subsequent crops, resulting in injury to sensitive crops and limiting productivity if severe. The increased use of soil residual herbicides in the United States for management of troublesome weeds in corn and soybean cropping systems has potential to result in more cases of carryover. Soil management practices have different effects on the soil environment, potentially influencing herbicide degradation and likelihood of carryover. Field experiments were conducted at three sites in 2019 and 2020 to determine the effects of corn (clopyralid and mesotrione) and soybean (fomesafen and imazethapyr) herbicides applied in the fall at reduced rates (25% and 50% of labeled rates) and three soil management practices (tillage, no-tillage, and a fall established cereal rye cover crop) on subsequent growth and productivity of the cereal rye cover crop and the soybean and corn crops, respectively. Most response variables (cereal rye biomass and crop canopy cover at cover crop termination in the spring, early season crop stand, and herbicide injury ratings, and crop yield) were not affected by herbicide carryover. Corn yield was lower when soil was managed with a cereal rye cover crop compared to tillage at all three sites while yield was lower for no-till compared to tillage at two sites. Soybean yield was lower when managed with a cereal rye cover crop compared to tillage and no-till at one site. Findings from this research indicate a low carryover risk for these herbicides across site-years when label rotational restrictions are followed and environmental conditions favorable for herbicide degradation exist, regardless of soil management practice on silt loam or silty clay loam soil types in the Midwest U.S. region.

Investigating the Performance of UV/PS/Tio2nps and UV/PI/Tio2nps Processes on Paraquat Herbicide Degradation in Aqueous Media: Statistical Optimization, Kinetic Study, and Estimation of Electrical Energy Consumption

Background: In this work, the performance of UV/PS/TiO2NPs and UV/PI/TiO2NPs as hybrid advanced oxidation processes for degradation of the herbicide paraquat in aqueous solution is studied.Results: The effects of several factors such as the UV irradiation, initial oxidant concentration, TiO2 nanoparticles dosage, and pH on the degradation efficiency are investigated. The process optimization is performed by the central composite design and the response surface methodology for 30 mg L-1 of the herbicide at 25 ˚C and 40 min. Based on the results, a degradation efficiency of 77 % and 90 % have been obtained for the UV/PS/TiO2NPs and UV/PI/TiO2NPs processes respectively, in the optimum conditions. The mineralization efficiency of the paraquat solution using UV/PS/TiO2NPs and UV/PI/TiO2NPs processes are about 32 % and 55%, respectively, after 40 min. The kinetic studies show that both processes follow a pseudo-first-order kinetic model, and the kinetic constants are 0.0299 min-1 for the PS process and 0.0604 min-1 for the PI process. The electrical energy consumption has been estimated to be about 481.60 kWh/m3 for the PS process and 238.41 kWh/m3 for the PI process.Conclusions: The degradation and mineralization efficiency of the paraquat solution using UV/PI/TiO2NPs process are more than UV/PS/TiO2NPs process in the optimum conditions after 40 min.

Bioleaching of iron from laterite soil using an isolated Acidithiobacillus ferrooxidans strain and application of leached laterite iron as Fenton’s catalyst in selective herbicide degradation

A novel isolated strain Acidithiobacillus ferrooxidans BMSNITK17 has been investigated for its bioleaching potential from lateritic soil and the results are presented. System conditions like pH, feed mineral particle size, pulp density, temperature, rotor speed influences bioleaching potential of Acidithiobcillus ferrooxidans BMSNITK17 in leaching out iron from laterite soil. Effect of sulfate addition on bioleaching efficiency is studied. The bioleached laterite iron (BLFe’s) on evaluation for its catalytic role in Fenton’s oxidation for the degradation of ametryn and dicamba exhibits 94.24% of ametryn degradation and 92.45% of dicamba degradation efficiency. Fenton’s oxidation performed well with the acidic pH 3. The study confirms the role of Acidithiobacillus ferrooxidans in leaching iron from lateritic ore and the usage of bioleached lateritic iron as catalyst in the Fenton’s Oxidation.

Investigating the synergistic effect of UV/PS/TiO2 and UV/PI/TiO2 processes on paraquat herbicide degradation in media aqueous: statistical optimization, kinetic study, and estimation of electrical energy consumption

In this paper, the performance of UV/PS/TiO2 and UV/PI/TiO2 as hybrid AOPs for degradation of paraquat (PQ) herbicide in aqueous solution has been studied. The effect of several factors such as UV irradiation, initial oxidant concentration, nano-TiO2 (TiO2NPs) dosage, and pH on the degradation efficiency was investigated. Process optimization was performed by Central Composite Design (CCD) and response surface methodology (RSM) for 30 mgL− 1 of herbicide at 25 ˚C and 40 min. Based on the results, for UV/PS/TiO2 process a degradation efficiency of 83% was obtained in the optimum condition of initial PS concentration of 400 mgL− 1, initial TiO2NPs concentration of 150 mgL− 1, and pH = 6.3. Also for UV/PI/TiO2 process, 87% degradation efficiency was achieved in the optimum condition of initial PI concentration of 88 mgL− 1, initial TiO2NPs dosage of 125.5 mgL− 1, and pH of 7.5. Mineralization efficiency of the PQ solution by using PS and PI were about 47.5% and 57%, respectively after 80 min. Kinetic studies showed that both process follow pseudo-first-order kinetic model and their kinetic constants were 0.0299 min− 1 for PS process and 0.0604 min− 1 for PI process. Electrical energy consumption was estimated about 481.60 kWh/m3 for PS process and 238.41 kWh/m3 for PI process.

Degradation of atrazine and bromacil in two forestry waste products

The persistence and degradation of two common herbicides, atrazine and bromacil in two organic media, wood pulp and sawdust were compared with two soils. The hypothesis tested was that herbicide degradation will be faster in high organic matter media compared to soil. Degradation of two herbicides was carried out in four different temperature regimes and in sterilised media. The degradation half-life (t½) was determined under above-mentioned conditions then compared to degradation in soil. The degradation as quantified by t½ of the herbicides was generally longer in both organic media. Although microbial degradation was an important factor in the mineralisation of these herbicides, overall, the pH of the media had a more profound effect on the desorption and subsequent degradation rate than the organic carbon content. The results of this study revealed that the hypothesis was only partially correct as organic matter content per se did not strongly relate to degradation rates which were mainly governed by pH and microbial activity.

The Effective Role of Soil Indigenous Fungi on 2.4-D Herbicide Degradation

The normal field soil environment safeguarded, via indigenous microbes in a native manner, with the aim of turning herbicide waste into productive bio-resources, through fungi activities. This study aims to determine the effective role of soil indigenous fungi on 2,4-D herbicide degradation. The research was conducted over a period of six weeks, on Iraqi cereal field. A total of eight fungi species, belonging to six genera, (Aspergillus candidus L. ATCC 1002, A. niger T. ATCC 16888, Curvularia lunata W. B1933, Penicillium sp. L. 1809, Rhizopus stolonifer L. B9770, Stachybotrys atra C. 1837, Trichoderma harzianum R. IOC 3844, and T. lignorum T. Hartz 1872), were isolated from the soil. During the exposure periods, fungal populations were differently affected, upon treatments with herbicide. The applied herbicide treatments showed different effects on growth and development of the isolated fungi. The results showed that, five of the eight fungi species (C. lunata B1933, Penicillium sp. 1809, R. stolonifer B9770, T. harzianum IOC 3844, and T. lignorum Hartz 1872) were greatly enhanced by the treatment process. However, two fungi (S. atra 1837, and A. candidus ATCC 1002) were affected negatively by the herbicide, while one (A. niger ATCC 16888) remained unaffected. Once extracted from the soil of wheat fields in Iraq, the fungus S. atra 1837, was first isolated. The highest inhibitory effect was caused by 2,4-D herbicide, on the toxigenic fungus S. atra, causing its disappearance from the field at the last week of application. The laboratory experiments showed similar herbicide effects on the isolated fungi at low and moderate levels, while those at the high level (800 µg /ml) were toxic. These results showed that the herbicide 2,4-D treatments have substantial effects on microbial population in the field. When applied at recommended field rate, the herbicide causes transient impacts on fungal population growth and biodiversity, with the majority of the organism becoming responsible for 2,4-D mineralization in the soil. Therefore, the use of 2,4-D herbicide does not only control weed population, but it also affects microbial activities, especially indigenous fungi in the soil.