Abstract Herbicide mineralization in the soil is affected by several factors, including the herbicide application history of the soil, soil moisture, and whether the herbicide is co-applied with another herbicide. The objective of this work was to evaluate S-metolachlor mineralization in the soil as affected by soil moisture content, history of herbicide application, and association with glyphosate. 14C-S-metolachlor mineralization increased with increasing soil moisture content. The average cumulative mineralization of S-metolachlor at 63 days of incubation was 0.03, 0.80, and 1.80% in air-dried, field capacity, and saturated soil, respectively. The mineralization rate of S-metolachlor was greater under saturated conditions and affected by the association with glyphosate. Greater mineralization of S-metolachlor occurred in cornfield soil with a history of S-metolachlor application. The average cumulative mineralization was 0.24% in cornfield and 0.89% in non-cultivated area. We can conclude that the higher the soil moisture content the higher S-metolachlor mineralization and that the mixture of this herbicide with glyphosate increased its degradation compared to the application of the herbicide alone. While there is evidence suggesting enhanced degradation of S-metolachlor in soil previously subjected to corn cultivation and S-metolachlor application, drawing a definitive conclusion is challenging due to the influence of sorption observed in our dataset.

Abstract Background: Clearfield® (CL) rice is one of the most successful tools for selective weedy rice control, using imidazolinone herbicides (IMI). However, IMI have residual soil activity and may carryover to non-tolerant crops growing in succession. It is necessary to find options to reduce IMI persistence in paddy rice fields. Objective: Evaluate the effect of water management on IMI dissipation in rice paddy and its carryover to soybean and non-CL rice. Methods: The herbicide mixture of imazapyr and imazapic totalizing 147 g a.i. ha−1 and 49 g a.i. ha−1, respectively, was applied half in preemergence (S3 stage – rice spike stage) and the other half in postemergence (V3-V4 rice stage). After herbicide application, a total of 21 samples were taken for analysis of residues. Soil samples were air dried and herbicides residues were analyzed using high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Results: Calculated field dissipation half-life (DT½) of imazapyr was 182.5 and 42.0 days in continuous flooding and intermittent water management, respectively. Imazapic had a DT½ of 96.3 days on intermittent water management. No adjustment for the dissipation regression parameters was obtained for imazapic in continuous water management. No reduction in yield components was observed in soybean when grown in soil with imidazolinone residues. On the other hand, non-CL rice showed decreased shoot dry weight and stem number. Conclusion: Imidazolinone herbicides have a longer half-life under continuous rice water management than intermittent. Therefore, growers can use intermittent irrigation in ares prone to IMI carryover and can use soybean in rotation.

Abstract RNA interference (RNAi) is a next-generation technology for weed management. Weeds would be sprayed with small RNAs (sRNAs) capable of inducing gene silencing (referred to as spray-induced gene silencing, SIGS) without involving the use of transgenes, reaching traditional targets in chemical control, targets that are not today more sensitive to herbicides and even new targets. Here we present the main challenges and opportunities for using SIGS as a practical tool for weed management. The development of SIGS in weed science has been slower compared to other crop protection areas such as entomology and plant pathology due to the difficulty of obtaining stable molecules that easily enter the plant, without off-target risks to crops, and that in small amounts guarantee systemic silencing with effectiveness. To overcome the challenges, it is necessary to achieve the synthesis of sRNAs on a large scale, making the field application practical and economical, develop formulations that protect sRNAs inside and outside the plant, and substantially increase the genomic and transcriptomic information available for weeds. Once these barriers have been overcome, SIGS technology could be similarly used in the field as herbicides are used today, spraying directly on the crop and selectively controlling weeds. This will provide a new tool for weed management, herbicide resistance management, and potentially exploration of new plant enzyme targets never before achieved by chemical control.

Abstract Background Eragrostis plana is the main invasive plant in the Pampa Biome of southern Brazil. This plant is highly competitive, tolerant to abiotic stresses, and very difficult to manage. Plants exposed to abiotic stresses and herbicides develop mechanisms that help alleviate or reduce damage caused by stressors and transmit this ability to the progenies. Objective The study’s objectives were to ascertain whether acclimatization to stress due to drought and sub-lethal doses of glyphosate may decrease plant sensitivity to glyphosate and investigate the possible memory mechanisms involved in this process. Methods A population of E. plana was submitted to drought, glyphosate, or a combination of drought plus glyphosate for two generations. The progenies were analyzed for sensitivity to the herbicide glyphosate and for biochemical, metabolites, and molecular responses. Results When testing sensitivity to glyphosate in the G 2 generations, the DRYxGLY (plants stressed with drought plus glyphosate) was the least sensitive (ED50 443.0 g a.e. ha-1), while CHK (without stresses) was the most sensitive (ED50 278.0 g a.e. ha-1). Evaluating the effects of glyphosate, the CHK population showed a greater accumulation of oxidative damage and shikimic acid. While DRYxGLY had greater antioxidant activity and higher expressions of the EPSPS and ABC-carrier MRP10 genes. Conclusions Recurrent selection with drought stress and sub-lethal rate of glyphosate (DRYxGLY) showed reduced sensitivity to glyphosate in the second generation ( G 2 ). The conjunction of factors, including the upregulation of EPSPS and the ABC MRP10 transporter, antioxidant enzymes seem to decrease the sensitivity of the DRYxGLY population to glyphosate.

Abstract Mixing herbicides is a common practice in agriculture, to optimize farm management practices, widen the weed control spectrum, enhance application efficiency, and manage herbicide resistance. Interactions between herbicides can occur within the spray tank, on the leaf surface, and/or inside the plant, resulting in physicochemical and physiological interactions. Additive, synergistic, or antagonistic effects can result from these interactions. Given the range in plant response and the potential for negative and positive outcomes for weed management, predicting herbicide interactions before using mixtures would be of great value. Therefore, the physiological responses in the literature can help to ensure efficient weed control and avoid unwanted effects in the field. This review compiles information on physiological and physicochemical interactions between herbicides, addressing the most known cases of synergism, antagonism, and additivity, as well as their physiological bases, and the methods for evaluating herbicide interactions. Reference models for herbicide interactions have been reported and they usually interfere interpretation of the mixture effect. Antagonistic interactions can increase the evolution of weed resistance by favoring the survival of individuals exposed to the herbicide. Physicochemical incompatibility in the spray tank usually causes herbicide antagonism, whereas both synergism and antagonism can result from increased or decreased uptake/translocation and from physiological changes in the plant. agriculture practices spectrum efficiency surface andor Additive synergistic value Therefore field additivity bases effect uptaketranslocation uptake translocation

Abstract Background: Weedy rice (Oryza sativa L.) is the main weed of rice crop. The high genetic variability of weedy rice contributes to the high phenotypic diversity between biotypes and different responses to environmental stress. Objective: The present study aimed to evaluate the response of imidazolinone-susceptible and -resistant weedy rice populations to increased atmospheric [CO2]. Methods: The experiment was arranged in a complete randomized design with six replications. The treatments included two [CO2] concentration (700 and 400 μmol mol-1) and three treatments: resistant genotype (IMI-resistant) treated with imazethapyr; resistant genotype without imazethapyr, and a susceptible genotype without imazethapyr. Results: The IMI-resistant and -susceptible weedy rice responded similarly to [CO2] enrichment. Enhanced [CO2] increased competitive ability of the weedy rice populations tested, by means of increased plant height. Weedy rice seed production also increased with enhanced [CO2] by means of increased photosynthesis rate and reduced transpiration (increased water use efficiency). Increased seed production also means increased weed persistence as it increases the soil seedbank size. The application of imazethapyr on IMI-resistant weedy rice did not alter its response to [CO2]; conversely, increased [CO2] did not change the resistance level of weedy rice to imazethapyr. High [CO2] increased spikelet sterility, but this beneficial effect was negated by the overall increase in production of filled grains. Conclusions: Enhanced [CO2] concentrations increases weedy rice growth, photosynthesis rates, seed production and spikelet sterility; the imidazolinone application does not affect the response of weedy rice to enhanced [CO2] affects weedy rice response to imidazolinone herbicide.

Abstract: Computer simulation was used to determine the potential of the Riohacha tourist district (Colombia), in the implementation of solar cooling by adsorption under local climatic conditions (ambient temperatures and global irradiation). The thermodynamics of the cycle are defined in the framework of the first law, using total heats, having as output parameter, the coefficient of performance (COP), the cooling effect and the minimum irradiation to produce ice. In the implementation, the algorithm took into account the Dubinin-Astakhove equation together with the parameters of the adsorption pair, which governs the adsorption in microporous solids and included the methanol saturation line. In the results, sensitivity graphs were obtained where the cycle behavior is reflected with respect to the maximum temperature, the average ambient temperatures, the COP, the minimum irradiation and the local irradiation during different typical days of the year. The results suggested the months of the year with the best potential to produce ice according to the maximum temperature of the cycle

Resumen: La simulación computacional se usó para determinar el potencial que tiene el distrito turístico de Riohacha (Colombia) en la implementación de la refrigeración solar por adsorción a las condiciones climáticas locales (temperaturas ambientes e irradiación global). La termodinámica del ciclo es definida en el marco de la primera ley, usando calores totales, teniendo como parámetros de salida el coeficiente de funcionamiento (COP), el efecto de enfriamiento y la irradiación mínima para producir hielo. En la implementación, el algoritmo tuvo en cuenta la ecuación de Dubinin-Astakhove junto con los parámetros propios de la pareja de adsorción, la cual rige la adsorción en sólidos microporosos y se incluyó la línea de saturación del metanol. En los resultados, se obtuvieron gráficos de sensibilidad donde se reflejan el comportamiento del ciclo con respecto a la temperatura máxima, las temperaturas promedio ambiente, el COP, la irradiación mínima y la irradiación local durante diferentes días típicos del año. Los resultados sugirieron los meses del año con mejores potenciales para producir hielo según la temperatura máxima del ciclo.

Num ecossistema agrícola, a redução do banco de sementes é um dos aspectos mais importantes no manejo de plantas daninhas; e em solos de várzeas, o arroz vermelho (Oryza sativa L.) é atualmente considerado a principal planta daninha. Nesse sentido, conduziu-se um experimento com o objetivo de avaliar a evolução do banco de sementes de arroz vermelho no solo em diferentes sistemas de semeadura de arroz irrigado e em alternativas de manejo do solo de várzea. O experimento foi instalado em campo por dois anos consecutivos na mesma área (safras agrícolas 1996/97 e 1997/98) em Santa Maria, RS, em solo classificado como Planossolo, com infestação média de 516 sementes viáveis de arroz vermelho/m². A estimativa do banco de sementes de arroz vermelho foi realizada através de 10 coletas de solo, utilizando um cilindro com 0,10m de diâmetro a 0,10m de profundidade. Após a coleta, os grãos foram separados do solo e realizado teste de tetrazólio para determinar a quantidade de sementes viáveis na amostra. As coletas foram realizadas antes da instalação do experimento (set/1996), após a colheita do primeiro ano (mai/1997) e após a colheita do segundo ano (mai/1998). Os resultados mostraram que o cultivo do arroz no sistema convencional promove aumento no banco de sementes de arroz vermelho, enquanto que a semeadura de arroz em solo inundado (mix de pré-germinado, prégerminado ou transplante de mudas) é tão eficiente na redução do banco de sementes de arroz vermelho quanto a rotação com o sorgo, o pousio do solo sem a presença de animais e também o preparo de verão.

In an agricultural ecosystem, the redution of weed seed bank is of utmost importance. In lowland areas, red rice (Oryza sativa) is the most important weed. Therefore, an experiment was conducted to evaluate the evolution of the red rice seed bank under different seeding systems and alternatives of soil management. The experiment was conducted during two years (1996/97 and 1997/98 growing seasons) in Santa Maria, RS in Albaqualf soil with an average infestation of 556 viable seeds per square meter. The assessement of the seed bank was conducted by ten samplings using a cylinder with 10cm of diameter and 10cm depth. After each sampling the seeds were separated and the number of viable seeds was determinated by tetrazolium test. The sampling were carried out before establishing the experiment (September 1996) after the first harvest (May 1997) and after the second harvest (May 1998). The results showed that the traditional rice cropping method increases the red rice seed bank, whereas the systems in which the rice is seeded in flooded soil (no tillage water seeded, water seeded and transplanted seedlings) are as efficient in reducing the red rice seed bank as the system that applies crop rotation with sorghum or fallow without the presence of grazing animals or soil tillage during summer.