clay and pretilachlor

Finding a method, which may indicate the contribution of soil parameters including organic matter, pH and clay to pretilachlor leaching (persistence) in the soil, with the use of a suitable indicator, which indicates pretilachlor presence in the soil is of significance. Accordingly, using undisturbed soil columns, four paddy fields (A, B, C, D) in the suburbs of Babol city (Mazandaran province, northern Iran) were sampled before the preparation and irrigation of the fields in April 2021. Soil samples were transferred into PVC pipes (divided into 2 cm layers) measuring 12 (height) × 10 cm (diameter), and were injected with pretilachlor at the recommended (1.75 L/ha) and high doses (3.5 L/ha). The surface layers of all fields had a higher concentration of pretilachlor and organic matter with the highest contribution to pretilachlor persistence followed by clay and pH. In the 0-4 cm depth, herbicide concertation was the lowest in field A (139 mg/kg) and the highest in field C (161 mg/kg). The corresponding values for organic matter were equal to 1.88 and 5.68%, respectively. The bioassay of rice (the indicator plant), with a significant correlation with chemical analysis results, indicated field A and field C had the pretilachlor infiltration of 6 and 4 cm, respectively. Accordingly, rice is a suitable plant indicator for measuring the presence of pretilachlor as examining its shoot length is a good criterion for bioassay. Additionally, changes in the amount of organic matter in different soil layers can be used to predict the leaching level of pretilachlor.

Topics: Acetanilides; Clay; Herbicides; Oryza; Plants; Soil

Effect of the wheat straw ash (WSA) on pretilachlor and the rice straw ash (RSA) on sulfosulfuron kinetics and adsorption behavior was studied. Kinetics study suggested that adsorption of herbicides in soil/soil + 0.2% ash mixture was best explained by the pseudo second order model. Ashes at 0.1%-0.5% levels increased adsorption of respective herbicide; but, effect varied with ash content and soil type. Effect of ash (0.2%) on herbicide's adsorption was more in the sandy loam soil (144%-188%) than in the clay loam soil (112%-122%) suggesting masking of ash particles. The Freundlich adsorption isotherm explained the adsorption of herbicides in the soils/soil + ash mixtures and sorption was highly nonlinear as 1/n (slope) values varied between 0.57 and 1.25 for pretilachlor and 0.32 and 0.77 for sulfosulfuron. Adsorption increased with increase in temperature. High surface area unburnt carbon in ashes was responsible for increase in adsorption and decrease in desorption of herbicides in ash mixed soils. The pH of soil/soil + ash mixtures affected herbicide adsorption, but effect was significant for pretilachlor. The negative free energy change (ΔG) values suggested that the sorption process was exothermic and spontaneous in nature. This study has implications in identifying the role of crop residue burning on fate of herbicides applied in succeeding crop.

Topics: Acetanilides; Adsorption; Carbon; Clay; Crops, Agricultural; Herbicides; India; Kinetics; Oryza; Pyrimidines; Soil; Soil Pollutants; Sulfonamides; Triticum

Understanding and quantifying the adsorption-desorption behaviour of herbicide in soil is imperative for predicting their fate and transport in the environment. In the present study, the effect of time and temperature on the adsorption-desorption behaviour of pretilachlor in soils was investigated using batch equilibration technique. The adsorption-desorption kinetics of pretilachlor in soils was two step process and was well described by pseudo-second-order kinetic model. Freundlich model accurately predicted the sorption behaviour of pretilachlor. The adsorption-desorption of pretilachlor varied significantly with the concentration, temperature and properties of soil viz. organic matter and clay content. All the studied soils had non-linear slopes (n < 1) and degree of nonlinearity increased with increase in clay, organic matter content and temperature (p < 0.05). Desorption of pretilachlor was hysteretic in studied soils and hysteresis coefficient varied from 0.023 to 0.275. Thermodynamic analysis showed that pretilachlor adsorption onto soils was a feasible, spontaneous and endothermic process which becomes more favourable at high temperature. It could be inferred that the adsorption of pretilachlor on soils was physical in nature.

Topics: Acetanilides; Adsorption; Clay; Herbicides; Humic Substances; Kinetics; Plants; Soil; Soil Pollutants; Temperature; Thermodynamics