Behavior of nursery-box-applied imidacloprid in micro paddy lysimeter

A micro paddy lysimeter (MPL) was employed to monitor the behavior of nursery-box-applied imidacloprid granules in the rice paddy environment using two treatment methods, i.e. before transplanting (BT) and at sowing (AS). Tested application rates were three-fold the recommended rate. Under a water management scenario in an actual field, the behavior of nursery-box-applied imidacloprid granules in paddy water and paddy soil in MPL was comparable with field monitoring data in the literature. Imidacloprid concentration in water peaked at 189±36 μg/L and 13.1±1.4 μg/L at 1 day after transplanting (DAT), and the halflives (DT) were 2.5 days, and 4.7 days for BT and AS treatments, respectively. In the soil profile, the maximum concentration of imidacloprid at 21 DAT was 65.6±0.4 μg/kg and 39.7±4.9 μg/kg in the 0-2.5 cm layer in the inter-row zone for BT and AS treatments, respectively. Imidacloprid was found in the 12.5-15.0 cm layer at 3.2±0.7 μg/kg for BT treatment and 13.7±3.8 μg/kg for AS treatment, in the inter-row zone. In AS treatment, imidacloprid mainly stayed in the root zone (0-5 cm surface soil layer), and its concentration was 895±4 μg/kg at 21 DAT. MPL presented as a convenient and alternative tool to monitor the behavior of nursery-box-applied pesticide in the rice paddy environment

Simulating the dissipation of two herbicides using micro paddy lysimeters

A set of packed micro paddy lysimeters, placed in a greenhouse, was used to simulate the dissipation of two herbicides, simetryn and thiobencarb, in a controlled environment. Data from a field monitoring study in 2003, including the soil condition and water balances, were used in the simulation. The herbicides were applied and monitored over a period of 21 d. The water balances under two water management scenarios, intermittent irrigation management (AI) and continuous irrigation management (CI), were simulated. In the AI scenario, the pattern of herbicide dissipation in the surface water of the field were simulated, following the first-order kinetics. In the CI scenario, similarity was observed in most lysimeter and field concentrations, but there were differences in some data points. Dissipation curves of both herbicides in the surface water of the two simulated scenarios were not significantly different (P > 0.05) from the field data except for intercept of the thiobencarb curve in the CI scenario. The distribution of simetryn and thiobencarb in the soil profile after simulation were also similar to the field data. The highest concentrations of both herbicides were found on the topsoil layer at 0-2.5 cm depth. Only a small amount of herbicides moved down to the deeper soil layers. Micro paddy lysimeters are thus a good alternative for the dissipation study of pesticides in the paddy environment

Nanobubble Water’s Promotion Effect of Barley (Hordeum vulgare L.) Sprouts Supported by RNA-Seq Analysis

The physiological promotion effect of nanobubble (NB) water on living organisms is still a poorly understood phenomenon which was discovered 1 decade ago. Here, we analyzed the barley (Hordeum vulgare L.) embryo transcriptome following the exposure to NB water and low-concentration hydrogen peroxide (H₂O₂) using RNA-Seq. We found that 349 genes were differentially expressed after 24 h exposure to NB water and 97 genes were differentially expressed after exposure to H₂O₂ solution. Gene ontology enrichment and cluster analyses revealed that NB water induced expression of genes related to cell division and cell wall loosening. RNA-Seq, quantitative real-time polymerase chain reaction, and enzyme activity measurements all pointed to gene-encoding peroxidases as a major factor responsible for the effects of physiological enhancement due to NB water. The exogenous hydroxyl radical (•OH) produced by NB water significantly increased the expression of genes related to peroxidase and NADPH, thus leading to an increased endogenous superoxide anion (O₂^•–) inside the barley seed. Appropriately, low concentrations of exogenously added reactive oxygen species (ROS) and endogenous ROS played important roles in plant growth and development. When ROS levels were low, the endogenous ROS was eliminated by ascorbate peroxidase and other peroxidases instead of activating the catalase and superoxidase dismutase. This data set will serve as the foundation for a system biology approach to understand physiological promotion effects of NB water on living organisms

Predicting rice pesticide fate and transport following foliage application by an updated PCPF-1 model

The Pesticide Concentration in Paddy Field (PCPF-1) model has been successfully used to predict the fate and transport of granular pesticides applied to the paddy fields. However, it is not applicable for pesticides in foliar formulation while previous studies have reported that foliar application may increase the risks of rice pesticide contamination to the aquatic environment due to pesticide wash-off from rice foliage. In this study, we developed and added a foliar application module into the PCPF-1 model to improve its versatility regarding pesticide application methods. In addition, some processes of the original model such as photodegradation were simplified. The updated model was then validated with data from previous studies. Critical parameters of the model were calibrated using the Sequential Uncertainty Fitting version 2 (SUFI-2) algorithm. The calibrated model simulated pesticide dissipation trend and concentrations with moderate accuracy in the two paddy compartments including rice foliage and paddy water. The accuracy of the predicted soil concentrations could not be evaluated since no observed data were available. Although the p-factor and r-factor obtained using the SUFI2 algorithm indicated that the uncertainty encompassed in the predicted concentrations was rather high, the daily predicted pesticide concentrations in rice foliage and paddy water were satisfactory based on the NSE values (0.36–0.89). The updated PCPF-1 model is a flexible tool for the environmental risk assessment of pesticide losses and the evaluation of agricultural management practices for mitigating pesticide pollution associated with rice production

Insecticide Washoff from Concrete Surfaces: Characterization and Prediction

Pesticide runoff from impervious surfaces is a significant cause of aquatic contamination and ecologic toxicity in urban waterways. Effective mitigation requires better understanding and prediction of off-site transport processes. Presented here is a comprehensive study on pesticide washoff from concrete surfaces, including washoff tests, experimental data analysis, model development, and application. Controlled rainfall experiments were conducted to characterize washoff loads of commercially formulated insecticides with eight different active ingredients. On the basis of the analysis of experimental results, a semimechanistic model was developed to predict pesticide buildup and washoff processes on concrete surfaces. Three pesticide product specific parameters and their time dependences were introduced with empirical functions to simulate the persistence, transferability, and exponential characteristics of the pesticide washoff mechanism. The parameters were incorporated using first-order kinetics and Fick’s second law to describe pesticide buildup and washoff processes, respectively. The model was applied to data from 21 data sets collected during 38 rainfall events, with parameters calibrated to pesticide products and environmental conditions. The model satisfactorily captured pesticide mass loads and their temporal variations for pesticides with a wide range of chemical properties (log <i>K</i>_OW = 0.6–6.9) under both single and repeated (1–7 times) rainfall events after varying set times (1.5 h∼238 days after application). Results of this study suggested that, in addition to commonly reported physicochemical properties for the active ingredient of a pesticide product, additional parameters determined from washoff experiments are required for risk assessments of pesticide applications on urban impervious surfaces

Fate and Transport of Nursery-Box-Applied Tricyclazole and Imidacloprid in Paddy Fields

The fate and transport of tricyclazole and imidacloprid in paddy plots after nursery-box application was monitored. Water and surface soil samples were collected over a period of 35 days. Rates of dissipation from paddy waters and soils were also measured. Dissipation of the two pesticides from paddy water can be described by first-order kinetics. In the soil, only the dissipation of imidacloprid fitted to the simple first-order kinetics, whereas tricyclazole concentrations fluctuated until the end of the monitoring period. Mean half-life (DT50) values for tricyclazole were 11.8 and 305 days, respectively, in paddy water and surface soil. The corresponding values of imidacloprid were 2.0 and 12.5 days, respectively, in water and in surface soil. Less than 0.9% of tricyclazole and 0.1% of imidacloprid were lost through runoff during the monitoring period even under 6.3 cm of rainfall. The pesticide formulation seemed to affect the environmental fate of these pesticides when these results were compared to those of other studies