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Fate and Transport of Nursery-Box-Applied Tricyclazole and Imidacloprid in Paddy Fields
2009
Phong, Thai Khanh | Nhung, Dang Thi Tuyet | Motobayashi, Takashi | Thuyet, Dang Quoc | Watanabe, Hirozumi
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.
Show more [+] Less [-]Modeling the temporal distribution of water, ammonium-N, and nitrate-N in the root zone of wheat using HYDRUS-2D under conservation agriculture
2020
Shafeeq, Poo Madhathil | Aggarwal, Pramila | Krishnan, Prameela | Rai, Vikas | Pramanik, Pragati | Das, Tapas Kumar
In the current study, the temporal distribution of both soil water and soil NO₃–N under several conservation agriculture (CA) practices during the wheat crop growth were characterized by HYDRUS-2D model. Treatments comprised of conventional tillage (CT), permanent broad beds (PBB), zero tillage (ZT), PBB with residue (PBB+R) and ZT with residue (ZT+R). Hydraulic inputs of the model, comprising the measured value of Kfₛ, α and n, obtained as the output of Rosetta Lite model were optimized through inverse modeling. Model predicted the daily change in soil water content (SWC) of the profile during the simulated period (62–91 DAS) with good accuracy (R² = 0.75; root mean squared error (RMSE) = 0.038). In general, soil water balance simulated from the model showed 50% lower cumulative drainage, 50% higher cumulative transpiration along with higher soil water retention, in PBB+R than CT. Reported values of the first-order rate constants, signify nitrification of urea to NH₄–N (μₐ) (day⁻¹) nitrification of NH₄–N to NO₃–N (μₙ) (day⁻¹) and the distribution coefficient of urea (Kd−in cm³ mg⁻¹) were optimized through inverse modeling. Later they were used as solute transport reaction input parameters of the model, to predict the daily change in NO₃–N of the profile with better accuracy (R² = 0.83; RMSE = 4.62). Since NH₄–N disappears fast, it could not be measured frequently. Therefore, not enough data could be generated for their use in the calibration and validation of the model. Results of simulation of daily NO₃–N concentration indicated a higher concentration of NO₃–N in the surface layer and its leaching losses beyond the root zone were relatively lesser in PBB+R, than CT, which resulted in less contamination of the belowground water. Thus, the study clearly recommended PBB+R to be adopted for wheat cultivation in maize–wheat cropping system, as it enhances the water and nitrogen availability in the root zone and reduce their losses beyond the root zone.
Show more [+] Less [-]A new method of rainfall-runoff modelling and its applications in catchment hydrology
1994
Littlewood, I.G. | Jakeman, A.J. (Institute of Hydrology, Wallingford, OX10 3BB (United Kingdom))
Comparison of soil thermal regimes in a deforested area with various grass cover in the Beskids Mts. [Czech Republic]
1998
Tuma, I. (Akademie Ved, Brno (Czech Republic). Ustav Ekologie Krajiny)
The studies of grass communities, which spread in deforested areas, also involved observations of soil thermal regimes. Three sites were chosen in order to determine differences in diurnal and seasonal variations of soil temperatures: (1) open site (barren) without plant cover, (2) site covered by a young, lower and thinner stand of Avenella flexuosa, and (3) old, dense stand of Calamagrostis villosa with a layer of plant litter on the soil surface. Soil temperatures were measured at the soil surface and in the soil depth of 5 and 10 cm. In summer months, the greatest differences in maximal temperatures recorded at the soil surface and at the 5, 10 cm depth between the bare site and the old stand of C. villosa represented 21.6, 15.9, 12.4 deg C, respectively. Soil temperatures measured in the bare plot in autumn months were lower than those in grass stands.
Show more [+] Less [-]Water balance and precipitation quality in spruce ecosystem
1995
Tuzinsky, L. (Lesnicky Vyskumny Ustav, Zvolen (Slovakia))