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

Abstract

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 eld, the behavior of nursery-box-applied imidacloprid granules in paddy water and paddy soil in MPL was comparable with eld 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 a er transplanting (DAT), and the halflives (DT 50 ) were 2.5 days, and 4.7 days for BT and AS treatments, respectively. In the soil pro le, 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.

Behavior of Butachlor and Pyrazosulfuron-ethyl in Paddy Water Using Micro Paddy Lysimeters under Different Temperature Conditions in Spring and Summer

“…The average butachlor concentrations were 356.9 ± 33.8 and 211.1 ± 18.6 lg/L for S1 and S2, respectively. The herbicide concentrations during 0 DAHA in this study were not monitored however the herbicide concentrations in paddy water between 0 and 1 DAHA were reported to vary greatly (Nhung et al 2009;Thuyet et al 2012). The variation became small after 1 DAHA.…”

“…The pH values were in agreement with previous studies. The daily average pH in MPL was about 8.3 (Nhung et al 2009) and the measured pH fluctuated between 7.7 and 10.7 with the average pH of 9.8 ± 0.8 (Thuyet et al 2012).…”

“…A MPL was installed according to the procedure described in previous studies (Thuyet et al 2010(Thuyet et al , 2012. Briefly, triplicate stainless steel MPL chambers of 50 9 35 9 30 cm (length 9 width 9 height), were filled with 3 soil layers: a glass bead layer (1 cm), a hardpan layer (2 cm), and a plow layer (14 cm) from bottom to top, respectively.…”

“…In Japan, outdoor lysimeters were used to develop mitigation techniques controlling the runoff of pesticides from paddy fields (Watanabe et al 2008). A micro paddy lysimeter (MPL) has proven to be a useful tool to investigate the fate and transport of pesticides in the rice paddy environment (Nhung et al 2009;Thuyet et al 2010Thuyet et al , 2012. Precise control of hydrological conditions in the MPL experiment enables a simplification of environmental scenarios while studying pesticide behavior in actual paddy fields (Nhung et al 2009;Thuyet et al 2010Thuyet et al , 2012.…”

“…Precise control of hydrological conditions in the MPL experiment enables a simplification of environmental scenarios while studying pesticide behavior in actual paddy fields (Nhung et al 2009;Thuyet et al 2010Thuyet et al , 2012. In addition, MPL experiments are economical and are not labor intensive (Thuyet et al 2012). Consequently, the aims of this study were to evaluate the environmental behavior of two herbicides, butachlor and pyrazosulfuron-ethyl, using a MPL with prescribed hydrological conditions under ambient temperatures in spring and summer for simulating two rice crop seasons, and to clarify the effects of temperature variation on the behavior of these herbicides during the different seasons.…”