Frederik Bøe

Research Scientist

(+47) 958 71 316
frederik.boe@nibio.no

Place
Ås O43

Visiting address
Oluf Thesens vei 43, 1433 Ås

To document See dataset

Abstract

Limited knowledge and experimental data exist on pesticide leaching through partially frozen soil. The objective of this study was to better understand the complex processes of freezing and thawing and the effects these processes have on water flow and pesticide transport through soil. To achieve this we conducted a soil column irrigation experiment to quantify the transport of a non-reactive tracer and the herbicide MCPA in partially frozen soil. In total 40 intact topsoil and subsoil columns from two agricultural fields with contrasting soil types (silt and loam) in South-East Norway were used in this experiment. MCPA and bromide were applied on top of all columns. Half the columns were then frozen at −3 °C while the other half of the columns were stored at +4 °C. Columns were then subjected to repeated irrigation events at a rate of 5 mm artificial rainwater for 5 h at each event. Each irrigation was followed by 14-day periods of freezing or refrigeration. Percolate was collected and analysed for MCPA and bromide. The results show that nearly 100% more MCPA leached from frozen than unfrozen topsoil columns of Hov silt and Kroer loam soils. Leaching patterns of bromide and MCPA were very similar in frozen columns with high concentrations and clear peaks early in the irrigation process, and with lower concentrations leaching at later stages. Hardly any MCPA leached from unfrozen topsoil columns (0.4–0.5% of applied amount) and concentrations were very low. Bromide showed a different flow pattern indicating a more uniform advective-dispersive transport process in the unfrozen columns with higher con- centrations leaching but without clear concentration peaks. This study documents that pesticides can be pre- ferentially transported through soil macropores at relatively high concentrations in partially frozen soil. These findings indicate, that monitoring programs should include sampling during snow melt or early spring in areas were soil frost is common as this period could imply exposure peaks in groundwater or surface water.

Abstract

Most studies on the effects of tillage operations documented the effects of tillage on losses through surface runoff. On flat areas, the subsurface runoff is the dominating pathway for water, soil and nutrients. This study presents results from a five-year plot study on a flat area measuring surface and subsurface runoff losses. The treatments compared were (A) autumn ploughing with oats, (B) autumn ploughing with winter wheat and (C) spring ploughing with spring barley (n = 3). The results showed that subsurface runoff was the main source for soil (67%), total phosphorus (76%), dissolved reactive phosphorus (75%) and total nitrogen (89%) losses. Through the subsurface pathway, the lowest soil losses occurred from the spring ploughed plots. Losses of total phosphorus through subsurface runoff were also lower from spring ploughing compared to autumn ploughing. Total nitrogen losses were higher from autumn ploughing compared to other treatments. Losses of total nitrogen were more influenced by autumn ploughing than by a nitrogen surplus in production. Single extreme weather events, like the summer drought in 2018 and high precipitation in October 2014 were crucial to the annual soil and nutrient losses. Considering extreme weather events in agricultural management is a necessary prerequisite for successful mitigation of soil and nutrient losses in the future.

To document See dataset

Abstract

Limited knowledge and experimental data exist on pesticide leaching through partially frozen soil. The objective of this study was to better understand the complex processes of freezing and thawing and the effects these processes have on water flow and pesticide transport through soil. To achieve this we conducted a soil column irrigation experiment to quantify the transport of a non-reactive tracer and the herbicide MCPA in partially frozen soil. In total 40 intact topsoil and subsoil columns from two agricultural fields with contrasting soil types (silt and loam) in South-East Norway were used in this experiment. MCPA and bromide were applied on top of all columns. Half the columns were then frozen at −3 °C while the other half of the columns were stored at +4 °C. Columns were then subjected to repeated irrigation events at a rate of 5 mm artificial rainwater for 5 h at each event. Each irrigation was followed by 14-day periods of freezing or refrigeration. Percolate was collected and analysed for MCPA and bromide. The results show that nearly 100% more MCPA leached from frozen than unfrozen topsoil columns of Hov silt and Kroer loam soils. Leaching patterns of bromide and MCPA were very similar in frozen columns with high concentrations and clear peaks early in the irrigation process, and with lower concentrations leaching at later stages. Hardly any MCPA leached from unfrozen topsoil columns (0.4–0.5% of applied amount) and concentrations were very low. Bromide showed a different flow pattern indicating a more uniform advective-dispersive transport process in the unfrozen columns with higher con- centrations leaching but without clear concentration peaks. This study documents that pesticides can be pre- ferentially transported through soil macropores at relatively high concentrations in partially frozen soil. These findings indicate, that monitoring programs should include sampling during snow melt or early spring in areas were soil frost is common as this period could imply exposure peaks in groundwater or surface water.