In the evaluation of the risk of pesticide leaching to groundwater, the soil surface is usually assumed to be level, although important crops like potato are grown on ridges. A fraction of the water from rainfall and sprinkler irrigation may flow along the soil surface from the ridges to the furrows, thus bringing about an extra load of water and pesticide on the furrow soil. A survey of the literature reveals that surface-runoff from ridges to furrows is a well-known phenomenon but that hardly any data are available on the quantities of water and pesticide involved. On the basis of a field experiment with additional sprinkler irrigation, computer simulations were carried out with the Pesticide Emission Assessment at Regional and Local scales model for separate ridge and furrow systems in a humic sandy potato field. Breakthrough curves of bromide ion (as a tracer for water flow) and carbofuran (as example pesticide) were calculated for 1-m depth in the field. Bromide ion leached comparatively fast from the furrow system, while leaching from the ridge system was slower showing a maximum concentration of about half of that for the furrow system. Carbofuran breakthrough from the furrow system began about a month after application and increased steadily to substantial concentrations. Because the transport time of carbofuran in the ridge soil was much longer, no breakthrough occurred in the growing season. The maximum concentration of carbofuran leaching from the ridge-furrow field was computed to be a factor of six times as high as that computed for the corresponding level field. The study shows that the risk of leaching of pesticides via the furrow soil can be substantially higher than that via the corresponding level field soil.

Cyanobacterial blooms pose a risk to wild and domestic animals as well as humans due to the toxins they may produce. Humans may be subjected to cyanobacterial toxins through many routes, e.g., by consuming contaminated drinking water, fish, and crop plants or through recreational activities. In earlier studies, cyanobacterial cells have been shown to accumulate on leafy plants after spray irrigation with cyanobacteria-containing water, and microcystin (MC) has been detected in the plant root system after irrigation with MC-containing water. This paper reports a series of experiments where lysis of cyanobacteria in abstracted lake water was induced by the use of hydrogen peroxide and the fate of released MCs was followed. The hydrogen peroxide–treated water was then used for spray irrigation of cultivated spinach and possible toxin accumulation in the plants was monitored. The water abstracted from Lake Köyliönjärvi, SW Finland, contained fairly low concentrations of intracellular MC prior to the hydrogen peroxide treatment (0.04 μg L⁻¹ in July to 2.4 μg L⁻¹ in September 2014). Hydrogen peroxide at sufficient doses was able to lyse cyanobacteria efficiently but released MCs were still present even after the application of the highest hydrogen peroxide dose of 20 mg L⁻¹. No traces of MC were detected in the spinach leaves. The viability of moving phytoplankton and zooplankton was also monitored after the application of hydrogen peroxide. Hydrogen peroxide at 10 mg L⁻¹ or higher had a detrimental effect on the moving phytoplankton and zooplankton.

Leaching of nitrogen (N) and phosphorus (P) from agricultural lands can cause serious environmental problems such as eutrophication. The objective of this study was to investigate the impacts of biochar application, tillage practices, and irrigation systems on nitrate and dissolved phosphorus (DP) concentrations in subsurface drainage water and grain yield of winter wheat using a strip-split plot design with 3 replications. Irrigation at three different levels (flood (Ifₗ), furrow (Ifᵤ), and sprinkler (Iₛ) systems) considered as main factor, tillage at two levels (reduced tillage (Tᵣ) and conventional systems (Tc)) as subplot factor, and bagasse biochar at two levels (without biochar (B₀) and 20 ton ha⁻¹ biochar (B₁)) as sub-subplot factor. Polyvinyl chloride (PVC) standpipes were used in each sub-subplot to collect leachate water at 100-cm depth. The results indicated that irrigation had significant effects on yield, collected water volume (CWV), nitrate, and DP concentrations (P < 0.01). Interaction of tillage and irrigation was significant for grain yield (P < 0.05). Biochar application only caused a significant decrease in nitrate concentration under sprinkler irrigation (P < 0.05), while no significant impact was observed under flood and furrow irrigation systems. Under sprinkler irrigation, the total nitrate collected in the PVC standpipes decreased by 37.51 and 34.29% compared with flood and furrow irrigations, respectively. Biochar application reduced the total nitrate collected by 16.84%, while difference among tillage treatments was negligible (4.51%). The total DP collected under sprinkler irrigation was lower in comparison with flood and furrow irrigations by 42.24 and 38.76%, respectively. Biochar application reduced the total DP collected by 10.84%, while reduced tillage increased the total DP collected by 8.90% compared with the conventional tillage.