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Eutrophication assessments in water management to quantify nutrient loads and identify mitigating measures seldom include the contribution from horse facilities. This may be due to lack of appropriate methods, limited resources, or the belief that the impact from horses is insignificant. However, the recreational horse sector is growing, predominantly in multi-functional peri-urban landscapes. We applied an ecosystem management approach to quantify nutrient loads from horse facilities in the Stockholm Region, Sweden. We found that horses increased the total loads with 30–40% P and 20–45% N, with average area-specific loads of 1.2 kg P and 7.6 kg N ha−1 year−1. Identified local risk factors included manure management practices, trampling severity, soil condition and closeness to water. Comparisons of assessment methods showed that literature standard values of area-specific loads and water runoff may be sufficient at the catchment level, but in small and more complex catchments, measurements and local knowledge are needed. [ABSTRACT FROM AUTHOR]

Phosphorus (P) losses from clay soils can be mitigated by introducing measures for improving soil structure. These include structure liming, where a mixture of CaO or Ca(OH)2 and CaCO3 is added to the soil. In a field experiment with separately tile-drained plots on a clay loam in Sweden, we examined the effects of structure liming on leaching of total-P, phosphate P (PO4-P) and total nitrogen (N) during three years after initial application. The treatments included two application rates (8 and 16 t ha−1) of a common product in comparison with a control (no lime). Effects of structure liming emerged during the second and third year after application, with 45 and 38% lower total-P leaching than in the unlimed control. A significant effect of the application rate was found in the third year. Nitrogen leaching and crop yield were not affected. As expected, soil pH raised following structure lime addition. Measurements of aggregate stability did not confirm the reduction in P leaching, indicating that it is important to measure P concentrations in drainage water directly when assessing the effect of structure liming. [ABSTRACT FROM AUTHOR]

A field experiment with separately tile‐drained plots was used to study the ability of oilseed radish (Rhaphanus sativus L.), as a cover crop sown after harvest of a main crop of cereals or peas, to reduce nitrogen (N) and phosphorus (P) leaching losses from a clay loam in southern Sweden over 6 years. In addition to oilseed radish in pure stand, two cover crop mixtures (hairy vetch (Vicia villosa) and rye (Secale cereale) for 3 years and oilseed radish in mixture with buckwheat (Fagopyrum esculentum) for 2 years) were tested. The cover crop plots (three replicates per treatment) were compared with unplanted plots as a control. Plots cropped with oilseed radish during autumn (August–November) had significantly smaller yearly mean N concentration in drainage water over 5 of 6 years compared with unplanted controls. Mineral N content in the soil profile in autumn was significantly less in oilseed radish plots than for control plots in all years. The cover crop mixtures of hairy vetch and rye or buckwheat and oilseed radish also showed the potential to reduce soil mineral N in autumn and N concentration in drainage water, compared with unplanted controls. The cover crops had no impact on P leaching. In conclusion, oilseed radish has the ability to reduce leaching losses of N, without increasing the risk of P leaching. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) losses, via both surface runoff and subsurface drainage water, were monitored in an agricultural field in northern Sweden for 32 yr. The objective was to determine losses of N and P in a long-term perspective in relation to meteorological factors and impacts of agricultural land use, with a focus on relative contributions of surface runoff and subsurface drainage water to N and P losses. In order to collect surface runoff water, an embankment was installed on three sides of the field, and the fourth side had an open ditch that drove runoff water to a measuring station. Subsurface water draining from the field was collected in a fishbone-shaped drainage system that terminated at the measuring station. In 50% of years (16/32), mean annual concentration of total N (TN) was significantly higher in subsurface drainage water than in surface runoff water. An opposing trend was seen for total P (TP), with mean annual concentration being significantly higher in surface runoff water than in subsurface drainage water in all but 3 of the 32 yr monitored. Years with a barley crop had higher TN concentration in subsurface drainage water but no difference in surface runoff compared with years with ley. In contrast, years with barley had lower TN concentration in surface runoff than years with ley, with no difference in TP in subsurface drainage water., (© 2022 The Authors. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)