Abstract
We estimated the changes in the losses of particulate and dissolved phosphorus (P) after treating 93 ha of agriculturalfields with gypsum (4 t ha–1) in a 245 ha catchment in southern Finland. Runoff was monitored using onlinesensors and manual sampling during one high-flow period before and six periods after the gypsum amendment.Turbidity recorded by the sensors correlated with particulate P analysed in the laboratory, which enabledthe evaluation of changes in particulate P from the online data. Using a covariance model, gypsum amendmentwas estimated to have reduced the loss of particulate P by 64%. The loss of dissolved reactive P appeared to decreaseby one third, but was estimated with less precision. No such changes were found during the same periodin a nearby ‘reference’ catchment, where gypsum was not used. Gypsum did not affect soil test values for P, K, Mgor Ca, but it did increase the ionic strength and soil test SO4. In clayey catchments discharging into the sea, gypsummay provide an efficient means to reduce P losses from field cultivation. The duration of the gypsum effect andimpact of SO4 associated with gypsum amendment on the ecology of rivers and lakes has yet to be determined.
Highlights
Many water bodies in Finland will not achieve the good ecological state demanded by the EU’s Water FrameworkDirective (2000/60/EC) unless nutrient loading from agriculture is drastically reduced (Ministry of the Environment 2009)
Highrisk sites for dissolved P losses include fields with high soil test P levels, which have a long history of manure application or cultivation of heavily fertilised high-value crops (Uusitalo et al 2007)
The mean conductivity of the soil/water suspension increased by about 50% from the initial level of
Summary
Many water bodies in Finland will not achieve the good ecological state demanded by the EU’s Water FrameworkDirective (2000/60/EC) unless nutrient loading from agriculture is drastically reduced (Ministry of the Environment 2009). Agricultural water protection measures targeting particulate or dissolved P encompass a variety of actions ranging from soil conservation and balanced fertilisation to implementing buffer zones and constructing wetlands. On top of these measures, there are novel techniques that can potentially have an enhanced impact on P losses from high-risk sites (Turtola et al 2010). These include the use of soil amendment such as natural materials, industrial (side) products and waste products Gypsum has been used as a soil amendment for a long time (Shainberg et al 1989), but its use in controlling P losses is relatively new
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