Abstract

Phosphorus (P) is an essential element in crop production, but P losses from agricultural soils are a major contributor to surface water eutrophication. This thesis examined the effects of chemical soil properties and soil structure, as governed by agricultural management practices, on P leaching from agricultural soils and how this leaching can be reduced. An initial investigation on the effect of plant-available P concentration in the soil (P-AL) on topsoil P leaching from five soils clearly showed that topsoil P leaching depends not only on P status, but also on other soil characteristics. In three of these soils, increased P leaching after manure application was further amplified by high P-AL, while manure application did not affect topsoil P leaching in the other two soils. In a study assessing different management practices on a clay soil and the possible effect on P losses via tile drains, great spatial variation in P leaching was observed in the field, even though P-AL and discharge volume were relatively uniform across the field. Incorporation of quicklime (CaO) significantly reduced P leaching losses, primarily of particulate P, which was the dominant P form in drainage water. The other management options evaluated (conventional ploughing/shallow tillage; no P application/balanced P application; broadcasting/band spreading of fertilizer P) had no significant effects on P leaching. However, some effects of these management strategies could have been overshadowed by the large spatial variation in the data. Stopping P application and removing soil P with harvested crops (phytomining) showed potential to reduce excessive P levels in soils. After 7-9 years of no P application to the four soils studied, topsoil P-AL was lowered but most soils still had excessive levels. Only one soil, a clay soil with the lowest P-AL value in the study, showed a significant downward trend in leaching of dissolved reactive P. New knowledge outcomes were that: (i) the relationship between P-AL and topsoil P leaching clearly differs between soils, especially after manure application; (ii) incorporation of quicklime is a promising option for reducing P leaching from clay soils; and (iii) high P-AL values and P leaching may be reduced after phytomining, but this mitigation strategy takes a very long time.

Keywords

phosphorus leaching; mitigation options; soil test P

Published in

Acta Universitatis Agriculturae Sueciae
2014, number: 2014:36
ISBN: 978-91-576-8020-4, eISBN: 978-91-576-8021-1
Publisher: Department of Soil and Environment, Swedish University of Agricultural Sciences

SLU Authors

• Svanbäck, Annika

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use
Agricultural Science
Soil Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/53794