Restriction of manure application on high phosphorus soils - Is current research supporting a restriction and what measures are in effect in different European countries?

University essay from Lunds universitet/Miljövetenskaplig utbildning

Abstract: The Swedish Water Authorities have proposed a measure to reduce phosphorus losses by restricting manure application on soils with high levels of plant available phosphorus. The aim of this thesis was to investigate if leaching of phosphorus will decrease if the measure is implemented, if the effect is restricted to soils with high phosphorus content and if other European countries have implemented similar measures. The measure was investigated by performing a meta-analysis on phosphorus leaching studies using lysimeters with undisturbed soil columns. Leaching was compared before and after application of manure. Data was split into subgroups in order to investigate which physical and chemical factors in soil and manure that affected phosphorus leaching. European legislation was investigated by contacting experts in the field from each country. When all data was included the meta-analysis showed an overall increase in phosphorus leaching and that high phosphorus soils were least affected when manure was applied. Subgroups for the factors application rate, preferential flow and lysimeter length had a significant influence on the results. When these subgroups were combined, the overall effect was unchanged, however, the difference between soil phosphorus levels disappeared. Among the investigated countries, Ireland is the only one restricting manure application on the basis of phosphorus concentration. Generally, manure application is restricted through the Nitrates Directive and by maximum application limits. The measure will have an effect on phosphorus leaching, but it is not optimized to target soils that are most susceptible to leaching when manured. In order to further decrease phosphorus leaching, factors identified in this thesis should be included in legislative measures. The measure will also result in a decrease in soil phosphorus, but consideration must be taken with regard to increasing CO2 emissions due to manure transports and the costs that follow for the farmers.

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