Utvärdering av fosforläckageefter stallgödsling med hjälp av lysimeterteknik : Evaluation of phosphorus leaching aftermanure application using lysimeter techniques

Based on laboratory studies with lysimeters, the concentrations of dissolved reactive phosphorus (DRP) and particulate phosphorus, which is the main part of other P (OVRP), has been studied in percolating water. The experiment was conducted through irrigation of small soil columns containing clay topsoil from an experimental field in Västergötland. Three rain simulations were consecutively performed. DRP concentrations in the percolating water ranged between 0.2 - 0.3 mg·L clearly related to the phosphorus concentration in the soil, measured in a soil extract of ammonium lactate (P-AL). Concentrations of OVRP were relatively low and ranged between 0.12 and 0.16 mg·L was not proven and the experiment may reflect how a relatively slow percolation of water may release DRP. In contrast, from observed fields with drainage systems quite high concentrations of OVRP are typically recorded. This is generally explained by fast flows through macropores in the soil and through the drain tile systems. Solid manure was applied to the lysimeters equal to a normal agricultural load (30 tons per ha), and thereafter another three rainfall were simulated. The load of manure increased the leaching of DRP approx. 7 times. The largest increase was observed from the soils with the highest P-ALnumbers. The relative boosts of DRP after manure application increased linearly relative to the PAL number of the soil and with a high correlation coefficient. Thus the results from the manure addition indicated that the soil with highest phosphorus concentrations released proportionally more phosphorus than soils with low P-AL numbers. The studies demonstrate the importance of adjusting the load of manure to the soil phosphorus content. Presently the spreading of manure is only restricted by the number of cattle/cultivated land, not to the P-AL number of the soil. -1. The amount of DRP percolating from four soils with different fertilization history was-1 in the percolating water passing through the topsoil. Any macropore flo