Phosphorus enrichment of the soils in a watershed

Abstract

By analysing total phosphorus along 15 soils cross-section in 5 parcels of an experimental water basin in Brittany, we obtained two verifications. The first one confirms, that total phosphorus retention in surface increase more than at 60 centimeters deeper. Buffering capacity in the 20 first centimeters of cultivated soil move from 1000 up to 2500 mg of total phosphorus per kg of soil: we observed that phosphorus adsorption can't easily reach 60 deep. A small part of it, especially polyphosphates correlated with aluminium and iron oxides, is supposed to move down. However we measured small quantities of phosphorus at 40 and 60 cm, that shows leaching exists, but in low contribution. The second and most important point is about the runoff. Different notes show us that the parcel slope has an effect on phosphorus accumulation in water during rainfalls. Particles of soil, move across the slope on short intervals. We observed these resettlements for 9 cross-sections nearby the Coët-Dan stream.