Nitrogen and phosphorus leaching and uptake by container birch seedlings (Betula pendula Roth) grown in three different fertilizations

Leaching of nitrogen (N) and phosphorus (P) through container peatmedium and N and P uptake by seedlings were determined in commercial productionof birch grown with three different types of fertilization. Half of the amountof nutrients was premixed into the peat medium and the other half was appliedasliquid (=fertigated) in the treatment (PF) commonly used in Finland. In twoother treatments all nutrients, either totally (P-VN) or partly (P-N) inslow-release form, were premixed into the peat. Independently of the treatment,the largest proportion (60 to 80%) of total N leached during May and June.During two growing seasons, the amounts of N leached from PF treatments (9 to36kg ha^–1) were as large as the amounts of Nleachedfrom P-VN and P-N treatments (24 to 46 kg ha^–1).Due to fertigations between container trays, however, the total N load perhectare was greatest in the PF treatments. In the soil water 0.5meter beneaththe container area, the N concentration varied from 10 to 60 mgl^–1. The morphological and chemical properties of theseedlings did not differ greatly between treatments.