Soil chemistry in a Pinus sylvestris stand after repeated treatment with two types of ammonium nitrate fertilizer

Soil chemistry was studied in a field experiment in a 50‐year old Pinus sylvestris stand. Plots had been fertilized five times during a 20‐year period with a total of 810 kg N ha‐1 in the form of ammonium nitrate, either with or without dolomite enrichment (totally 120 kg Ca and 60 kg Mg ha‐1). The experiment had a randomized block design, including a total of six replicates. Soil sampling was performed in 1989, 14 months after the latest fertilizer addition. Samples were taken from the mor layer, the eluvial layer, and the three. top 3‐cm layers of the spodic horizon. Both fertilizers increased concentrations and amounts of C and N in the mor layer. They also resulted in a small increase of the pH in this layer (0.2–0.3 units). In the uppermost 3 cm of the spodic horizon, a very minor decrease was detected ( ≤ 0.1 unit). Despite the pH increase in the mor layer, the amount of titrable acidity tended to increase in this layer (30% over control for both fertilizers; not significant). For the whole analysed profile, the amount of titrable acidity was indicated to be increased by 5% for both fertilizers (not significant). The treatment with dolomite enrichment almost doubled the amount of exchangeable Ca and Mg in the two uppermost horizons. Both fertilizers reduced the amount of plant‐available P and K in the same horizons. The decrease under the control was 33% for P and 20% for K.