Gödsling runt poppelstubbar med stubbskott

In 2012 three experiments on fertilization of poplar stumps was established on former farmland in southern Sweden where trial no. 1 was located at lat. 58° 08’ N., long. 12° 40’ E. and trial nos. 2 and 3 at lat. 55° 29’ N., long. 13° 39’ E. The poplar stands were 20-year-old when they were harvested in 2011. The number stems per hectare was 1250, 707 and 707 with a mean diameter at breastheight (DBH) of 24.6±0.4, 25.1±0.3 and 25.1±0.3 respectively. The diameter at 0.1 m height above stump for the sprouts was 7.5 mm in trial no.1 and 11.1 and 13.2 mm respectively for trial nos. 2 and 3. Around the stumps with a radius of 5 m the ground was fertilized in autumn 2012 with 75 and 150 kg N per hectare. Totally 30 stumps were included in each trial: 10 as a control, 10 fertilized with 75 and 150 N ha-1 each. Next year in spring 5 stumps of the fertilized stumps with 75 and 150 kg ha-1 were fertilized again with 75 and 150 kg N ha-1. The trials have been revised 2012, 2013 and 2014. The number of sprouts stump-1 three years after treatment (2014) ranged between 9 and 17 for trial no. 1. For trial nos. 2 and 3 the number ranged between 9 and 14 and 12 and 15 respectively. Fertilized stumps produced taller sprouts with higher DBH than unfertilized. Mean diameter at breastheight (DBH) was 20.7 mm for trial no. 1 and 29.9 and 33.4 mm respectively for trial nos. 2 and 3. Sprouts in trial no. 1 were shorter than in the other two trials. In trial no. 1 sprouts with repeated fertilizing 150 kg N ha-1 were tallest, 415 cm, compared with unfertilized, 335 cm. In trial nos. 2 and 3 sprouts with repeated fertilizing (150 kg N ha-1) were tallest, 592 and 584 cm compared with 516 and 548 cm for unfertilized.