Abstract

Three woody species Forsythia x intermedia ‘Lynwood’, Weigela ‘Bristol Ruby’, and Prunus laurocerasus ‘Otto Luyken’ were grown in 5 liter (# 1.3) containers with white peat and peat-reduced substrates. Plants were fertilized by a controlled-release or organic fertilizer. The aim was to investigate the relation between mineral N-content in the substrate and growth and N-uptake of the plants. Plant biomass was influenced by the mineral N-content in the substrate and by the substrate, but not by the type of fertilizer. Plant biomass of plants in the white peat substrate was significantly greater than plants grown in the peat-reduced substrates. Different equations describe the relation between mineral N in the substrate and biomass. Only for the white peat substrate in June and August was the slope of these regressions significant and the determination coefficient (r²) high. Dry matter of above ground biomass was 38% of fresh matter. The root-to-shoot ratio varied widely. There was a significant exponential relation between the biomass and the height of the plants, but not with the number of shoots. The N-content of the plant was related to its fresh matter. The findings establish a possibility to deduce N-uptake from plant biomass and thus improve fertilization.