Production of containerized boxwood with different substrates and fertilizer rates

In container nursery stock production, sustainability involves a reduction in the utilization of peat and appropriate nutrient and water management to allow good plant growth and reduce losses by leaching. In this experiment boxwood (Buxus sempervirens L.) was cultivated in 2.6 L plastic containers containing a peat-based substrate (sphagnum peat moss and pumice 4:1, v/v) or a compost-peat substrate (compost, sphagnum peat moss and pumice 2:2:1, v/v). Three rates (3, 5 and 7 g per L of substrate) of a controlled release fertilizer (Osmocote® pro 8-9 months, 18-9-10 + 2 MgO + micronutrients) were also tested. Plant growth and leachate nutrient concentration were assessed to evaluate plant response and potential nutrient losses. At the end of the growing season plants grown in the compost-peat substrate had higher height, growth index, fresh and dry weight of leaves, shoots and roots. Increasing the rate of fertilizer positively affected plant growth, the highest plant height, width, growth index, fresh and dry weights of all plant organs being obtained with the application of 7 g L-1. Concentrations of NO3-N, P and K in the leachate were, in general, higher in the very firsts leachate sampling. Concentrations of Ca and Mg varied little during the experiment. At the beginning of the experiment, leachate from peat-based substrate had higher NO3-N and Ca and lower K and Mg concentrations than those from compost-peat substrate. NO3-N and P concentrations in the leachates were highest when the top rate of fertilizer was applied.