INFLUENCE OF INCREASING AMOUNTS OF NITROGEN ON RHODODENDRON
In a field trial the influence of increasing amounts of nitrogen on growth and quality of Rhododendron catawbiense 'Grandiflorum' and on residual nitrate content of soil has been investigated. Optimal growth is attainable with a N fertilization of 100 kg/ha. There was no significant influence of nitrogen on the number of flower buds. With 100 kg N/ha the plants also showed acceptable leaf colour. Hence N demand of Rhododendron is lower than formerly assumed. N uptake was relatively low (50 kg N/ha at the beginning of optimum). N uptake by yield unit (between 50 and 60 kg N/10.000 kg fresh material) is comparable to other nursery crops and allows the estimation of N uptake by measuring yield. Therefore an existing computer program for fertilization of nursery crops is applicable, leading to ecologically and economically sound fertilization. Overfertilization results in very high residual nitrogen content of soil.
Alt, D., Hinrichs, H. and Kohstall, H. (1994). INFLUENCE OF INCREASING AMOUNTS OF NITROGEN ON RHODODENDRON. Acta Hortic. 364, 89-94