Tall cabbage (Brassica oleracea, var. costata, cv. Penca de Mirandela) is very popular in Portugal. It forms part of the traditional Christmas Eve dinner every year. The nurseries are prepared in the middle of summer and the young plants transplanted late in August. The highest growth rates of this vegetable as well as the highest demands for nitrogen (N) occur in October and early November, a typical rainy period where there is a high risk of nitrate leaching. Therefore, the use of slow release N fertilisers may be a viable option as a sound N fertilization strategy for this production system. The objectives of the research were to examine the effect on crop yield of three materials that delay N availability to plants and also to monitor when N becomes available lo the crop. Results of a pot experiment are presented where tail cabbage was grown in the autumn as a main crop and Italian ryegrass (Lolium multiflorum L.) was sown in spring in-order to evaluate the residual effect of fertilisers.
