Reduction of nutrient run-off by the use of coated slow-release fertilizers on two container-grown nursery crops

The agricultural district of Pistoia (Tuscany, Italy) is one of the most important sites in Europe for the production of Hardy Ornamental Nursery Stock (HONS). One of the main problems of this sector is the environmental impact of the pot cultivation, mainly due to an incorrect irrigation scheduling that leads to high nitrogen and phosphorus losses. The aim of this research has been to compare the effects of the traditional fertigation versus new fertilization strategies, based on the use of controlled slow-release fertilizers (CRFs), on plant growth and on nitrogen and phosphorus run-off in two container HONS species (Photinia × fraseri and Prunus laurocerasus). Every week, plant height, cumulate irrigation and drainage volume were measured on four replicates for each treatment and species. Every four weeks two average samples of drainage water and irrigation water for each treatment and species were analysed, determining total nitrogen and phosphorus content, in order to draft a water and nutrient balance. The three different fertilization strategies did not produce any relevant effect on the final plant height and all plants were ranked in the top quality market category. The data confirmed that the use of CRFs could contribute to a huge reduction of nitrogen and phosphorus run-off in the environment and could be a winning strategy for the fertilization of HONS in nitrate vulnerable zones.