Reduction of nitrogen leaching from nursery potting mixes by Chabazite

Due to coarse textured, fast-draining growing media with poor buffer capacity, nitrogen leaching after heavy rainfall is a major concern in container nurseries. The amendment of growing media with Chabazite – a natural zeolite with high ammonium (NH4+) exchange capacity – in combination with NH4+ fertilization might reduce nitrogen losses significantly. This was tested in a pot trial with Photinia fraseri. Growing media amended with Chabazite were compared with a pumice containing growing medium as control. Chabazite was used on the one hand untreated and on the other hand it was charged with ammonium sulfate ((NH4)2SO4) with loads of 1 and 5 g ammonium nitrogen (NH4-N) pot‑1. During the first part of the trial, pots with untreated Chabazite were repeatedly fertilized with NH4+ and leached after each fertilizer application. Pots with charged Chabazite were also leached on the same dates. In the second part, pots with untreated Chabazite received an excessive NH4+ supply and were leached several times afterwards. In both parts of the trial, NH4+ was adsorbed by Chabazite after fertilization. Higher amounts of NH4+ were leached from growing media with pumice than from those with untreated Chabazite. In leachates from growing media with NH4+-charged Chabazite, higher amounts of nitrate (NO3-) were only found in the case of charging with 5 g N pot‑1. Whereas after excessive NH4+ fertilization leaching of NH4+ remained low in presence of Chabazite, summing up to 5% of the applied N, in the control leached NH4+ was 28% of fertilized NH4+. Thus, it can be concluded that fertilized NH4+ was adsorbed to Chabazite and thus protected from direct leaching as well as from nitrification and subsequent leaching as NO3-. This protection decreased with increasing NH4+ charging of Chabazite. Hence, the combination of Chabazite with repeated NH4+ fertilization is a promising approach to reduce nitrogen leaching from container nurseries.

Beiträge zu wissenschaftlicher Konferenz/Tagung
Reduction of nitrogen leaching from nursery potting mixes by Chabazite
Acta Hort.
Dr. Annette Bucher , Dr. Dieter Lohr , Prof. Dr. Elke Meinken
Bucher, Annette; Lohr, Dieter; Meinken, Elke (2021): Reduction of nitrogen leaching from nursery potting mixes by Chabazite. Acta Hort. 1327, S. 161-166. DOI: 10.17660/ActaHortic.2021.1327.21