Potential leaching of nitrate and ammonium, following the application of fertilisers in a typical calcareous soil from Malta

Abstract

Water is the most important resource, which is why it is required by all organisms to survive. The Maltese islands lack rivers and lakes from where potable water can be pumped, so water is currently being extracted from the groundwater table. Due to over-extraction and bad agricultural practices, the groundwater in Malta is facing two escalating problems; nitrate contamination and high salinity. Some areas have already exceeded the EU nitrate limit, rendering ground water, unpotable and hence, increasing the dependency on reverse osmosis plants. The aim of this study is to observe and measure the potential leaching of nitrate and ammonium following the application of various fertilisers on a typical calcareous soil from Malta. Five fertilisers; (potassium nitrate, ammonium sulphate, ammonium nitrate, urea and dairy cattle manure) which are the most popular with Maltese farmers, were applied to a calcareous soil at the rate of 300 kg/ ha of nitrogen and the levels of nitrate, ammonium, salinity and pH were measured in the leachate. The potassium nitrate treatment has demonstrated to have the highest nitrate leaching potential (average of 1884.54 ppm and 3420.06 ppm), followed by ammonium sulphate. Manure had the highest ammonium leaching potential (1.24 ppm and 1.35 ppm respectively), followed by urea. This implies that farmers should opt for ammonium-nitrogen fertilisers amended perhaps with nitrification inhibitors, rather than nitrate-nitrogen fertilisers, since the leaching potential of ammonium is very low compared to that of nitrate.