Abstract
Phosphorus (P) is an essential growth-limiting nutrient that cannot be synthetically produced. Mineral P fertilisers are typically applied to crops to sustain modern farming practice and food production. These fertilisers are generally derived from finite phosphate ore, for which there is much concern over long-term sustainability. To address these concerns, various technologies have been developed to recover P from municipal wastewater treatment plants. One product recovered from these processes is struvite, which is a precipitate formed of magnesium, ammonium, and phosphate. To analyse the fertilisation value of the recovered struvite, field trials were conducted on perennial ryegrass (Lolium perenne) over three growing seasons, analysing the dry matter yield of recovered struvite fertiliser. The trial was based on a three-crop silage system designed to mimic typical Irish agricultural practice. This research highlights that recovered struvite as a fertiliser provides additional benefits including increasing the soil P levels. The struvite test case produced a statistically significantly increased soil P level from the baseline of Morgan’s extractable P content of 6.4 mg/L to the optimum Morgan’s soil P level of 11.13 mg/L. The findings of this research provide insight into the added benefits of recovered struvite fertiliser as a sustainable renewable P fertiliser.
Highlights
The trial commenced on the 8 April 2018, with the C Comp test case producing the most significant average quantity of dry matter (DM) at 7050 ± 892 kg/ha
Field trials were conducted over three years mimicking typical Irish agricultural practice and climatic conditions, simulating fertiliser end-use, assessing the effectiveness of recovered struvite on long term field trials, and meeting the need highlighted by Degryse et al [15]
During each annual growing season, three individual grass crops were cut and measured to determine the DM yield and weekly grass DM measurements were taken throughout the season
Summary
Phosphorus (P) is a naturally occurring finite mineral, regarded as a vital building block used in the growth and reproduction of all living organisms. The industrialisation of agriculture over the past 70 years has significantly changed farming practice. This shift has led to the application of mineral P fertilisers to replace P removed by crop harvests [1]. The application of mineral fertilisers has become an integral part of modern agriculture and is vital to sustaining current farming practices and food production; in 2020, Irish agricultural used 44,393 tonnes of P fertiliser, an increase of 3% on the previous year [2,3,4].
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