Adding nanoparticles to soil could improve its water retention and nutrient-release qualities, according to Pakistan researchers
Synthetic fertilisers have never been more popular. Since the 1960s, the world’s use of nitrogen-based fertilisers has increased nine-fold, while the use of compounds based on phosphorus has tripled. In many cases, fertilisers like these are hugely beneficial for food production, but their uncontrolled use can degrade land quality, and with 40-75% lost due to leaching, fertilisers can cause wider environmental issues. But in a recent Microporous and Mesoporous Materials paper [DOI: 10.1016/j.micromeso.2016.06.020], researchers from five Pakistan universities have shown that zeolite nanocomposites loaded with nutrients could be used as a sustainable slow-release fertiliser, in all soil conditions.
Most agricultural plants need a total of 16 nutrients in order to thrive, 13 of which are extracted from the soil through its roots. And zeolites – the name given to minerals that consist of hydrated aluminosilicates – have long been known to improve the soil’s ability to retain these nutrients in the soil. Recently, this has led to a growing interest in their use in fertilisers, but this team has shown that thanks to their high surface area, nano-zeolites show particular promise. To assess their performance in real-world conditions, the researchers synthesised two samples – porous zeolite nanoparticles, on average 6.05 nm in diameter, and zeolite nano-composites (ZNC), which were made by impregnating the nanoparticles with macro (N, P, K, Ca, Mg, S) and micro-nutrients (Fe, Zn, Cu). Both samples were added to sieved soil to be characterised.
In terms of ion exchange, which defines the efficacy of the retention and release of agricultural nutrients, the ZNC was shown to exchange both cations and anions simultaneously. In addition, the composite was found to be stable at high temperatures, and to retain a low electrical conductivity – both important considerations in terms of crop health. And the ZNC could hold more than half of its weight in water, which means it can help retain moisture in soils.
Most importantly, these researchers found that their composite nanoparticles released nutrients over a much longer period of time than conventional fertilisers. It means that ZNCs could act as a continuous source of both macro and micro-nutrients throughout the crop’s growth, while improving the soil’s water retention and reducing leaching events.
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A. Lateef, R. Nazir, N. Jamil, S. Alam, R. Shah, M. N. Khan, M. Saleem, “Synthesis and characterization of zeolite based nano-composite: An environment friendly slow release fertilizer”, Microporous and Mesoporous Materials 232 (2016) 174-183. DOI: 10.1016/j.micromeso.2016.06.020