Abstract
Background and aimRecycled sources of phosphorus (P), such as struvite extracted from wastewater, have potential to substitute for more soluble manufactured fertilisers and help reduce the long-term threat to food security from dwindling finite reserves of phosphate rock (PR). This study aimed to determine whether struvite could be a component of a sustainable P fertiliser management strategy for arable crops.MethodsA combination of laboratory experiments, pot trials and mathematical modelling of the root system examined the P release properties of commercial fertiliser-grade struvite and patterns of P uptake from a low-P sandy soil by two different crop types, in comparison to more soluble inorganic P fertilisers (di-ammonium phosphate (DAP) and triple super phosphate (TSP)).ResultsStruvite had greatly enhanced solubility in the presence of organic acid anions; buckwheat, which exudes a high level of organic acids, was more effective at mobilising struvite P than the low level exuder, spring wheat. Struvite granules placed with the seed did not provide the same rate of P supply as placed DAP granules for early growth of spring wheat, but gave equivalent rates of P uptake, yield and apparent fertiliser recovery at harvest, even though only 26 % of struvite granules completely dissolved. Fertiliser mixes containing struvite and DAP applied to spring wheat have potential to provide both optimal early and late season P uptake and improve overall P use efficiency.ConclusionsWe conclude that the potential resource savings and potential efficiency benefits of utilising a recycled slow release fertiliser like struvite offers a more sustainable alternative to only using conventional, high solubility, PR-based fertilisers.Electronic supplementary materialThe online version of this article (doi:10.1007/s11104-015-2747-3) contains supplementary material, which is available to authorized users.
Highlights
Phosphorus (P) is a plant nutrient essential for cellular function and plant growth
We conclude that the potential resource savings and potential efficiency benefits of utilising a recycled slow release fertiliser like struvite offers a more sustainable alternative to only using conventional, high solubility, phosphate rock (PR)-based fertilisers
Some caution is required in relating the results of pot experiments to field conditions, these results suggest that struvite granules do act as a slow release fertiliser compared to more soluble fertilisers, and that this slow rate of P release from struvite granules may be closer to the development of the crop root system’s capacity to take up P and may result in greater P-use efficiency (Sutton et al 1983; Massey et al 2009)
Summary
P is often applied in the form of processed phosphate salt granules that dissolve into soil pore water and increase plant P uptake. Controlled struvite precipitation can be triggered in specialised reactors by manipulation of the sludge digestion process to overcome these problems (Baur 2009) This can produce struvite granules that are useable as a magnesium ammonium phosphate fertiliser product for agriculture, whilst reducing plant effluent P concentrations discharged to watercourses (Baur 2009; Schauer et al 2011). Recycled sources of phosphorus (P), such as struvite extracted from wastewater, have potential to substitute for more soluble manufactured fertilisers and help reduce the long-term threat to food security from dwindling finite reserves of phosphate rock (PR). Peter J Talboys and James Heppell are joint first authors.
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