Russet Burbank potato response to struvite and single superphosphate fertilisation in soils of contrasting phosphate retention capacities.

Phosphorus (P) is essential for potato (Solanum tuberosum) growth, supporting root development, canopy expansion, and tuber formation. However, conventional P fertilisers such as single superphosphate (SSP) are often highly water-soluble, making SSP prone to soil fixation and leaching, reducing fertiliser use efficiency and contributing to environmental concerns. Struvite (MgNH₄PO₄·H₂O) is a slow-release P fertiliser that may provide a more sustained supply of P during crop growth, although struvite’s low initial solubility raises questions about its effectiveness during early crop development.

This study compared the response of Russet Burbank potato (Solanum tuberosum cv. ‘Russet Burbank’) to struvite and SSP fertiliser regimes in soils with contrasting P-retention capacities under glasshouse conditions. Five fertiliser treatments were applied: no-P fertiliser (negative control), and struvite and SSP at 100 and 200 kg P/ha. These fertiliser treatments were incorporated into potting mixes made of a low P-retention Pallic soil (ASC = 12%) and a moderate P-retention Brown soil (ASC = 22%).

Plant emergence, canopy development, plant height, disease, and deficiency scores were measured over an 86 day growth period. Post-harvest measurements included root and shoot dry weight, total and fine root length, tuber initiation, tuber fresh weight and harvest index. Fertiliser treatment influenced most growth parameters, whilst soil type had minimal influence. Struvite treatments had an accelerated emergence rate relative to the negative control, while SSP treatments did not differ from the negative control. Regardless of soil P-retention, struvite treatments also produced a larger mean leaf area and shoot biomass than SSP at equivalent rates, with the highest struvite treatment producing up to 77% more leaf area than the negative control, while SSP did not significantly differ from the negative control.

Root development was enhanced under struvite fertilisation, particularly in the low P-retention soil, where the highest struvite application rate produced the largest mean root biomass and length. Tuber initiation was also highest under struvite fertilisation, with up to 67% more tubers per plant than SSP treatments. However, tuber fresh weight was not affected by fertiliser treatment, likely due to the shortened growth period limiting full tuber bulking.

Overall, struvite effectively supplied P to support early potato growth and generally outperformed or matched SSP for measured canopy and root development parameters. These results highlight the potential of struvite as a slow-release P fertiliser alternative, although further full-season research and field trials are required to determine its impact on final tuber yield.