Inagro evaluates the fertilization potential of P-saturated iron coated sand on maize

19 December 2019 - Published by Charlotte Boeckaert
Can iron coated sand (ICS) saturated with P be used as a fertilizer for maize? That was what Inagro tested in the past months.

Within NuReDrain, the capacity of ICS to absorb phosphorus is being tested. Once the ICS is saturated with P from agricultural water, the ICS must be removed and replaced with new ICS. Reuse of the saturated material as a fertilizer would be a great step ahead towards circularity and would contribute to conserve the earth's limited phosphorus resources.

Last April 2019 Inagro set up a pot trial with maize. Maize was chosen because this crop has a high phosphorus demand throughout the season, especially during its early growth stage. The following questions had to be tackled:

  • Does ICS saturated with P has a potential as P-fertiliser when sown in a soil low in phosphorus concentration?
  • Can the addition of P-solubilizing bacteria (PSB), in combination with P-saturated ICS, deliver a positive effect towards dry matter yield of the crop?


Installation of the pot trial (10/04/2019)


The pot trial was designed in open air. The starting point was a soil low in P concentration. Each treatment received an equal start dose of nitrogen and potassium. P was applied via different products:

  • Control without treatment
  • APP (ammonium polyphosphate) as reference
  • TSP (triple superphosphate) as reference
  • ICS with PSB1
  • ICS with PSB2

Half June, an interim harvest was done to analyse the nutrient content during the youth growth stage. Total nitrogen, potassium and phosphorus were analysed on the plants. The measured P content was significantly highest in the object treated with APP while plots that received ICS contained significantly the lowest level of P in comparison with all  other plots.


At the end of July a final harvest was done. The results showed that the treatments with ICS, in combination with or without PSBs, did not result in an adequate P-fertilization. The overall conclusion is that the ICS treatments showed the lowest P-content, smallest plants and lowest relative yield at harvest and this in comparison with treatments that received a phosphorus fertilization with APP or TSP.



Emergence of the maize plants (03/07/2019)