Fe-polyphosphate formulations were tested as a replacement for Fe-chelates in hydroponic nutrient solutions for growing cucumbers. The researchers found that polyphosphates can bind iron ions and deliver them to plant roots, but they work best at low pH levels and with higher iron concentrations. High pH levels and low iron supply can lead to lower plant growth and iron content in the tissue. Polyphosphates may help with iron delivery to plants in hydroponic systems, but more research is needed to see how well they work in real-world farming.