Effectiveness of iron sludge and fulvic acid for prevention of iron chlorosis in soybean

Drinking water company Vitens produces iron sludge and fulvic acid as by-products of their drinking water production process. This study investigated the effectiveness of iron sludge as a source of iron for soybean. A pot experiment was performed with a soybean variety that is susceptible for Fe chlorosis, grown on a clay soil from Tricht (Netherlands) and a calcareous soil from Canaveralejo (Spain). In the Tricht soil, no symptoms of iron chlorosis were observed in any treatment. In the Canaveralejo soil, soybean suffered from iron chlorosis, and iron sludge, with or without fulvic acid, reduced symptoms of iron chlorosis and yield loss as compared to the control treatment. However, iron sludge was not as effective as Fe-HBED since this treatment gave an even higher yield and showed no symptoms of iron chlorosis during the course of the experiment.