Crop Response to Ferrous Sulfate in Banded Gels of Hydrophilic Polymers

Abstract

AbstractIron deficiences are widespread and difficult to correct by soil application. Banded hydrogels containing FeSO4 have the potential to act as a matrix for minimizing contact of the applied Fe with soil. Three greenhouse pot experiments were conducted to determine response of grain sorghum [Sorghum bicolor (L.) Moench] to FeSO4 banded alone or with hydrated commercial gel‐forming polymers in Epping silt loam (loamy, mixed (calcareous), mesic, shallow Ustic Torriorthent), a calcareous, Fe‐deficient soil. Sorghum dry‐matter production and Fe uptake after 6‐wk growth periods were highest with FeEDDHA and lowest with FeSO4, each banded alone. Plant availability of applied FeSO4 was increased by banding FeSO4 in some hydrated polymers (mainly polyacrylamides). Apparently, the banded gels provided an environment that maintained the included FeSO4 in a more available form, which resulted in greater crop response to the applied Fe. Results of a laboratory experiment indicated that band application of FeSO4 in hydrated polymers did not affect the rate of oxidation of the applied Fe2+ to Fe3+. However, total extractable Fe (by 0.05 M HCl + 0.0125 M H2SO4 or by 1 M HCl) was higher in soil near banded hydrated FeSO4 with polymer formulations than FeSO4 banded alone. This suggests that the applied FeSO4 had reacted with soil to a much greater extent when it was banded alone rather than with the hydrated polymers.