Crop Response to Ferrous Sulfate in Banded Gels of Hydrophilic Polymers

Abstract

Abstract Iron deficiences are widespread and difficult to correct by soil application. Banded hydrogels containing FeSO 4 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 FeSO 4 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 FeSO 4 , each banded alone. Plant availability of applied FeSO 4 was increased by banding FeSO 4 in some hydrated polymers (mainly polyacrylamides). Apparently, the banded gels provided an environment that maintained the included FeSO 4 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 FeSO 4 in hydrated polymers did not affect the rate of oxidation of the applied Fe 2+ to Fe 3+ . However, total extractable Fe (by 0.05 M HCl + 0.0125 M H 2 SO 4 or by 1 M HCl) was higher in soil near banded hydrated FeSO 4 with polymer formulations than FeSO 4 banded alone. This suggests that the applied FeSO 4 had reacted with soil to a much greater extent when it was banded alone rather than with the hydrated polymers.