Soil application of ferrous-containing compounds to eliminate ferrous sulfate deficiency has been economically possible on a field scale.
Ferric sulphate and ferrous suflateare not effective as soil applications at economically feasible rates. Some products under development may be useful for soil application. Because the problem of ferrous deficiency is associated with high pH and excessive calcium carbonate in the soil, the possibility of lowering the soil pH to correct the problem has been suggested. The rate of sulphur necessary to accomplish this on calcareous soils is not economically feasible.
Ferrous deficiency can be controlled by several means other than soil application. On medium testing soils, selection of a crop or crop variety less sensitive to ferrous deficiency can be effective. Manure or sewage sludge at the rate of 15 to 20 tons per acre on a dry weight basis may be effective for several seasons.
Applying ferrous as a foliar spray is effective in restoring green color to plants, but may not restore top yields. Ferrous sprays are most effective when applied to young plants and when repeated at 10-day to two-week intervals. Ferrous sulphate monohydrate or ferrous chelates can be used as a spray. Ferrous deficiency is best corrected by spraying the crop with a 2 percent ferrous (ferrous) sulfate solution (1 percent for potatoes) at the rate of 15 to 30 gallons per acre beginning 10 to 15 days after crop emergence. Repeat application at 10-day intervals if yellowing of foliage persists.
Ferrous fertilization is recommended only for those field crops that are sensitive to low soil ferrous levels: corn, sorghum, sudan, sorghum-sudan hybrids, beans and potatoes. Since the root system can not absorb Fe element by soil treatment, spray the crop with ferrous sulfate solutions can correct this condition effectively.