Table 3.

Treatment of chlorotic sweet gum in 1977.

TreatmentNumber of treesColor rating1Twig growth (inches) 1978
May 1977July 1977July 1978July 1979
Ferric citrate2116.38.78.37.49.0
Ferric ammonium citrate3106.18.18.07.18.6
Ferric ammonium citrate + NPK4106.78.38.07.87.8
Ferric ammonium citrate + N5106.38.17.96.77.1
NPK6106.68.38.17.36.4
NPK + slow-release N7   66.58.17.87.06.0
N (slow-release)7   95.77.16.86.65.5
Control116.47.67.76.65.2
  • Average tree size: 12.0 in dbh (range 5-33 in).

  • 1 Colorcode: 1-6, shades of yellow; 7-10, shades of green; 10, dark green.

  • 2 Purified powder form, 1¼ g/hole, holes 4 in (10 cm) apart.

  • Medicap Fe28, size 0, 3/8 in (1.1 cm), trees 4-11 in (10-28 cm) dbh; size 000, 0.5 in (1.27 cm) in larger trees.

  • 4 Medícap formulation of Fe + soluble NPK, size 000 in trees 4-11 in dbh and size 11/16 in (2.1 cm) in larger trees.

  • Medicap formulation of Fe28 and slow-release N, size 0 in trees 4-11 in dbh and size 000 in larger trees.

  • 5 Medicap formulation with soluble NPK alone, size 0 in trees 4-11 in dbh and size 000 in larger trees.

  • 7 Medicap formulation with slow-release N only, size 0 used in trees 4-11 in dbh and size 000 in larger trees.

  • 8 Medicap formulation of slow-release N, size 000 used in trees 4-11 in dbh and 11/16 in cartridge in larger trees.