Three or six ounces of colloidal phosphate were applied either in planting hole or on soil surface while planting loblolly pine in East Texas. Combination of phosphate in the planting hole with NK on soil surface increased diameter growth for four years and the height growth for 18 years after planting.
Bilan, M. Victor and Gillespie, Marcey A., "Long term response of loblolly pine to colloidal phosphate" (1985). Faculty Publications. 223.