Growth of Scotch Pine Trees in Bluegrass Sod as Affected by Fertilizer Depth, Release Rate, and Season of Application

Abstract

Five-year-old Scotch pine (Pinus sylvestris L.) trees growing in bluegrass (Poa pratensis L.) sod were fertilized at two depths with liquid, granular, or compressed (Tree Stake) fertilizer. Trees were fertilized in the fall when dormant or in the spring when in active growth. Annual increase in trunk caliper was used to measure tree growth over two growing seasons. Increase in trunk caliper was least with liquid, greatest with compressed, and intermedidate with granular fertilizer. Granular and compressed fertilizer placed 15 cm (6 in) below the soil surface resulted in greater increase in trunk caliper than shallower placement. Liquid fertilizer placed shallow, which deposited some fertilizer at the soil surface, resulted in greater increase in trunk caliper than deeper placement. Spring fertilization resulted in greater increase in trunk caliper than fall fertilization, presumably because fertilizer nutrients were available during spring growth when the pines were able to absorb nutrients rapidly.