Fertilizer Rate and Number of Applications
Impact Growth of Trees in Field Soil
Edward F. Gilman and Michael D. Marshall
Abstract: Fertilizer recommendations for producing shade trees in nursery field soil in North America appear to be based on tradition and tree performance; there is little empirical data. This study was designed to examine efficacy of reducing traditional or historical fertilizer amount (rate) and number of applications for two taxa and to present a protocol for growers to test fertilizer use efficiency. A traditional rate of fertilizer was applied along with four others: zero, one-third, two-thirds, or one-and-one-third traditional. Fertilizer was divided into one, two, three (traditional), or four equal amounts applied during the growing season. The study was conducted on a fine sand field soil with 680 trees of each taxa in adjacent plots of the same field. There were 16 factorial treatment combinations plus a non-fertilized control. Fertilizer rate cut to one-third of the historical rate, and number of applications reduced from three to either one or two, resulted in little if any reduction in trunk diameter or height growth over the four-year period. These taxa appeared to grow almost regardless of nitrogen application strategy. Growers can partner with a research team to find an efficient fertilizer rate and number of applications that could cut production costs.
Keywords: Fertilizer; Nursery; Tree Height; Trunk Diameter.