Nitrogen accumulation and use by a young loblolly pine plantation in Southeast Oklahoma: effects of fertilizer formulation and date of application.

摘要

Practices that enhance crop tree nitrogen (N) accumulation and use improve the efficiency of fertilizer applications. This study was established to explore the N accumulation and use by a young loblolly pine (Pinus taeda) plantation in response to: (1) season of fertilizer application, (2) herbaceous vegetation suppression; and (3) fertilizer formulation. Water soluble and slow release urea formulations were applied to single-tree plots in January/February, April, June, August, and October of 2001 and 2002. The plantation is located in southern McCurtain County, Oklahoma, USA. Herbaceous vegetation was suppressed where appropriate with glyphosate. Foliage N accumulation was measured 1 and 2 months after fertilizer application and N use efficiency was measured 1 year after fertilizer application. Between 0.3 and 8.0% of applied N was recovered by the foliage within 1 month of application and 7-26% of applied N was used for stem growth within 1 year of application. In both years of this study, summer and autumn applications recorded the highest N accumulation and use. Herbaceous vegetation suppression in a 3-year-old plantation (with average tree height of 6 feet in January 2001) enhanced N accumulation and use. N accumulation and use of slow release urea was similar to or lower than that of water soluble urea in both years of the study..