Nutritional Augmentation of Jeffrey Pine Saplings on a Harsh Sierran Site

Broadcast fertilization with an array of amendments was examined for its capacity to reinvigorate growth and enhance nutrition of a 12-yr-old Jeffrey pine (Pinus jeffreyi Grev. & Balf.) plantation growing on an acidic Sierra Nevada surface mine site. Selected amendments consisted of Viking Brand 21-7-14, Free Flow 29-3-4, High N 22-4-6 + Minors, and Milorganite 6-2-0 + Iron—formulations that differed substantially in critical characteristics including N sources and the duration of release, and each was administered using three rates of application. All formulations stimulated sapling growth during some stage of the study, especially when applied at the highest rates, but the Free Flow amendment, which features urea as the predominant N source, the High N formulation, which is a controlled release fertilizer, and Milorganite, an organic amendment based on municipal biosolids, sustained growth enhancement longer than the Viking amendment, which relies exclusively upon ammoniacal and nitrate N forms and lacks any provision for metering nutrient release. As indicated by foliar analysis, increased availability and uptake of N probably accounted for most of the added growth induced by fertilization, although improved P nutrition likely contributed as well. However, in addition to the N and P responses, fertilized saplings were frequently lower in Mn, B, and Al—all of which may be phytotoxic at elevated concentrations. Further support for the possible linkages between foliar concentrations noted above and sapling growth responses were provided by the concentrations of these elements in the mine soil, which was low in N and P but high in Mn, B, and Al. This study reports approaches to nutritional augmentation on degraded sites suitable for use during the sapling stage of tree development.