Abstract
A three-year study was initiated to evaluate the effectiveness of fertilization at outplanting with two controlled release nutrient amendments, High N 22-4-6 + Minors and Gromax 21-6-2 + Minors, and minisite application of dolomitic lime in enhancing the establishment and nutrition of bareroot Jeffrey pine (Pinus jeffreyi Grev. & Balf.) seedlings on a strongly acidic Sierra Nevada surface mine site. Fertilization rates of 8 g and 16 g per seedling and a single liming rate of 32 g were examined. Controlled release fertilization produced a substantial seedling growth response, more so with the High N than the Gromax formulation and with the 16 g rather than the 8 g rate. In contrast, liming suppressed growth and induced excessive seedling mortality. Among numerous fertilization effects on nutrition over the course of the study, increases in foliar N, P, and K, reductions in several potentially phyto-toxic elements including Mn and Al, and elevation of Ca/Al, Mg/Al, K/Al, Mg/Mn, and K/Mn molar ratios were prominent and likely responsible in large part for the favorable responses to this treatment. Liming had relatively little influence on nutrition, and much of that was probably detrimental, as exemplified by the lower Mg/Al, Ca/Mn, Mg/Mn, Ca/Cu, and Mg/Cu ratios of seedlings with lime during the critical first season when the preponderance of the mortality occurred. Nevertheless, it is likely that, as applied here, this amendment impaired seedling water relations on a site already limited by moisture availability, and this was of primary importance in the overall unfavorable response. Viewed in total, this study readily demonstrated the benefits that controlled release fertilization can provide in the reforestation of surface mines and similar harsh sites in the Sierra Nevada, but also revealed that minisite lime application at the rate used here was counterproductive and therefore further experimentation is necessary before this practice is routinely employed.
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