Sulphur Fertilization Of Lodgepole Pine

Widespread sulphur (S) deficiencies have been detected in lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stands in the Sub-Boreal Spruce biogeoclimatic zone of central interior British Columbia. Field experiments in this region have shown that addition of sulphate-S to nitrogen (N) fertilization treatments rapidly increases foliar S concentrations, and usually improves tree growth responses relative to N-only treatments. However, there is an insufficient scientific basis for choosing this S form over more slowly available elemental S-based fertilizers. To address this knowledge gap, this study was begun in 2001 to compare the behaviour of sulphate-S and elemental-S fertilizers in an area-based fertilizer trial, using stable isotope tracer methods to examine the fate and transformations of fertilizer S. Fertilizer treatments were applied to two lodgepole pine stands, near Fraser Lake (Holy Cross site) and in the Bowron River valley (Kenneth Creek site), in fall 2002. This establishment report reviews background literature relevant to this study, details the experimental design and methods used, and documents the initial soil and stand conditions at the time the experimental treatments were installed. ‍?Pre-treatment analyses indicated that mineral soils at these sites have low total S concentrations, which are typical of the British Columbia central interior and are among the lowest reported in the temperate and boreal zones worldwide. Concentrations of other total and (or) available soil macronutrients (N, Ca, Mg, K, P) were usually higher at the Holy Cross site than at the Kenneth Creek site. Lodgepole pine foliar analyses indicated that S deficiency was more pronounced at the former site. Ratios of background S stable isotopes in lodgepole pine foliage and soils differed sufficiently from those of the applied S fertilizers to make a tracer experiment feasible.