The results from the initial series of area-based fertilization installations (EP 886.01a), combined with those from fertilizer screening trials, indicated that S and/or B deficiencies may have been induced, or aggravated, following N addition at some lodgepole pine study sites. In 1986, four area-based field installations (2 SBS, 1 ICH, 1 MS) were established to determine whether adding S, or S plus B, in combination with N would produce larger growth gains than with N alone. Stand ages ranged from 14 to 60 years old at the time of installation establishment.
To determine the magnitude and duration of growth response following fertilization with nitrogen alone, and nitrogen combined with sulphur and boron.
At two study sites, three replicates of each of three treatments (unfertilized, 200 kg N/ha, 200 kg N/ha + 58 kg S/ha) are applied to area-based plots. At one site, the NS treatment is replaced with a NSB treatment providing (kg/ha): 200N, 58S, and 1.4B. The remaining installation tests a "Complete mix" treatment (N, P, K, Mg, S, B) in addition to the unfertilized, N, NS, and NSB treatments.
All of the installations were re-measured at 3-year intervals for a total of 15 years. Measurements included diameter at breast height, total height, height to live crown, tree form and damage. Foliar nutrient data were also obtained from all treatment plots prior to fertilization and after 1, 3, and 6 years. Two of the installations are still active and are re-measured at 6-year intervals.
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