Long-term effects of lime application on 15N availability to Sitka spruce seedlings growing in pots containing peat soils

Abstract

The long-term effects of liming a peat soil on nitrogen availability to 3-year-old Picea sitchensis seedlings were assessed in greenhouse experiments. Seedlings were planted in pots containing either unlimed or limed peat soils that had been limed 28 years earlier. The plants were harvested in October 1993, April 1994 and July 1994 with these dates representing 100, 160 and 263 days after planting respectively. Concentration of extractable NO 3 – in the limed peat was higher than in the unlimed peat. Liming also resulted in increases in extractable organic N and total extractable N in the peat. On all harvesting occasions, percentage 15 N utilization and total N were reduced in plants grown on the limed peat. Decreased concentrations of N in the fine-root fractions were apparent for plants grown on the limed peat at the October and July harvests only. During the growing season, the above-ground parts of the plant were the dominant sinks for nitrogen. The needles and fine roots were the major fractions for the utilization of 15N particularly in April and July. The only effect of a limed peat on dry weight of plant fractions was a decrease in fine-root dry weight when plants were examined in October 1993. On all harvesting occasions, populations of mycorrhizae were decreased and roots were blackened for plants grown in the limed peat soil.