ISSN:
1573-5036
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary The movement of N in an 11-year-old slash pine forest ecosystem was followed over two growing seasons by using N15-labeled ammonium sulphate, applied in the spring at 0, 56, and 224 kg N/ha. The initial uptake of P32, applied as concentrated superphosphate at 90 kg P/ha, and of labeled N from the highest application rate was followed in two trees for 71 days. Dry weather following fertilizer application delayed uptake and both isotopes were first observed in the foliage 7 days after application. While uptake of P32 was at a steady rate between the third and tenth week, the uptake of N15 declined, due to reduced availability in the soil, after seven weeks. Concentrations of both isotopes were greater in the lower foliage than in the upper crown. The N15 levels were higher in currently developing foliage than in older foliage, while the reverse was true for P32. The maximum concentration of labeled-N occurred in the foliage at about 12 weeks. At this time the current foliage had derived 8.5 per cent of its N from the fertilizer in the low-N treatment and 27.5 per cent at the high-N treatment. However, N15 uptake into the developing foliage continued, at a reduced rate, until mid winter. In the second growing season, the foliage formed in the previous growing season decreased in total and labeled-N content due to translocation to newly developing tissue. The N15 leached rapidly through the litter with only 9 per cent of the applied N, in the high-N treatment, occurring in the litter at the end of 6 weeks. In the first 12 weeks the amount of N15 in the litter and topsoil decreased rapidly (to 21 per cent in the high-N plots) but changed little thereafter. This decrease was related to uptake and probably to leaching.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01928507
