An attempt to assess the optimum nitrogen level in Norway spruce under field conditions
Tamm, Carl Olof
Two long-term field experiments are described, aiming at an assessment of the optimum internal level of nitrogen in spruce needles. The experiments were laid out in 1957 and 1958 in two young spruce plantations, one on an old field and one on forest land. Three or four nitrogen regimes, respectively, were maintained by annual application of ammonium nitrate fertiliser. Half the plots received also PK fertiliser. Both growth and nutrient levels in the stand were followed by measurements at close intervals. The nutrient studies concerned the percentages of nitrogen, phosphorus, potassium, calcium and magnesium in autumn samples of exposed current needles. The nitrogen application increased growth in both experiments. At first both height and diameter growth were affected. Later, the main growth increase was in diameter and volume growth. Also PK application increased volume yield. Possible secondary effects of the fertiliser applications and the relationships between internal nutrient levels and growth are discussed in some detail. The value of long-term optimum nutrition experiments in the future study of forest nutrition is pointed out.
nitrogen; Norway spruce; field experiments; needles
Studia Forestalia Suecica
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