Influence of shoot age on growth and nutrient uptake patterns in a willow plantation

Abstract

The seasonal patterns of growth and nutrient uptake of a short-rotation Salixviminalis L. plantation located along the southeastern coast of Sweden were investigated during 1981. One-year-old shoots of clone 683 yielded 9.6 t dry weight ha⁻¹ of stems and 4.2 t dry weight ha⁻¹ of leaves; whereas the same cultural treatment during the 2nd year after coppicing yielded 13.3 and 8.2 t dry weight ha⁻¹, respectively. Maximums in foliage dry weight occurred between early August and early September in the older shoots (6.3 t ha⁻¹) and in late September in the younger shoots (3.5 t ha⁻¹). Foliage and stem growth early in the season were markedly higher in the 2-year-old shoots than in the 1-year-old shoots. N uptake increased rapidly shortly after the first fertilizer application in all three investigated plots. Aboveground N uptake ranged from 140 to 191 kg ha⁻¹ year⁻¹. From the onset of liquid fertilization until the end of the growing season the aboveground N uptake ranged from 92 to 98 kg N ha⁻¹; the total N fertilization during this period was 120 kg N ha⁻¹. Nitrogen productivity varied between clones and was higher for 2- than for 1-year-old shoots. Greater relative amounts of biomass and N were allocated to leaves on the 2-year-old shoots. The amount of N allocated to stems for producing 11 of stem biomass decreased from 4.3 to 2.5 kg during the 2nd year after coppicing.