Nitrogen (N) balance is a factor of dramatic importance for the sustainability of bioenergy crops, either herbaceous or woody ones, in terms of their energetic and CO2 balances, greenhouse gases emission, environmental contamination and biofuel quality. Poplars are frequently used worldwide for bioenergy coppice plantations, with very high planting densities and extremely short rotation cycles (2-5 years). These factors strongly affect the N balance of bioenergy plantations, with very high N uptake, for the frequent harvests of large quantity of biomass constituted of thousands of small sized shoots, with a relative high bark:wood ratio. We studied the relationships between tree morphological yield traits (stem diameter and height, dendromass yield, branchiness, and number of shoots on stool - N. shoots stool-1) and N removal, in the harvested biomass, and N use efficiency (NUE). The research was conducted in two experimental plantations in Italy (sites of Vinovo and Bigarello), comparing Italian hybrids poplar clones: four new selections for bioenergy (AF2, AF6, Monviso, 83.140.138) and I214, as control clone. After two biennial coppice rotations, N removal was found to be primarily influenced by the biomass production and a relationship between biomass yield and N removal was established. These data can be used for a first refinement of criteria of N fertilization of the woody crop, either in the case of the use of chemical fertilizers or as organic wastes for their disposal into bioenergy plantations (phytoremediation). Coppicing improved dramatically the amount of N removal, as a consequence of strong changes in morphological traits and density of shoot populations. Morphological stem/shoot traits, at clonal level, were found to be correlated to the N content in the woody tissues, as well as to the NUE of the clones. At the end of the first cycle, low branchiness was found to be correlated to low N content (N%), and indirectly to high NUE at clonal level. After coppicing, a low level of shoots on stool was found to be correlated with low N% and high NUE. Clone AF2 was the one presenting high NUE, low branchiness and low N. shoots stool-1; combining these characteristics with high biomass production in the studied experiments. Clone AF2 was one of the most productive clones also in other experiments in Italy, as well as in preliminary tests in other European countries. Cultivar selection of poplar for bioenergy production should be aimed at selecting genotypes with low branchiness and N. shoots stool-1, as in the case of clone AF2. In the case of maximizing N uptake, as for phytoremediation, clone Monviso was the one matching high biomass yield with low NUE due to high branchiness and number of shoots on stool.
Are tree morphological determinants indicators of Nitrogen Use Efficiency (NUE) in hybrid Populus clones for bioenergy plantations?
Pierluigi Paris;
2012
Abstract
Nitrogen (N) balance is a factor of dramatic importance for the sustainability of bioenergy crops, either herbaceous or woody ones, in terms of their energetic and CO2 balances, greenhouse gases emission, environmental contamination and biofuel quality. Poplars are frequently used worldwide for bioenergy coppice plantations, with very high planting densities and extremely short rotation cycles (2-5 years). These factors strongly affect the N balance of bioenergy plantations, with very high N uptake, for the frequent harvests of large quantity of biomass constituted of thousands of small sized shoots, with a relative high bark:wood ratio. We studied the relationships between tree morphological yield traits (stem diameter and height, dendromass yield, branchiness, and number of shoots on stool - N. shoots stool-1) and N removal, in the harvested biomass, and N use efficiency (NUE). The research was conducted in two experimental plantations in Italy (sites of Vinovo and Bigarello), comparing Italian hybrids poplar clones: four new selections for bioenergy (AF2, AF6, Monviso, 83.140.138) and I214, as control clone. After two biennial coppice rotations, N removal was found to be primarily influenced by the biomass production and a relationship between biomass yield and N removal was established. These data can be used for a first refinement of criteria of N fertilization of the woody crop, either in the case of the use of chemical fertilizers or as organic wastes for their disposal into bioenergy plantations (phytoremediation). Coppicing improved dramatically the amount of N removal, as a consequence of strong changes in morphological traits and density of shoot populations. Morphological stem/shoot traits, at clonal level, were found to be correlated to the N content in the woody tissues, as well as to the NUE of the clones. At the end of the first cycle, low branchiness was found to be correlated to low N content (N%), and indirectly to high NUE at clonal level. After coppicing, a low level of shoots on stool was found to be correlated with low N% and high NUE. Clone AF2 was the one presenting high NUE, low branchiness and low N. shoots stool-1; combining these characteristics with high biomass production in the studied experiments. Clone AF2 was one of the most productive clones also in other experiments in Italy, as well as in preliminary tests in other European countries. Cultivar selection of poplar for bioenergy production should be aimed at selecting genotypes with low branchiness and N. shoots stool-1, as in the case of clone AF2. In the case of maximizing N uptake, as for phytoremediation, clone Monviso was the one matching high biomass yield with low NUE due to high branchiness and number of shoots on stool.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
