Data on standing biomass, mean annual increment of carbon stock, and nutrient accumulation in 40 industrial plantations at 21 sites in 11 countries are summarised. Aboveground biomass and mean annual increment of carbon near the harvest age, of these plantations ranged from 44 to 324 t ha-1 and from 3.1 to 22.9 tC ha-1 yr-1, respectively. Plantations managed on a short rotation are expected to accumulate carbon rapidly. However, there are large variations of biomass accumulation depending on site conditions. There is concern about the potential decrease of productivity caused by nutrient loss by intensive and repeated harvesting. It is important to determine the nutrients removed and conserve them as much as possible to prevent productivity loss and for sustainable management of industrial plantations. Careful management of the nutrient cycle through residue retention and fertiliser application is necessary to maintain high productivity.
Tag: plant residues
Nitrogen uptake of maize (Zea mays. L) from isotope-labeled biomass of Paraserianthes falcataria grown under controlled conditions
Roots can be an important though poorly quantified source of nitrogen (N) in agroforestry systems. Nitrogen uptake of maize using P. falcataria below- and aboveground biomass separately, and their combination, as source of N, was assessed in a controlled experiment using 15N isotope labeling techniques. The 15N-direct and the 15N-indirect labeling techniques were compared for discrepancies in measuring N cycling from P. falcataria tree residues. N contribution to maize production was as follows; 40–57% from below ground biomass and 10–18% from above ground biomass (P < 0.05). Residue N use efficiency (%rNE) by maize was between 99 and 106% for belowground biomass, 4–4.5% for aboveground biomass. This implies that though nutrient release characteristics of aboveground biomass are commonly used as a basis for selection of agroforestry trees, those of belowground biomass would be of fundamental importance as well. Combining P. falcataria below and aboveground biomass did not result in significant (P < 0.05) effects on N recovered by maize, suggesting the absence of decomposition interactions between the two bio-chemically contrasting residues. There were no significant methodological differences reflected in measured N cycled by maize from leaves (Ndfr); 15% and 18% as estimated by 15N direct and indirect method, respectively. The two methods compared very well (P < 0.05) as tools of estimating N cycling from surface applied leaves. However, the ability of the direct method to measure N without disturbing either the tree or the soil, would make it a more attractive and valuable tool in N cycling studies in agroforestry systems.