title: Canopy and leaf composition drive patterns of nutrient release from pruning residues in a coffee agroforest.
abstract: In a coffee agroforest, the crop is cultivated under the shade of fruit-bearing and nitrogen (N)-fixing trees. These trees are periodically pruned to promote flowering and fruiting as well as to make nutrients stored in tree biomass available to plants. We investigated the effect of canopy composition and substrate quality on decomposition rates and patterns of nutrient release from pruning residues in a coffee agroforest located in Costa Rica's Central Valley. Initial phosphorus (P) release was enhanced under a canopy composed solely of N-fixing, Erythrina poeppigiana compared to a mixed canopy of Erythrina and Musa acuminata (banana). Both initial and final N release were similar under the two canopy types. However, after five months of decomposition, a higher proportion of initial N had been released under the single canopy. Although patterns of decomposition and nutrient release were not predicted by initial substrate quality, mass loss in leaf mixtures rates were well predicted by mean mass loss of their component species. This study identifies specific pruning regimes that may regulate N and P release during crucial growth periods, and it suggests that strategic pruning can enhance nutrient availability. For example, during the onset of rapid fruit growth, a two-species mixture may release more P than a three-species mixture. However, by the time of the harvest, the two- and three-species mixtures have released roughly the same amount of N and P. These nutrients do not always follow the same pattern, as N release can be maximized in single-species substrates, while P release is often facilitated in species mixtures. Our study indicates the importance of management practices in mediating patterns of nutrient release. Future research should investigate how canopy composition and farm management can also mediate on-farm nutrient losses.
authors: The Earth Institute at Columbia University, Tropical Agriculture and Rural Environment Program, Lamont Campus, Lamont Hall, 61 Route 9W, Palisades, New York 10964, USA. ktully@columbia.edu
authors: Katherine L
authors: KL
authors: Tully
authors: Deborah
authors: D
authors: Lawrence
mesh_terms: D000383:Agriculture / Q000379:methods*; D001673:Biodegradation, Environmental; D040503:Coffea / Q000737:chemistry / Q000502:physiology*; D003364:Costa Rica; D017753:Ecosystem; D009584:Nitrogen; D010758:Phosphorus / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry*; D018547:Plant Stems; D012987:Soil / Q000737:chemistry; D013997:Time Factors; D014197:Trees / Q000145:classification*
chemical_list: D012987:Soil; D010758:Phosphorus; D009584:Nitrogen