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Dynamics of carbon stock, greenhouse gas emissions, and energy use of selected coffee-based (Coffea arabica L.) agroforestry farms in Timor Leste
Dissertation Abstract:
Agroforestry is an important carbon sequestration strategy because of carbon storage potential in its multiple plant species and soil as well as its applicability in agricultural lands and in reforestation. The study was conducted in selected coffee-based agroforestry farms in Gleno, Ermera District, Timor Leste. It aimed to determine the amount of carbon stocks, greenhouse gas emissions and energy used in the management of coffee-based agroforestry farms. Results revealed that agroforestry coffee cropping pattern had a carbon stock composed of 6.425 Mg ha-1 biomass, 2.01 Mg ha-1 necromass, and 157.17 Mg ha-1 soil organic carbon. For the carbon stock stored in the monoculture coffee cropping pattern, a biomass of 5.321 Mg ha-1, necromass of 1.32 Mg ha-1, and soil organic carbon of 128.74. Mg ha-1 were recorded while for the pruned coffee cropping pattern, biomass of 2.771 Mg ha-1, necromass of 1.82 Mg ha-1, and soil organic carbon of 69.29 Mg ha-1 were found. The greenhouse gas emission CO2 absorbed by coffee plants across cropping patterns were the following: agroforestry coffee, 24.156 t/ha-1, monoculture coffee, 19.520 t/ha-1 and pruned coffee, 10.177 t/ha-1. The TEI (total energy input) of each agroforestry coffee farm was derived from direct, indirect, and embedded energy inputs. For coffee-based agroforestry, a total of 26.44 Mcal ha-1 was recorded from the use of farm trucks (19.22 Mcal ha-1) and motorcycle (7.22 Mcal ha-1). For the indirect energy, the largest consumption of energy was in the use of pesticides with 442.43 Mcal ha-1 (5049.90 LDOE ha-1). The use of pesticides in large quantities made the indirect energy to increase compared to the indirect energy needs from other processes. The lowest energy input was field visit monitoring with 4.61 Mcal ha-1 (52.62 LDOE). The monoculture coffee had a total direct energy input of 46.28 Mcal ha-1 derived from the use of farm trucks (33.65 Mcal ha-1) and motorcycle (12.63 Mcal ha-1). The largest indirect energy input was observed in the use of fertilizers, particularly N with 2043.1 Mcal ha-1 (23318.80 LDOE Mcal ha-1) and followed with the use of pesticide (Glyphosate) with 442.43 Mcal ha-1 (507.12 LDOE Meal ha-1). For human labor, weeding, field visit monitoring and picking activities required high energy input while insecticide spraying required the lowest amount of energy input. The pruned coffee cropping pattern had a total direct energy input of 46.29 Mcal ha-1 derived from the use of farm trucks (33.65 Mcal ha-1) and motorcycle (12.64 Mcal ha-1). The largest indirect energy input was observed in the use of organic fertilizers (705.08 Mcal ha-1) followed by inorganic fertilizer (N) with 664.50 Meal ha-1 (7584.60 LDOE Mcal ha-1) and followed with the use of pesticide (Glyphosate) with 481.17 Mcal ha-1 (5492.07 LDOE Mcal ha-1).
Abovementioned results reveal that coffee-based agroforestry system shows the important role of woody stems of coffee plants on the emission of GHG gases. Energy both direct and indirect forms are necessary in the management of agroforestry farms. Energy from animal labor is higher than energy required from human labor. Cost and use of pesticides recorded the highest while field visit monitoring the lowest. The use of inorganic fertilizers was more expensive than organic fertilizers. The total energy ratio in the management of coffee-based agroforestry farm of 1.67 Meal ha-1 indicates that the agroforestry practices are suitable for development because of a > 1 energy ratio. With these findings, further study is required to account for different qualities and management of inputs to enable effective calculation of the carbon footprints (CF) from different cropping patterns and management strategies, and eventually come up with a more effective climate change mitigation strategies from site-specific studies.