Oil palm is cultivated by agro-industries and smallholders for vegetable oil production. Good farm management practices with balanced soil and plant macronutrients are needed to attain optimum yields. Smallholder oil ...Oil palm is cultivated by agro-industries and smallholders for vegetable oil production. Good farm management practices with balanced soil and plant macronutrients are needed to attain optimum yields. Smallholder oil palm farmers of Dibombari Sub-Division, Cameroon, suffer from low on farm yields which could emanate from the agronomic practices implemented, which also has an influence on the soil and plant macronutrient status. This study provides information on the agronomic practices, soil and plant macronutrients status in smallholder oil palm fields. Structured questionnaires were administered to 200 farmers to collect data on their agronomic practices, using a stratified random sampling design. Soil and plants were sampled from plantations of different age groups (control, >0 - 4 years, >4 - 8 years and >8 - 15 years’ plantations) in four locations of the Sub-Division (i.e. Dibombari-central, Bonamateke, Bomono and Nkapa) using a randomized complete block design. Data collected, was analyzed using descriptive and inferential statistics. The results showed that 65% of farmers planted Tenera variety, with majority of them below the standards for weeding (81%), fertilizer use (100%), pruning (62%), pest/disease control (90.5%) and harvesting (96%) practices. Soil macronutrients were low across the different plantations except P which was optimal at >0 - 4 years and >4 - 8 years’ plantations but low at >8 - 15 years’ plantation. Similarly, for plant macronutrients, N and P were optimal across the different plantations, while K and Mg were optimal at >0 - 4 years’ plantation but low at >4 - 8 years and >8 - 15 years’ plantations. Thus, agronomic practices and macronutrient status of soil and plants were below standards in smallholder oil palm plantations of Dibombari, leading to low yields of fresh fruit bunches.展开更多
Integrated pest management （IPM） is widely practiced in commercial oil palm agriculture. This management system is intended to minimize the number of attacks by pest insects such as bagworms on crops, as well as cur...Integrated pest management （IPM） is widely practiced in commercial oil palm agriculture. This management system is intended to minimize the number of attacks by pest insects such as bagworms on crops, as well as curb economic loss with less dependency on chemical pesticides. One practice in IPM is the use of biological control agents such as predatory insects. In this study, we assessed the response of predatory natural enemies to pest outbreak and water stress, and document the habitat associations of potential pest predators. The abundances of 2 predatory insect species, namely Sycanus dichotomus and Cosmolestes pictieeps （Hemiptera： Reduviidae）, were compared bagworm outbreak sites and nonoutbreak sites within oil palm plantations. We also examined habitat characteristics that influence the abundances of both predatory species. We found that the abundance of C. picticeps was significantly higher in bagworm outbreak sites than in nonoutbreak sites. There were no significant differences in the abundance ofS. dichotomus among outbreak and non-outbreak sites. Both species responded negatively to water stress in oil palm plantations. Concerning the relationship between predatory insect abundance and in situ habitat quality characteristics, our models explained 46.36% of variation for C. picticeps and 23.17% of variation for S. dichotomus. Both species of predatory insects thrived from the planting of multiple beneficial plants in oil palm plantations. The results suggest that C. picticeps can be used as a biological agent to control bagworm populations in oil palm plantations, but S. dichotomus has no or little potential for such ecosystem service.展开更多
The variation in solar environments during succession in sago forests is thought to affect the growth of many plant species. To clarify the pattern of plant colonization in sago forests at various successional stages,...The variation in solar environments during succession in sago forests is thought to affect the growth of many plant species. To clarify the pattern of plant colonization in sago forests at various successional stages, we constructed eleven 10 m × 10 m quadrats in different solar conditions in sago forests, measured and calculated the relative illumination intensity, collected all plant species in these quadrats, and used two chloroplast gene sequences—the rbcL gene of ferns and the trnL intron of angiosperms to molecularly identify them. The number of ferns increased while the number of herbaceous species decreased during the process of succession. Moreover, the number of woody species was not significantly correlated with the relative light intensity. Based on these results, it can be concluded that woody species colonized and grew at various successional stages but herbaceous species and ferns did the same in the early and late successional stages, respec-tively, in the sago forest.展开更多
The steam turbine is a prime mover that converts kinetic energy in steam into rotational mechanical energy through the impact or reaction of the steam against the blades. The aim of this study is to design a steam tur...The steam turbine is a prime mover that converts kinetic energy in steam into rotational mechanical energy through the impact or reaction of the steam against the blades. The aim of this study is to design a steam turbine for a small scale steam power plant with target of producing electricity. The turbine is driven by the heat energy from palm kernel shells as a renewable energy source obtained at a lower or no cost. The study was concentrated on design of turbine elements and its validation using computer packages. Specifically, the microturbine design was limited to design, modeling, simulation and analysis of the rotor, blades and nozzle under the palm kernel shell as fuel for the micro power plant. In blade design, stress failures, efficiency and blade angle parameters were considered. In casing volume design, the overall heat transfer and mean temperature, and different concepts were applied. The thermal distribution on stator and rotor was considered in order to determine its level of tolerance. The design software packages used for design validation were Solidworks and Comsol Multiphysics for analysis. Simulation results showed that the designed steam turbine can adequately tolerate change in stress/load, torsion/compression, temperature and speeds.展开更多
文摘Oil palm is cultivated by agro-industries and smallholders for vegetable oil production. Good farm management practices with balanced soil and plant macronutrients are needed to attain optimum yields. Smallholder oil palm farmers of Dibombari Sub-Division, Cameroon, suffer from low on farm yields which could emanate from the agronomic practices implemented, which also has an influence on the soil and plant macronutrient status. This study provides information on the agronomic practices, soil and plant macronutrients status in smallholder oil palm fields. Structured questionnaires were administered to 200 farmers to collect data on their agronomic practices, using a stratified random sampling design. Soil and plants were sampled from plantations of different age groups (control, >0 - 4 years, >4 - 8 years and >8 - 15 years’ plantations) in four locations of the Sub-Division (i.e. Dibombari-central, Bonamateke, Bomono and Nkapa) using a randomized complete block design. Data collected, was analyzed using descriptive and inferential statistics. The results showed that 65% of farmers planted Tenera variety, with majority of them below the standards for weeding (81%), fertilizer use (100%), pruning (62%), pest/disease control (90.5%) and harvesting (96%) practices. Soil macronutrients were low across the different plantations except P which was optimal at >0 - 4 years and >4 - 8 years’ plantations but low at >8 - 15 years’ plantation. Similarly, for plant macronutrients, N and P were optimal across the different plantations, while K and Mg were optimal at >0 - 4 years’ plantation but low at >4 - 8 years and >8 - 15 years’ plantations. Thus, agronomic practices and macronutrient status of soil and plants were below standards in smallholder oil palm plantations of Dibombari, leading to low yields of fresh fruit bunches.
文摘Integrated pest management （IPM） is widely practiced in commercial oil palm agriculture. This management system is intended to minimize the number of attacks by pest insects such as bagworms on crops, as well as curb economic loss with less dependency on chemical pesticides. One practice in IPM is the use of biological control agents such as predatory insects. In this study, we assessed the response of predatory natural enemies to pest outbreak and water stress, and document the habitat associations of potential pest predators. The abundances of 2 predatory insect species, namely Sycanus dichotomus and Cosmolestes pictieeps （Hemiptera： Reduviidae）, were compared bagworm outbreak sites and nonoutbreak sites within oil palm plantations. We also examined habitat characteristics that influence the abundances of both predatory species. We found that the abundance of C. picticeps was significantly higher in bagworm outbreak sites than in nonoutbreak sites. There were no significant differences in the abundance ofS. dichotomus among outbreak and non-outbreak sites. Both species responded negatively to water stress in oil palm plantations. Concerning the relationship between predatory insect abundance and in situ habitat quality characteristics, our models explained 46.36% of variation for C. picticeps and 23.17% of variation for S. dichotomus. Both species of predatory insects thrived from the planting of multiple beneficial plants in oil palm plantations. The results suggest that C. picticeps can be used as a biological agent to control bagworm populations in oil palm plantations, but S. dichotomus has no or little potential for such ecosystem service.
文摘The variation in solar environments during succession in sago forests is thought to affect the growth of many plant species. To clarify the pattern of plant colonization in sago forests at various successional stages, we constructed eleven 10 m × 10 m quadrats in different solar conditions in sago forests, measured and calculated the relative illumination intensity, collected all plant species in these quadrats, and used two chloroplast gene sequences—the rbcL gene of ferns and the trnL intron of angiosperms to molecularly identify them. The number of ferns increased while the number of herbaceous species decreased during the process of succession. Moreover, the number of woody species was not significantly correlated with the relative light intensity. Based on these results, it can be concluded that woody species colonized and grew at various successional stages but herbaceous species and ferns did the same in the early and late successional stages, respec-tively, in the sago forest.
文摘The steam turbine is a prime mover that converts kinetic energy in steam into rotational mechanical energy through the impact or reaction of the steam against the blades. The aim of this study is to design a steam turbine for a small scale steam power plant with target of producing electricity. The turbine is driven by the heat energy from palm kernel shells as a renewable energy source obtained at a lower or no cost. The study was concentrated on design of turbine elements and its validation using computer packages. Specifically, the microturbine design was limited to design, modeling, simulation and analysis of the rotor, blades and nozzle under the palm kernel shell as fuel for the micro power plant. In blade design, stress failures, efficiency and blade angle parameters were considered. In casing volume design, the overall heat transfer and mean temperature, and different concepts were applied. The thermal distribution on stator and rotor was considered in order to determine its level of tolerance. The design software packages used for design validation were Solidworks and Comsol Multiphysics for analysis. Simulation results showed that the designed steam turbine can adequately tolerate change in stress/load, torsion/compression, temperature and speeds.
