Alternative Land Use Options for Philippine Grasslands: A Bioeconomic Modeling Approach Using the WaNuLCAS Model

In the Philippines, pure grasslands occupy 1.8 million ha and another 10.8 million ha (33% of the country’s total land area) is under extensive cultivation mixed with grasslands and scrub. Most of these grasslands are under-utilised and dominated by Imperata cylindrica. Imperata grasslands generally represent areas of degraded soils that are acidic, low in organic matter and susceptible to erosion. However, conversion of these grassland areas into upland farms planted to annual crops and perennial trees is proliferating at a fast rate. This is triggered by the interacting factors of rapidly increasing population, the system of landholding, scarcity of jobs and the declining arable area in the lowlands

Alternative Land Use Options for Philippine Grasslands: A Bioeconomic Modeling Approach Using the WaNuLCAS Model

In the Philippines, pure grasslands occupy 1.8 million ha and another 10.8 million ha (33% of the country\u27s total land area) is under extensive cultivation mixed with grasslands and scrub. Most of these grasslands are under-utilised and dominated by Imperata cylindrica. Imperata grasslands generally represent areas of degraded soils that are acidic, low in organic matter and susceptible to erosion. However, conversion of these grassland areas into upland farms planted to annual crops and perennial trees is proliferating at a fast rate. This is triggered by the interacting factors of rapidly increasing population, the system of landholding, scarcity of jobs and the declining arable area in the lowlands

Hedgerow Systems and Livestock in Philippine Grasslands: GHG Emissions

Hedgerow systems are widely adopted in the smallholder farms in the sloping grassland areas of Claveria, Mindanao, Philippines. The system is effective in addressing soil erosion problems and in conserving the topsoil. Gmelina arborea and Eucalyptus deglupta are two fast-growing timber species that are planted in hedgerow systems while maize is planted in the alley areas in between the hedgerows. Livestock holdings are widespread in Claveria, with 74% of the households having livestock. Cattle and carabao are the most common livestock in smallholder farms providing draught power for land preparation and transportation. In hedgerow systems, fodder tree leaves and crop residues are fed to livestock, while animal manure is added to the soil. Thus, these systems may serve as both a source and sink of methane and nitrogen oxides, depending on the management practices and component trees and crops of the system. This study aims to estimate methane emissions from livestock holdings and nitrogen oxide emissions through fertilization, tree litterfall and decomposition, maize residue incorporation and livestock manure from G. arborea and E. deglupta hedgerow systems

Hedgerow Systems and Livestock in Philippine Grasslands: GHG Emissions

Hedgerow systems are widely adopted in the smallholder farms in the sloping grassland areas of Claveria, Mindanao, Philippines. The system is effective in addressing soil erosion problems and in conserving the topsoil. Gmelina arborea and Eucalyptus deglupta are two fast-growing timber species that are planted in hedgerow systems while maize is planted in the alley areas in between the hedgerows. Livestock holdings are widespread in Claveria, with 74% of the households having livestock. Cattle and carabao are the most common livestock in smallholder farms providing draught power for land preparation and transportation. In hedgerow systems, fodder tree leaves and crop residues are fed to livestock, while animal manure is added to the soil. Thus, these systems may serve as both a source and sink of methane and nitrogen oxides, depending on the management practices and component trees and crops of the system. This study aims to estimate methane emissions from livestock holdings and nitrogen oxide emissions through fertilization, tree litterfall and decomposition, maize residue incorporation and livestock manure from G. arborea and E. deglupta hedgerow systems

Growth and survival of tilapia Oreochromis niloticus (Linnaeus, 1758) submitted to different temperatures during the process of sex reversal Crescimento e sobrevivência de tilápias Oreochromis niloticus (Linnaeus, 1758) submetidas a diferentes temperaturas durante o processo de inversão sexual

The objective of this research was to evaluate the sex reversal technique using 17&#945;--methyltestosterone (MT) hormone, submitted to temperature modification of fry Nilo tilapia storage, aiming to get the data of sex reversal combined with growth performance and fry survival. The experiment was performed at UFLA Fish Culture Station, using tilapia fry (0,008 ± 0.002 g e 0,9 ± 0.1 cm) obeying a totally randomized experimental delineation in a factorial scheme 4x4, in 4 temperatures (26º, 28º, 30º, 32ºC) and 4 hormonal doses (0, 20, 40, 60mg of MT/kg of ration) during 28 days, with 5 repetitions. As temperature raised, weight gain rate, size and survival increased (p<0.01); however, this temperature raise was not effective in modifying males ratio (p>0.01), which occurred only due to the used hormone treatment. The dose of 40 mg of MT/kg of ration provided similar results to those of 60mg of MT/kg of ration. Hence, the temperature band from 26º to 32ºC does not affect sex reversal rate, but temperatures around 30ºC improves the performance of tilapias related to the growth and survival, and the dose of 40 mg of MT/kg of ration is enough to achieve monosex populations.<br>Objetivou-se, neste trabalho, avaliar a técnica de inversão sexual utilizando hormônio 17&#945;-metiltestosterona (MT), submetidas à modificação da temperatura de estocagem das pós-larvas de tilápia, visando obter os melhores dados de inversão sexual aliado à performance de crescimento e sobrevivência das pós-larvas. O experimento foi conduzido na Estação de Piscicultura da UFLA, utilizando pós-larvas (0,008 ± 0,002 g e 0,9 ± 0,1 cm) de tilápia em delineamento experimental inteiramente casualizado em esquema fatorial 4x4, com 4 temperaturas (26º, 28º, 30º e 32ºC) e 4 doses hormonais (0, 20, 40 e 60mg de MT/kg de ração) durante 28 dias, com 5 repetições. À medida que se elevou a temperatura, a taxa de ganho de peso, o tamanho e a sobrevivência foram maiores (p<0,01); entretanto, esse aumento na temperatura não foi suficiente para alterar a proporção de machos (p>0,01), que ocorreu apenas em função do hormônio utilizado. A dose de 40 mg de MT/kg de ração proporcionou resultados semelhantes aos da dose de 60 mg de MT/kg de ração. Portanto, a faixa de temperatura entre 26º e 32ºC não influencia na taxa de inversão sexual, mas temperaturas em torno de 30ºC melhoram o desempenho das tilápias quanto ao crescimento e à sobrevivência, e a dose de 40 mg de MT/kg de ração é suficiente para a obtenção de populações monossexo

Produção de populações monossexo macho de tilápia-do-nilo da linhagem Chitralada Production of monosex male nile tilapia populations of the Chitralada strain

A fim de avaliar o efeito da alta temperatura na proporção de sexos da tilápia-do-nilo (Oreochromis niloticus) da linhagem Chitralada, foram conduzidos dois experimentos. No primeiro foram analisados, por 28 dias, os efeitos da temperatura de 35ºC, em relação ao controle (27ºC), iniciando-se dez dias após a eclosão. Foi encontrada diferença significativa na proporção de sexos, sendo que o maior porcentual de machos foi encontrado no tratamento de temperatura alta (72,39%), em comparação com o controle (62,27%). Não foram encontradas diferenças de peso corporal e de comprimento total entre os tratamentos. No segundo experimento, foram analisados os efeitos dos períodos de exposição à temperatura de 35ºC, aos 7, 14, 21 e 28 dias, iniciando-se dez dias após a eclosão. Não houve diferença na proporção de sexos entre os períodos de exposição. Foram encontradas diferenças significativas entre os tratamentos, tanto para peso corporal como para comprimento total. Nos dois experimentos, as taxas de sobrevivência relacionaram-se diretamente com a ocorrência de canibalismo, significativamente maior a 35ºC. Os efeitos significativos da temperatura na proporção de sexos, no primeiro experimento, indicam a termossensibilidade na linhagem Chitralada.<br>The effect of high temperature on sex ratio in the Chitralada strain of Nile tilapia (Oreochromis niloticus) was tested using two experiments. Primarily, the animals were exposed to a high (35ºC) or control (27ºC) water temperature for a 28-day-period, beginning ten days after hatching. A significant difference in sex ratio was found. The highest proportion of males was in the high temperature group (72.39%), compared with the control group (62.27%). No differences were found for total length or body weight between the groups. In the second experiment, the effect of exposure times (7, 14, 21 and 28 days starting ten days post hatching) at a constant temperature of 35ºC was tested. No differences were found in sex ratio between groups. A significant difference was found between treatments for body weight and total length. In both experiments, the survival rate had a direct relationship with the occurrence of cannibalism, which was significantly higher at 35ºC. The significant temperature effect on sex ratio found in the first experiment indicates the thermosensitivity of the Chitralada strain