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The population in the high mountains of the northwest provinces of Vietnam belongs to the poorest population in the country. Among the reasons behind this are the high frequency of minority groups in the region and the infertile soils of the steep slopes. As a result of the diversified elevation in northwest Vietnam, farmers are forced to cultivate fields with a gradient of more than 25 %. Additionally, the heavy rainfall events in the region increase the runoff, which is the main mechanism in erosion. Erosion leads to loss of bulk soil, and large losses of plant nutrients. In addition to erosion, nutrient leakage also occurs especially where a surplus of nutrients is applied. This is often the case when fertilizers are not applied with care. Nutrients are a limiting factor within agriculture, and with better nutrient management, the yield, and thus the farmers' economy, increases.The overall aim of this study was to locate and quantify sources and sinks of nutrients within the ten chosen farms. To achieve this aim, two specific objectives were researched. The first objective was to quantify the farm gate balance to get an overall idea of nutrient surplus and deficit and environmental risks. The second objective was to quantify and map out the internal flows i.e the field balances and the nutrients lost during manure storage. This will help locate sources and sinks of nutrients within each farm. Additionally, it will show if the grass strips help absorb nutrients lost through erosion.The study was carried out in Mai Son District in Son La Province in northwest Vietnam. The data was mainly collected through interviews with farmers on ten farms in the study area, as well as observations made during the field visit. Five farms with cows were chosen, while five farms had no cows. The farms mainly grew maize, longan, mango, and forage grass. Additionally, analyses were made on the nitrogen, phosphorous and potassium concentration in the compost, and the nitrogen concentr

The population in the high mountains of the northwest provinces of Vietnam belongs to the poorest population in the country. Among the reasons behind this are the high frequency of minority groups in the region and the infertile soils of the steep slopes. As a result of the diversified elevation in northwest Vietnam, farmers are forced to cultivate fields with a gradient of more than 25 %. Additionally, the heavy rainfall events in the region increase the runoff, which is the main mechanism in erosion. Erosion leads to loss of bulk soil, and large losses of plant nutrients. In addition to erosion, nutrient leakage also occurs especially where a surplus of nutrients is applied. This is often the case when fertilizers are not applied with care. Nutrients are a limiting factor within agriculture, and with better nutrient management, the yield, and thus the farmers' economy, increases.The overall aim of this study was to locate and quantify sources and sinks of nutrients within the ten chosen farms. To achieve this aim, two specific objectives were researched. The first objective was to quantify the farm gate balance to get an overall idea of nutrient surplus and deficit and environmental risks. The second objective was to quantify and map out the internal flows i.e the field balances and the nutrients lost during manure storage. This will help locate sources and sinks of nutrients within each farm. Additionally, it will show if the grass strips help absorb nutrients lost through erosion.The study was carried out in Mai Son District in Son La Province in northwest Vietnam. The data was mainly collected through interviews with farmers on ten farms in the study area, as well as observations made during the field visit. Five farms with cows were chosen, while five farms had no cows. The farms mainly grew maize, longan, mango, and forage grass. Additionally, analyses were made on the nitrogen, phosphorous and potassium concentration in the compost, and the nitrogen concentr

Grasses of the Urochloa genus have been widely used in crop-livestock integration systems or as cover crops in no-till systems such as in rotation with maize. Some species of Urochloa have mechanisms to reduce nitrification. However, the responses of microbial functions in crop-rotation systems with grasses and its consequence on soil N dynamics are not well-understood. In this study, the soil nitrification potential and the abundance of ammonifying microorganisms, total bacteria and total archaea (16S rRNA gene), nitrogen-fixing bacteria (NFB, nifH), ammonia-oxidizing bacteria (AOB, amoA) and archaea (AOA, amoA) were assessed in soil cultivated with ruzigrass (Urochloa ruziziensis), palisade grass (Urochloa brizantha) and Guinea grass (Panicum maximum). The abundance of ammonifying microorganisms was not affected by ruzigrass. Ruzigrass increased the soil nitrification potential compared with palisade and Guinea grass. Ruzigrass increased the abundance of N-fixing microorganisms at the middle and late growth stages. The abundances of nitrifying microorganisms and N-fixers in soil were positively correlated with the soil N–NH4+ content. Thus, biological nitrogen fixation might be an important input of N in systems of rotational production of maize with forage grasses. The abundance of microorganisms related to ammonification, nitrification and nitrogen fixing and ammonia-oxidizing archea was related to the development stage of the forage grass.

The effects of nitrogen fertilizer sources (urea and ammonium nitrate) applied at different rates on the yield and quality of Megathyrsus maximus cv. Mombasa were compared in this study. The nitrogen rates applied after each monthly harvest were 0, 50, 100, 150 and 200 kg N/ha (i.e., 0, 150, 300, 450 and 600 kg N/ha/year). The N fertilizer sources did not affect the Mombasa grass response to any of the production and nutritional characteristics; however, increasing nitrogen rates there was significantly increased dry matter yield and crude protein percentage, and decreased neutral detergent fiber (NDF) concentrations. Dry matter yield in control treatments was 31.3 t/ha, and responses reached a maximum of 30% with the application of 150 kg N/ha/cut, but considering the economical rate, the better economic return occurs with the application of 115 kg N/ha/cut. As urea has a lower price per unit of N than ammonium nitrate, it seems to be the best choice of fertilizer. Further studies are needed to determine why the dry matter yields of forage were so high and in what seasons should N fertilizer be applied when resources are limited. Longer-term studies would confirm these findings and assess the losses of N to the atmosphere or by leaching, especially at the higher rates., RESUMEN Este estudio comparó los efectos de las formas de fertilizante nitrogenado (urea y nitrato de amonio) a tasas variables en el rendimiento y la calidad de Megathyrsus maximus cv. Mombasa. Las tasas de nitrógeno fueron 0, 50, 100, 150 y 200 kg N / ha después de cada cosecha mensual, es decir, 0, 150, 300, 450 y 600 kg N / ha / temporada. La forma de fertilizante N no afectó las respuestas en ningún parámetro, pero el aumento de las tasas de nitrógeno aumentó significativamente el rendimiento de materia seca y el porcentaje de proteína bruta, y disminuyó las concentraciones de FDN. Los rendimientos de materia seca en los trata mientos de control fueron de 31,3 t DM / ha y las respuestas alcanzaron un máximo del 30% con una aplicación de 150 kg N / ha / mes, pero en vista de la tasa económica, el mejor retorno económico se produce con la aplicación de 115 kg N / ha / mes. Como la urea es más barata por unidad de N que el nitrato de amonio, parece ser el fertilizante de elección. Se necesitan más estudios para determinar por qué los rendimientos básicos de forraje fueron tan altos y en qué estaciones se debe aplicar fertilizante con N cuando los recursos son limitados. Los estudios a más largo plazo confirmarían estos hallazgos y evaluarían las pérdidas de N en la atmósfera y mediante la lixiviación, especialmente en las tasas más altas.

The effects of nitrogen fertilizer sources (urea and ammonium nitrate) applied at different rates on the yield and quality of Megathyrsus maximus cv. Mombasa were compared in this study. The nitrogen rates applied after each monthly harvest were 0, 50, 100, 150 and 200 kg N/ha (i.e., 0, 150, 300, 450 and 600 kg N/ha/year). The N fertilizer sources did not affect the Mombasa grass response to any of the production and nutritional characteristics; however, increasing nitrogen rates there was significantly increased dry matter yield and crude protein percentage, and decreased neutral detergent fiber (NDF) concentrations. Dry matter yield in control treatments was 31.3 t/ha, and responses reached a maximum of 30% with the application of 150 kg N/ha/cut, but considering the economical rate, the better economic return occurs with the application of 115 kg N/ha/cut. As urea has a lower price per unit of N than ammonium nitrate, it seems to be the best choice of fertilizer. Further studies are needed to determine why the dry matter yields of forage were so high and in what seasons should N fertilizer be applied when resources are limited. Longer-term studies would confirm these findings and assess the losses of N to the atmosphere or by leaching, especially at the higher rates., RESUMEN Este estudio comparó los efectos de las formas de fertilizante nitrogenado (urea y nitrato de amonio) a tasas variables en el rendimiento y la calidad de Megathyrsus maximus cv. Mombasa. Las tasas de nitrógeno fueron 0, 50, 100, 150 y 200 kg N / ha después de cada cosecha mensual, es decir, 0, 150, 300, 450 y 600 kg N / ha / temporada. La forma de fertilizante N no afectó las respuestas en ningún parámetro, pero el aumento de las tasas de nitrógeno aumentó significativamente el rendimiento de materia seca y el porcentaje de proteína bruta, y disminuyó las concentraciones de FDN. Los rendimientos de materia seca en los trata mientos de control fueron de 31,3 t DM / ha y las respuestas alcanzaron un máximo del 30% con una aplicación de 150 kg N / ha / mes, pero en vista de la tasa económica, el mejor retorno económico se produce con la aplicación de 115 kg N / ha / mes. Como la urea es más barata por unidad de N que el nitrato de amonio, parece ser el fertilizante de elección. Se necesitan más estudios para determinar por qué los rendimientos básicos de forraje fueron tan altos y en qué estaciones se debe aplicar fertilizante con N cuando los recursos son limitados. Los estudios a más largo plazo confirmarían estos hallazgos y evaluarían las pérdidas de N en la atmósfera y mediante la lixiviación, especialmente en las tasas más altas.

The aim of the current study was to evaluate the ensiling characteristics of silages prepared from Guinea grass, Stylo legume or Stylo legume mixed with Guinea grass (50:50 w/w). Guinea grass and Stylo legume were harvested 45 and 60 days after regrowth, respectively and treated with a fermented juice of lactic acid bacteria (FJLB) prior to being ensiled. After 45 days, selected ensiling characteristics were determined. The nutritive value of rations based on the experimental silages was evaluated using six male, rumen cannulated crossbred Anglo Nubian × Native goats in a replicated 3 × 3 Latin square design study. Concentrate was provided at 0.9% body weight and experimental silages ad libitum. Apparent fecal macronutrient digestibility was determined. The pH values, NH3-N and lactic acid contents were not different between the silages but greater contents (P < 0.05) of acetic and butyric acid were found in the silage prepared from Guinea grass. Voluntary silage intake was similar for the three silages. Digestibility of dry and organic matter did not differ between treatments. However, the digestibility of crude protein, neutral detergent fiber and acid detergent fiber was greater (P < 0.05) when the rations contained silage from Stylo legume instead of Guinea grass. In conclusion, the process of fermentation of silages is similar for Stylo legume and Guinea grass. The feeding of rations based on silage from Stylo legume versus Guinea grass can enhance animal production due to its higher nutritive value.

Livestock production in the tropics is constrained by decline in quantity and quality of the predominant tropical grasses during the growing season. Incorporation of forage legumes into grassland agriculture has been used as a panacea to mitigate the problem. However, in tropical regions, not much of success has been achieved due to strong competitive ability of the grass which reduces the content of the companion legume. It is with this background that four experiments were conducted to evaluate the compatibility of grass-legume mixtures and their suitability for plantation livestock integration. An investigation into the nature of competition between Panicum maximum (guinea grass) and each of the following legumes of contrasting growth habits; Stylosanthes guianensis (stylo), Centrosema pubescens (centro) Macroptilium bracteatum (burgundy) and Arachis pintoi (arachis) showed that dry matter yield in guinea-centro mixtures (2:2 and 3:1) species combination tended to be higher than the corresponding grass monoculture (differences were not significant). Mean relative yield total values were higher in guinea-stylo (1.41) and guinea-centro (1.4) the values seemed to be higher at 2:2 species combination except in the case of guinea-burgundy. The climbing/trailing legume (centro) appeared to be more compatible with guinea grass especially at 2:2 species combination compared to the erect (stylo), erect/climbing (burgundy) and prostrate (arachis) legumes. Compatibility of forage mixtures evaluated at 50:50 species combination in relation to dry matter yield and chemical composition indicates that guinea-arachis produced significantly greater (P<0.01) cumulative total dry matter yield compared to other mixtures. However, the yield was not significantly different from that of guinea monoculture. The erect legume (stylo) produced significantly higher (P<0.01) cumulative total dry matter yield than arachis in mixture with guinea. Similarly, relative yield of stylo tended to be

Livestock production in the tropics is constrained by decline in quantity and quality of the predominant tropical grasses during the growing season. Incorporation of forage legumes into grassland agriculture has been used as a panacea to mitigate the problem. However, in tropical regions, not much of success has been achieved due to strong competitive ability of the grass which reduces the content of the companion legume. It is with this background that four experiments were conducted to evaluate the compatibility of grass-legume mixtures and their suitability for plantation livestock integration. An investigation into the nature of competition between Panicum maximum (guinea grass) and each of the following legumes of contrasting growth habits; Stylosanthes guianensis (stylo), Centrosema pubescens (centro) Macroptilium bracteatum (burgundy) and Arachis pintoi (arachis) showed that dry matter yield in guinea-centro mixtures (2:2 and 3:1) species combination tended to be higher than the corresponding grass monoculture (differences were not significant). Mean relative yield total values were higher in guinea-stylo (1.41) and guinea-centro (1.4) the values seemed to be higher at 2:2 species combination except in the case of guinea-burgundy. The climbing/trailing legume (centro) appeared to be more compatible with guinea grass especially at 2:2 species combination compared to the erect (stylo), erect/climbing (burgundy) and prostrate (arachis) legumes. Compatibility of forage mixtures evaluated at 50:50 species combination in relation to dry matter yield and chemical composition indicates that guinea-arachis produced significantly greater (P<0.01) cumulative total dry matter yield compared to other mixtures. However, the yield was not significantly different from that of guinea monoculture. The erect legume (stylo) produced significantly higher (P<0.01) cumulative total dry matter yield than arachis in mixture with guinea. Similarly, relative yield of stylo tended to be

In a series of five experiments carried out in growth cabinet and glasshouse environment, potted plants of Guinea grass (Panicum maximum Jacq.) cultivars were subjected to different cutting heights and environmental conditions. Herbage accumulation, leaf and tiller morphogenesis, leaf tissue turnover and tiller dynamics were evaluated. In one study three cultivars, Aruana, Mombaça and Tanzânia were grown for 18 months in miniature swards where plants were subjected to two defoliation heights (150 and 300mm), and productivity and tiller dynamics were evaluated. Cultivar and defoliation intensity effects on herbage production, leaf morphogenesis and tiller population density were observed. Herbage DM harvested from Mombaça was 32.3 and 31.7% more than Tanzânia and Aruana, respectively. There were also seasonal effects on tiller appearance rate and tiller death rate associated with flowering. A greater proportion of tillers flowered in cv. Tanzânia than cv. Mombaça. Two further experiments quantitatively described leaf turnover and associated morphogenetic characters in potted plants of the same three cultivars. One of these carried out in a growth cabinet included three defoliation regimes (50 mm, 200 mm, or uncut) and leaf turnover and the distribution of various tiller categories within the plants were measured. The other, carried out in a glass house, examined leaf turnover and site filling responses in undefoliated established plants. Higher temperature in the growth cabinet increased LAR, LER, FLL, and senescence and reduced site filling, LLS and NLL, and these effects were greater than cultivar effects. Severe defoliation (50 mm) initially resulted in increased tiller number per plant in all cultivars, but later decreased tiller number per plant through tiller death. The next experiment was established to determine limits of plasticity in potted plants of cv. Mombaça and cv. defoliation intensities (100, 200 and 400 mm height). Herbage growth and net accumulatio