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The objective of the research was to evaluate two initial availabilities (8200 and 14 500 kg of Dry Plant Matter per hectare) of Andropogon gayanus at a grazing pressure of 1100 LW/100kg DPM. The research was carried out at the Quilichao Experimental Substation, of the International Center for Tropical Agriculture (CIAT), at Cauca, Colombia. It was a completely random design, with four replications. Forage availability was measured by the double visual range method, 40 random observations were made, at the beginning, every two hours during the first six hours and then every four hours until reaching 72 hours, the residence time of the steers on the plot was three days. The six steers were zebu-type, weighing in average 350 kg of live weight. The results obtained show that there are statistical differences (P <0,05) between initial grazing pressures. In this sense, it is concluded that the lower initial availability of grass Andropogon gayanus correlates positively with leaf, stem, inflorescence and dead material percentage; while the correlation is inverse with the relationship between the stem and the leaf, the crude protein and ash. In addition, the discharge rate decreases when the grazing intensity increases., El objetivo de la investigación fue evaluar dos disponibilidades iniciales (8200 y 14 500 kg de MSV por hectárea) de Andropogon gayanus a una presión de pastoreo (1100 PV/100kg MSV). La investigación se realizó en la Subestación Experimental Quilichao del Centro Internacional de Agricultura Tropical (CIAT) en Cauca, Colombia. El diseño fue completamente al azar, con cuatro réplicas. La disponibilidad de forraje fue medida por el método de doble rango visual, se realizaron 40 observaciones al azar, al inicio, cada dos horas durante las primeras seis horas y luego cada cuatro horas hasta llegar a las 72 h, el tiempo de permanencia de los novillos en la parcela fue de tres días. Los seis novillos eran tipo cebú, de 350 kg de peso vivo en promedio. Los resultados obtenidos muestran que existen diferencias estadísticas (P< 0,05) entre presiones iniciales de pastoreo. En ese sentido, se concluye que a menor disponibilidad inicial la gramínea Andropogon gayanus se correlaciona positivamente con el porcentaje de hoja, tallo, inflorescencia y material muerto; mientras que la correlación es inversa con la relación del tallo con la hoja, la proteína cruda y la ceniza. Además, la tasa de descarga desciende cuando la intensidad de pastoreo se incrementa.

The objective of the research was to evaluate two initial availabilities (8200 and 14 500 kg of Dry Plant Matter per hectare) of Andropogon gayanus at a grazing pressure of 1100 LW/100kg DPM. The research was carried out at the Quilichao Experimental Substation, of the International Center for Tropical Agriculture (CIAT), at Cauca, Colombia. It was a completely random design, with four replications. Forage availability was measured by the double visual range method, 40 random observations were made, at the beginning, every two hours during the first six hours and then every four hours until reaching 72 hours, the residence time of the steers on the plot was three days. The six steers were zebu-type, weighing in average 350 kg of live weight. The results obtained show that there are statistical differences (P <0,05) between initial grazing pressures. In this sense, it is concluded that the lower initial availability of grass Andropogon gayanus correlates positively with leaf, stem, inflorescence and dead material percentage; while the correlation is inverse with the relationship between the stem and the leaf, the crude protein and ash. In addition, the discharge rate decreases when the grazing intensity increases., El objetivo de la investigación fue evaluar dos disponibilidades iniciales (8200 y 14 500 kg de MSV por hectárea) de Andropogon gayanus a una presión de pastoreo (1100 PV/100kg MSV). La investigación se realizó en la Subestación Experimental Quilichao del Centro Internacional de Agricultura Tropical (CIAT) en Cauca, Colombia. El diseño fue completamente al azar, con cuatro réplicas. La disponibilidad de forraje fue medida por el método de doble rango visual, se realizaron 40 observaciones al azar, al inicio, cada dos horas durante las primeras seis horas y luego cada cuatro horas hasta llegar a las 72 h, el tiempo de permanencia de los novillos en la parcela fue de tres días. Los seis novillos eran tipo cebú, de 350 kg de peso vivo en promedio. Los resultados obtenidos muestran que existen diferencias estadísticas (P< 0,05) entre presiones iniciales de pastoreo. En ese sentido, se concluye que a menor disponibilidad inicial la gramínea Andropogon gayanus se correlaciona positivamente con el porcentaje de hoja, tallo, inflorescencia y material muerto; mientras que la correlación es inversa con la relación del tallo con la hoja, la proteína cruda y la ceniza. Además, la tasa de descarga desciende cuando la intensidad de pastoreo se incrementa.

The objective of the research was to evaluate two initial availabilities (8200 and 14 500 kg of Dry Plant Matter per hectare) of Andropogon gayanus at a grazing pressure of 1100 LW/100kg DPM. The research was carried out at the Quilichao Experimental Substation, of the International Center for Tropical Agriculture (CIAT), at Cauca, Colombia. It was a completely random design, with four replications. Forage availability was measured by the double visual range method, 40 random observations were made, at the beginning, every two hours during the first six hours and then every four hours until reaching 72 hours, the residence time of the steers on the plot was three days. The six steers were zebu-type, weighing in average 350 kg of live weight. The results obtained show that there are statistical differences (P <0,05) between initial grazing pressures. In this sense, it is concluded that the lower initial availability of grass Andropogon gayanus correlates positively with leaf, stem, inflorescence and dead material percentage; while the correlation is inverse with the relationship between the stem and the leaf, the crude protein and ash. In addition, the discharge rate decreases when the grazing intensity increases., El objetivo de la investigación fue evaluar dos disponibilidades iniciales (8200 y 14 500 kg de MSV por hectárea) de Andropogon gayanus a una presión de pastoreo (1100 PV/100kg MSV). La investigación se realizó en la Subestación Experimental Quilichao del Centro Internacional de Agricultura Tropical (CIAT) en Cauca, Colombia. El diseño fue completamente al azar, con cuatro réplicas. La disponibilidad de forraje fue medida por el método de doble rango visual, se realizaron 40 observaciones al azar, al inicio, cada dos horas durante las primeras seis horas y luego cada cuatro horas hasta llegar a las 72 h, el tiempo de permanencia de los novillos en la parcela fue de tres días. Los seis novillos eran tipo cebú, de 350 kg de peso vivo en promedio. Los resultados obtenidos muestran que existen diferencias estadísticas (P< 0,05) entre presiones iniciales de pastoreo. En ese sentido, se concluye que a menor disponibilidad inicial la gramínea Andropogon gayanus se correlaciona positivamente con el porcentaje de hoja, tallo, inflorescencia y material muerto; mientras que la correlación es inversa con la relación del tallo con la hoja, la proteína cruda y la ceniza. Además, la tasa de descarga desciende cuando la intensidad de pastoreo se incrementa.

The objective of the research was to evaluate two initial availabilities (8200 and 14 500 kg of Dry Plant Matter per hectare) of Andropogon gayanus at a grazing pressure of 1100 LW/100kg DPM. The research was carried out at the Quilichao Experimental Substation, of the International Center for Tropical Agriculture (CIAT), at Cauca, Colombia. It was a completely random design, with four replications. Forage availability was measured by the double visual range method, 40 random observations were made, at the beginning, every two hours during the first six hours and then every four hours until reaching 72 hours, the residence time of the steers on the plot was three days. The six steers were zebu-type, weighing in average 350 kg of live weight. The results obtained show that there are statistical differences (P <0,05) between initial grazing pressures. In this sense, it is concluded that the lower initial availability of grass Andropogon gayanus correlates positively with leaf, stem, inflorescence and dead material percentage; while the correlation is inverse with the relationship between the stem and the leaf, the crude protein and ash. In addition, the discharge rate decreases when the grazing intensity increases., El objetivo de la investigación fue evaluar dos disponibilidades iniciales (8200 y 14 500 kg de MSV por hectárea) de Andropogon gayanus a una presión de pastoreo (1100 PV/100kg MSV). La investigación se realizó en la Subestación Experimental Quilichao del Centro Internacional de Agricultura Tropical (CIAT) en Cauca, Colombia. El diseño fue completamente al azar, con cuatro réplicas. La disponibilidad de forraje fue medida por el método de doble rango visual, se realizaron 40 observaciones al azar, al inicio, cada dos horas durante las primeras seis horas y luego cada cuatro horas hasta llegar a las 72 h, el tiempo de permanencia de los novillos en la parcela fue de tres días. Los seis novillos eran tipo cebú, de 350 kg de peso vivo en promedio. Los resultados obtenidos muestran que existen diferencias estadísticas (P< 0,05) entre presiones iniciales de pastoreo. En ese sentido, se concluye que a menor disponibilidad inicial la gramínea Andropogon gayanus se correlaciona positivamente con el porcentaje de hoja, tallo, inflorescencia y material muerto; mientras que la correlación es inversa con la relación del tallo con la hoja, la proteína cruda y la ceniza. Además, la tasa de descarga desciende cuando la intensidad de pastoreo se incrementa.

Traditional yam-based cropping systems (shifting cultivation, slash-and-burn, and short fallow) often result in deforestation and soil nutrient depletion. The objective of this study was to determine the impact of yam-based systems with herbaceous legumes on dry matter (DM) production (tubers, shoots), nutrients removed and recycled, and the soil fertility changes. We compared smallholders' traditional systems (1-year fallow of Andropogon gayanus-yam rotation, maize-yam rotation) with yam-based systems integrated herbaceous legumes (Aeschynomene histrix/maize intercropping-yam rotation, Mucuna pruriens/maize intercropping-yam rotation). The experiment was conducted during the 2002 and 2004 cropping seasons with 32 farmers, eight in each site. For each of them, a randomized complete block design with four treatments and four replicates was carried out using a partial nested model with five factors: Year, Replicate, Farmer, Site, and Treatment. Analysis of variance (ANOVA) using the general linear model (GLM) procedure was applied to the dry matter (DM) production (tubers, shoots), nutrient contribution to the systems, and soil properties at depths 0–10 and 10–20 cm. DM removed and recycled, total N, P, and K recycled or removed, and soil chemical properties (SOM, N, P, K, and pH water) were significantly improved on yam-based systems with legumes in comparison with traditional systems.

Traditional yam-based cropping systems (shifting cultivation, slash-and-burn, and short fallow) often result in deforestation and soil nutrient depletion. The objective of this study was to determine the impact of yam-based systems with herbaceous legumes on dry matter (DM) production (tubers, shoots), nutrients removed and recycled, and the soil fertility changes. We compared smallholders' traditional systems (1-year fallow of Andropogon gayanus-yam rotation, maize-yam rotation) with yam-based systems integrated herbaceous legumes (Aeschynomene histrix/maize intercropping-yam rotation, Mucuna pruriens/maize intercropping-yam rotation). The experiment was conducted during the 2002 and 2004 cropping seasons with 32 farmers, eight in each site. For each of them, a randomized complete block design with four treatments and four replicates was carried out using a partial nested model with five factors: Year, Replicate, Farmer, Site, and Treatment. Analysis of variance (ANOVA) using the general linear model (GLM) procedure was applied to the dry matter (DM) production (tubers, shoots), nutrient contribution to the systems, and soil properties at depths 0–10 and 10–20 cm. DM removed and recycled, total N, P, and K recycled or removed, and soil chemical properties (SOM, N, P, K, and pH water) were significantly improved on yam-based systems with legumes in comparison with traditional systems.

The social, economic, and environmental impacts of invasive plants are well recognized. However, these variable impacts are rarely accounted for in the spatial prioritization of funding for weed management. We examine how current spatially explicit prioritization methods can be extended to identify optimal budget allocations to both eradication and control measures of invasive species to minimize the costs and likelihood of invasion. Our framework extends recent approaches to systematic prioritization of weed management to account for multiple values that are threatened by weed invasions with a multi-year dynamic prioritization approach. We apply our method to the northern portion of the Daly catchment in the Northern Territory, which has significant conservation values that are threatened by gamba grass (Andropogon gayanus), a highly invasive species recognized by the Australian government as a Weed of National Significance (WONS). We interface Marxan, a widely applied conservation planning tool, with a dynamic biophysical model of gamba grass to optimally allocate funds to eradication and control programs under two budget scenarios comparing maximizing gain (MaxGain) and minimizing loss (MinLoss) optimization approaches. The prioritizations support previous findings that a MinLoss approach is a better strategy when threats are more spatially variable than conservation values. Over a 10-year simulation period, we find that a MinLoss approach reduces future infestations by ~8% compared to MaxGain in the constrained budget scenarios and ~12% in the unlimited budget scenarios. We find that due to the extensive current invasion and rapid rate of spread, allocating the annual budget to control efforts is more efficient than funding eradication efforts when there is a constrained budget. Under a constrained budget, applying the most efficient optimization scenario (control, minloss) reduces spread by ~27% compared to no control. Conversely, if the budget is unlimited it

Effective fire management relies on the ability to assess the potential risk that a fire event poses to the community so that fire managers can ensure sufficient resources are available to respond to unplanned fires. Fuel loads are a major contributor to fire risk and any significant changes to fuel load should be incorporated into fire risk models. An example is the invasion of Australia’s tropical savannas by the high biomass African grass Andropogon gayanus Kunth (gamba grass). Fine fuel load (grass and twigs <6 mm) in a heavily invaded landscape has increased from 6 to 10 t ha−1. Consequently, in 2010, the Bureau of Meteorology created two 20 km 2 radius ‘primary response zones’, which are defined areas of dense invasion in the greater Darwin region in which fire risk is assessed using an estimate of increased fuel load. In this paper, we quantify the effect of the increased (invaded) fuel load on the assessment of fire risk. We do this by modelling the daily McArthur Mark 4 Grassland Fire Danger Index (GFDI) for the fire seasons in 2012 and 2013 using both native (6 t ha−1) and invaded fuel loads. We show that the number of days with GFDI >50 (the threshold for fire weather warnings and fire bans) has increased and the length of the severe-risk fire season has extended, resulting in substantial increases in fire management costs. This has safety and resource implications for fire manage-ment agencies as the area of invasion increases across northern Australia.

1992

1983

The effects of different irrigation levels and nitrogen rates on the dry matter (DM) yield, nitrogen use efficiency and bromatological composition of andropogon grass (Andropogon gayanus 'Planaltina') were evaluated. The experiment consisted in a completely randomized block design, with three repetitions, with 2x4 factorial arran- gement, being two irrigation levels (50% and 80% of evaporation of the Class A evaporation: ECA) and four N levels (200, 400, 600 and 800 kg/ha/ year) applied as urea, divided in function of the cuts number (16.7, 33.3, 50.0 e 66.7 kg/ha/month). The water supply applied presented similar behaviors in relationship to the total dry matter productivity, leaves and stems. The water supply of 80% ECA provided the smaller leaf/stem ratio. The nitrogen fertilization influenced positively the total dry matter productivity, leaves and stems productivities however, the leaf/stem ratio and nitrogen use efficiency decreased. The crude protein contents of leaves and culms were not affected by water supply, but were increased by N fertilization. The NDF and ADF contents were negatively influenced by the largest water supply. The 50% of ECA irrigation presented the best results, associated to the application of 800 kg of N/ha/year, considering the productivity, broma- tological composition and the possibility of economy of water, with consequent reduction in the costs of herbage production., Foram avaliados os efeitos de diferentes lâminas de irrigação e doses de nitrogênio sobre a produção, eficiência do uso do nitrogênio e composição bromatológica do capim-andropogon (Andropogon gayanus 'Planaltina'). O delineamento experimental foi em blocos casualizados, num esquema fatorial 2x4, com três repetições; sendo dois níveis de irrigação (50% e 80% da evaporação do Tanque Classe A, ECA) e quatro níveis de N (200, 400, 600 e 800 kg/ha/ano) aplicados na forma de uréia e fracionados em função do núme- ro de cortes (16,7; 33,3; 50,0 e 66,7 kg de N/ha/ mês). As lâminas de irrigação aplicadas apresentaram comportamentos semelhantes em relação à produtividade de matéria seca total, de folhas e colmos. A lâmina de 80% de ECA proporcionou menor relação folha/colmo. A adubação nitrogenada influenciou positivamente a produtividade de matéria seca total, de folhas e colmos, no entanto, diminuiu a relação folha/colmo e a eficiência de utilização do nitrogênio. Os teores de proteína bruta das folhas e colmos não foram influenciados pelas lâminas de irrigação aplica- das, mas aumentou linearmente com a adubação nitrogenada. Os teores de FDN e FDA apre- sentaram influência negativa da maior lâmina de irrigação. A irrigação de 50% de ECA, associada à aplicação de 800 kg de N/ha/ano, apresentou os melhores resultados, considerando-se a pro- dutividade, relação folha/colmo, composição bromatológica e a possibilidade de economia de água, com conseqüente redução nos custos de produção da forragem.

The effects of different irrigation levels and nitrogen rates on the dry matter (DM) yield, nitrogen use efficiency and bromatological composition of andropogon grass (Andropogon gayanus 'Planaltina') were evaluated. The experiment consisted in a completely randomized block design, with three repetitions, with 2x4 factorial arran- gement, being two irrigation levels (50% and 80% of evaporation of the Class A evaporation: ECA) and four N levels (200, 400, 600 and 800 kg/ha/ year) applied as urea, divided in function of the cuts number (16.7, 33.3, 50.0 e 66.7 kg/ha/month). The water supply applied presented similar behaviors in relationship to the total dry matter productivity, leaves and stems. The water supply of 80% ECA provided the smaller leaf/stem ratio. The nitrogen fertilization influenced positively the total dry matter productivity, leaves and stems productivities however, the leaf/stem ratio and nitrogen use efficiency decreased. The crude protein contents of leaves and culms were not affected by water supply, but were increased by N fertilization. The NDF and ADF contents were negatively influenced by the largest water supply. The 50% of ECA irrigation presented the best results, associated to the application of 800 kg of N/ha/year, considering the productivity, broma- tological composition and the possibility of economy of water, with consequent reduction in the costs of herbage production., Foram avaliados os efeitos de diferentes lâminas de irrigação e doses de nitrogênio sobre a produção, eficiência do uso do nitrogênio e composição bromatológica do capim-andropogon (Andropogon gayanus 'Planaltina'). O delineamento experimental foi em blocos casualizados, num esquema fatorial 2x4, com três repetições; sendo dois níveis de irrigação (50% e 80% da evaporação do Tanque Classe A, ECA) e quatro níveis de N (200, 400, 600 e 800 kg/ha/ano) aplicados na forma de uréia e fracionados em função do núme- ro de cortes (16,7; 33,3; 50,0 e 66,7 kg de N/ha/ mês). As lâminas de irrigação aplicadas apresentaram comportamentos semelhantes em relação à produtividade de matéria seca total, de folhas e colmos. A lâmina de 80% de ECA proporcionou menor relação folha/colmo. A adubação nitrogenada influenciou positivamente a produtividade de matéria seca total, de folhas e colmos, no entanto, diminuiu a relação folha/colmo e a eficiência de utilização do nitrogênio. Os teores de proteína bruta das folhas e colmos não foram influenciados pelas lâminas de irrigação aplica- das, mas aumentou linearmente com a adubação nitrogenada. Os teores de FDN e FDA apre- sentaram influência negativa da maior lâmina de irrigação. A irrigação de 50% de ECA, associada à aplicação de 800 kg de N/ha/ano, apresentou os melhores resultados, considerando-se a pro- dutividade, relação folha/colmo, composição bromatológica e a possibilidade de economia de água, com conseqüente redução nos custos de produção da forragem.

Introduced African grasses are invading the tropical savannas of northern Australia and displacing native grasses. Andropogon gayanus Kunth. (Gamba grass) was introduced into the Northern Territory as a pasture species, but has now established outsideof pastoral properties and is considered an environmental weed in the savannas of the Northern Territory. We found that, compared with sites dominated by native grasses, sites invaded by gamba grass had (1) increased fire intensities by more than threetimes; (2) reduced available soil nitrate levels by 70%; (3) trebled grass water use; and (4) more than halved deep drainage of water. Gamba grass therefore has the ability to out-compete native species, and alter catchment hydrology to the detriment of wetlands and streams.

The control of two exotic grasses, Andropogon gayanus (gamba grass) and Pennisetum polystachion (mission grass) represent a major management challenge in Australia's tropical savannas. Understanding the size and longevity of the soil seed bank can assist in understanding the management requirements for these species, such as on-going control requirements. This study assessed the seed longevity of mission and gamba grasses, and the seed bank in sites densely invaded by either gamba or by mission grass, and compared them with uninvaded sites. The germinable seed bank of the exotic grasses declines markedly from the dry season to the early wet season, whereas the germinable native seed bank increases during this time. Longevity trials suggest that the proportion of exotic seeds carried over is low, ~2.3 and 0.1% for gamba and mission grass, respectively. The carryover of the exotic seed bank demonstrates the importance of ongoing control. The seed bank of native species in the invaded sites was higher than the exotic seed bank, and it represents a natural source of seed for rehabilitation following control.

L'étude floristique de différents types de jachère dans des zones à forte et à faible densité de population montre que la valeur de ces herbages est très variable. L'âge de la jachère n'est pourtant pas le facteur principal. L'exploitation pastorale permanente, en bloquant l'évolution naturelle progressive, et en maintenant les jachères à un niveau de dégradation extrême qui empêche la reconstitution du sol, apparaît comme le facteur décisif. Cependant, la mise en défens momentanée de ces jachères pendant 1 à 4 ans, suivie d'une gestion pastorale adaptée, permet d'accroître globalement la productivité fourragère du terroir tout en rehaussant le niveau de fertilité du sol.

L'étude floristique de différents types de jachère dans des zones à forte et à faible densité de population montre que la valeur de ces herbages est très variable. L'âge de la jachère n'est pourtant pas le facteur principal. L'exploitation pastorale permanente, en bloquant l'évolution naturelle progressive, et en maintenant les jachères à un niveau de dégradation extrême qui empêche la reconstitution du sol, apparaît comme le facteur décisif. Cependant, la mise en défens momentanée de ces jachères pendant 1 à 4 ans, suivie d'une gestion pastorale adaptée, permet d'accroître globalement la productivité fourragère du terroir tout en rehaussant le niveau de fertilité du sol.

La culture irriguée de certaines graminées réputées à hauts rendements fourragers implique en premier lieu le choix d'un matériel végétal sélectionné et l'adoption d'une technologie d'exploitation permettant à ces plantes d'exprimer leurs potentialités et de fournir leurs meilleurs rendements. Cette étude a permis de mettre en évidence l'importance particulière de certaines techniques culturales, parmi lesquelles les apports en éléments minéraux et le rythme de l'exploitation semblent les plus importants, si l'on veut maximiser la production fourragère et l'efficience de l'utilisation de l'eau. Les résultats obtenus pendant 5 années consécutives ont montré le rôle particulier d'une fumure azotée suffisante. Ils ont également permis de mettre en évidence l'intérêt particulier des Panicum maximum

L'action des techniques culturales, mises en oeuvre pour maximiser la production fourragère et l'efficience de l'utilisation de l'eau, doit non seulement se manifester sur le plan quantitatif, mais également sur la qualité nutritive et la valeur alimentaire des fourrages produits. Les observations effectuées au Sénégal pendant plusieurs années consécutives ont pu montrer que la double action d'une fumure minérale suffisante (azotée en particulier) et l'établissement d'un calendrier d'exploitation rationnel permettent non seulement d'élever et de régulariser la production fourragère, mais aussi ses qualités alimentaires et nutritionnelles. Dans ce domaine, l'utilisation des Panicum maximum ne doit pas simplement être basée sur les performances productives des lignées sélectionnées, mais aussi sur leurs qualités bromatologiques

La culture irriguée de certaines graminées réputées à hauts rendements fourragers implique en premier lieu le choix d'un matériel végétal sélectionné et l'adoption d'une technologie d'exploitation permettant à ces plantes d'exprimer leurs potentialités et de fournir leurs meilleurs rendements. Cette étude a permis de mettre en évidence l'importance particulière de certaines techniques culturales, parmi lesquelles les apports en éléments minéraux et le rythme de l'exploitation semblent les plus importants, si l'on veut maximiser la production fourragère et l'efficience de l'utilisation de l'eau. Les résultats obtenus pendant 5 années consécutives ont montré le rôle particulier d'une fumure azotée suffisante. Ils ont également permis de mettre en évidence l'intérêt particulier des Panicum maximum

L'action des techniques culturales, mises en oeuvre pour maximiser la production fourragère et l'efficience de l'utilisation de l'eau, doit non seulement se manifester sur le plan quantitatif, mais également sur la qualité nutritive et la valeur alimentaire des fourrages produits. Les observations effectuées au Sénégal pendant plusieurs années consécutives ont pu montrer que la double action d'une fumure minérale suffisante (azotée en particulier) et l'établissement d'un calendrier d'exploitation rationnel permettent non seulement d'élever et de régulariser la production fourragère, mais aussi ses qualités alimentaires et nutritionnelles. Dans ce domaine, l'utilisation des Panicum maximum ne doit pas simplement être basée sur les performances productives des lignées sélectionnées, mais aussi sur leurs qualités bromatologiques