Abstract The estimation of aerial biomass of grasses contributes to carrying out efficient and sustainable management of rangelands. This study aimed to generate new equations to estimate the aerial biomass of grasses present in rangelands in Nuevo León, Mexico, based on data collected from the total number (n= 745) of individuals of the five species of grasses: Cenchrus ciliaris Linnaeus, Pappophorum bicolor Fourn, Aristida purpurea Nutt, Tridens texanus Watson and Paspalum pubiflorum Fourn present in the sampling plots. Using the maximum height and the height of the vegetative stems, the aerial, basal, and compressed diameters, and volumes measured in each of the collected individuals, linear (stepwise) and nonlinear equations were generated to estimate the aerial biomass (dry matter basis) of the grasses cut at ground level. Six general equations with the best statistical fit for the total species collected were selected. General equation III had the best values of R2 =0.88 and AIC =3079, using the five variables evaluated. General equation IV had an R2 =0.86 and AIC =3530, using only the variable compressed diameter. The selected specific equations estimated the aerial biomass of the grasses Cenchrus ciliaris (R2=0.88, r=0.94), Pappophorum bicolor (R2 =0.86, r =0.92), Aristida purpurea (R2=0.92, r=0.96), Tridens texanus (R2 =0.91, r =0.96), and Paspalum pubiflorum (R2 =0.93, r = 0.97). The new equations are a reliable alternative to indirectly estimate the aerial biomass of the grasses of the rangelands of northeastern Mexico in a faster and less expensive manner than the traditional method.

Resumen La estimación de biomasa aérea de pastos contribuye a realizar un manejo eficiente y sostenible de los agostaderos. El objetivo del presente estudio fue generar nuevas ecuaciones para estimar la biomasa aérea de pastos presentes en agostaderos, en Nuevo León, México, basado en datos colectados del total (n=745) de los individuos de las cinco especies de pastos: Cenchrus ciliaris Linnaeus, Pappophorum bicolor Fourn, Aristida purpurea Nutt, Tridens texanus Watson y Paspalum pubiflorum Fourn presentes en las parcelas de muestreo. Utilizando la altura máxima y la de los tallos vegetativos, los diámetros aéreo, basal y comprimido, y volúmenes medidos en cada uno de los individuos colectados, se generaron ecuaciones lineales (stepwise) y no lineales, para estimar la biomasa aérea (base materia seca) de los pastos cortados a ras de suelo. Se seleccionaron seis ecuaciones generales con el mejor ajuste estadístico para el total de las especies colectadas. La ecuación general III tuvo los mejores valores de R2=0.88 y AIC=3079, utilizando las cinco variables evaluadas. La ecuación general IV estimó con R2=0.86 y AIC= 3530, utilizando solo la variable de diámetro comprimido. Las ecuaciones específicas seleccionadas estimaron la biomasa aérea de los pastos Cenchrus ciliaris (R2=0.88, r=0.94), Pappophorum bicolor (R2=0.86, r=0.92), Aristida purpurea (R2=0.92, r=0.96), Tridens texanus (R2=0.91, r=0.96), y Paspalum pubiflorum (R2=0.93, r=0.97). Las nuevas ecuaciones son una alternativa confiable para estimar indirectamente la biomasa aérea de los pastos de los agostaderos del noreste de México, de forma más rápida y menos costosa que el método tradicional.

Resumen Introducción. Los pastos son la principal fuente de alimento en los sistemas ganaderos y pueden ser un nicho adecuado para insectos con funciones beneficiosas y dañinas. Objetivo. Estimar la entomofauna asociada a tres especies de pastos, Cenchrus ciliaris, Chloris gayana y Megathyrsus maximus, en condiciones del Caribe colombiano. Materiales y métodos. Se realizaron diez muestreos en dos estaciones contrastantes, de baja y alta precipitación (agosto a octubre de 2018 y enero a marzo de 2019), se utilizaron tres especies forrajeras (Cenchrus ciliaris, Megathyrsus maximus, Chloris gayana), en un área de 1000 m2. Los artrópodos fueron identificados por orden y familia y tipificados por grupos funcionales. Se estimaron índices de diversidad y abundancia por pastos y estaciones, así como su correlación con el clima. Se realizó un análisis de correspondencia simple. Resultados. Se recolectaron 380 insectos de siete órdenes y 35 familias, con mayor abundancia para Hemiptera y Coleoptera. El índice de diversidad de Shannon fue más alto para todos los órdenes de C. gayana, excepto para Hemiptera en C. ciliaris. Los fitófagos se encontraron en mayor porcentaje (66,84 %), seguidos de los depredadores (27,11 %). La abundancia de insectos estuvo influenciada por la interacción entre la estación y el pasto, mostró un incremento a bajas temperaturas, excepto para M. maximus. Los pastos representaron microambientes adecuados para mantener la diversidad de insectos, los órdenes Hemiptera y Coleoptera fueron los más numerosos y representativos de los grupos funcionales fitófagos y depredadores, respectivamente. Conclusión. La entomofauna de C. gayana, C. ciliaris y M. maximus fue similar en abundancia y diversidad de insectos, sin embargo, la abundancia dependió de la influencia de la estación y de los pastos.

Abstract Introduction. Pastures are the primary source of food in livestock systems and can be a suitable niche for insects with beneficial and harmful functions. Objective. To estimate the entomofauna associated with three species of pastures, Cenchrus ciliaris, Chloris gayana, and Megathyrsus maximus, in conditions of the Colombian Caribbean. Materials and methods. Ten samplings were carried out in two contrasting periods (August to October 2018 and January to March 2019), three forage species (Cenchrus ciliaris, Megathyrsus maximus, Chloris gayana) within 1000 m2 were used. Arthropods were identified by order and family and typified by functional groups. Diversity and abundance indices by pasture and season were estimated, as well as their correlation with climate. A simple correspondence analysis was performed. Results. A total of 380 insects from 7 orders and 35 families were collected, with the greatest abundance for Hemiptera and Coleoptera. The Shannon’s diversity index was higher for all orders of C. gayana, except for Hemiptera in C. ciliaris. Phytophages were found in a higher percentage (66.84 %), followed by predators (27.11 %). Insect abundance was influenced by the interaction between season and pasture, showing an increase at low temperatures, except for M. maximus. Pastures represented adequate microenvironments to maintain the diversity of insects, the Hemiptera and Coleoptera orders being the most numerous and representative of the functional groups of phytophages and predators, respectively. Conclusion. The entomofauna of C. gayana, C. ciliaris, and M. maximus was similar in insect abundance and diversity, however, insect abundance depended on the influence of the season and pastures.

Resumen Antecedentes: La alteración del reservorio de carbono, tiene implicación en la modificación a los ciclos biogeoquímicos. El cambio de uso y cobertura de suelo (CUCS) es uno de los principales precursores de estas alteraciones. Como consecuencia de las actividades primarias que ocurren en zonas áridas, los reservorios de carbono son continuamente modificados. La poca información y heterogeneidad de estas zonas incrementan la incertidumbre sobre los efectos en la dinámica del carbono por CUCS. El desarrollo de nuevas metodologías, como la incorporación del análisis de imágenes aéreas RGB (rojo/verde/azul) de alta-resolución, permitirá monitorear extensiva y continuamente el carbono en zonas áridas. Preguntas: ¿Es posible estimar almacén de carbono aéreo utilizando imágenes RGB obtenidas mediante vehículos aéreos no tripulados? Sitio y años de estudio: Comunidades de matorral subtropical y pradera de buffel localizadas en la región central de Sonora, México. Agosto-octubre, 2019 y 2020. Métodos: a) Se realizaron censos de vegetación leñosa in situ, para estimar almacén de carbono en biomasa aérea (ACBA) con ecuaciones alométricas (método directo), b) Se calculó ACBA, utilizando ecuaciones alometricas y métricas de vegetación obtenidas de imágenes RGB (método indirecto). Resultados: La introducción de buffel implica la reducción de individuos leñosos, y disminución del ACBA. En total, el matorral contiene 10.35 Mg C/ha, y la pradera 3.20 Mg C/ha. Se encontró correlación y significancia entre método directo e indirecto. Conclusiones: Establecer buffel, reduce el ACBA hasta un 70 %. El uso de imágenes RGB permitió estimar ACBA en zonas áridas/semiáridas.

Abstract Background: The alteration of the carbon reservoir stored in vegetation, imply the modification of biogeochemical cycles. The change of land use and cover (CUCS) is one of the main drivers for these alterations. As a consequence of the primary activities occurring in arid/semiarid lands, carbon reservoirs are continually modified. The limited information and heterogeneity of these environments increase the uncertainty regarding the effects on carbon dynamics consequence of CUCS. The development of new methodological approaches, such as the incorporation of aerial high-resolution RGB (red/green/blue) imagery analyses, will allow extensive and continuous monitoring of carbon in arid zones. Questions: Is it possible to estimate aboveground carbon stock using RGB images obtained by Unmanned Aerial Vehicles? Site and years of study: Subtropical scrub and buffel grassland communities, located in the central Sonora, Mexico. August-October 2019 and 2020. Methods: a) In situ woody vegetation censuses were carried out to estimate carbon stock in aerial biomass (ACBA) using allometric equations (direct method), b) ACBA was calculated, using allometric equations and vegetation metrics obtained from aerial RGB images. Results: The introduction of buffel grassland implies the reduction of woody individuals, therefor, a decrease in ACBA. In total, the scrub contains 10.35 Mg C/ha, and buffel grassland around 3.20 Mg C/ha. There are correlation and significance between direct and indirect methods. Conclusions: Establishing buffel grassland reduces the ACBA, up to 70 %. The use of RGB images allowed us to estimate ACBA in arid zones.

Resumen En el trópico mexicano la ganadería está basada en sistemas de producción extensivos y es importante conocer el contenido nutricional de los forrajes, por ello el objetivo del presente estudio fue evaluar la composición química de: Cenchrus ciliaris L., Megathyrsus maximus cv Guinea, Ixophorus unisetus y Megathyrsus maximus cv Tanzania, gramíneas establecidas y utilizadas con frecuencia en el trópico para la alimentación animal. Las muestras provenientes del Rancho ‘San Luis Tenango’, Tonaya, Jalisco se analizaron en el Laboratorio de Nutrición Animal, Departamento de Zootecnia, Universidad Autónoma Chapingo. Se determinó: cenizas (Cen), proteína cruda (PC), extracto etéreo (EE), fibra detergente neutro (FDN), contenido celular (CC), fibra detergente ácido (FDA) y celulosa (Cel). El análisis de los datos se hizo con tres repeticiones y cada repetición se consideró una unidad experimental. Se realizaron la correlación de Pearson y la separación de medias por Tukey (p< 0.05). La PC resultó correlacionada positivamente con Cen y CC y negativamente con FDN y FDA (p< 0.05). Megathyrsus maximus cv Guinea fue la especie forrajera con mayor cantidad de PC (12.9 g (100 g)-1), seguida por (p< 0.05) Megathyrsus maximus cv Tanzania (8.7 g (100 g)-1). Megathyrsus maximus cv Guinea mostró el mayor porcentaje de Cen, 11.7 g (100 g)-1 y los valores más bajos valores de FDA y Cel y su valor de FDN (74.8 g (100 g)-1) fue bajo (p< 0.05), levemente superior al de Ixophorus unisetus (73.5 g (100 g)-1). Por tanto, Megathyrsus maximus cv Guinea fue la gramínea con mayor valor nutricional.

Abstract In the Mexican tropics, livestock farming is based on extensive production systems, and it is important to know the nutritional content of forages, therefore the objective of this study was to evaluate the chemical composition of: Cenchrus ciliaris L., Megathyrsus maximus cv Guinea, Ixophorus unisetus and Megathyrsus maximus cv Tanzania, grasses established and frequently used in the Tropics for animal feed. The samples from the locality ‘San Luis Tenango’, Tonaya, Jalisco were analyzed at the Laboratory of Animal Nutrition, Department of Zootechnics, Chapingo Autonomous University. The following was determined: ashes (Ash), crude protein (CP), ethereal extract (EE), neutral detergent fiber (NDF), cellular content (CC), acid detergent fiber (ADF) and cellulose (Cel). Data analysis was performed with three repetitions and each repetition was considered an experimental unit. Pearson’s correlation and the separation of means by Tukey (p< 0.05) were performed. CP was positively correlated with Ash and CC and negatively correlated with NDF and ADF (p< 0.05). Megathyrsus maximus cv Guinea was the forage species with the highest amount of CP (12.9 g (100 g)-1), followed by (p< 0.05) Megathyrsus maximus cv Tanzania (8.7 g (100 g)-1). Megathyrsus maximus cv Guinea showed the highest percentage of Ash, 11.7 g (100 g)-1 and the lowest values of ADF and Cel and its NDF value (74.8 g (100 g)-1) was low (p< 0.05), slightly higher than that of Ixophorus unisetus (73.5 g (100 g)-1). Therefore, Megathyrsus maximus cv Guinea was the grass with the highest nutritional value.

RESUMO No cenário das mudanças climáticas, o estudo das emissões de gases do efeito estufa (GEE) e de medidas de mitigação na Caatinga são estratégicos e podem fornecer a base para planos de mitigação. Objetivou-se avaliar os fluxos de CO2, CH4 e N2O do solo, bem como determinar uma linha de base anual para as emissões de GEE, em um sistema de produção silvipastoril de referência no semiárido brasileiro, a fim de fornecer subsídios para estudos futuros de mitigação das emissões de GEE. Os fluxos de GEE foram monitorados durante um ano, em pastagem de capim buffel e em área de Caatinga pastejada e nativa, as quais são componentes de um sistema silvipastoril de longa duração. Os fluxos de CO2 variaram de -19,98 a 179,12 mg m-2 h-1 de C-CO2, os de CH4 de -76,21 a 113,87 µg m-2 h-1 de C-CH4, os de N2O de -1.043,12 a 471,37 µg m-2 h-1 de N-N2O e a umidade do solo foi o principal fator limitante para os fluxos de GEE. As emissões totais convertidas para CO2-equivalente nas áreas antropizadas foram menores que na área de vegetação nativa (65 % para o capim buffel e 741 % para a Caatinga pastejada). Portanto, pode-se afrmar que as emissões de GEE nas áreas pastejadas no bioma Caatinga não são tão altas quanto na Caatinga nativa, o que é um importante indicador da sustentabilidade ambiental do sistema silvipastoril avaliado.

ABSTRACT In the climate change scenario, studying greenhouse gases (GHG) emissions and measures of mitigation in the Caatinga biome are strategic and may provide a basis for mitigation plans. This study aimed to evaluate the soil CO2, CH4 and N2O fluxes, as well as determining an annual baseline for GHG emissions, in a reference site of silvopastoral production system in the Brazilian semiarid region, in order to provide subsidies for future studies on GHG emissions mitigation. The GHG fluxes were monitored over one year, in a buffel grass pasture and in grazed and native Caatinga areas, which are components of a long-term silvopastoral system. The CO2 fluxes ranged from -19.98 to 179.12 mg m-2 h-1 of CO2-C, CH4 fluxes from -76.21 to 113.87 µg m-2 h-1 of CH4-C, N2O fluxes from -1,043.12 to 471.37 µg m-2 h-1 of N2O-N and the soil moisture was the main factor limiting the GHG fluxes. The total emissions converted to CO2-equivalent in the anthropized areas were lower than in the native area (65 % for the buffel grass pasture and 741 % for the grazed Caatinga). Therefore, it is possible to afrm that the GHG soil emissions from grazed areas in the Caatinga biome are not as high as in the native Caatinga, what is an important indication of the environmental sustainability of the evaluated silvopastoral system.

RESUMO O silvopastura permite a diversificação da produção e o aumento dos benefícios econômicos, sociais e ambientais para os utentes do solo, pois é um manejo integrado de árvores, pastagens e gado que constitui uma das melhores opções a serem implementadas no Chaco Paraguaio, devido à pecuária e a uma estrutura florestal existente. Esta pesquisa foi realizada em propriedades privadas nos departamentos de Boquerón e Presidente Hayes na Região Ocidental do Paraguai, com o objetivo de determinar o teor de nitrogênio no solo de sistemas silvopastoris associados a Prosopis spp. (alfarrobo). Foram estabelecidas oito parcelas de 1,0 ha cada, nas quais todas as alfarrobeiras foram medidas para a estimativa da biomassa florestal, a partir de amostras de pastagens sob e fora da copa das árvores onde, além disso, foram extraídas amostras de solo em profundidades de 0-10 cm e 10-30 cm para determinar o teor de nitrogênio, estimado a partir da matéria orgânica do solo. Nos inventários florestais foram identificados indivíduos da família Fabaceae, seguidos pelas famílias Apocynaceae, Bignonaceae, Capparaceae, Rhamnaceae, Sapotaceae e Zhygophyllacea, sendo o gênero Prosopis (alfarroba) o mais abundante associado às pastagens das espécies Megathyrsus maximus, Digitaria decumbens e Cenchrus ciliaris. Conclui-se que não há diferenças significativas no teor de nitrogênio nos solos dos sistemas silvopastoris entre as duas condições de insolação estudadas, mas entre as duas profundidades, concentrando-se nos primeiros 10 centímetros.

ABSTRACT Silvopasture allows the diversification of production and the increase of economic, social and environmental benefits for land users, since it is an integrated management of trees, pasture and livestock, which constitutes one of the best options to be implemented in the Paraguayan Chaco, due to livestock and an existing forest structure. This research was carried out in private properties in the Departments of Boquerón and Presidente Hayes, in the Western Region of Paraguay, with the objective of determining the nitrogen content in the soil of silvopastoral systems associated with Prosopis spp. (carob tree). Eight plots of 1.0 ha each were established, in which all the carob trees were measured for the estimation of forest biomass, from samples of pastures under and outside the canopy of the trees where, in addition, soil samples were extracted at depths of 0-10 cm and 10-30 cm to determine the nitrogen content, estimated from soil organic matter. In the forest inventories, individuals of the Fabaceae family were identified, followed by the Apocynaceae, Bignonaceae, Capparaceae, Rhamnaceae, Sapotaceae and Zhygophyllacea families, with the Prosopis genus (carob) being the most abundant, associated with pastures of Megathyrsus maximus, Digitaria decumbens and Cenchrus ciliaris species. It is concluded that there are no significant differences in nitrogen content in the soils of silvopastoral systems between the two conditions of insolation studied, but between the two depths, concentrating in the first 10 centimeters.

RESUMEN La silvopastura permite la diversificación de la producción y el incremento de los beneficios económicos, sociales y ambientales para los usuarios del suelo, pues se trata de un manejo integrado de árboles, pastura y ganado, que constituye una de las mejores opciones para ser implementadas en el Chaco paraguayo, debido a la ganadería y a una estructura forestal existente. Esta investigación se realizó en propiedades privadas de los Departamentos Boquerón y Presidente Hayes, de la Región Occidental de Paraguay, con el objetivo de determinar el contenido de nitrógeno en el suelo de sistemas silvopastoriles asociados a Prosopis spp. (algarrobo). Se establecieron ocho parcelas de 1,0 ha cada una, en las cuales se midieron todos los algarrobos para la estimación de biomasa forestal, a partir de muestras de pasturas bajo y fuera de la copa de los árboles donde, además, se extrajeron muestras de suelos a profundidades de 0-10 cm y de 10-30 cm para determinar el contenido de nitrógeno, estimado a partir de la materia orgánica del suelo. En los inventarios forestales fueron identificados individuos de la familia Fabaceae, seguidos por las familias Apocynaceae, Bignonaceae, Capparaceae, Rhamnaceae, Sapotaceae y Zhygophyllacea, siendo el género Prosopis (algarrobo) el más abundante asociadas con pasturas de las especies de Megathyrsus maximus, Digitaria decumbens y Cenchrus ciliaris. Se concluye que no existen diferencias significativas en cuanto al contenido de nitrógeno en los suelos de sistemas silvopastoriles entre las dos condiciones de insolación estudiadas, pero si entre las dos profundidades concentrándose en los diez primeros centímetros.

ABSTRACT. The objective of this study was to evaluate the production and chemical composition of three forage species at different regrowth intervals. A 3 x 4 randomized-block factorial design with three forage species (Andropogon, Buffel, and Massai) and four regrowth intervals (21, 35, 49, and 63 days) was used. There was no interaction (p > 0.05) between forage species and regrowth interval on any of the chemical components evaluated. The crude protein content decreased but the contents of neutral detergent fiber, acid detergent fiber and hemicellulose increased with increasing regrowth interval (p > 0.05). Only the contents of crude protein and ether extract were similar (p > 0.05) among grasses. A significant interaction was observed (p < 0.05) between forage species and regrowth interval on forage mass. Andropogon grass had the highest forage mass at 63 days (3,270.1 kg ha-1 DM cut-1) and the highest productivity regardless of the regrowth interval (19.1 t ha-1 DM year-1). Therefore, Andropogon grass was the most productive forage among the tested species. Pastures should be managed with shorter growth intervals due to the highest crude protein level and the lowest contents of neutral detergent fiber and acid detergent fiber.

Abstract The white-tailed deer is the most important game species in Mexico. Knowledge about the components of the vegetation is important in management plans and influences the presence and maintenance of this species. The taxonomic diversity and productivity of a desert scrub in Coahuila was characterized and the value of said ecosystem in the conservation of deer populations was emphasized. The Canfield line and Adelaide method were used in the four seasons of the year, from October 2018 to August 2019, at the Management Unit for Wildlife Conservation Rancho San Juan, municipality of Monclova, Coahuila, Mexico. The importance value index (IVI) of each plant species per station and the Shannon diversity index were estimated. Biomass production was expressed in kg ha-1 per station and stratum. 46 species of plants were identified, some foragers such as Acacia berlandieri and Acacia rigidula. In addition, plants that provide thermal protection such as Cenchrus ciliaris and Yucca filifera. According to IVI, Agave lechuguilla (59.78 %) in spring, Hilaria mutica in summer (62.02 %) and autumn (86.59 %), and Cenchrus ciliaris in winter (107.00 %) were the most important. The middle stratum contributed a greater amount of biomass (> 1 000 kg ha-1) unlike the upper stratum, which produced less (≤ 250 kg ha-1). The desert scrub species that make up grasses and shrubs provide the fundamental resources for the development of Odocoileus virginianus populations in the area.

Resumen El venado cola blanca es la especie cinegética más importante en México. El conocimiento sobre los componentes de la vegetación es importante en los planes de manejo e influyen en la presencia y mantenimiento de ese taxón. Se caracterizó la diversidad taxonómica y productividad de un matorral desértico en Coahuila y se enfatizó el valor de dicho ecosistema en la conservación de las poblaciones del venado; para ello, se utilizaron la línea Canfield y el método Adelaide en las cuatro estaciones del año, de octubre 2018 a agosto 2019, en la Unidad de Manejo para la Conservación de la Vida Silvestre Rancho San Juan, Monclova, Coahuila. Se estimó el Índice de Valor de Importancia (IVI) de cada especie vegetal por estación y el índice de Diversidad de Shannon. La producción de biomasa se expresó en kg ha-1 por estación y estrato. Se identificaron 46 taxa de plantas, algunas forrajeras: Acacia berlandieri y Acacia rigidula, además de otras que ofrecen protección térmica: Cenchrus ciliaris y Yucca filifera. De acuerdo al IVI, Agave lechuguilla (59.78 %) en primavera, Hilaria mutica en verano (62.02 %) y otoño (86.59 %), así como Cenchrus ciliaris en invierno (107.00 %) registraron las cifras más altas. El estrato medio aportó mayor cantidad de biomasa (> 1 000 kg ha-1), a diferencia del estrato superior que produjo menos (≤ 250 kg ha-1). Los taxones del matorral desértico que conforman pastos y arbustos brindan los recursos fundamentales para el desarrollo de las poblaciones de Odocoileus virginianus en el lugar.

Global climate change is evident and poses serious threats to the sustainability of traditional rangeland livestock production systems. This study tested the feeding potential of perennial grasses of Cholistan Desert for various species of ruminants at different physiological stages. Eight common and nutritionally important grass species (Cenchrus ciliaris, Stipagrostis plumose, Panicum antidotale, Cymbopogon jwarancusa, Cenchrus pennisitiformis, Lasiurus scindicus, Ochthochloa compressa and Vetiveria zizanioides) were investigated for in situ degradation parameters according to Nordic feed evaluation system (NorFor) standards. The collected, dried and milled grass samples were incubated for 0, 4, 8, 16, 24, and 48 hours to determine dry matter and crude protein biodegradation and additionally for 96 and 168 hours for neutral detergent fibre degradation in the rumens of lactating Nili-Ravi buffalo and Cholistan Desert cows and heifers (two from each species and from each physiological stage). All of these grass species influenced the dry matter, crude protein and neutral detergent fibre degradation fractions significantly. The overall effective degradability of dry matter for asymptotic extent of degradation did not differ. However, the potentially degradable but insoluble fraction and rate of degradation were influenced significantly by the species of the animals. All the proximate parametric characteristics of perennial desert grasses were within the nutrient range for typical ruminant diets except for crude protein. It was concluded that rumen availability of grasses was highly influenced by grass species. However, these grasses are equally nutritionally important for various species of ruminants for example buffalo versus cattle at different physiological stages and heifers versus lactating animals.

The objective of the study was to establish guidelines for the viability test of seeds by tetrazolium in Cenchrus ciliaris using the Panicum protocols (ISTA, 2012). We worked with fascicles (dispersion unit) of Cenchrus ciliaris of the Texas cultivar from which caryopses were extracted to perform the tests. The appropriate method for cutting caryopses and the staining times were determined and two concentrations of tetrazolium solution were tested. In addition, after adjusting the conditions, evaluation protocols were developed. The adequate conditions to perform the viability test are 18 h of seed wetting between papers at a temperature of 20 °C, incomplete longitudinal cut through the embryo, tetrazolium concentration at 0.5 or 1 % and 10 hours of staining at 30 °C. The staining maps allow differentiating accurately the viability of the caryopses.

El objetivo del estudio fue establecer lineamientos para realizar el test de viabilidad de semillas por tetrazolio en Cenchrus ciliaris utilizando los protocolos de Panicum (ISTA, 2012). Se trabajó con fascículos (unidad de dispersión) de Cenchrus ciliaris del cultivar Texas de los cuales se extrajeron cariópsides para realizar los ensayos. Se determinó el método apropiado de corte de cariópsides y los tiempos de tinción; se probaron dos concentraciones de solución de tetrazolio. Además, se desarrollaron protocolos de evaluación. Las condiciones adecuadas para realizar el test de viabilidad son: 18 h de humedecimiento entre papel a temperatura de 20 °C; corte longitudinal incompleto a través del embrión; concentración de tetrazolio al 0,5 o 1 % y 10 h de tinción a 30 °C. Los mapas de tinción permiten diferenciar de forma precisa la viabilidad de las cariópsides.

The objective of the work was to determine the Leaf-Stem Relationship (L-S R) in natural and cultivated grasses of the Semiarid Western Chaco of Trancas department, Tucumán, Argentina, at the phenological stage of flowering. Trichloris crinita, Setaria leiantha and Aristida adscencionis (natural) and Chloris gayana cv. Common and Cenchrus ciliaris cv. Texas 4464 (cultivated) species were evaluated. The sampling was carried out cutting the whole forage plant at ground level. In each plant, leaves and stems were separated, and dried in stove until constant weight. The L-S R resulted from dividing the dry weight of the leaf component into the dry weight of the stem component, for each of the species and samples evaluated. The data obtained were analyzed by means of an analysis of variance for a completely randomized design. Results show that the L-S R of grasses in similar phenological stage, presents a great variability allowing inferring that, as the result of having a more favorable L-S R towards the leaf component, C. ciliaris and S. leiantha would have better nutritional value in full bloom, than C. gayana, T. crinita and A. adscencionis. Knowing L-S R of a forage allows guiding on the most appropriate time for consumption, the level of defoliation to apply during grazing and its place within a sequence of use in relation to other species of the same period of grazing.

El objetivo del trabajo fue determinar la Relación Hoja-Tallo (R H-T) en gramíneas naturales y cultivadas del Chaco Occidental Semiárido del departamento Trancas, Tucumán, Argentina, en el estado fenológico de floración. Las especies evaluadas fueron Trichloris crinita, Setaria leiantha y Aristida adscencionis (naturales) y Chloris gayana cv. Común y Cenchrus ciliaris cv. Texas 4464(cultivadas). El muestreo se realizó cortando a la altura de la superficie del suelo toda la mata de forraje. En cada planta cosechada se procedió a la separación de las hojas y los tallos, los cuales fueron secados en estufa hasta obtener un peso constante. La R H-T resultó de dividir el peso seco del componente hoja en el peso seco del componente tallo en todas las especies y muestras evaluadas. Los datos obtenidos se analizaron mediante análisis de la varianza para un diseño completamente aleatorizado. Los resultados indican que la R H-T de gramíneas en similar estado fenológico, presenta una gran variabilidad permitiendo inferir que, en función de tener una R H-T más favorable al componente hoja, C. ciliaris y S. leiantha tendrían mejor valor nutricional en plena floración, que C. gayana, T. crinita y A. adscencionis. Conocer la R H-T de una forrajera, puede orientar sobre el momento más adecuado para su consumo, el nivel de defoliación a aplicar durante el pastoreo y/o su lugar dentro de una secuencia de utilización en relación a otras especies de igual época de pastoreo.

Buffelgrass (Cenchrus ciliaris L.) a native pasture species of Africa is widely used in arid regions because of its forage productivity and quality. It could become serious invasive species, not only for crops but also in natural vegetation. Buffelgrass is highly affected by low temperatures at all stages of its life cycle. The objective was to determine the behavior of three buffelgrass cultivars (Americana, Biloela, Texas 4464) under cold stress and define the critical temperatures. To determine the effect of cold stress on the plasma membrane, foliage damage and survival (regrowth), it was evaluated relative electrical conductivity (ECr) of leaves, percentage of foliar damage and the ability of regrowth after exposure to 2 temperatures (-5°C and -10°C) with 2 exposure times (4 and 7 hours). The results showed a higher percentage of foliar damage and greater ECr as temperature decreased and hours of exposure increased. A similar response was observed when survival (regrowth) was evaluated. There were no significant differences among cultivars in both temperature treatments and time when the regrowth was evaluated.

El buffelgrass (Cenchrus ciliaris L.) es una especie forrajera nativa de África ampliamente utilizada en las regiones áridas debido a su productividad forrajera y calidad. En muchos casos puede convertirse en una especie invasora, no solo para los cultivos, sino también para la vegetación natural. El buffelgrass es afectado por las bajas temperaturas en todas las etapas del ciclo de vida. El objetivo del presente trabajo fue determinar el comportamiento de tres variedades de buffelgrass (Americana, Biloela, Texas 4464) ante condiciones de frío y definir las temperaturas críticas. Para determinar el efecto de estrés por bajas temperaturas sobre la membrana plasmática, daños de follaje y la supervivencia (rebrote), se evaluó la conductividad relativa (ECr) de hojas, porcentaje de daño foliar y la capacidad de rebrote después de la exposición de las plantas y plántulas a 2 temperaturas (-5°C y -10°C) durante 2 períodos (4 y 7 horas). Los resultados mostraron un mayor porcentaje de daño foliar y mayor conductividad relativa. Medida que disminuía la temperatura y aumentaba las horas de exposición. Una respuesta similar se observó cuando se evaluó la supervivencia (rebrote). No hubo diferencias significativas entre cultivares en ambos tratamientos de temperatura y tiempo cuando se evaluó el rebrote.

Abstract A field trial was conducted, in order to evaluate the effect of the inoculation of two biofertilizers and a biostimulant on agroproductive variables of buffel grass (Cenchrus ciliaris L.), under conditions of agricultural drought. For such purpose, the isolate Ho5 (Bradyrhizobium sp.), EcoMic® (Funneliformis mosseae) and Quitomax® were used. The experimental design was randomized blocks, with nine treatments and eight replicas, and an ANOVA was performed. The differences among means were found through Fisher’s LSD. The following variables were evaluated: aerial part dry weight, stem length, spike length, spike dry weight, inflorescence and inoculation efficiency index (IEI). The best treatments in most of the studied variables were: EcoMic®+Quitomax®+Ho5, Ho5+EcoMic® and Ho5+Quitomax®, for showing higher results than the absolute control and other inoculated treatments. With the combination of EcoMic®+Quitomax®+Ho5, there was a high percentage of inflorescence (71 %); which suggests that the inclusion of Quitomax® in such combination should have influenced this variable effectively. It is concluded that the combination of the biofertilizers with Quitomax®, in general, showed a higher effect than the control; although EcoMic®+Quitomax®+Ho5 stood out, due to its superiority with regards to other treatments. On the other hand, the application of each biofertilizer, or of Quitomax®, alone, did not show higher results than the absolute control in most of the variables. To evaluate treatments in which these biopreparations were combined in different pasture grasses and different soil types, as well as the long-term effect of these biopreparations on the plant, is recommended.

Resumen Se llevó a cabo un experimento de campo, con el objetivo de evaluar el efecto de la inoculación de dos biofertilizantes y un bioestimulante en variables agroproductivas de buffel (Cenchrus ciliaris L.), en condiciones de sequía agrícola. Para ello, se utilizó el aislado Ho5 (Bradyrhizobium sp.), EcoMic® (Funneliformis mosseae) y Quitomax®. El diseño experimental fue de bloques al azar, con nueve tratamientos y ocho réplicas, y se realizó un ANOVA. Las diferencias entre medias se hallaron mediante LSD de Fisher. Se evaluaron las variables: peso seco de la parte aérea, longitud del tallo, longitud de la espiga, peso seco de la espiga, inflorescencia e índice de eficiencia de la inoculación (IEI). Los mejores tratamientos en la mayoría de las variables estudiadas fueron: EcoMic®+Quitomax®+Ho5, Ho5+EcoMic® y Ho5+Quitomax®, por mostrar resultados superiores al control absoluto y a otros tratamientos inoculados. Con la combinación de EcoMic®+Quitomax®+Ho5, hubo un porcentaje alto de inflorescencia (71 %); lo que sugiere que la inclusión de Quitomax® en dicha combinación debió influir de manera efectiva en esta variable. Se concluye que la combinación de los biofertilizantes con Quitomax®, de forma general, mostró un efecto superior al control; aunque se destacó EcoMic®+Quitomax®+Ho5, por su superioridad con respecto a otros tratamientos. Por otra parte, la aplicación de cada biofertilizante, o de Quitomax®, de forma aislada, no mostró resultados superiores al control absoluto en la mayoría de las variables. Se recomienda evaluar los tratamientos donde se combinaron estos biopreparados en diferentes gramíneas pratenses y diferentes tipos de suelo, así como el efecto a largo plazo de dichos biopreparados en la planta.

This study was carried out to examine the degradation dynamics of neutral detergent fibre (NDF) and the profile of volatile fatty acids that originate from the fermentation of buffel grass (Cenchrus ciliaris, L.) with various levels of ammonia in the growth medium. The treatments consisted of six levels of ammonia in the growth medium (0, 5, 10, 15, 20 and 30 mg/dL), which were obtained by adding urea. These in vitro incubation times were evaluated in three replicates per time for 0, 3, 6, 9, 12, 24, 36, 48, 72 and 96 hours. Rumen concentrations of acetate and propionate responded quadratically to the ammonia levels. The treatment with 15 mg/dL of ammonia nitrogen in the rumen fluid provided mean acetate and propionate contents of 57.6 mM and 23.1 mM, respectively. Urea addition elevated the degradation rate of potentially degradable fraction of NDF (pdNDF) from 2.5% to 20.1% in comparison with the treatment without urea and to a reduction in estimated discrete lag time from 0.34 to 2.31 hours. Urea supplementation increased the specific microorganism growth rate from 2.6% to 20.1%. At the end of the incubation trial, NDF degradation showed a quadratic response, with maximum value obtained at 17.76 mg/dL of ammonia in the rumen fluid. Urea improves the degradation dynamics of NDF from deferred buffel grass and increases the concentrations of acetate and propionate.

Abstract: The silvopastoral system renders the livestock production more sustainable because the interaction between its components brings benefits to the soil, to the grassland, livestock and trees; furthermore, it enhances the productivity and the diversification of production. To know the characteristics of these systems, a study was carried out in private properties located in the Paraguayan Chaco, where eight permanent plots of 1 ha each were established in which all Prosopis spp. (carob) individuals were measured and identified, and samples were drawn from grasslands of subplots located beneath the canopy of the trees and beyond to compare their biomass; soil samples were also obtained under the same conditions, at two different depths -0 to 10 cm and 10 to 30 cm- with the purpose of comparing the content of organic matter and carbon/nitrogen ratio (C/N). The arboreal component consisted of Prosopis alba (white carob tree) and Prosopis nigra (black carob tree), in association with cultivated grassland composed mostly by Panicum maximum cv Gatton panic (Gatton Panic), Digitaria decumbens (Pangola grass), and Cenchrus ciliaris (Buffel grass). The presence of the carob trees influenced the biomass of the grassland, which was more abundant beneath the tree crowns than outside of them. The organic matter in the soil exhibited no significant differences between the conditions of sun and shade, but it differed between depths; in contrast, the C/N ratio did not change under any of the conditions.

Resumen: El sistema silvopastoril permite que la producción ganadera sea más sustentable, porque la interacción entre sus componentes aporta beneficios al suelo, a la pastura, al ganado y a los árboles; además de, un aumento en la productividad y la diversificación de la producción. Para conocer las características de dichos sistemas, se llevó a cabo un estudio en propiedades privadas ubicadas en el Chaco Paraguayo, donde se instalaron ocho parcelas permanentes de 1 ha cada una, en las que se midieron todos los individuos de Prosopis spp. (algarrobo), se identificaron y extrajeron muestras de pastura de subparcelas situadas bajo la copa de los árboles y fuera de ella para comparar su biomasa; también se obtuvieron muestras de suelo en las mismas condiciones, a dos profundidades: de 0 a 10 cm y de 10 a 30 cm, con el propósito de comparar el contenido de materia orgánica y la Relación Carbono/Nitrógeno (C/N). El componente arbóreo estaba integrado por Prosopis alba (algarrobo blanco) y Prosopis nigra (algarrobo negro) asociados a pastura cultivada compuesta en forma mayoritaria por Panicum maximum cv Gatton panic (Gatton panic), Digitaria decumbens (pasto pangola) y Cenchrus ciliaris (pasto buffel). La presencia de los algarrobos influyó sobre la biomasa de la pastura, pues sus registros fueron mayores bajo las copas que fuera de estas. La materia orgánica en el suelo no presentó diferencias significativas entre condición de sol y de sombra, pero sí al variar la profundidad; en cambio, la Relación C/N no varió en ninguna de las condiciones.