Seasonal Patterns of Herbage Accumulation Dynamics in Marandu Palisadegrass Subjected to Intensities of Continuous Stocking Management

It is relatively well reported in the literature that pastures can have similar forage net accumulation when managed with contrasting structures. However, we hypothesized that the patterns of forage accumulation dynamics of pastures managed at different canopy heights is dependent on environmental conditions. The experimental treatments were four canopy heights (10, 20, 30, and 40 cm), allocated to experimental units according to a randomized complete block design with four replicates and evaluated throughout four contrasting environmental seasons (Summer, Autumn, Winter-Early Spring, and Late Spring). Under favourable growing conditions greater forage accumulation was observed in pastures maintained taller; on the contrary, under more stressful conditions, net forage accumulation rate reduced as canopy height increased. Such patterns of responses were related to compensations between tiller population density and tissue flows during summer and late spring and the reduced capacity of taller canopies to compensate lower population with greater growth rates during autumn and winter-early spring. Pastures subjected to intensities of continuous stocking management change their patterns of forage growth as they transitioned from favourable to more abiotic stressful conditions suggesting that warm-season perennial grasses demand seasonal adjustments in grazing heights in order to maximize herbage production

State of Knowledge in Tiller Dynamics

Persistence of sown pastures is a concern for pastoral production worldwide. Fundamentally, when a pasture does not persist the problem can be expressed in terms of inadequate new tiller production or excessive tiller death. However, the collection of data to build an understanding of sward dynamics at this level is time consuming. Tiller survival diagrams are presented for a range of temperate and tropical grass species including Lolium perenne, Lolium multiflorum, Festuca arundinacea, Festuca pratensis, Phleum pratense, Bromus willdenowii, Cynodon dactylon, Brachiaria brizantha, Panicum maximum, Chloris gayana and Paspalum notatum. It is shown that each grass has a unique perennation strategy and accordingly unique strengths and weaknesses that confer persistence or lack of persistence in different situations. There is also confusion in extension circles about the trade-off between tiller size and tiller density and how to detect a suboptimal tiller density. Grass swards respond to high herbage mass by increase of tiller size and reduction in tiller density, but reduction in tiller density is often mistaken for sward decline. A distinctionmust be made between size/density compensation and sward decline. Increased understanding of sward dynamics at this level should help in the evolution of management practices that improve persistence on a range of grassland types

Morning and Afternoon Sampling and Herbage Chemical Composition of Rotationally Stocked Elephant Grass cv. Napier

Nutrient intake by grazing animals depends on the amount of dry matter consumed and its chemical composition. Forage grasses, as with any other plants, produce assimilates during the day via photosynthesis to sustain live tissues, plant growth and organic reserves (Taiz and Zeiger 2013). In that context, herbage chemical composition may vary according to variations in the photosynthesis-respiration balance throughout the day. From dawn to dusk the balance increases and herbage dry matter content as well as concentration of soluble carbohydrates increase, the reverse happening from dusk to dawn. That could interfere with nutritive value and nutrient intake of grazing animals (Delagarde 2000), since for a given bite volume the amount of herbage and its composition could vary depending on the time of the day. That could have implications for rotationally managed pastures, indicating a potential effect of time of changing animals from one paddock to the other as a management strategy. Against that background, the objective of this experiment was to evaluate dry matter (DM) content and the concentration of soluble carbohydrates (SC), crude protein (CP), neutral (NDF) and acid (ADF) detergent fibre in herbage samples harvested during the morning and afternoon periods from rotationally stocked elephant grass cv. Napier

State of knowledge in tiller dynamics

Persistence of sown pastures is a concern for pastoral production worldwide. Fundamentally, when a pasture does not persist the problem can be expressed in terms of inadequate new tiller production or excessive tiller death. However, the collection of data to build an understanding of sward dynamics at this level is time consuming. Tiller survival diagrams are presented for a range of temperate and tropical grass species including Lolium perenne, Lolium multiflorum, Festuca arundinacea, Festuca pratensis, Phleum pratense, Bromus willdenowii, Cynodon dactylon, Brachiaria brizantha, Panicum maximum, Chloris gayana and Paspalum notatum. It is shown that each grass has a unique perennation strategy and accordingly unique strengths and weaknesses that confer persistence or lack of persistence in different situations. There is also confusion in extension circles about the trade-off between tiller size and tiller density and how to detect a suboptimal tiller density. Grass swards respond to high herbage mass by increase of tiller size and reduction in tiller density, but reduction in tiller density is often mistaken for sward decline. A distinctionmust be made between size/density compensation and sward decline. Increased understanding of sward dynamics at this level should help in the evolution of management practices that improve persistence on a range of grassland types.La persistencia de los pastos sembrados es una preocupación para la producción pastoril a nivel mundial. Fundamentalmente, cuando una pastura no persiste, el problema puede expresarse en términos de producción inadecuada de nuevos macollos o muerte excesiva de macollos. Sin embargo, la recopilación de datos para comprender la dinámica de los céspedes a este nivel requiere mucho tiempo. Se presentan diagramas de supervivencia de macollos para una variedad de especies de pastos templados y tropicales que incluyen Lolium perenne, Lolium multiflorum, Festuca arundinacea, Festuca pratensis, Phleum pratense, Bromus willdenowii, Cynodon dactylon, Brachiaria brizantha, Panicum maximum, Chloris gayana y Paspalum notatum. Se muestra que cada pasto tiene una estrategia de perennación única y, en consecuencia, fortalezas y debilidades únicas que le confieren persistencia o falta de persistencia en diferentes situaciones. También existe confusión en los círculos de extensión acerca de la compensación entre el tamaño de los retoños y la densidad de los retoños y cómo detectar una densidad de retoños subóptima. Las praderas de hierba responden a una gran masa de forraje mediante el aumento del tamaño de los macollos y la reducción de la densidad de los macollos, pero la reducción de la densidad de los macollos a menudo se confunde con la disminución del césped. Se debe hacer una distinción entre la compensación de tamaño/densidad y la disminución del césped. Una mayor comprensión de la dinámica de los pastos a este nivel debería ayudar en la evolución de las prácticas de gestión que mejoran la persistencia en una variedad de tipos de pastizales.Estación Experimental Agropecuaria PergaminoFil: Matthew, Cory. Massey University. Institute of Agriculture and Environment; Nueva ZelandiaFil: Agnusdei, Monica Graciela. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; ArgentinaFil: Assuero, Silvia G. Universidad Nacional de Mar del Plata; ArgentinaFil: Sbrissia, André F. Santa Catarina State University; BrasilFil: Scheneiter, Jorge Omar. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Silva, Sila C. da. Universidade de Sao Paulo; Brasi

Herbage Accumulation and Animal Performance on Xaraes Palisade Grass Subjected to Intensities of Continuous Stocking Management

The large majority of species used in Brazil belong to the Brachiaria and Panicum genus, with marandu paladisadegrass (Brachiaria brizantha (Hochst. ex A. Rich) cv. Marandu) being the main cultivated forage grass species (Santos Filho 1996). Brachiaria brizantha cv. xaraés (xaraes palisade grass) was released as an option for diversifying forage species, and it had the advantages of fast regrowth and herbage yield, favouring larger stocking rates and animal productivity (Euclides et al. 2008; 2009). The objective of this study was to evaluate herbage accumulation and animal performance of beef cattle steers grazing continuously stocked xaraes palisade grass managed at 15, 30 and 45 cm

Grazing Management Flexibility in Pastures Subjected to Rotational Stocking Management: Herbage Production and Chemical Composition of Kikuyu-Grass Swards

Several recent papers published on tropical pastures have pointed out that under rotational stocking management regrowth should be interrupted when canopy light interception is 95% (LI). Further, these studies have revealed a positive and high correlation between LI and sward height, allowing LI management targets to be defined in terms of sward height. However, there are some indications that lower pre-grazing heights relative to those targets would result in similar leaf accumulation without interfering with sward persistence. The objective of this paper was to verify a possible flexibility of such pre-grazing height targets. A replicated experiment was conducted with treatments corresponding to four pre-grazing height targets (25 cm, corresponding to a canopy light interception of 95%; 20; 15 and 10 cm), which were associated with a single severity of grazing equivalent to removal of 50% of initial height, leaving four post-grazing heights (12.5, 10.0, 7.5 and 5 cm, respectively). Preliminary results indicated that there were no differences in rate of herbage accumulation, herbage yield and crude protein, NDF and ADF contents on swards managed with the pre-grazing targets of 15, 20 and 25 cm. Swards managed with the 10 cm pre-grazing target had the highest contents of CP and lowest contents of NDF and ADF, but herbage accumulation was reduced. Overall, the findings indicate that there may be some flexibility in targets of pre-grazing sward height, provided that defoliation severity is moderate and does not interfere with herbage yield and quality. In that context, targets of pre-grazing sward height defined in terms of canopy light interception would correspond to the maximum value of the possible range of values to be used

Sward structure of marandu palisadegrass subjected to continuous stocking and nitrogen-induced rhythms of growth

Acceleration of the growth rhythm of plants using nitrogen fertiliser alters the rates of physiological processes like growth and senescence and may cause significant changes in sward structure, interfering with plant and animal responses. The objective of this experiment was to evaluate sward structure of marandu palisadegrass (Brachiaria brizantha) maintained at 30 cm under continuous stocking and subjected to contrasting rhythms of growth from January 2007 to April 2008. These were generated using or not nitrogen fertiliser, and comprised four experimental treatments as follows: control (non-fertilised), 150, 300 and 450 kg ha-1 of N. Acceleration of the growth rhythm of plants was associated with increases in leaf and stem bulk density, and resulted in larger LAI and total bulk density on swards subjected to faster (fertilised with 300 and 450 kg ha-1 of N) than those subjected to slower rhythms of growth (non-fertilised or fertilised with 150 kg ha-1 of N). Variations in dead material bulk density were associated with seasonal variations in climatic conditions, and were not influenced by growth rhythms. During autumn/winter and early spring (dry period of the year) swards subjected to faster, relative to those subjected to slower rhythms of growth, had larger proportion of leaves on the top horizons. On the other hand, sward structure did not vary among rhythms of growth at times of the year when there was no limitation in the availability of climatic growth factors (late spring and summer), indicating that when control of the grazing process is efficient, changes in sward structure are basically a function of seasonal variations in climatic growth conditions and phenological state of plants.A aceleração do ritmo de crescimento das plantas por meio da adubação nitrogenada altera a velocidade dos processos fisiológicos, atuando sobre o crescimento e a senescência, podendo refletir-se em alterações importantes sobre a estrutura do dossel. Avaliou-se a estrutura do dossel forrageiro de pastos de capim-marandu (Brachiaria brizantha) mantidos a 30 cm de altura por meio de lotação contínua e submetidos a ritmos de crescimento contrastantes de janeiro de 2007 a abril de 2008. Os distintos ritmos de crescimento foram criados por meio da utilização de adubação nitrogenada, segundo os tratamentos: sem adubação (controle), 150, 300 e 450 kg ha-1 de N. A aceleração do ritmo de crescimento dos pastos resultou em aumentos de densidade volumétrica de folhas e de colmos, refletindo em maior IAF e densidade volumétrica total em pastos submetidos aos ritmos de crescimento mais acelerados (adubados com 300 e 450 kg ha-1 de N) relativamente àqueles submetidos a ritmos de crescimento mais lentos (pastos não adubados e/ou adubados com 150 kg ha-1 de N). Variações em densidade volumétrica do material morto estiveram associadas a flutuações estacionais das condições climáticas, e não foram influenciadas pelos ritmos de crescimento avaliados. Na época da seca (outono/inverno e início de primavera), os pastos submetidos aos ritmos de crescimento mais acelerados apresentaram maior proporção de folhas no horizonte superior do dossel. Por outro lado, a estrutura do dossel não variou entre os ritmos de crescimento nas épocas de maior disponibilidade de fatores de crescimento (final de primavera e verão), indicando que quando o controle do processo de pastejo é feito de maneira eficiente, mudanças em estrutura são função basicamente de variações estacionais em condições climáticas e estádio fenológico das plantas