Forage performance and cattle production as a function of the seasonality of a Brazilian tropical region / Forage performance and cattle production as a function of the seasonality of a Brazilian tropical region

This study aimed to evaluate forage yield, tiller population density, canopy height, nutritional value as well as cattle performance in alternate stocking from three tropical forage cultivars. The experiment followed a randomized block design, in a 3 x 3 factorial scheme with three replications. Three forage cultivars (Marandu, Massai and Xaraés) distributed in nine hectares were evaluated in three dry season periods (transition wet/dry, dry, and end of dry season), with repeated measures over time. The following variables were evaluated: canopy height, leaf: stem ratio, forage mass, leaf mass, stem mass and dead material mass. Total digestible nutrients, crude protein and in vitro dry mass digestibility were evaluated regarding forage nutrition. Animal performance, using 36 eleven-month-old animals (half-blood Nelore), was evaluated by the daily average gain and weight gain by area. During pre-grazing, canopy height presented interaction among forage cultivars and the evaluated periods. The average daily gain showed no interaction among cultivars and period of the year the similarity in animal performance among the cultivars Marandu and Massai show that the Massai grass can be used as an alternative for forage diversification under an alternate management system.

This study aimed to evaluate forage yield, tiller population density, canopy height, nutritional value as well as cattle performance in alternate stocking from three tropical forage cultivars. The experiment followed a randomized block design, in a 3 x 3 factorial scheme with three replications. Three forage cultivars (Marandu, Massai and Xaraés) distributed in nine hectares were evaluated in three dry season periods (transition wet/dry, dry, and end of dry season), with repeated measures over time. The following variables were evaluated: canopy height, leaf: stem ratio, forage mass, leaf mass, stem mass and dead material mass. Total digestible nutrients, crude protein and in vitro dry mass digestibility were evaluated regarding forage nutrition. Animal performance, using 36 eleven-month-old animals (half-blood Nelore), was evaluated by the daily average gain and weight gain by area. During pre-grazing, canopy height presented interaction among forage cultivars and the evaluated periods. The average daily gain showed no interaction among cultivars and period of the year the similarity in animal performance among the cultivars Marandu and Massai show that the Massai grass can be used as an alternative for forage diversification under an alternate management system.

Morphogenic, structural characteristics and population stability index of ryegrass tillers submitted to stocking methods / Características morfogênicas, estruturais e índice de estabilidade populacional de perfilhos de azevém submetidos a métodos de lotação

This study aimed to evaluate the morphogenic and structural characteristics and the population stability index of ryegrass (Lolium multiflorum Lam.) tillers when the pasture was submitted to two stocking methods during grazing cycles. The experimental design was a complete randomized block, with repeated measurements over time (n=6 cycles), two treatments (stocking methods) and three area replicates. In the continuous stocking method, the highest population density of tillers was observed. The highest tiller weight occurred in the rotational stocking method. The morphogenic variables and the other structural variables were not altered by the stocking methods and showed differences during the grazing cycles. The tiller population stability index was similar in the two pasture management strategies, and both can be used for ryegrass management considering this parameter.

Este estudo teve como objetivo avaliar as características morfogênicas, estruturais e o índice de estabilidade populacional de perfilhos do azevém (Lolium multiflorum Lam.) quando a pastagem foi submetida a dois métodos de lotação, durante ciclos de pastejo. O delineamento experimental foi em blocos completos casualizados, com medidas repetidas ao longo do tempo (n = 6 ciclos), dois tratamentos (métodos de lotação) e três repetições de área. No método de lotação contínua, foi observada a maior densidade populacional de perfilhos. O maior peso de perfilhos ocorreu no método de lotação rotativa. As variáveis morfogênicas e as demais variáveis estruturais não foram alteradas pelos métodos de lotação e apresentaram diferenças durante os ciclos de pastejo. O índice de estabilidade populacional de perfilhos foi semelhante nas duas estratégias de manejo do pasto e ambas podem ser utilizadas para o manejo do azevém considerando-se esse parâmetro.

Contribution of tiller age category to herbage accumulation of Marandu palisadegrass under two fertilization regimes / Contribuição da categoria de idade do perfilho para o acúmulo de forragem de capim-marandu sob dois regimes de fertilização

Based on the hypothesis that climate and fertilizers influence the proportion of tiller age categories in the canopy and, consequently, in herbage accumulation, the objective of this study was to determine the population density and the contribution of tiller age categories for herbage accumulation of Urochloa brizantha cv. Marandu during the year and in response to phosphate and nitrogen fertilization. The treatments consisted of two fertilization strategies: low and high fertilization and three tiller ages (young, mature and old), evaluated at four times of the year: winter, early and late spring, and summer. The total number of tillers and the proportion of young tillers were higher in late spring and summer. The growth and herbage accumulation rates showed a typical seasonal pattern and were higher in the canopy under high fertilization. Old tillers contributed more to control the total stem growth rate, as well as the canopy senescence rate. The highest percentage of young tillers is related to the high herbage accumulation in the Marandu palisadegrass canopy.(AU)

Levando em consideração que os fertilizantes e o clima podem influenciar na faixa etária de perfilhos de um dossel e consequentemente no acúmulo de forragem, o objetivo desse trabalho foi determinar a densidade populacional e a contruibuição das faixas etárias de perfilhos para o acúmulo de forragem Uruchloa brizanta cv Marandu durante o ano e em resposta a fertização com fosfato e nitrogênio. O tratamento foi constituido de duas estratégias de fertilização: baixa e alta fertilização e três faixas etárias de perfilhos (jovem, maduro e velho) avaliadas em quatro épocas do ano (inverno, início e fim da primavera e verão). O número total de perfilhos e a proporção de perfilhos jovens foram maiores no final da primavera e no verão. As taxas de crescimento e de acumulação de forragem mostraram um padrão sazonal típico e foram maiores no dossel com alto nivel de fertilização do que com baixo nível de fertilizante. O perfilho velho contribuiu mais para controlar as taxas de crescimento total do caule, bem como para a taxa de senescência do dossel. A maior porcentagem de perfilhos jovens está relacionada ao alto acúmulo de forragem no dossel do capimmarandu.(AU)

Morphogenetic and structural traits of tillers and herbage accumulation of Tanganyika grass under shading levels / Características morfogênicas e estruturais de perfilhos e acúmulo de forragem do capim-tanganica sob níveis de sombreamento

This study aimed to evaluate the effect of tree shading levels on tillers' morphogenetic and structural traits, besides the herbage accumulation of Tanganyika grass (Megathyrsus maximus Jacq. cv. Tanganyika). For that, an experiment was carried out from December 2010 to March 2012, under a completely randomized design, with four treatments (shading levels) and five repetitions. Phyllochron (PHY), leaf and stem elongation rates (LER and SER, respectively), number of leaves per tiller (NLT), leaf blade length (LBL), stem length (ST), tiller population density (TPD), leaf (LGR) and stem growth rates (SGR), senescence rate (SR) and herbage accumulation rate (HAR) were assessed. Excepted by the LER and NLT, the shading levels influenced the other morphogenetic variables (P<0.05), positively or negatively. Except in the spring, the TPD linearly increased because of the shading levels (P<0.05). At tiller level, except in the spring, the LBL linearly increased with the shading levels (P<0.05). In general, the SL linearly decreased with the shading levels. Regarding the growth rates, summer II and spring provided greater values, and the lowest one occurred in autumn (P<0.05). The adjustments of both morphogenetic and structural traits ensured the Tanganyika grass a great adaptation to the shaded environment.(AU)

Objetivou-se avaliar o efeito do sombreamento arbóreo sobre as características morfogênicas e estruturais dos perfilhos e acúmulo de forragem do capim-Tanganica (Megathyrsus maximus Jacq. cv. Tanganica). Para tanto, um experimento foi conduzido, de dezembro de 2010 a março de 2012, sob delineamento inteiramente casualizado com quatro tratamentos (níveis de sombreamento) e cinco repetições. Foram avaliados: filocrono (FIL), taxas de alongamento de lâminas foliares (TAlLF) e de colmos (TAlC), número de folhas vivas por perfilho (NFVP), comprimento de lâminas foliares (CLF), comprimento de colmo (CC), densidade populacional de perfilhos (DPP), taxas de crescimento de lâminas foliares (TCLF) e de colmos (TCC), taxa de senescência (TS) e taxa de acúmulo de forragem (TAF). Exceto para TAlLF e NFVP, todas as demais varáveis morfogênicas foram influenciadas (P<0.05), de maneira positiva ou negativa pelos níveis de sombreamento. Exceto na primavera, a DPP aumentou linearmente sob maiores níveis de sombreamento (P<0.05). Em nível de perfilho, exceto na primavera, o CLF aumentou linearmente com o aumento do nível de sombreamento (P<0.05). Além disso, de maneira geral, o CC reduziu de maneira linear com o aumento do nível de sombreamento. Quanto às taxas de crescimento, o verão II e a primavera proporcionaram maiores valores, e as menores taxas foram registradas no outono (P<0.05). Os ajustes das características morfogênicas e estruturais garantiram ao capim-Tanganica ótima adaptação ao ambiente sombreado.(AU)

Morphogenetic and structural traits of Ipyporã grass subjected to nitrogen fertilization rates under intermittent grazing / Características morfogênicas e estruturais do capim-ipyporã submetido a doses de adubação nitrogenada sob pastejo intermitente

This study examined the effects of annual nitrogen (N) rates of 100 and 200 kg ha-¹ on the morphogenetic and structural traits of Ipyporã grass (Brachiaria brizantha × Brachiaria ruziziensis) under intermittent grazing during the seasons of the year. The experiment was laid out in a randomized-block design with two treatments and three area replicates. Ipyporã grass pastures were grazed by beef cattle. Morphogenetic and structural traits of the forage canopy were evaluated using the marked-tiller technique. Forage accumulation and tiller density (TD) were also evaluated. Significant interaction effects (P < 0.05) between N rates and seasons were observed for the rest period, leaf lifespan (LLS), phyllochron, stem elongation rate (SER) and final leaf length (FLL). During winter, the rest period was shorter (40 vs. 50 days) in the pastures fertilized with 200 kg ha-¹ N. Conversely, in winter, the pastures fertilized with 100 kg ha-¹ N showed higher LLS, SER and phyllochron values, but lower FLL values. There was no isolated effect of N rates (P > 0.05) on forage accumulation rate; leaf appearance, elongation or senescence rates; leaf:stem ratio; or TD. However, the effect of seasons was significant for these variables, with the highest values occurring during spring and summer. The use of 200 kg ha-¹ N in Ipyporã grass pastures reduces the seasonality of forage production.

O objetivo foi avaliar os efeitos das doses anuais de 100 e 200 kg ha-¹ de nitrogênio (N) sobre as características morfogênicas e estruturais do capim-ipyporã, em lotação intermitente durante as estações do ano. O delineamento experimental foi em blocos ao acaso, com dois tratamentos e três repetições de área. Os pastos de capim-ipyporã foram submetidos ao pastejo por bovinos de corte. Foram avaliadas as características morfogênicas e estruturais do dossel forrageiro por meio da técnica de perfilhos marcados. Também foi avaliado o acúmulo de forragem e a densidade populacional de perfilhos (DPP). Foi observada interação significativa (P < 0,05) das doses de N e estações do ano para o período de descanso (PD), duração de vida das folhas (DVF), filocrono, taxa de alongamento de colmos (TAlC) e comprimento final das folhas (CFF). Durante o inverno, o PD foi menor (40 vs 50 dias) nos pastos adubados com 200 kg ha-¹ de N. Em contra partida, no inverno, os pastos adubados com 100 kg ha-¹ de N apresentaram maiores valores para DVF, filocrono e TAlC, e menores para o CFF. Não foi observado efeito isolado de doses de N (P > 0,05) para as taxas de acúmulo de forragem; de aparecimento, alongamento e de senescência de folhas, relação folha:colmo e para a DPP. No entanto, o efeito das estações foi significativo para estas variáveis, com os maiores valores observados durante a primavera e verão. O uso de 200 kg ha-¹ de N para pastos de capim-ipyporã promove redução da estacionalidade de produção da forrageira.

Forage performance and cattle production as a function of the seasonality of a Brazilian tropical region

This study aimed to evaluate forage yield, tiller population density, canopy height, nutritional value as well as cattle performance in alternate stocking from three tropical forage cultivars. The experiment followed a randomized block design, in a 3x3 factorial scheme with three replications. Three forage cultivars (Marandu, Massai and Xaraés) distributed in nine hectares were evaluated in three dry season periods (transition wet/dry, dry,and end of dry season), with repeated measuresover time. The following variables were evaluated: canopyheight, leaf: stem ratio, forage mass, leaf mass, stem mass and dead material mass. Total digestible nutrients, crude protein and in vitrodry mass digestibility were evaluated regarding forage nutrition. Animal performance, using 36 eleven-month-old animals (half-blood Nelore),was evaluated by the daily average gain and weight gain by area. During pre-grazing, canopy height presented interaction among forage cultivars and the evaluated periods. The average daily gain showed no interaction amongcultivarsand period of the year the similarity in animal performance amongthe cultivars Marandu and Massai show that the Massai grass can be used as an alternative for forage diversification under an alternate management system.(AU)

Forage performance and cattle production as a function of the seasonality of a Brazilian tropical region

This study aimed to evaluate forage yield, tiller population density, canopy height, nutritional value as well as cattle performance in alternate stocking from three tropical forage cultivars. The experiment followed a randomized block design, in a 3 x 3 factorial scheme with three replications. Three forage cultivars (Marandu, Massai and Xaraés) distributed in nine hectares were evaluated in three dry season periods (transition wet/dry, dry, and end of dry season), with repeated measures over time. The following variables were evaluated: canopy height, leaf: stem ratio, forage mass, leaf mass, stem mass and dead material mass. Total digestible nutrients, crude protein and in vitro dry mass digestibility were evaluated regarding forage nutrition. Animal performance, using 36 eleven-month-old animals (half-blood Nelore), was evaluated by the daily average gain and weight gain by area. During pre-grazing, canopy height presented interaction among forage cultivars and the evaluated periods. The average daily gain showed no interaction among cultivars and period of the year the similarity in animal performance among the cultivars Marandu and Massai show that the Massai grass can be used as an alternative for forage diversification under an alternate management system.(AU)

Morphogenic and structural characteristics of Panicum cultivars during the establishment period in the Brazilian Northeast

This study aimed to evaluate the morphogenic and structural characteristics of six Panicum maximum cultivars during the establishment period. A completely randomized block design with four replicates and six treatments (Tamani, Mombaça, Massai, Tanzania, Aruana and Zuri cultivars) was used. Morphogenic (leaf appearance rate, leaf elongation rate e stem elongation rate), structural (final leaf length, tiller population density e number of leaves per tiller) and productive (forage mass, leaf blade mass, stem mass, senescent material mass and leaf:stem ratio) characteristics were evaluated. There was no difference (p > 0.05) between the cultivars in terms of the number of live leaves per tiller (2.95 leaves/tiller). Mombaça cultivar had (p 0.05) between cultivars. However, leaf appearance rate was higher (p < 0.05) in Tanzania (0.07 leaves tiller day-1) than in Aruana cultivar (0.05 leaves tiller day-1). Leaf blade mass was higher (p < 0.05) in Mombaça cultivar (1518.31 kg DM ha-1), whereas Massai showed higher (p < 0.05) leaf:stem ratio (9.25). Panicum cultivars Tamani, Tanzania and Massai establishment after 75 days, while the other cultivars establish at 105 days of sowing in the Brazilian Northeast.

Morphogenic and structural characteristics of Panicum cultivars during the establishment period in the Brazilian Northeast

This study aimed to evaluate the morphogenic and structural characteristics of six Panicum maximum cultivars during the establishment period. A completely randomized block design with four replicates and six treatments (Tamani, Mombaça, Massai, Tanzania, Aruana and Zuri cultivars) was used. Morphogenic (leaf appearance rate, leaf elongation rate e stem elongation rate), structural (final leaf length, tiller population density e number of leaves per tiller) and productive (forage mass, leaf blade mass, stem mass, senescent material mass and leaf:stem ratio) characteristics were evaluated. There was no difference (p > 0.05) between the cultivars in terms of the number of live leaves per tiller (2.95 leaves/tiller). Mombaça cultivar had (p < 0.05) higher canopy height (50.64 cm) compared with other cultivars. The highest (p < 0.05) tiller population density was observed in Tamani (235.90 tillers m-2) and Massai (201.60 tillers m-2) cultivars. Leaf lifespan (54.18 days), phyllochron (17.40 days/leaf) and leaf senescence rate (0.87 cm tiller day-1) were not different (p > 0.05) between cultivars. However, leaf appearance rate was higher (p < 0.05) in Tanzania (0.07 leaves tiller day-1) than in Aruana cultivar (0.05 leaves tiller day-1). Leaf blade mass was higher (p < 0.05) in Mombaça cultivar (1518.31 kg DM ha-1), whereas Massai showed higher (p < 0.05) leaf:stem ratio (9.25). Panicum cultivars Tamani, Tanzania and Massai establishment after 75 days, while the other cultivars establish at 105 days of sowing in the Brazilian Northeast.(AU)

Tillering dynamics in spring and summer of marandu palisade grass pastures previously used under deferred grazing / [Dinâmica de perfilhamento na primavera e no verão de pastagens de capim-marandu previamente utilizadas sob pastejo diferido]

This work was conducted to evaluate the effect of deferred pasture condition of Brachiaria brizantha cv. Marandu in the late winter on tillering during the growing season. The treatments were three pasture conditions at late winter: short pasture, tall pasture and tall/mown pasture. In September and October, tiller appearance rate (TApR) and tiller mortality rate (TMoR) were greater in the tall/mown pasture. In November and December, tall pasture presented greater TApR. From November to January the TMoR was greater in the tall pasture. The tiller stability index of short and tall/mown pastures were greater in October. The short pasture presented a greater tiller number than the tall and tall/mown pastures during the entire experimental period. Deferred and short pasture of marandu palisade grass at late winter presents in general lower tiller mortality and higher population density of tillers from the early spring onwards, in comparison to tall pasture. The mowing of marandu palisade grass with high forage mass at the late winter, although it only temporarily compromises the population stability of tillers, also stimulates its fast tillering from spring on.(AU)

Este trabalho foi conduzido com o objetivo de avaliar o efeito da condição da pastagem diferida de Brachiaria brizantha cv. Marandu ao final do inverno sobre o perfilhamento durante a estação de crescimento. Os tratamentos foram três condições de pastagem no final do inverno: pasto baixo, pasto alto e pasto alto/roçado. Nos meses de setembro e outubro, a taxa de aparecimento de perfilhos (TApP) e a taxa de mortalidade de perfilhos (TMoP) foram maiores na pastagem alta/roçada. Nos meses de novembro e dezembro, a pastagem alta apresentou maior TApP. De novembro a janeiro, a TMoP foi maior na pastagem alta. Os índices de estabilidade de perfilhos das pastagens baixas e altas/roçadas foram maiores em outubro. A pastagem baixa apresentou maior número de perfilhos do que as pastagens altas e altas/roçadas durante todo o período experimental. A pastagem diferida e baixa de capim-marandu no final do inverno apresenta, em geral, menor mortalidade de perfilhos e maior densidade populacional de perfilhos no início da primavera, em comparação com a pastagem alta. A roçada do capim-marandu com alta massa de forragem ao final do inverno, embora comprometa apenas temporariamente a estabilidade populacional dos perfilhos, também estimula o perfilhamento rápido a partir da primavera.(AU)

Establishment of Brachiariacultivars in the soil-climatic conditions of the Brazilian semi-arid region

This study aimed was the establishment of the genus Brachiaria in the Brazilian semi-arid region. The experiment was conducted from April to June 2016, as a randomized-block experimental design with five treatments and four replicates. Treatments were represented by five Brachiaria cultivars, namely, Marandu, Paiaguás, Piatã, Xaraés and Basilisk. Morphogenetic (leaf appearance rate, leaf elongation rate e stem elongation rate) and structural characteristics (final leaf length, tiller population density e number of leaves per tiller, forage mass, leaf blade mass, stem mass, senescent material mass and leaf:stem ratio) of the forage cultivars were evaluated. Canopy height fitted a linear regression model (P<0,05), with estimated daily increases of 0.50, 0.53, 0.53, 0.54 and 0.56 cm for cvs Basilisk, Marandu, Paiaguás, Piatã and Xaraés, respectively. The number of live leaves in cvs Basilisk and Paiaguás increased linearly (p < 0.05), by 4.3 and 2.8 leaves per tiller, respectively, during the 60-day period. The recommended height at which the growth of Brachiaria cultivars should be interrupted is upon reaching 25 to 35 cm. In the soil-climatic conditions of the Brazilian semi-arid region, the Brachiaria cultivars Basilisk, Marandu, Paiaguás, Piatã and Xaraés are established at 75 days after sowing, which is the recommended time for performing the first harvest or lenient grazing to stimulate tillering.(AU)

Establishment of Brachiariacultivars in the soil-climatic conditions of the Brazilian semi-arid region

This study aimed was the establishment of the genus Brachiaria in the Brazilian semi-arid region. The experiment was conducted from April to June 2016, as a randomized-block experimental design with five treatments and four replicates. Treatments were represented by five Brachiaria cultivars, namely, Marandu, Paiaguás, Piatã, Xaraés and Basilisk. Morphogenetic (leaf appearance rate, leaf elongation rate e stem elongation rate) and structural characteristics (final leaf length, tiller population density e number of leaves per tiller, forage mass, leaf blade mass, stem mass, senescent material mass and leaf:stem ratio) of the forage cultivars were evaluated. Canopy height fitted a linear regression model (P<0,05), with estimated daily increases of 0.50, 0.53, 0.53, 0.54 and 0.56 cm for cvs Basilisk, Marandu, Paiaguás, Piatã and Xaraés, respectively. The number of live leaves in cvs Basilisk and Paiaguás increased linearly (p < 0.05), by 4.3 and 2.8 leaves per tiller, respectively, during the 60-day period. The recommended height at which the growth of Brachiaria cultivars should be interrupted is upon reaching 25 to 35 cm. In the soil-climatic conditions of the Brazilian semi-arid region, the Brachiaria cultivars Basilisk, Marandu, Paiaguás, Piatã and Xaraés are established at 75 days after sowing, which is the recommended time for performing the first harvest or lenient grazing to stimulate tillering.

Forage mass and canopy structure of Zuri and Quênia guineagrasses pasture under rotational stocking

This work evaluated the productive and structural characteristics of the BRS Zuri and BRS Quênia cultivars under rotational stocking management. The evaluations were divided into five periods according to rainfall regime (high, medium, and low rainfall) during 16 months of the years 2016-2018. Pastures were grazed when canopies intercepted 95% of incident light to stubbles corresponding to 50% of the pre-grazing height. The pre- and post-grazing heights varied as a function of cultivar, with higher values for BRS Zuri (89 and 49 cm) than for BRS Quênia (78 and 45 cm). No differences in canopy lowering percentage, forage mass, and stem and dead material dry masses between cultivars were observed, with averages of 41.3%, 5,856, 1,835, and 841 kg ha−1, respectively. The post-grazing canopy height was lower in the second year, which resulted in higher values of canopy lowering percentage (51%). The highest value for leaf:stem ratio for both cultivars was observed in the high rainfall period of the second year. Higher average tiller population density was observed for BRS Quênia (477 tillers m−2) than for BRS Zuri (260 tillers m−2) for all the rainfall periods. Forage bulk density was similar between cultivars and varied according to the periods evaluated, with the highest value observed during the dry period of the year. Forage mass, as well as its component fractions, did not vary between cultivars, but was influenced by the studied periods. The cultivars showed high leaf mass in the pre-grazing forage mass with an average value of 3,174 kg ha−1. The cultivars are similar in morphological composition and offer high yield potential when managed under a rotational grazing system.

Defoliation intensity and leaf area index recovery in defoliated swards: implications for forage accumulation

This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.

Defoliation intensity and leaf area index recovery in defoliated swards: implications for forage accumulation

This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.(AU)

Implantação do capim paiaguás em monocultivo ou em sistema de integração com outras culturas / Establishment of paiaguas palisadegrass in monoculture or in an integration system with other crops

Objetivou-se avaliar características produtivas e estruturais do capim paiaguás implantado em monocultivo e em integração com culturas agrícolas em 2018 e 2019. Os tratamentos avaliados foram: capim paiaguás (CP) em monocultivo e CP integrado com milho, CP integrado com sorgo e CP integrado com soja. O delineamento experimental utilizado foi o de bloco ao acaso, com 4 repetições (parcelas de 160 m²). Foram avaliadas a altura, a densidade populacional de perfilhos, a produção de massa seca e densidade volumétrica da massa seca total, de folhas, colmos e material morto. Os dados foram analisados pelo teste de Tukey a 5% de probabilidade. A produção de massa seca total foi maior no cultivo integrado em relação ao monocultivo. O capim paiaguás em integração com milho apresentou menores produções de massa seca total, de lâmina foliar e de colmos. A porcentagem de lâminas foliares foi maior no capim paiaguás integrado em 2018 e em monocultivo e integrado com milho e soja em 2019. Maiores porcentagens de colmos foram registradas no capim paiaguás em monocultivo em 2018 e em integração com sorgo em 2018 e 2019. De maneira geral, maiores alturas foram encontradas no capim paiaguás em monocultivo e menores no integrado com o milho. As maiores densidades populacionais de perfilhos foram registradas no capim paiaguás em monocultivo e menores no capim paiaguás integrado com milho e sorgo. A integração com culturas agrícolas reduz a produção do capim paiaguás. A cultura agrícola acompanhante altera a composição da forragem produzida pelo capim paiaguás.

The objective of this study was to evaluate the productive and structural characteristics of Paiaguas palisadegrass established in monoculture and intercropped with agricultural crops in 2018 and 2019. The evaluated treatments were: Paiaguas palisadegrass (PP) in monoculture, PP intercropped with maize, PP intercropped with sorghum, and PP intercropped with soybean. The experimental design used was a randomized block, with 4 replications (plots of 160 m²). Sward height, tiller density, dry mass production, and bulk density of total dry matter, of leaves, of stems, and of dead material were evaluated. The data were analyzed using the Tukey test at 5% probability. The total dry mass was higher in intercropping than in monoculture. Paiaguas palisadegrass intercropped with maize showed lower productions of total dry mass, leaf blade, and stems. The percentage of leaf blades was higher in Paiaguas palisadegrass intercropped in 2018 and in monoculture and intercropped with maize and soybean in 2019. Higher percentages of stems were registered in Paiaguas palisadegrass in monoculture in 2018 and in intercropping with sorghum in 2018 and 2019. In general, higher heights were found in Paiaguas palisadegrass in monoculture and smaller when intercropped with maize. The highest tiller densities were observed in Paiaguas palisadegrass in monoculture and the lowest in Paiaguas palisadegrass intercropped with maize and sorghum. Intercropping with agricultural crops reduces the production of Paiaguas palisadegrass. The accompanying agricultural crops alter the composition of the forage produced by the Paiaguas palisadegrass.

Multivariate analysis reveals genetic diversity in Paspalum notatum Flügge

The objective of this study was to evaluate 94 Paspalum notatum genotypes over two growing seasons to estimate genetic dissimilarity through agronomic traits and the distance between genotypes. This information is used to create an ideotype from the best averages obtained for the set of characteristics evaluated. Seven apomitic, three sexual, and 81 hybrid genotypes were compared with native genotypes "André da Rocha", "Bagual", and cultivar "Pensacola" as controls. There is genetic variability in P. notatum for the studied characteristics, and distinct genotypes with superior characteristics can be used in new combinations between apomictic and sexual plants to obtain hybrids. The characters with the greatest relative contribution to the dissimilarity between the genotypes were tiller density, stem dry mass, and leaf dry mass yield. Thus, these characteristics are suitable criteria to infer genetic distance studies in P. notatum. The selection index based on the ideotype is an auxiliary tool in the breeding process. The ideotype must be based on characteristics of interest according to the objective of the breeding program, as well as on the breeder's prior knowledge in relation to culture.

Cultivar, sowing density, or time of emission: What influences mortality and performance of wheat tillers the most? / Cultivar, densidade de semeadura ou momento da emissão: o que influencia mais a mortalidade e desempenho de perfilhos de trigo?

The emission and survival of wheat tillers can be influenced by several factors. This study aimes to evaluate the influence of sowing density, tillering potential, and temporal order of emission on the survival, and performance of individual tillers by contrasting the tillering potential of wheat cultivars. The experiment design consisted of a randomized block design with four replications, in a 2×4 factorial scheme, consisting of two wheat cultivars (TBIO Toruk and TBIO Sossego) and four sowing densities (208, 312, 416, and 500viable seeds m−2). Tillers were identified weekly, according to the temporal order of emission, for four consecutive weeks. The study evaluated emission, survival, and productive performance of all tillers, in addition to plant height, peduncle length, stem diameter, fresh weight, and presence of grains. The overall mortality of emitted tillers was 24%. A decrease of 73% in emission and 92% in tiller survival was observed over a period of four weeks. The increased sowing density led to a decrease of 43% in emission and 44%in tiller survival. The cultivar Sossego presented less tillering potential, but with higher survival rate than Toruk. The first two emitted tillers represented 77% of the total emitted tillers. Surviving tillers emitted in the first week were responsible for 40% of the total presence of grains at the end of the wheat cycle.

A emissão e sobrevivência de perfilhos em trigo depende de diversos fatores. Neste estudo, objetivou-seavaliar a influência da densidade de semeadura, do potencial de perfilhamento e da ordem temporal de emissão de perfilhos, na emissão, na sobrevivência e no desempenho de perfilhos individuais em cultivares de trigo contrastantes quanto ao potencial de perfilhamento. O experimento foi realizado emdelineamento de blocos casualizados, com quatro repetições, em esquema fatorial 2x4; sendo duas cultivares de trigo (TBIO Toruk e TBIO Sossego) e quatro densidades de semeadura (208; 312; 416 e 500 sementes aptas m−2). Os perfilhos foram identificados semanalmente, conforme a ordem temporal de emissão durante quatro semanas consecutivas. Foram avaliadas a emissão, a sobrevivência e o desempenho produtivos de todos os perfilhos, além disso, foram avaliadas a altura de plantas, comprimento do pedúnculo, diâmetro de colmo, massa verde e presença de grãos. A mortalidade geral de perfilhos emitidos foi de 24%. Houve um decréscimo de 73% na emissão e 92% na sobrevivência de perfilhos ao longo de quatro semanas. O aumento da densidade de semeadura promoveu decréscimo de 43% na emissão e 44% na sobrevivência de perfilhos. A cultivar Sossego apresentou menor potencial de perfilhamento, mas com sobrevivência superior a Toruk. Os dois primeiros perfilhos emitidos representaram 77% do total de perfilhos emitidos. Perfilhos sobreviventes emitidos na primeira semana foram responsáveis por 40% do total da presença de grãos ao final do ciclo.

Cultivar, sowing density, or time of emission: What influences mortality and performance of wheat tillers the most? / Cultivar, densidade de semeadura ou momento da emissão: o que influencia mais a mortalidade e desempenho de perfilhos de trigo?

The emission and survival of wheat tillers can be influenced by several factors. This study aimes to evaluate the influence of sowing density, tillering potential, and temporal order of emission on the survival, and performance of individual tillers by contrasting the tillering potential of wheat cultivars. The experiment design consisted of a randomized block design with four replications, in a 2×4 factorial scheme, consisting of two wheat cultivars (TBIO Toruk and TBIO Sossego) and four sowing densities (208, 312, 416, and 500viable seeds m−2). Tillers were identified weekly, according to the temporal order of emission, for four consecutive weeks. The study evaluated emission, survival, and productive performance of all tillers, in addition to plant height, peduncle length, stem diameter, fresh weight, and presence of grains. The overall mortality of emitted tillers was 24%. A decrease of 73% in emission and 92% in tiller survival was observed over a period of four weeks. The increased sowing density led to a decrease of 43% in emission and 44%in tiller survival. The cultivar Sossego presented less tillering potential, but with higher survival rate than Toruk. The first two emitted tillers represented 77% of the total emitted tillers. Surviving tillers emitted in the first week were responsible for 40% of the total presence of grains at the end of the wheat cycle.(AU)

A emissão e sobrevivência de perfilhos em trigo depende de diversos fatores. Neste estudo, objetivou-seavaliar a influência da densidade de semeadura, do potencial de perfilhamento e da ordem temporal de emissão de perfilhos, na emissão, na sobrevivência e no desempenho de perfilhos individuais em cultivares de trigo contrastantes quanto ao potencial de perfilhamento. O experimento foi realizado emdelineamento de blocos casualizados, com quatro repetições, em esquema fatorial 2x4; sendo duas cultivares de trigo (TBIO Toruk e TBIO Sossego) e quatro densidades de semeadura (208; 312; 416 e 500 sementes aptas m−2). Os perfilhos foram identificados semanalmente, conforme a ordem temporal de emissão durante quatro semanas consecutivas. Foram avaliadas a emissão, a sobrevivência e o desempenho produtivos de todos os perfilhos, além disso, foram avaliadas a altura de plantas, comprimento do pedúnculo, diâmetro de colmo, massa verde e presença de grãos. A mortalidade geral de perfilhos emitidos foi de 24%. Houve um decréscimo de 73% na emissão e 92% na sobrevivência de perfilhos ao longo de quatro semanas. O aumento da densidade de semeadura promoveu decréscimo de 43% na emissão e 44% na sobrevivência de perfilhos. A cultivar Sossego apresentou menor potencial de perfilhamento, mas com sobrevivência superior a Toruk. Os dois primeiros perfilhos emitidos representaram 77% do total de perfilhos emitidos. Perfilhos sobreviventes emitidos na primeira semana foram responsáveis por 40% do total da presença de grãos ao final do ciclo.(AU)

Mombaça grass yield as a function of nitrogen fertilization based on the use of the chlorophyll meter / Produtividade do capim mombaça em função da adubação nitrogenada baseada no uso do clorofilômetro

The objective of this study was to evaluate the yield and agronomic efficiency of mombaça grass achieved with the management of nitrogen fertilization, based on the nitrogen sufficiency index (NSI) calculated using measurements obtained with a chlorophyll meter. The experiment was conducted in the field, in São Luís de Montes Belos - GO, Brazil, from November 2016 to May 2018, as a randomized-block design with six treatments and five replicates. Treatments consisted of six N fertilization management strategies (M), namely, M1 - reference, with 150 kg ha-1 N per application; M2 - recommended, with 50 kg ha-1 N per application; M3 - 50 kg ha-1 N when NSI < 98%; M4 - 50 kg ha-1 N when NSI < 94%; M5 - 50 kg ha-1 N when NSI < 90%; and M6 - control treatment, without N application. The NSI was monitored based on the relative chlorophyll content obtained with the chlorophyll meter. Forage canopy height, tiller density, and yield were evaluated. At the end of the 2nd cycle, the recommended, reference, NSI98%, NSI94%, and NSI90% treatments had received 1,050, 350, 300, 250, and 0 kg N ha-1. Control treatment obtained the lowest dry biomass yield, whereas the recommended, NSI98%, and NSI94% treatments showed the highest. Thus, N doses between 1,950 and 300 kg ha-1, in the second cycle, provided statistically equivalent yields in mombaça grass. Considering the DM of both evaluation cycles, the highest yield was achieved with the NSI98% and NSI94% treatments. The application of N doses of 250 to 1050 kg ha-1 provided similar yields. Therefore, the adoption of a nitrogen sufficiency index below 98% and 94% as a parameter allows a reduction and rational use of nitrogen fertilizer.(AU)

Objetivou-se com esse trabalho avaliar a produtividade e eficiência agronômica do capim Mombaça, obtidas com o manejo da adubação nitrogenada, baseada no ISN calculado com as medidas do clorofilômetro. O experimento foi conduzido a campo em São Luís de Montes Belos, GO, de novembro de 2016 a maio de 2018. O delineamento utilizado foi em blocos casualizados, com seis tratamentos e cinco repetições. Os tratamentos foram constituídos por seis manejos de adubação nitrogenada: M1 - Referência com aplicação de 150 kg ha-1 N por aplicação; M2 - Recomendado com 50 kg ha-1 N por aplicação; M3 - 50 kg ha-1 de N quando o ISN < 98%, M4 - 50 kg ha-1 de N quando o ISN < 94%, M5 - 50 kg ha-1 de N quando o ISN < 90% e M6 - Tratamento controle, sem aplicação do N. O monitoramento do ISN foi realizado em função do Índice Relativo de Clorofila (IRC) obtido com o clorofilômetro. Avaliou-se altura do dossel forrageiro, densidade populacional de perfilhos e produtividade. Para matéria seca (MS), ao fim do 2º ciclo, os tratamentos recomendados, referência, ISN 98, 94 e 90% haviam totalizado 1.050, 350, 300, 250 e 0 kg N ha-1. O tratamento controle apresentou a menor produção e os tratamentos recomendado, ISN 98% e 94% as maiores. Portanto doses entre 1.950 e 300 kg N ha-1, no segundo ciclo, promoveram produções estatisticamente equivalentes no capim Mombaça. Considerando a MS dos dois ciclos de avaliação, as maiores produtividades foram nos tratamentos ISN 98% e 94%. A aplicação de doses de 250 a 1050 kg N ha-1 proporcionaram produções semelhantes. Portanto o uso do ISN 98% e 94% como parâmetros possibilita redução e uso racional do fertilizante nitrogenado.(AU)