Productive characteristics, chemical composition, in vitro digestibility, and degradation kinetics of two Brachiaria grasses at different regrowth ages.

The study aimed at the effect of different regrowth ages on chemical, productive, and morphological characteristics, in addition to the kinetics of gas production and in vitro digestibility of grasses of the genus Brachiaria. The treatments consisted of two regrowth ages (21 and 35 days) and two grass species (Brachiaria brizantha and B. ruziziensis), in plat with a dimension of 10 × 10 with four replications, totaling 16 plats in a completely randomized design. The regrowth age did not change the leaf:stem ratio of the grasses. Ruziziensis-grass had higher crude protein (CP) content in leaves than Marandu-grass (14.0% versus 10.9% respectively). Marandu-grass leaf had higher NDF content than Ruziziensis-grass (65.0 and 58.3%, respectively) and ADF content (39.6 and 33.2%, respectively). The accumulation rate is high in Marandu-grass regardless of the age of regrowth; however, the in vitro digestibility of dry matter of Ruziziensis-grass is better both in the leaf and in the stem. The regrowth age did not influence the dry matter (DM) and neutral detergent fiber (NDF) in vitro digestibility (ivD) of the leaves. The ivDNDF of leaves of both types of grass were similar. There was an increase in the ivDDM of stem when the regrowth age was 21 days. The DM degradation rate was higher in Marandu-grass at both regrowth ages, and the total gas production was higher at 21 days. The parameters evaluated in the dual-pool logistic model showed interaction for age and cultivar, except for fractions λ (lag time) and total gas production. Marandu-grass presented a greater volume of gas for the rapidly degradable fraction and a lower degradation rate. There was a significant interaction for the parameters evaluated in the models between ages and grasses. The exponential model showed interaction in all fractions. Grasses had reduced CP content and increased fibrous fraction as a function of age, with no reduction in leaf DM and NDF digestibility. The Ruziziensis-grass has higher digestibility at the regrowth ages evaluated, while Marandu-grass has higher yields. We recommend adjusting the in vitro degradation kinetics by the dual-pool logistic model.

Ingestive behavior of Girolando steers supplemented on tropical pastures.

In this study, we evaluated the feeding behavior of Girolando steers on Brachiaria brizantha cultivar Marandu pastures. Twenty-two animals with an average initial weight of 209.09 ± 8.18 kg were distributed in a completely randomized design in a 3 × 2 factorial arrangement (three seasons and two nutritional plans (NP)) with 11 replicates, as follows: rainy season 1 (NP1, mineral mixture ad libitum, and NP2, nitrogen/energy supplement [2 g.kg‒1 body weight [BW]]); dry season (NP1, nitrogen/energy supplement [1 g.kg‒1 BW], and NP2, nitrogen/energy supplement [2 g.kg‒1 BW]); and rainy season 2 (NP1, mineral mixture ad libitum, and NP2, nitrogen/energy supplement ([1 g.kg‒1 BW]). Total chewing time was longer in NP1 (566.44 vs 528.33 min.day‒1 in NP2) (p < 0.05). The grazing, idle, trough, and total chewing times were affected by the interaction between nutritional plans and seasons. The period expended grazing was longer for the NP1. The idle time was affected by the nutritional plans and was lower for the NP1. Feeding at the trough was not affected by the nutritional plans. The animals of the NP2 showed the highest feed efficiencies in DM and NDF (0.91 and 0.52 vs 0.75 and 0.45 in NP1, respectively). Rainy season 2 had the highest efficiencies. The feeding behavior changes according to the supplementation level. Nutritional plan 2 in the second rainy season presented the best results.

How does the condition of the pasture in late winter influence the plant and animal responses in the subsequent seasons?

This study aimed to test the hypotheses: (i) the deferred pasture with lower height in late winter has greater herbage accumulation rate (HAR) and better structure, which facilitates the animal selective grazing during the subsequent spring and summer; (ii) the mowed of high pasture in late winter improves the sward structure but decreases its HAR from the spring. Four pasture condition in late winter of Urochloa brizantha cv. Marandu were evaluated: low (24.1 cm and 2,420 kg.ha-1 of DM); low/mowed (25.2 cm and 2,198 kg.ha-1 of DM, mowed at 8.0 cm); high (49.0 cm and 3,837 kg.ha-1 of DM); and high/mowed (50.0 cm and 4,211 kg.ha-1 DM, mowed at 8.0 cm). The highest live leaf blade percentage (LLBP) and the lowest dead stem percentage (DSP) occurred in the mowed pastures. The live stem (LSP) and dead leaf blade percentages of the grazing simulation sample were higher in the high pasture. This same pattern of response occurred for apparent selectivity indices (ASI) of the live leaf blade and live stem. The ASI of the dead leaf blade was greater in the high pasture, intermediate in the mowed pastures, and lower in the low pasture. The ASI of the dead stem was lower in the low pasture. The HAR was higher in low pasture. Our results support the first hypothesis. The mowing of high pasture in late winter improves the sward structure and the animal selective grazing but does not decrease the HAR during spring and summer.

Does amount of cut vegetal residue on the canopy influence growth and the structural characteristics of marandu palisadegrass?

The pasture mowing in late winter removes the old forage, improving the pasture structure in spring and summer. However, the residue after mowing can affect tillering, thus limiting forage production and the structural characteristics of pasture. We hypothesized that the high amount of cut vegetal residues on the plants in late winter causes a decrease in forage production and modifies the structural characteristics of the forage canopy during the spring and summer. The treatments were four cut vegetal residues (0; 2,000; 4,000 and 8,000 t ha-1 of natural material) deposited on Urochloa brizantha cv. Marandu canopy in late winter. After that, the forage production and structure characteristics were evaluated during the spring and summer for two years. The complete randomized block design, with four replications, was used. The defoliation management was characterized by the adoption of pre- and post-cut heights of 25 and 15 cm, respectively. For both years, there was no effect of cut vegetal residue on all the characteristics evaluated. No variable was affected by the interaction cut vegetal residue amount × year of evaluation. The dead leaf blade percentage was greater in year 2 (6.9%) than in year 1 (3.5%). The average values of variables were live leaf blade percentage = 84.2%; live stem percentage = 8.7%; dead stem percentage = 1.9%; number of vegetative tiller = 653 tiller/m2; number of reproductive tiller = 5 tiller m-2. The forage production rate presented an average value of 46 kg/ha/day of dry matter. The cut vegetal residue amount of up to 8,000 t/ha of natural material on the plants in late winter does not affect the forage production or modifies the structural characteristics of marandu palisadegrass during the subsequent spring and summer.

The sward height at the early stockpiling period modifies the structural characteristics of marandu palisadegrass under continuous stocking

The control of sward height at the early stockpiling period influences the structural characteristics of stockpiled sward in winter. So, we conducted this work on the Cerrado region of Brazil based on the hypothesis that the reduction of pasture height at the beginning of stockpiling period results in: (i) lower stock of forage mass; and (ii) higher live leaf mass, but lower stem mass in stockpiled pasture during the winter. The treatments were four sward heights (15, 25, 35, and 45 cm) at early stockpiling period of marandu palisadegrass (Brachiaria brizantha syn. Urochloa brizantha cv. Marandu). The experiment was conducted in a completely randomized design, with three replications (paddocks with 800 m²). The stockpiled swards were evaluated during the grazing period in winter on days 7 (beginning), 45 (middle) and 90 (end). The vegetative tiller number (VEGT), live leaf mass (LLM) and leaf area index (LAI) were greater in the 15 cm stockpiled pasture than the other treatments. Greater heights (35 and 45 cm) at stockpiling resulted in greater forage mass than lower heights (15 and 25 cm). The VEGT, LLM, number of reproductive tillers, live stem mass, forage mass and LAI values were higher at the beginning than at the end of the grazing period. Our hypothesis has been proven, so that the reduction of sward height of the marandu palisadegrass at the beginning of the stockpiling period results in lesser forage mass, but with better structural characteristics.

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)

Morphogenetic, structural and production traits of marandu grass under nitrogen rates in Neo soil / [Características morfogênicas, estruturais e produtivas do capim-marandu sob doses de nitrogênio em Neossolo]

Most sandy soils have low natural fertility and low levels of organic matter, making nitrogen (N) fertilization essential. Thus, five doses of N were applied (0, 75, 125, 175 and 225mg dm-³) in a randomized block design to evaluate the effects of nitrogen fertilization on the morphogenetic, structural and production characteristics of Brachiaria brizantha cv. Marandu in a Quartzarenic neosoil. The doses of N did not affect the height of the canopy. The leaf elongation rate, final leaf length and number of live leaves increased linearly at the doses of N. Leaf appearance rate, stem elongation rate, leaf lifespan, phyllochron, leaf senescence rate and tiller density showed a quadratic response to the rates There was also an effect of N rates in herbage mass, leaf mass, stem mass, which increased linearly. Brachiaria brizantha cv. Marandu cultivated in Quartzarenic neosoil requires higher doses of N, 175 and 225mg dm-³. Under these conditions, increases in its morphogenetic, structural and productive characteristics are observed. These findings may not be repeated in the most fertile soils with the greatest capacity to supply N.(AU)

A maioria dos solos arenosos tem baixa fertilidade natural e baixos teores de matéria orgânica, tornando a adubação com nitrogênio (N) essencial. Assim, foram aplicadas cinco doses de N (0, 75, 125, 175 e 225mg dm-³) em delineamento de blocos ao acaso, para se avaliarem os efeitos da adubação com nitrogênio nas características morfogênicas, estruturais e produtivas da Brachiaria brizantha cv. Marandu, em um Neossolo Quartzarênico. As doses de N não afetaram a altura do dossel. A taxa de alongamento foliar, o comprimento final da folha e o número de folhas vivas aumentaram linearmente em função das doses de N. A taxa de aparecimento de folhas, a taxa de alongamento do caule, o tempo de vida da folha, o filocrono, a taxa de senescência foliar e a densidade de perfilhos apresentaram resposta quadrática às doses de N. A massa da forragem, a massa foliar e a massa do caule aumentaram linearmente. Brachiaria brizantha cv. Marandu cultivada em Neossolo Quartzarênico requer maiores doses de N, 175 e 225mg dm-³. Nessas condições, são observados aumentos em suas características morfogenéticas, estruturais e produtivas. Esses achados podem não se repetir nos solos mais férteis e com maior capacidade de suprir N.(AU)

First Occurrence and Population Dynamics of Blissus pulchellus (Hemiptera: Blissidae) in Brazil: a new pest of pastures in Roraima

ABSTRACT Cattle production is one of the main economic activities in the state of Roraima, and insect pest attacks in pastures have a negative effect on this sector in the region. Little is known about the species that cause damage to forage fields in the state. This study presents the first report of the occurrence of the chinch bug Blissus pulchellus Montandon (Hemiptera: Blissidae) in Roraima, Brazil and a description of the population dynamics of this pest in pasture areas in this state. Pasture areas were sampled in nine municipalities of Roraima to detect the insect. The population dynamics study was conducted for two years in Alto Alegre municipality, two of which have Brachiaria brizantha cv. Marandu and one of Megathrysus maximus cv. Mombaça (Poaceae) crops. Blissus pulchellus was found in all sampled areas, except in Rorainópolis and São João da Baliza. High densities of this bug were found in in Alto Alegre. This is the first report of B. pulchellus in Brazil. The factors that affect the population dynamics and the damage caused by this insect pest to pastures as well as the risk of dispersal of this pest in Brazil are discussed.

Brachiaria brizantha Grass as a Feedstock for Ethanol Production

HIGHLIGHTS Brachiaria brizantha proved to be a promising biomass for ethanol production. Fermentation was not impaired by the inhibitors furfural and hydroxymethylfurfural.

Abstract Different lignocellulosic biomasses are found worldwide and each country has its own important industrial crop that can be converted into high-value products, such as ethanol. Therefore, evaluation of new biomasses to be used in biorefineries is important to decrease the dependence on non-renewable resources and to guarantee sustainable development. This work evaluated Brachiaria brizantha, a grass commonly used as animal forage, and the standard biomass for 2G-ethanol, sugarcane bagasse. The chemical compositions of both biomasses were determined and different times and temperature of acid pretreatment were tested. Morphological analysis via scanning electron microscopy showed more deconstructed fibers after harsher biomass pretreatments. Simultaneous saccharification and fermentation of pretreated Brachiaria brizantha presented higher efficiency than when using sugarcane bagasse as the carbon source. A biomass conversion of 46 % was achieved when Brachiaria brizantha grass was pretreated with 2% sulfuric acid for 60 minutes. Moreover, fermentation was not impaired by the inhibitors furfural and hydroxymethylfurfural. It was concluded that Brachiaria brizantha is a promising biomass for ethanol production.

Mowing and lowering the marandu palisadegrass sward height at late winter improve the sward structure / A roçada e a redução da altura do capim-marandu no final do inverno melhora a estrutura do pasto

The structure of the sward is important because it influences the responses of plants and animals in grazing conditions. The objective with this work was to evaluate the structural characteristics of the Marandu palisade grass pasture (Brachiaria brizantha syn. Urochloa brizantha) during spring and summer, depending on the condition of the sward at the end of winter. Four grazing conditions at the end of winter were evaluated: short (24.1 cm), short (25.2 cm)/mown (8 cm), tall (49.0 cm) and tall (50.0 cm)/mown (8 cm). The foliar area index was lower in the tall pasture than in the tall/mown pasture. The mass and the volumetric density of dead stem were higher in the tall pasture, intermediate in the short pasture, and lower in mowed pastures. At the beginning of the grazing period, the live stem mass was higher in the tall pasture. At the beginning and middle of the grazing period, the volumetric density of dead leaf lamina was lower in mowed pastures. At the beginning of the pasture period, the short pasture had a higher tiller number (TN). In the middle of the grazing period, the short and short/mown pastures had higher TN. At the end of the pasture period, the lowest TN value occurred in the tall pasture. The tall pasture at the end of winter presents an unfavorable structure to the animal in grazing, while the mowing and reduction in the height of the marandu palisade grass improves the structure of the sward in spring and summer.

A estrutura do pasto é importante porque influencia as respostas de plantas e animais em condições de pastejo. O objetivo com este trabalho foi avaliar as características estruturais do pasto de capim-marandu (Brachiaria brizantha syn. Urochloa brizantha) durante a primavera e o verão, em função da condição do pasto no fim do inverno. Quatro condições de pasto no fim do inverno foram avaliadas: baixo (24,1 cm), baixo (25,2 cm)/roçado (8 cm), alto (49,0 cm) e alto (50,0 cm)/roçado (8 cm). O índice de área foliar foi menor no pasto alto do que no pasto alto/roçado. A massa e a densidade volumétrica de colmo morto foram maiores no pasto alto, intermediárias no pasto baixo, e inferiores nos pastos roçados. No início do período de pastejo, a massa de colmo vivo foi maior no pasto alto. No início e meio do período de pastejo, a densidade volumétrica de lâmina foliar morta foi menor nos pastos roçados. No início do período de pastejo, o pasto baixo apresentou maior número de perfilho (NP). No meio do período de pastejo, os pastos baixo e baixo/roçado tiveram maior NP. No fim do período de pastejo, o menor valor de NP ocorreu no pasto alto. O pasto alto no fim do inverno apresenta estrutura desfavorável ao animal em pastejo, enquanto que a roçada e a redução da altura do capim-marandu melhora a estrutura do pasto na primavera e no verão.

Seed conditioning process in the sanitary quality of marandu grass seeds / Processo de condicionamento de sementes na qualidade sanitária de sementes de capim-marandu

The purpose of seed conditioning process is to separate seeds and their associated structures into different fractions and retain only good and healthy seeds. Thus, the aim of this study was to evaluate the effects the stages of seed conditioning have on the sanitary quality of marandu grass seeds. The seeds were sampled before and during the seed conditioning process, i.e., after exiting the air-screen cleaner and sieves (seeds discharged from the top, middle and bottom sieves), the first gravity separator (seeds drifting around the table, upper and intermediate discharge) and second gravity separator (upper, intermediate and lower discharge). The sanitary analysis was performed using the filter paper method with and without surface disinfestation of the seeds, which were incubated at 20±2°C, with a photoperiod of 12 hours for seven days. The experiment was conducted in a completely randomized design, in a 2x6 factorial scheme (surface disinfestation x stages of the seed conditioning process) and ten replications. The data was submitted to analysis of variance, using the F test and, when significant, the means of the treatments were compared using the Tukey test at 5% probability. It was concluded that it is not possible to improve the sanitary quality of marandú grass seeds through the seed conditioning process.

A finalidade do beneficiamento de sementes é separar as sementes e suas estruturas associadas em diferentes frações e reter apenas sementes boas e saudáveis. O objetivo deste trabalho foi avaliar o efeito das etapas do beneficiamento sobre a qualidade sanitária de sementes de capim-marandú. As sementes foram amostradas antes e durante o beneficiamento: após a saída da máquina de ar e peneiras (descarga das peneiras superior, intermediária e fundo), primeira mesa gravitacional (deriva ao redor da mesa, descarga superior e intermediária) e segunda mesa gravitacional (descarga superior, intermediária e inferior). A análise sanitária foi realizada pelo método do papel de filtro com e sem desinfestação superficial das sementes, as quais foram incubadas a 20 ± 2 °C, com fotoperíodo de 12 h durante sete dias. O experimento foi conduzido em delineamento inteiramente casualizado, em esquema fatorial 2x6 (desinfestação superficial x etapas do beneficiamento) e dez repetições. Os dados foram submetidos à análise de variância pelo teste F e quando significativa, as médias dos tratamentos comparadas pelo teste de Tukey, a 5% de probabilidade. Foi possível concluir que o beneficiamento não é capaz de melhorar a qualidade sanitária das sementes de capim-marandú.

The morphogenesis of marandu palisadegrass at fixed or variable heights in different seasons of the year / Morfogênese do capim-marandu em alturas fixas ou variáveis ​​em diferentes estações do ano

Height variations in a sward over the year may be efficient for increasing plant growth, compared with maintenance of the sward at a constant height. Thus, this experiment was conducted from February 2013 to May 2014 to characterise the development of Urochloa brizantha syn. Brachiaria brizantha cv.Marandu (marandu palisadegrass), managed under three defoliation strategies: constant height (30 cm during the entire experimental period), increasing height (15 cm in the winter, 30 cm in the spring, and 45 cm in the summer), and decreasing height (45 cm in the winter, 30 cm in the spring, and 15 cm in the summer). The experimental design was completely randomised, in a split-plot arrangement, with four replicates. Phyllochron was higher in the winter, but leaf and stem elongation rates and the number of live leaves per tiller were lower compared with the spring and summer. In the summer, the swards under increasing height displayed a higher phyllochron than those under decreasing and constant height. When comparing seasons, the highest leaf senescence rate occurred in spring. In the winter, the sward with increasing height had shorter leaves and stems, in contrast to the summer. The sward under decreasing height showed a high stem elongation rate in the spring. Marandu palisadegrass has great flexibility in terms of defoliation management and a typical seasonal development pattern. Modifying the sward height results in a gradual change in the development of marandu palisadegrass and generates residual effects on the subsequent season.

As variações de altura em um pasto ao longo do ano podem ser eficientes em aumentar o crescimento das plantas, em comparação com a manutenção do pasto a uma altura constante. Assim, este experimento foi conduzido de fevereiro de 2013 a maio de 2014 para caracterizar o desenvolvimento de Urochloa brizantha syn. Brachiaria brizantha cv. Marandu (capim-marandu) manejado com três estratégias de desfolhação: altura constante (30 cm durante todo o período experimental), altura crescente (15 cm no inverno, 30 cm na primavera e 45 cm no verão) e altura decrescente (45 cm no inverno, 30 cm na primavera e 15 cm no verão). O delineamento experimental foi inteiramente casualizado, em esquema de parcelas subdivididas, com quatro repetições. O filocrono foi maior no inverno, mas as taxas de alongamento de folhas e caules e o número de folhas vivas por perfilho foram menores em comparação com a primavera e o verão. No verão, o relvado em altura crescente apresentou filocrono maior do que em altura decrescente e constante. Entre as estações, a maior taxa de senescência foliar ocorreu na primavera. No inverno, o pasto com o aumento da altura apresentava folhas e caules mais curtos, ao contrário do verão. O relvado em altura decrescente apresentou alta taxa de alongamento na primavera. O capim-marandu possui grande flexibilidade em termos de manejo de desfolha e um padrão típico de desenvolvimento sazonal. A modificação da altura do pasto resulta em uma mudança gradual no desenvolvimento do capim-marandu e gera efeitos residuais na estação subsequente.

Number and morphology of tiller age groups during summer in Marandu palisadegrass pastures previously used under deferred grazing / Número e morfologia de faixas etárias de perfilhos durante o verão em pastos de capim-marandu previamente utilizados sob pastejo diferido

The relative contribution of young, mature and old tillers in the canopy influences the production and structure of the pasture. The objective with this work was to evaluate the balance between tiller appearance and tiller death (BAL) during spring and early summer, the morphology and percentages of young, mature and old tillers in Brachiaria brizantha cv. Marandu (marandu palisadegrass) with three conditions in late winter: short (24.1 cm), tall (49.0 cm) and tall (50.0 cm)/mown (8 cm). Tall and tall/mown pastures presented higher BAL in September and October, respectively. In January, BAL was higher in short and tall/mown pastures than in tall pasture. The tiller number was higher in short pasture, intermediate in tall/mown pasture and lower in tall pasture. The percentage of old tillers was higher in short and tall pastures compared to tall/mown pasture. The percentage of live leaf lamina reduced, while the percentage of dead leaf lamina increased with tiller age. Mowing of the tall marandu palisadegrass pasture in late winter increases the renewal of tillers in the spring and decreases the percentage of old tillers in the summer. The old tillers present worse morphology than young tillers.

A contribuição relativa de perfilhos jovens, maduros e velhos no dossel influencia a produção e a estrutura do pasto. O objetivo com o trabalho foi avaliar durante a primavera e o início do verão o balanço entre aparecimento e mortalidade de perfilho (BAL), a morfologia e as percentagens de perfilhos jovens, maduros e velhos nos pastos de Brachiaria brizantha cv. Marandu (capim-marandu) com três condições ao fim do inverno: baixo (24,1 cm), alto (49,0 cm) e alto (50,0 cm)/roçado (8 cm). Os pastos alto e alto/roçado apresentaram maior BAL em Setembro e Outubro, respectivamente. Em Janeiro, o BAL foi maior nos pastos baixo e alto/roçado do que no pasto alto. O número de perfilho foi maior no pasto baixo, intermediário no pasto alto/roçado e menor no pasto alto. As percentagens de perfilhos jovens e velhos foram maiores nos pastos baixo e alto, em comparação ao pasto alto/roçado. A percentagem de lâmina foliar viva reduziu, enquanto que a percentagem de lâmina foliar morta aumentou com a idade do perfilho. A roçada do pasto alto de capim-marandu no fim do inverno aumenta a renovação de perfilho na primavera e diminui a percentagem de perfilho velho no pasto no verão. O perfilho velho apresenta pior morfologia do que o perfilho jovem.

Crotalaria species in succession to soybean for the management of Pratylenchus brachyurus / Espécies de Crotalaria em sucessão à soja para o manejo de Pratylenchus brachyurus

ABSTRACT: Soybean is the main agricultural crop in the State of Mato Grosso do Sul, Brazil. It is primarily cultivated in a crop succession system, in wich soybean is grown in spring/summer, followed by corn or graminaceous pastures in autumn/winter as a second crop. Due to the intensive cultivation, new phytosanitary problems have arisen, among them the root-lesion nematode, Pratylenchus brachyurus, which besides causing damage to plant roots, can be important gateway for other soil pathogens. The recent occurrence of high nematode population densities has brought great concern due to the limited resistant soybean genotypes available. Besides, the use of nematicides only reduces nematodes populations temporarily. A viable alternative for the control of soil nematodes could be the use of Crotalaria spp. in succession or rotation with soybean. Crotalaria is immune or a bad host to the nematode, besides having high capacity of biological nitrogen fixation. Thus, the objective of the present research was to define the best way of insertion of this legume as a second crop in soybean production systems to reduce the population density of the root-lesion nematode. Two experiments were carried out: one in the field, in an infested area, and other in a greenhouse. In both experiments, the treatments were: 1) Zea mays, 2) Brachiaria brizantha cv. Xaraés,, 3) Z. mays + Crotalaria spectabilis, 4) Z. mays + C. ochroleuca, 5) B. brizantha cv. Xaraés + C. spectabilis, 6) B. brizantha cv. Xaraés + C. ochroleuca, 7) C. spectabilis, and 8) C. ochroleuca. The effect of the treatments was evaluated by estimating the number of nematodes in the roots of autumn/winter crops, as well as in the roots of the soybean cultivated in the sequence. The cultivation of both Crotalaria species provided suppression of the nematode population. However, when intercropped with corn or Xaraés palisade grass, the suppressive effect of Crotalaria was supplanted by corn and Xaraés palisadegrass susceptibility to the root-lesion nematode.

RESUMO: A soja é a principal cultura agrícola explorada no Estado do Mato Grosso do Sul, cultivada prioritariamente no sistema de sucessão com milho safrinha. Com expansão da cultura, novos problemas fitossanitários surgiram, como o nematoide das lesões radiculares, Pratylenchus brachyurus. A ocorrência recente de altas densidades populacionais do nematoide trouxe preocupação pela limitada quantidade de genótipos de soja resistentes e o uso de nematicidas reduzir temporariamente a população. Uma alternativa viável para controle seria o uso de crotalária em sucessão ou rotação com a soja, pois esta é má hospedeira ou imune a nematoides. Assim, o objetivo do presente trabalho foi definir a melhor forma de inserção dessa leguminosa em sucessão com soja para redução da densidade populacional do Pratylenchus brachyurus. O trabalho consistiu de dois experimentos: à campo, em uma área infestada, e em casa de vegetação. Os tratamentos utilizados em ambos experimentos foram: 1) Zea mays, 2) Brachiaria brizantha cv. Xaraés, 3) Z. mays + Crotalaria spectabilis, 4) Z. mays + C. ochroleuca, 5) Xaraés + C. spectabilis, 6) Xaraés + C. ochroleuca, 7) C. spectabilis, 8) C. ochroleuca. O efeito dos tratamentos sobre densidade populacional do nematoide foi avaliado por: estimativa do número de nematoides nas raízes; cálculo da variação da população durante todo o experimento; fator de reprodução e; características fitotécnicas. O cultivo das espécies de Crotalaria, sem consorciação, proporcionaram supressão da população dos nematoides. Todavia o efeito supressor das crotalárias consorciadas foi suplantado pela suscetibilidade do milho e Xaraés ao Pratylenchus brachyurus.

Apparent selectivity of sheep in deferred marandu palisadegrass pastures with variable initial heights / Seletividade aparente de ovinos em pastos de capim-marandu diferidos com alturas iniciais variáveis

The objective of this study was to evaluate the apparent selectivity of sheep in marandu palisadegrass (Urochloa brizantha cv. Marandu) pastures with four heights at the beginning of the deferment period (15, 25, 35 and 45cm). The deferment period was 92 days and started on 03/21/2014. Evaluations occurred in the beginning (first week), middle (45th day) and end (92nd day) of the grazing period, in winter (06/21/2014 to 09/21/2014). Deferred pastures with 15 and 25cm presented lower forage mass (FM), but higher live leaf (LL) percentage in FM than deferred pastures with 35 and 45cm. The live stem percentage in the FM and the apparent selectivity index (ASI) of the LL were superior in the deferred pasture with 45cm. The dead stem (DS) percentage in the grazing simulation (GS) and the ASI of this morphological component were lower in the pasture with 15cm, compared to the deferred pasture with 45cm. The FM and the LL percentages in FM and in the GS sample decreased, while the DS percentages in FM and in GS sample increased with the grazing period. Marandu palisadegrass with 15cm at beginning of the deferment period improves the morphology of the deferred pasture. Selective grazing is difficult during the grazing period.(AU)

Objetivou-se avaliar a seletividade aparente de ovinos em pastos de capim-marandu (Urochloa brizantha cv. Marandu) com quatro alturas no início do diferimento (15, 25, 35 e 45cm). O período de diferimento foi de 92 dias e iniciou em 21/03/2014. As avaliações ocorreram no início (primeira semana), meio (45° dia) e fim (92° dia) do período de pastejo, no inverno (21/06/2014 a 21/09/2014). Os pastos diferidos com 15 e 25cm apresentaram menor massa de forragem (MF), mas maior percentual de folha viva (FV) na MF do que os pastos diferidos com 35 e 45cm. O percentual de colmo vivo na MF e o índice de seletividade aparente (ISA) da FV foram superiores no pasto diferido com 45cm. O percentual de colmo morto (CM) na simulação de pastejo (SP) e o ISA desse componente morfológico foram menores no pasto diferido com 15cm, em comparação ao diferido com 45cm. A MF e os percentuais de FV na MF e na amostra de SP se reduziram, enquanto os percentuais de CM na MF e na amostra de SP aumentaram com o período de pastejo. O capim-marandu com 15cm no início do período de diferimento melhora a morfologia do pasto diferido. O pastejo seletivo é dificultado no decorrer do período de pastejo.(AU)

Improved Pastures Support Early Indicators of Soil Restoration in Low-input Agroecosystems of Nicaragua.

Pasture degradation hinders livestock production and ecosystem services that support rural smallholder communities throughout Latin America. Silvopastoral systems, with improved pasture cultivars (especially Brachiaria spp.) and multipurpose trees, offer a promising strategy to restore soils and improve livelihoods in the region. However, studies evaluating the impact of such systems on pasture productivity and soil health under realistic smallholder constraints are lacking. We evaluated the impact of improved pasture grass and tree establishment on a suite of soil health indicators in actively grazed, low-input, farmer-managed silvopastoral systems. In August 2013, paired pasture treatments (improved grass with trees vs. traditional pastures) were established on nine farms with similar land-use histories near Matagalpa, Nicaragua. On each farm, one treatment was left as traditional pasture with naturalized grass (Hyparrhenia rufa), while the adjacent treatment was sown with the improved grass (Brachiaria brizantha cv. Marandu) and planted with tree saplings without fertilizer. In August 2015, we measured standing biomass and a suite of chemical, biological, and physical soil health variables. Improved silvopastoral systems with B. brizantha produced more standing grass biomass and supported higher levels of earthworm populations and permanganate oxidizable carbon (POXC) compared to the traditional control. Correlations suggest that earthworms and POXC were associated with incipient improvements to soil aggregate stability and water holding capacity. We report measurable improvements to soil health just two years following the establishment of improved pasture systems under common smallholder management practices and suggest that these systems, even with minimal fertility inputs, have the potential to enhance regional sustainability.

Inclusion of licuri meal in the diet of pasture dairy cows.

The objective of this study was to evaluate the inclusion of increasing levels of licuri meal as a substitute for soybean bran in the diet of pasture-based dairy cows and its effects on the intake, nutrient digestibility, and milk production and composition. Eight crossbred Holstein/Zebu cows were used in two 4 × 4 Latin square plots. The diets contained increasing percentage of licuri meal (0.0, 4.16, 7.09, and 9.45%) in the total diet, replacing soybean bran. The inclusion of licuri meal in the diet affected total dry matter intake and dry matter intake in relation to body weight, which presented a quadratic effect. The same behavior was observed for the consumption of EE, CP, TDN, and NDFap. The NFC consumption showed a linear decrease with the addition of the by-product in the diet. There was no influence of the inclusion of the licuri meal on the digestibility of the DM, CP, NFC, and TDN, while the digestibility of the NDFap and EE presented increasing linear effect. There was a reduction of milk production and food efficiency with the inclusion of increasing levels of the meal. The fat content in milk showed a linear increasing effect. Ditto for cholesterol. It is recommended to include not more than 7.00% of licuri meal for lactating cows with an average production of 20 kg day-1.

Intake, digestibility, and growth performance of Girolando bulls supplemented on pasture in Bahia, Brazil.

The objective of this trial was to evaluate intake, digestibility, and growth performance of Girolando bulls submitted to two nutritional planes while grazing on Brachiaria brizantha cv. Marandu pasture. Twenty-two animals, with average initial body weight = 209.1 ± 8.2 kg, were used in this trial. The experimental design was repeated measurements, in a 2 × 3 factorial arrangement, with two nutritional planes (NP1 and NP2) and three seasons of the year, with 11 replicates per treatment. The animals of the NP1 received mineral mixture ad libitum during rainy season 1 (15 February through 5 July 2014), energy protein supplement in the amount of 1 g d kg BW-1 during the dry season (from 6 July through 22 November 2014), and again mineral mixture ad libitum during rainy season 2 (from 23 November 2014 through 9 March 2015). The NP2 animals received 2 g d kg BW-1, 2 g d kg BW-1, and 1 g d kg BW-1 of energy-protein supplement in the respective seasons of the year. Forage intakes were similar between nutritional planes, 6.8 and 7.6 kg DM day-1 and 2.1 and 2.22% BW for NP1 and NP2, respectively. There was no statistical difference (level) between the intakes of neutral detergent fiber corrected for ash and protein (4.1 and 4.3 kg day-1 and 1.2 and 1.3% BW, respectively for nutritional planes 1 and 2). For the other nutrients, NP2 showed greater values. The highest intakes and digestibilities of dry matter, organic matter, and non-fiber carbohydrate were in rainy season 2. Performance and feed conversion were similar among NPs. This study showed that lower levels of supplementation could be done in order to reduce feeding costs with no impact on performance.

Biological and economic performance of genetic groups under different diets / Desempenho biológico e econômico de grupos genéticos sob diferentes dietas

A grazing trial to evaluate biological and economic efficiencies for rearing young animals exclusively on pasture from weaning at 7 months of age, with average initial weight of 220 ± 12 kg, to slaughter was conducted from May 2006 to October 2007. Two levels of combined supplementation during the first dry period and four genetic groups (F1 Angus-Nellore; ½Braford-»Angus-»Nellore; ½Brahman-»Angus-»Nellore; and ⅝Charolais-⅜Nellore) were used following a 4 by 2 factorial arrangement and eight replications in a completely randomized design. During both dry periods, eight paddocks of deferredBrachiaria brizantha were utilized. During the first dry period, concentrated mix (CM) and protein-mineral mixture (PMM) were provided in quantities of 0.8% and 0.2% of body weight (BW), respectively, for 142 days. During the subsequent rainy period, the animals were transferred to eight guinea grass paddocks for 197 days. During the second dry period, the animals were allocated to the same eight palisade grass paddocks used during the previous dry season. Steers had received supplementary diet with the same CM used before at 0.8% of BW. Animals supplemented with CM gained more BW than those supplemented with PMM; however, during the rainy season, steers supplemented with PMM performed better than those receiving CM during the preceding dry period. Using concentrate since the first dry season is a risky option in economic terms, as only the Angus-Nellore group showed a positive but small gain.(AU)

O experimento foi conduzido de maio de 2016 a outubro de 2017 com o objetivo de avaliar as eficiências biológica e econômica de animais exclusivamente em pastos, da desmama ao abate. Foram avaliados dois níveis de suplementação alimentar combinados com quatro grupos genéticos durante o período seco: F1 Angus-Nelore; ½Braford-»Angus-»Nelore; ½Brahman-»Angus-»Nelore; e⅝Charolais-⅜Nelore, seguindo-se um arranjo fatorial 4 x 2 com oito repetições em delineamento completamente ao acaso. Durante os dois períodos secos avaliados, oito piquetes de Brachiaria brizantha diferida foram utilizados. No primeiro período seco, mistura concentrada (MC) e mistura mineral múltipla (MMM) foram fornecidas nas quantidades de 0,8 e 0,2% do peso vivo (PV), respectivamente, durante 142 dias. Durante a estação das águas subsequente, todos os animais foram transferidos para oito piquetes de Panicum maximum, por 197 dias. No segundo período seco, os animais foram alocados nos mesmos oito piquetes de braquiária utilizados no período seco anterior e receberam suplementação alimentar MC, no mesmo nível, 0,8% PV utilizado anteriormente. Animais suplementados com MC apresentaram maior ganho de peso que animais recebendo MMM; entretanto, durante o período chuvoso, estes animais apresentaram melhor desempenho que àqueles que receberam MC durante o período seco. Animais Angus-Nelore apresentaram desempenho superior aos demais cruzamentos, destacando-se a precocidade da raça em alcançar o ponto de abate. A utilização de suplemento concentrado desde a primeira seca após desmama é uma opção de risco econômico, uma vez que apenas o grupo genético Angus-Nelore apresentou pequeno incremento positivo de ganho.(AU)

Persistence of picloram in soil with different vegetation managements.

Herbicides with long residual period may increase the risk of environmental contamination. Adequate management of forage can reduce the half-life of the picloram, one of the most herbicides used in weed control. This study aims to determine the half-life of picloram, using high-performance liquid chromatography in a cultivated soil with Brachiaria brizantha trimmed or not. Brachiaria brizantha was cultivated in 60 pots filled with samples of oxisol, and 30 others were kept uncultivated with this forage. This plant was cut off close to the ground, after 60 days of emergency on 30 vessels. Picloram was applied in all of the plots. Soil samples were collected at 2, 16, 30, 44, 58, 72, 86, 120, 150, and 180 days after the application of this herbicide. These samples were air-dried and stored at - 20 °C. Picloram was extracted by HPLC/UV-Vis detector. Half-life of this herbicide was calculated using kinetics models. The mere presence of roots in treatment with signalgrass cutoff did not reduce the concentrations of this herbicide, except when the emergence of new leaves occurred. The absence of B. brizantha cultivation in areas with application of picloram increases the risk of environmental contamination and successive crops due to the half-life of this herbicide. Brachiaria brizantha reduced half-life picloram and environmental risk in pastures. The validation method is suitable for determining picloram in low concentrations in soil.