Avaliação técnica e econômica da adubação nitrogenada em Urochloa brizantha cv. Marandu na Região do Vale do Acre, Brasil

Objetivou-se avaliar o desempenho técnico e econômico da adubação nitrogenada de Uroclhoa brizantha cv. Marandu na região do vale do Acre, entre os meses de agosto de 2011 a junho de 2012. Os tratamentos consistiram de sete doses de nitrogênio (0; 33,75; 67,50; 101,25; 135,00; 168,75 e 202,50kg de N/ha/ano), correspondendo a 0; 75; 150; 225; 300; 375 e 450kg ureia/ha respectivamente. As aplicações foram realizadas a lanço, distribuídas em três etapas. Com o acréscimo das dosagens de nitrogênio observou-se aumento não linear na matéria seca, proteína bruta, cinzas e extrato etéreo nas amostras analisadas, que assim, apresentaram bons parâmetros de valor nutritivo e de desenvolvimento. A dosagem de nitrogênio que obteve melhor desempenho em relação ao custo da adubação nitrogenada foi a de 67,50kg de N/ha, pois este apresentou os melhores custos de produção (U$49,86 de MS e U$30,36 de PB) tornando-se a opção mais vantajosa economicamente. A dosagem de nitrogênio que apresentou melhor desempenho agronômico foi de 168,75Kg N/ha, apresentando valor de proteína bruta de 17,78%. Os parâmetros de valor nutritivo e de desenvolvimento da forrageira tropical U. brizantha cv. Marandu utilizada na região do vale do Acre apresentaram desempenho agronômico satisfatório.

Contribution of tiller age category to herbage accumulation of Marandu palisadegrass under two fertilization regimes

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.

Composición nutricional de seis gramíneas tropicales del estado de Jalisco, México

El objetivo de este estudio fue evaluar la composición química de seis gramíneas forrajeras para el trópico húmedo y seco mexicano: Andropogon gayanus, Andropogon gerardii, Cenchrus ciliaris, Chloris gayana, Megathyrsus maximus y Urochloa brizantha. Las muestras se colectaron en noviembre de 2019, en Tonaya, Jalisco, México. Se determinaron: materia seca, cenizas, proteína cruda (total e insoluble), extracto etéreo, fibra detergente neutro, fibra detergente ácido, hemicelulosa, lignina y celulosa. La evaluación se realizó en el Laboratorio de Nutrición Animal del Departamento de Zootecnia, Universidad Autónoma Chapingo, Texcoco, Estado de México. Cada gramínea se evaluó por triplicado y cada repetición se consideró como unidad experimental. Las medias de composición química fueron separadas mediante la prueba de Tukey (p < 0.05). La correlación entre cada par de variables (p < 0.05) se estimó mediante el coeficiente de Pearson (p < 0.05). A mayor porcentaje de proteína total (p < 0.05) menor porcentaje de extracto etéreo y mayores porcentajes de cenizas y de proteína insoluble. Además, a mayor porcentaje de proteína insoluble, menor porcentaje de lignina (p < 0.05). Probablemente, la proteína se concentra en su fracción insoluble a expensas del extracto etéreo y la lignina. Consecuentemente, gran-tallo-azul (Andropogon gerardii) mostró porcentajes altos de proteína total (10.27%) y cenizas (7.88%), y bajos de lignina (5.23%) y extracto etéreo (1.37%); pero su proteína insoluble no fue tan elevada (2.06%) como la de guinea (Megathyrsus maximus) (6.08%). Por tanto, A. gerardii tuvo el mejor contenido nutricional a los 35 días de rebrote.

FORRAGEIRAS TROPICAIS EM CONSÓRCIO COM MILHO E ADUBAÇÃO NITROGENADA SOBRE AS PROPRIEDADES FÍSICAS DO SOLO

Os sistemas integrados de produção lavoura-pecuária (SIPAs) em associação ao sistema de semeadura direta, sofrem ação do pisoteio animal ou do tráfego intenso de máquinas agrícolas, podendo resultar em alterações nas propriedades físicas do solo. O objetivo deste trabalho foi avaliar o efeito da adubação nitrogenada e manejos das forrageiras tropicais nas propriedades físicas do solo. O experimento foi realizado entre outubro de 2017 e janeiro de 2020, em Marechal Cândido Rondon – PR, em blocos ao acaso, com parcelas sub-subdivididas com uma testemunha adicional e quatro repetições. As parcelas foram constituídas por duas espécies forrageiras consorciadas com o milho: Urochloa brizantha e Magathyrsus maximum, mais a testemunha adicional (milho solteiro). As subparcelas consistiram nos manejos das forrageiras: fenação e pastejo; e nas sub-subparcelas, a presença ou ausência de adubação nitrogenada. Foram determinadas: densidade do solo (Ds), porosidade total (Pt), macro (Ma) e microporosidade (Mi), além da resistência do solo à penetração (Rp). A utilização de nitrogênio (N) em cobertura nas forrageiras após os manejos, aumentou a quantidade de Ma na camada de 0-0,05 m para o primeiro ano. Os valores de Ds estão acima do limite considerado crítico para o desenvolvimento das plantas, porém, com tendência à redução. A adoção do SIPA, independente da espécie forrageira utilizada e manejo adotado, seja fenação ou pastejo, não comprometeu a qualidade física do solo, sendo assim, uma ótima alternativa para a diversificação da produção na propriedade.

Estructura del pasto forrajero con cultivares de Urochloa brizantha bajo sombra

This study evaluated the structure of swards planted with Urochloa brizantha cv. BRS Paiaguas and BRS Piata under the eucalyptus shading system, fertilized via foliar at the beginning of the dry and rainy seasons. The experiment followed a randomized block design with a 4×2×2 (4 leaf fertilizer levels × 2 systems × 2 seasons) factorial arrangement. The results were analyzed using the GLIMMIX PROC of SAS University while means were compared by the T-test at 5%. Foliar fertilizer had a significant (P≤0.05) effect on cv. BRS Paiaguas stem mass under shading while the 3 and 6 L/ha levels produced the lowest (P≤0.05) masses. The forage and root masses were not significantly affected (P≥0.05) by the systems and seasons whereas the dead material mass was not influenced by the seasons. The shading system resulted in (P≤0.05) significantly lower dead material mass for both cultivars and higher (P≤0.05) leaf and stem masses for the cv. BRS Piata. In the rainy season, leaf and stem masses were greater (P≤0.05). Foliar fertilization up to 6 L/ha favored the stem control in cv. BRS Paiaguas under shading. The resulting masses of forage, dead material, and root allow concluding that the cultivars adapted well to the shading and dry season.

An Overview of the Genetics and Genomics of the Urochloa Species Most Commonly Used in Pastures

Pastures based on perennial monocotyledonous plants are the principal source of nutrition for ruminant livestock in tropical and subtropical areas across the globe. The Urochloa genus comprises important species used in pastures, and these mainly include Urochloa brizantha, Urochloa decumbens, Urochloa humidicola, and Urochloa ruziziensis. Despite their economic relevance, there is an absence of genomic-level information for these species, and this lack is mainly due to genomic complexity, including polyploidy, high heterozygosity, and genomes with a high repeat content, which hinders advances in molecular approaches to genetic improvement. Next-generation sequencing techniques have enabled the recent release of reference genomes, genetic linkage maps, and transcriptome sequences, and this information helps improve our understanding of the genetic architecture and molecular mechanisms involved in relevant traits, such as the apomictic reproductive mode. However, more concerted research efforts are still needed to characterize germplasm resources and identify molecular markers and genes associated with target traits. In addition, the implementation of genomic selection and gene editing is needed to reduce the breeding time and expenditure. In this review, we highlight the importance and characteristics of the four main species of Urochloa used in pastures and discuss the current findings from genetic and genomic studies and research gaps that should be addressed in future research.

Silicon Mitigates Nutritional Stress of Nitrogen, Phosphorus, and Calcium Deficiency in Two Forages Plants

Forages are one of the most cultivated crops in the world. However nutritional deficiency is common, specifically in N, P and Ca in many forages growing regions. Silicon (Si) can attenuate the stress caused by nutritional deficiency, but studies on the effects of Si supply on in forages plants are still scarce. This research was carried out to evaluate whether the Si supply can mitigate the effects of N, P and Ca deficiencies of two forages and the physiological and nutritional mechanisms involved. Two experiments were carried out with two forage species (Urochloa brizantha cv. Marandu and Megathyrsus maximum cv. Massai). Was used nutrient solution under balanced nutrition conditions and nutritional stress due to the lack of N, P and Ca combined with the -Si and +Si. The deficiencies of N, P and Ca in both forages cultivation caused damage to physiological and nutritional variables, hence decreasing the plant dry matter. However, in both species forages the addition of Si to the nutrient solution decreased the extravasation of cellular electrolytes and increased the content of phenolic compounds, the green color index, the quantum efficiency of photosystem II, the efficiencies of use of N, P and Ca and the production of shoot dry mass. The beneficial effects of Si were evidenced in stressed and non-stressed plants. The research emphasized the advantage of using Si for the growth of U. brizantha and M. maximum under N, P and Ca deficiency, contributing to their sustainable cultivation.

Does the lowering strategy before the stockpiling period modify the marandu palisade grass production and structure?

ABSTRACT The objective was to identify lowering strategies for Urochloa brizantha cv. Marandu in the beginning of the stockpiling period that increase forage production and improve the structure of stockpiled canopies. Three lowering strategies were evaluated: maintenance of marandu palisade grass with 15cm four months before the stockpiling period; maintenance of palisade grass with 30cm for four months, and lowering to 15cm before the stockpiling period; and maintaining of palisade grass at 45cm for four months, and lowering to 15cm before the stockpiling period. The experimental design was completely randomized, with four replications. At the end of stockpiling, the number of reproductive tillers and forage mass were higher in the canopy under 15/15cm than in the others; the percentage of live leaf was higher in the canopy under 45/15cm than under 15/15cm. Forage production during the stockpiling period was higher in the canopy under 15/15cm and lower in the under 45/15cm. Maintaining 15cm marandu palisadegrass for four months before the stockpiling period increases forage production during this period. The lowering of the marandu palisadegrass from 45 to 15cm at the beginning of the stockpiling period improves the structure of the stockpiled canopy.

Effect of Amazonian tree species on soil and pasture quality in silvopastoral systems

ABSTRACT With the expansion of livestock in the Amazon region, a high percentage of pasture areas are degraded and unproductive. Novel strategies are needed, including the use of native tree species, to simultaneously achieve economic and ecosystem benefits. This study aimed at assessing the effects of five multipurpose native tree species on soil fertility and forage quality of Urochloa brizantha pastures in the southern Amazon. Soil and forage samples were collected under the crown and adjacent to 25 isolated trees belonging to five species during a dry and a rainy season. The presence of native trees positively affected the level of potassium, calcium and manganese in the soil, as well as the mineral matter and crude protein of the forage, especially in the dry season, suggesting a protective effect against the seasonal drought. The tree species had variable effects on soil fertility and forage quality. Soil under Apeiba tibourbou had higher potassium levels, while the forage under Handroanthus serratifolius had higher protein and fiber content. Our results indicate that it is important to diversify silvopastoral systems in the Amazon through the use of native tree species, contributing to the design of novel silvopastoral strategies in the region. Common multipurpose tree species with widespread natural distribution could be used as a complementary aspect of pasture management to provide a protective effect against drought, contribute to enhanced nutrient cycling and even increase forage quality.

Morphogenesis of stockpiled Marandu, Piatã, Xaraés and Paiaguás brachiariagrass cultivars

ABSTRACT The objective this study was to identify differences in the morphogenic patterns of four Urochloa brizantha cultivars (marandu, piatã, xaraés and paiaguás grasses) during the stockpiling period. A completely randomized design was used, with three replications, in experimental plots of 9m². The evaluations took place over 2 years. The grasses were stockpiled for 92 (Year 1) and 95 (Year 2) days. The leaf appearance rate of paiaguás grass was higher, compared to other grasses. In Year 1, the stem elongation rate of xaraés grass was higher than other grasses. At the end of stockpiling period of Year 1, the tiller population density (TPD) was higher in the paiaguás grass, intermediate in the xaraés and marandu grasses and lower in the piatã grass. At the end of the stockpiling period in Year 2, TPD was higher in the paiaguás grass canopy, intermediate in the marandu and piatã grasses canopies, and lower in the xaraés grass canopy. Paiaguás grass has greater leaf growth during the stockpiling period and is therefore suitable for use under stockpiled grazing. Xaraés grass has high stem elongation during the stockpiling period, which is why its use under stockpiled grazing must be accompanied by adjustments in pasture management.