BRS Zuri Research Articles

Defoliation Dynamics on Grazing Horizons in Pastures Intercropped by Panicum maximum, Brachiaria brizantha, and Brachiaria decumbens

The aim of this study was to quantify and verify the defoliation dynamics process of the Panicum maximum, Brachiaria brizantha, and Brachiaria decumbens intercropping during the formation of four grazing horizons in lenient grazing intensities and high grazing intensity. Pastures were managed in a pregrazing height of 70 cm, and as post-grazing height, the criteria of 40% and 60% were used in relation to the pre-grazing height. The experimental design used was a completely randomized design with a 3x4 factorial arrangement. The first factor was the cultivars of intercropped grasses consisted of 3 cultivars, i.e., BRS Zuri, Xaraés, and Basilisk. The second factor was grazing horizons consisted of 4 levels, i.e., I: one; II: two; III: three; IV: four. In the intercropping managed with 40% of the forage canopy height removal, oscillations were observed in the severity of defoliation of the extended tiller among the intercropped species, in which the tiller reduction of the ‘Basilisk’ was 32% lower in relation to ‘BRS Zuri’. In the intercropping managed with 60% of the forage canopy height removal intensity, disproportionality was observed among the grasses, because the ‘Basilisk’ suffered a higher severity and frequency of pseudostem defoliation. In intercropped pastures managed under grazing intensities of 40%, as the animal explores the grazing horizons, the vertical distribution of the pseudostem could modify the shape and positioning of the depth of the bite, leading the animal to perform less selective grazing among the species. Due to the higher supply of pseudostem mass at the intensity of 60%, it was possible to infer that there was a reduction in forage intake.

Evaluation and reparametrization of mathematical models for prediction of the leaf area of <i>Megathyrsus maximus</i> cv. BRS Zuri

The aim of this study was to verify the precision and accuracy of 5 models for leaf area prediction using length and width of leaf blades of Megathyrsus maximus cv. BRS Zuri and to reparametrize models. Data for the predictor variables, length (L) and width (W) of leaf blades of BRS Zuri grass tillers, were collected in May 2018 in the experimental area of Embrapa Gado de Corte, Mato Grosso do Sul, Brazil. The predictor variables had high correlation values (P<0.001). In the analysis of adequacy of the models, the first-degree models that use leaf blade length (Model A), leaf width × leaf length (Model B) and linear multiple regression (Model C) promoted estimated values similar to the leaf area values observed (P>0.05), with high values for determination coefficient (>80%) and correlation concordance coefficient (>90%). Among the 5 models evaluated, the linear multiple regression (Model C: β0 = -5.97, β1 = 0.489, β2 = 1.11 and β3 = 0.351; R² = 89.64; P<0.001) and as predictor variables, width, length and length × width of the leaf blade, are the most adequate to generate precise and exact estimates of the leaf area of BRS Zuri grass.

Silicon Contribution Via Nutrient Solution in Forage Plants to Mitigate Nitrogen, Potassium, Calcium, Magnesium, and Sulfur Deficiency

This study aimed to evaluate whether silicon application in the nutrient solution is efficient in relieving stress caused by nutrient deficiency (N, K, Ca, Mg, and S) in the forages BRS Zuri (Panicum maximum) and BRS RB331 Ipypora (Brachiaria ruziziensis × Brachiaria brizantha). Two experiments were carried out in a greenhouse with both forages, with plants grown in a nutrient solution in pots filled with washed sand. Treatments were arranged in a completely randomized block design, with five replications and consisted of complete solution (control) and individual omission of nitrogen, potassium, calcium, magnesium, and sulfur in the absence (−Si) and presence of silicon (+Si) at a concentration of 2 mmol L−1 applied via nutrient solution as stabilized potassium sodium silicate. The dry mass of the shoot, root, and clump residual material, accumulation and use efficiency of nutrients, and the description of symptoms of nutritional deficiency were evaluated. Silicon addition in the nutrient solution favored shoot dry matter production and root dry matter production of both forages, in treatments with K, Ca, and Mg omission; the same effect was not observed for N and S. We conclude that the application of silicon attenuates the effects of potassium, calcium, and magnesium deficiency in forages BRS Zuri and BRS RB331 Ipypora, as it increases the accumulated shoot dry mass, due to the greater efficiency in the use of these nutrients. The beneficial effect of silicon was not important in forage plants with nitrogen and sulfur deficiency.

Nitrogen in Shoots, Number of Tillers, Biomass Yield and Nutritive Value of Zuri Guinea Grass Inoculated with Plant-Growth Promoting Bacteria

The objective of this study was to evaluate the effects of plant growth-promoting bacteria (PGPB) strains of Azospirillum brasilense, Pseudomonas fluorescens and Rhizobium tropici on biomass yield, number of tillers, nitrogen accumulation and nutritive value of shoots of Megathyrsus (syn. Panicum) maximus cultivar BRS Zuri (Zuri Guinea grass). For that, one experiment was performed for 14 months to evaluate inoculation and re-inoculation with Azospirillum brasilense strains Ab-V5 and Ab-V6, Pseudomonas fluorescens strain CCTB 03 and of co-inoculation with Rhizobium tropici strain CIAT 899 + A. brasilense strain Ab-V6 combined with N-fertilizer (100 kg of N ha-1). Shoot dry weight yield (SDWY), number of tillers (NT), total N concentration (TNC), total N uptake (TNU) and nutritive value of Zuri Guinea grass was evaluated for eight cuts, and inoculation increased all parameters. In the NT, the treatments inoculated with PGPB were superior to the positive non-inoculated control receiving N-fertilizer, by up to 36%. For the accumulated of SDWY the treatment re-inoculated with P. fluorescens CCTB 03 after each cut was statistically superior tin 7% the positive control. The PGPB when combined N-fertilizer also increased SDWY, NT, the relative chlorophyll index, TNC, total N uptake, neutral detergent fiber, acid detergent fiber, crude protein and in vitro digestibility dry matter of Zuri Guinea grass. The results indicate that PGPB can represent a sustainable alternative for reducing the use of N-fertilizers. The lower effects of re-inoculation with PGPB on the nutrition or yield of Zuri Guinea grass, demonstrating that the determination of the method of application and periodicity of inoculation still require investigation.

Yield, yield components and nutrients uptake in Zuri Guinea grass inoculated with plant growth-promoting bacteria

The objective of this study was to evaluate the effects of strains of Azospirillum brasilense, Pseudomonas fluorescens and Rhizobium tropici on biomass yield and nutrients uptake of shoots and roots of Megathyrsus (syn. Panicum) maximus cultivar BRS Zuri (Zuri Guinea grass) inoculated with plant growth-promoting bacteria (PGPB). Treatments consisted of inoculation and re-inoculation with A. brasilense strains Ab-V5 and Ab-V6, P. fluorescens strain CCTB 03 and of co-inoculation with R. tropici strain CIAT 899 + A. brasilense Ab-V6, with or without N-fertilizer (100 mg dm-3). Evaluations were performed on three cuts for the determination of root and shoot dry weight yield, morphological compositions, tiller mass, number of tillers, and nutrient uptake. Inoculation with bacteria in association with N-fertilizer increased N, NH4+, Ca, Fe, Mn and Zn accumulation in shoots and P and K uptake in roots. P. fluorescens and co-inoculation with R. tropici CIAT 899 + A. brasilense Ab-V6 increased the relative chlorophyll index in relation to the non-inoculated control. As expected, PGPB were not able to fully replace N-fertilization. However, when combined with N-fertilizer, the PGPB increased yield, the relative chlorophyll index, and the uptake of N, NH4+, Ca, Zn, Mn and Fe of Zuri Guinea grass. The results indicate that PGPB can represent a sustainable alternative for reducing the use of N-fertilizers. There were no effects of re-inoculation with PGPB on the nutrition or yield of Zuri Guinea grass, demonstrating that the determination of the method of application and periodicity of inoculation still require investigation.

Dynamics of defoliation of associated grasses

The behavior of variables related to defoliation dynamics was evaluated, and their respective oscillations in two intercropping of tropical climate grasses managed under two grazing intensities. We used pastures formed with two intercropping (BRS Zuri, Xaraés and Basilisk; BRS Quênia, Marandu and BRS Paiaguás), managed in two grazing intensities: 40 and 60% of the pre-grazing height. In the consortium between BRS Zuri, Xaraés and Basilisk, the first canonical variable explained 72.1 and 79.2% of the total variation of the defoliation pattern for the grazing intensity levels of 40 and 60%. In the consortium between BRS Quênia, Marandu and BRS Paiaguás, the first canonical variable explained 84.3 and 89.0% of the total variation of the defoliation pattern for the grazing intensity levels of 40 and 60%. The choice of forage species of tropical climate to form the consortium may be decisive in order to perpetuate plant diversity. From the population density of tillers, it is possible to observe that grasses belonging to functional groups A and B (Zuri, Xaraés, BRS Quênia and Marandu) have a higher probability of coexisting in the same area. The choice of forage species for the establishment of intercropped pastures is important to ensure the coexistence between them and the persistence of the consortium. The analysis of canonical variables assists in explaining the dynamics of defoliation of intercropping through the estimates of severity and frequency of defoliation of extended tiller and pseudostem.

Tropical Forage Grasses Intercropped Under Lenient Grazing Intensities Promote Greater Soil Cover

The diversity of grasses in the intercropping promotes greater soil cover regardless of the grazing intensity used. The aim was evaluated how cultivation systems (monoculture and intercropped) influence the proportion of soil discovered under different grazing intensities. The experiment was conducted at the premises of the Brazilian Agricultural Research Company. The pastures were combined two cultivation systems: monoculture of Panicum maximum cv. BRS Zuri; intercropping of Panicum maximum cv. BRS Zuri, Brachiaria brizantha cv. Xaraes and Brachiaria decumbens cv. Basilisk. Four evaluation cycles were performed, which totaled in 2136 observations. In the contrast between evaluation cycles, it is possible to infer that cycles II, III and IV have a negative effect in relation to cycle I, because after the first evaluation there is an increase in the proportion of soil discovered in the pastures studied. In relation to cultivation systems, the intercropped managed at high grazing intensities impacts negative effects, and it is possible to observe the highest values of uncovered soil, as well as the lowest tussock distribution values. The intercropping of tropical climate pastures has greater soil cover when managed in lenient grazing intensity.

Nitrogen and Phosphate Fertilization Maximize Grass BRS Zuri Performance

The low nutrients levels available in pasture formation reduces the forage yield. Soil correction and fertilization practices are considered priorities in the planning, renovation or recovery of pastures. The aimed of this experiment was to evaluate the effect of nitrogen and phosphate fertilization rate in productivity of the Panicum maximum cv. BRS Zuri. The experimental design was a randomized block design in a 3×4 factorial arrangement, with three doses of superphosphate (0.0, 80.0 and 160.0 kg.ha-1) and four doses of ammonium nitrate (0.0; 20.0; 40.0 and 60.0 kg.ha-1), with three replicates. The following parameters were evaluated at 120 days after implantation: green mass and dry matter yield, plant height, number of plants and tillers per square meter. The doses of 80.0 and 160.0 kg.ha-1 of P2O5 and 60.0 kg.ha-1 of nitrogen combined to each other showed the best results for forage yield.

Chemical composition of Panicum maximum ‘BRS Zuri’ subjected to levels of salinity and irrigation depths

The study of cultivars with moderate flood tolerance is essential to their use in pastures irrigated with saline water. The aim of this study was to evaluate the chemical composition of Panicum maximum ‘BRS Zuri’ under the effect of different irrigation depths and levels of salinity. A randomised block design of split plots was used with five replications per treatment. The treatments resulted from the combination of three levels of water salinity (S1 = 0.6, S2 = 1.8 and S3 = 3.0 dS m-1) and four levels of irrigation (I1 = 60%, I2 = 80%, I3 = 100% and I4 = 120% of the evapotranspiration). The chemical composition of the grass, Panicum maximum ‘BRS Zuri’, cut at 28 days, was evaluated over two cycles. There was an interaction between the factors (salinity x irrigation depth x cycle) for the dry matter (DM) content. With the increase in irrigation depth, there was a linear reduction in the crude protein (CP) content in both cycles. The neutral detergent fibre (NDF) and cellulose (CEL) content increased linearly as a function of the irrigation depth, while the lignin (LIG) content decreased linearly with irrigation depth. It was concluded that high levels of salinity cause reductions in the dry matter content in response to increased water availability and extension of the cultivar cycles. The reduction in saline levels under low water availability results in a higher CP content. Salinity has a negative effect on the NDF, ADF, HEM, CEL and LIG content as the irrigation depth increases.

Morfogênese, características estruturais e acúmulo de forragem do Megathyrsus maximus brs zuri submetido a adubação nitrogenada

A adubação nitrogenada possibilita aumentar a capacidade de suporte das pastagens, entretanto, o uso de elevadas doses pode causar efeitos negativos no crescimento de gramíneas forrageiras. A partir do pressuposto, objetivou-se avaliar a influência de doses crescentes de nitrogênio sob as características morfogênicas e estruturais, acúmulo de biomassa e eficiências de conversão e recuperação do nitrogênio em pastagem de Megathyrsus maximus cv. BRS Zuri. Foram testadas cinco doses de nitrogênio (0, 200, 400, 600 e 800 Kg de nitrogênio/ha) em delineamento experimental de blocos casualizados, com quatro repetições. Foi observado comportamento quadrático para as taxas de alongamento e aparecimento foliar, tempo de vida e o filocrono. Houve aumento no número de perfilhos e na produção de matéria seca quando as plantas foram submetidas à adubação, porém, tanto a eficiência de utilização quanto a recuperação aparente do nitrogênio reduziram linearmente com o aumento do nível de nitrogênio. O uso de fertilizante nitrogenado promoveu melhora nas características morfogênicas (P<0,05) exceto para taxa de alongamento de colmo e taxa de senescência foliar que se mantiveram estáveis. A Adubação com nitrogênio acelera as taxas de crescimento do Megathyrsus maximus cv. BRS Zuri. As respostas máximas nas variáveis morfogênicas, no número de folhas vivas e totais por perfilho são obtidas com doses próximas de 500 kg/ha, enquanto que doses variando de 600 a 647 kg/ha proporcionam maior tamanho de folha por perfilho, densidade populacional de perfilhos e produção de matéria seca. As eficiências de utilização e recuperação do nitrogênio reduzem com o aumento das doses de nitrogênio.

Performance of young Nellore bulls on guineagrass pastures under rotational stocking in the Brazilian Cerrado

New highly productive guineagrass (Megathyrsus maximus syn. Panicum maximum) cultivars have been released in Brazil and grazing trials are necessary to evaluate their carrying capacity and forage quality. The objective of this study was to evaluate the liveweight gains of young Nellore bulls grazing 3 guineagrass cultivars under rotational stocking. The experiment was carried out in Planaltina (Federal District, Brazil) during a single rainy (November‒April) and dry (May‒August) season. Treatments were Massai (control), BRS Tamani and BRS Zuri cultivars. Zuri and Tamani pastures provided greater average daily liveweight gains (ADG) (0.38 and 0.42 kg/head, respectively) over the experimental period than Massai (0.28 kg/head). For all cultivars liveweight gains decreased markedly from May onwards at the beginning of the dry season. Nevertheless, bulls grazing Tamani and Zuri pastures still gained 0.20 kg/hd/d until late August, while those on Massai pastures gained only 0.08 kg/hd/d. The differences in ADGs can be explained to some extent by differences in quality of available forage. In vitro dry matter digestibility of plucked samples of Massai was 555 g/kg, compared with 621 g/kg for Tamani and 590 g/kg for Zuri. Crude protein concentration in plucked samples was also greater for Tamani and Zuri (71.9 and 74.2 g/kg, respectively) than for Massai (62.2 g/kg). As feed wastage was particularly high in Massai, further studies are needed to verify if higher stocking rates during the wet season could result in greater production of live weight per ha on this cultivar, assuming that ADG does not decrease further with the increased stocking rate.

Productive and morphophysiological responses of Panicum maximum Jacq. cv. BRS Zuri to timing and doses of nitrogen application and defoliation intensity

AbstractThe response of plants to nitrogen fertilization is subject to several factors, including the level of stress caused by defoliation. After defoliation, the plant needs to adjust its energy balance to meet the demands of shoot and root recovery. Our objective was to evaluate the production of forage mass and other morphophysiological responses of zurigrass (Panicum maximum cv. BRS Zuri) subjected to five nitrogen doses (0, 20, 40, 60 and 80 mg/dm3) that were applied at two stages (after the cut and after the appearance of the first leaf on the tiller) under two defoliation intensities (15 and 30 cm of residual height). The pot experiment was conducted in a greenhouse in a completely randomized design with three replications, and the forage mass, as well as other morphophysiological traits, was measured in three regrowth cycles after the first standardization cut. Moreover, to understand the effect of cutting height on the root system, the root mass and root carbohydrate content were evaluated at zero, seven and 14 days after the standardization cut. The root mass reduced after 7 days since cutting under the low residual height (15 cm), but no effects on the root carbohydrate content were observed. The dose of nitrogen had a marked effect on most of the variables analyzed, leading to a linear increase in the root mass, the SPAD chlorophyll content and the harvested forage mass, whereas the number of tillers increased quadratically in response to the nitrogen dose. An increase was observed in the harvested forage mass for plants under the 15 cm of residue treatment compared with those under the 30‐cm treatment (16.0 vs. 13.6 g/pot), but no effect was observed for the time of nitrogen application.

PSXI-3 Tussock dynamics in pastures of BRS Zuri and BRS Quênia under rotational stocking.

PSXI-3 Tussock dynamics in pastures of BRS Zuri and BRS Quênia under rotational stocking.

IDENTIFICATION OF IDEOTYPES BY CANONICAL ANALYSIS IN Panicum maximum

Grouping of genotypes by canonical variable analysis is an important tool in breeding. It allows the grouping of individuals with similar characteristics that are associated with superior agronomic performance and may indicate the ideal profile of a plant for the region. The objective of the present study was to define, by canonical analysis, the agronomic profile of Panicum maximum plants adapted to the Agreste region. The experiment was conducted in a completely randomized design with 28 treatments, 22 genotypes of Panicum maximum, and cultivars Mombasa, Tanzania, Massai, Milenio, BRS Zuri, and BRS Tamani in triplicate in 4-m² plots. Plots were harvested five times and the following traits were evaluated: plant height; total, leaf, and stem; dead dry matter yields; leaf:stem ratio; leaf percentage; and volumetric density of forage. The analysis of canonical variables was performed based on the phenotypic means of the evaluated traits and on the residual variance and covariance matrix. Genotype PM34 showed higher mean leaf dry matter yield under the conditions of the Agreste of Alagoas (on average 53% higher than cultivars Mombasa, Tanzania, Milenio and Massai). It was possible to summarize the variation observed in eight agronomic characteristics in only two canonical variables accounting for 81.44 % of the data variation. The ideotype plant adapted to the conditions of the Agreste should be tall and present high leaf yield, leaf percentage, and leaf:stem ratio, and intermediate values of volumetric density of forage.