Brachiaria Brizantha Research Articles

A quantitative revision of the waterlogging tolerance of perennial forage grasses

Waterlogging tolerance of eight C4 and seven C3 perennial forage grasses was reviewed. The median waterlogging duration was similar between species’ type, ranging between 18 and 21 days. Inter- and intra-species variability was found in shoot and root biomass in response to waterlogging. Urochloa brizantha (C4), Brachiaria hybrid (C4) and Dactylis glomerata (C3) were the less tolerant species to waterlogging (shoot biomass median of 45%, 53% and 80% of controls), while U. humidicola (C4), Paspalum dilatatum (C4), Festuca arundinacea (C3) and Lolium perenne (C3) were the most tolerant (shoot biomass median of 97%, 101%, 87% and 94% of controls). A similar ranking of responses was found among species for root biomass. The formation of aerenchyma/root porosity (a key trait for waterlogging tolerance) was evaluated mainly in U. humidicola and P. dilatatum (C4 waterlogging-tolerant species), which showed considerable constitutive porosity (13% and 32%) and final values of 30% and 41% under waterlogging. Net photosynthesis and stomatal conductance as typical leaf physiological responses matched species’ waterlogging tolerance, with the impact of hypoxia higher in C3 than in C4 species. Gaps in knowledge about waterlogging tolerance in forage grasses are: (i) additional studies on C3 perennial grasses for temperate pasture areas prone to waterlogging, (ii) identification of traits and responses aiding plant recovery after waterlogging (and also during the stress), (iii) reassessment of waterlogging tolerance considering plant developmental stage (e.g. adult vs young plants), and (iv) evaluation of sequential (i.e. waterlogging − drought) and combined (i.e. waterlogging + salinity) stresses, which often co-occur in pasture lands.

Carcass characteristics, meat quality and composition of lambs finished in cultivated pastures

Abstract Thirty-two Santa Ines male lambs, not castrated, were distributed in a randomized block design to evaluate the effects of different tropical forage cultivars (two Panicum maximum (Syn. Megathyrsus maximus): Aruana and Massai, and two Brachiaria brizantha (Syn. Urochloa brizantha) Marandu and Piata) on carcass characteristics, quality, physical composition, and meat chemistry. The data were subjected to an analysis of variance, and the means compared using the Tukey test at 5% significance. There was no effect of cultivars on body weight, slaughter weight, and biometric measurements of the carcass. The Aruana and Piata cultivars provided higher weights of hot and cold carcasses when compared to the Massai and the Marandu had no significant differences compared to the others. The animals kept in the pasture of the Aruana cultivar showed higher shank yields. However, forage cultivars did not affect the ribeye area or subcutaneous fat thickness. There was also no effect of cultivar on pH, temperature, cooking losses, cooling losses, and meat shear strength. The cultivars did not change the quality and composition of the meat. However, the Aruana, Piata, and Marandu cultivars were the ones that provided higher carcass weights and ham yields.

Tussock and tiller population dynamics on rotationally stocked Piatã palisadegrass (

Context Integrated crop–livestock–forestry systems can be an alternative to monoculture pastures; however, the effect of the arboreal component on tillering and tussock dynamics of understorey grass canopy is not well understood. Aims Our objective was to evaluate the patterns of tillering dynamics, population stability and tussock distribution of Piatã palisadegrass (Urochloa brizantha) as affected by contrasting shading regimes in the Brazilian Amazon biome. Methods The following three shading regimes were assessed: pasture with no trees (no shading, NS), moderate shading (MS, 338 trees ha−1), and intense shading (IS, 714 trees ha−1). Pastures were rotationally grazed by dairy heifers. Paddocks from MS and IS were stratified into three sampling strips, including two closer to the tree rows (i.e. lateral) and one between the two lateral strips (i.e. central). Two methods for monitoring sward canopy light interception (LI) were used for IS regime, namely, LI taken under the tree canopy (i.e. inside) and LI was taken above the tree canopy (i.e. outside). Key results Relative to NS, there was a reduction in photosynthetically active radiation transmittance of 18.1% and 37.1% on MS and 49.9% and 52.0% on IS for central and lateral shading strips respectively. Overall, the increase in shading level was associated with a decrease in average tussock perimeter, tiller population density, and an increase in the frequency of bare ground. Conclusions Our findings clearly indicate the key role of the light environment as a determinant of Piatã palisadegrass horizontal structure. Implications It highlights the importance of planning the levels of tree density and layout in areas of crop–livestock–forestry integration.

Impact of treated sewage effluent on soil fertility, salinization, and heavy metal content

A long-term experiment (2013 to 2017) of treated sewage effluent (TSE) levels via fertigation in a humid tropical region was installed in Jaboticabal, state of São Paulo, Southeast of Brazil, to evaluate the impact of TSE on soil fertility and the potential for salinization and heavy metal contamination of an Oxisol. The area was cultivated with Urochloa brizantha under the application of four TSE levels at the irrigation depth (0, 11, 60, and 100% TSE) during the four years of the experiment. The TSE chemical composition was monitored throughout the experimental period. The heavy metal levels and soil fertility were evaluated in the 0-0.10 and 0.10-0.20 m layers at the end of the four years of the experiment. Fertigation using TSE did not increase the concentration of potentially toxic elements (As, Cd, Cu, Hg, Mo, Ni, Pb, Se, and Zn) in the soil due to their low concentration in the effluent. A higher Na concentration was also observed at high TSE levels (60 and 100%). However, the sodium adsorption rate in the TSE was low, generating no potential for soil salinization and sodification. Fertigation with TSE levels increased soil fertility, increasing by more than 10% the P content and base saturation in the soil compared to control. According to the chemical attributes evaluated in the soil and effluent, this long-term study showed that TSE application via fertigation in humid tropical regions on clayey soils cultivated with forage grasses is recommended.

Estimating productivity and nutritive value of Marandu palisadegrass using a proximal canopy reflectance sensor

Abstract In intensive livestock production systems, estimating forage production and its nutritive value can assist farmers in optimizing pasture management, stocking rate, and feed supplementation to animals. In this study, we aimed to use vegetation indices, determined using a proximal canopy reflectance sensor, to estimate the forage mass, crude protein content, and nitrogen in live forage of Marandu palisadegrass (Urochloa brizantha). Pasture canopy reflectance was measured at three wavelengths (670, 720, and 760 nm) using a Crop Circle device equipped with an ACS-430 sensor. Total forage mass, plant-part composition, leaf area index (LAI), and crude protein content were assessed during 14 growth cycles in a pasture under four management regimes, comprising different combinations of two N fertilization rates and two irrigation schedules. For each forage assessment, pasture canopy reflectance data were used to calculate the following vegetation indices: normalized difference vegetation index, normalized difference red edge, simple ratio index (SRI), modified simple ratio, and chlorophyll index. In addition, we also performed analyses of the linear and exponential regressions between vegetation indices and total forage mass, leaf + stem mass, leaf mass, LAI, crude protein content, and nitrogen in live forage. The best estimates were achieved for total forage mass, leaf + stem mass, leaf mass, and nitrogen in live forage using SRI (R2 values between 0.72 and 0.79). When estimating pasture productive variables (total forage mass, leaf + stem mass, leaf mass, and LAI) from SRI, the equations showed R2 values between 0.69 (leaf mass) and 0.74 (LAI) and relative errors ranging from 19% to 21%. For each of the water and nitrogen supply conditions evaluated, this index facilitated the monitoring of forage mass time series and nitrogen in live forage and the extraction of this nutrient by the pasture.

Produtividade de mandioca em cultivo convencional e plantio direto em sistemas de integração lavoura-pecuária

Abstract The objective of this work was to evaluate cassava (Manihot esculenta) crop yield, as well as soil density and carbon content, under no tillage and conventional cultivation, in rotation with palisade grass (Urochloa brizantha) subjected to grazing. Treatments consisted of cassava cultivated as follows: in conventional tillage after 2 (CC-2P) and 4 (CC-4P) years of pasture; in no-tillage after 2 (NTC-2P) and 4 (NTC-4P) years of pasture; and with perennial pasture (PP) of palisade grass. The CC-2P treatment showed higher cassava yield in the 2016/2017 crop year (63.29 Mg ha-1) than NTC-2P (47.85 Mg ha-1). However, in the 2018/2019 crop year, no significant yield differences were observed between CC-4P (60.95 Mg ha-1) and NTC-4P (60.68 Mg ha-1). Between 2012 and 2019, soil carbon content (0-10 cm) decreased in the CC-2P treatment. In 2019, carbon stock was higher for NTC-4P compared with CC-4P and CC-2P, increasing from 16.41 to 21.46 Mg ha-1 between 2012 and 2019. Cassava yield varies depending on crop year, whereas soil carbon content decreases after CC-2P, but increases after NTC-4P.

Supplementation of Lambs on Tropical Aruana (Megathyrsus Maximus) or Marandu (Brachiaria Brizantha) Grass: Body Weight Gain, Intake, Digestibility, and Production Costs

Supplementation of Lambs on Tropical Aruana (Megathyrsus Maximus) or Marandu (Brachiaria Brizantha) Grass: Body Weight Gain, Intake, Digestibility, and Production Costs

Morphogenetic and structural traits of Ipyporã grass subjected to nitrogen fertilization rates under intermittent grazing

ABSTRACT: 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.

Sequential cutting of Urochloa brizantha cv. MG 5 changes flowering season and seed production components

ABSTRACT: In tropical grass seed production fields, reducing plant size can increase the solar radiation to the base of the plant canopy and improve the quantity and quality of the seeds produced. This research studied the responses of the production components, the productivity, and the seed quality of U. brizantha cv. MG-5 to different canopy sequential cuttings under cultivation conditions in rain fed systems. Two experiments were carried out (agricultural year 2015/16 (s1) and 2016/17 (s2)) in a randomized block experimental design with four repetitions. The treatments consisted of sequential cut-off, indicating the month of the last cut and the agricultural year: for the 2015/16 agricultural year: Aug - s1, Sep - s1, Oct - s1, Nov - s1, Dec - s1, Jan - s1, and Feb - s1; for the 2016/17 agricultural year: Aug - s2; Set - s2; Nov - s2; Dec - s2; Jan - s2, and Feb - s2. Plant growth biometrics, seed quality variables, and productivity were evaluated. The sequential cut strategy increased the productivity and quality of pure seeds when the final cuts were done between November and December. Cuts performed after December increased the reproductive components. However, in the region in question, rainfall levels compromised seed filling; and therefore productivity and quality since the flowering of these cuttings (January and February) occurs in May.

Weight gain and enteric methane production of cattle fed on tropical grasses

Context Planted grasses are becoming an increasingly important feed resource for tropical smallholder ruminant production; yet, limited research has been conducted to quantify productivity or enteric methane (CH4) production of animals consuming these grasses. Aim An experiment was conducted to assess yields and nutritional attributes of the following three tropical grasses: Cenchrus purpureus var. Kakamega 1 (Napier), Chloris gayana var. Boma (Rhodes) and Urochloa brizantha var. Xaeres (Brachiaria), and quantify enteric CH4 production of cattle fed on them. Methods Yearling Boran steers (n:18; initial liveweight 216 ± 5.8 kg (mean ± s.e.m.) were allocated to one of three grasses, in a completely randomised design and fed ad libitum for two feeding periods, each period lasting for 70 days. Intake, liveweight (LW), apparent total-tract digestibility and enteric CH4 production were assessed. The grasses used were grown on site and biomass yields were monitored over a 2-year period. Animal growth was also simulated to a final weight of 350 kg, and the amount of feed and size of land required to produce, and days to reach final weight, were estimated. Key results Mean voluntary dry-matter intake (DMI) and ADG were higher (P < 0.05) in Period 2 than in Period 1, but did not differ among treatments (P > 0.05) within period. Methane yield (MY; CH4 g/DMI kg) was similar among treatments (26.7–28.5, P = 0.26) but Napier had a higher CH4 conversion factor [Ym; CH4 (MJ)/gross energy intake (MJ)] than did Rhodes and Brachiaria (0.0987 vs 0.0873 and 0.0903 respectively; P = 0.013). Our modelling indicated that steers consuming Rhodes took at least 30 more days to reach the target LW, required larger land area for feed production and produced more enteric CH4 than did the other two diets. Conclusion Even though animal performance and MY among treatments did not differ, the animals had higher MY and Ym than currently estimated by the Intergovernmental Panel on Climate Change. Implication The three grasses supported similar animal growth rate, implying that growing of higher-yielding grasses such as Napier offers an opportunity to optimise land productivity in the tropics. However, suitable feeding practices such as protein supplementation need to be explored to enhance ruminant production and reduce enteric CH4 production.

The use of computer vision to classify Xaraés grass according to nutritional status in nitrogen

This study is based on the principle that vegetation indexes (VIs), derived from the RGB color model obtained from digital images, can be used to characterize spectral signatures and classify Brachiaria brizantha cv. Xaraes according to nitrogen status (N). From colorimetric data obtained from leaf blade images acquired in the fi eld, three artifi cial neural networks were evaluated according to the performance in the classifi cation of N status: Feedforward Backpropagation (FFBP), Cascade Forward Backpropagation (CFBP) and Radial Base function (RBFNN). Four N fertilization rates were applied to generate contrasting N contents in the plants. The youngest completely expanded leaves from 60 tillers were detached at each regrowth cycle of 28 days, thus their images and leaf N content were obtained. Samples were then classifi ed as defi cient ( 20.1 g N kg-1 DM). The VIs were selected by principal component analysis and the performance of the networks evaluated by the accuracy. The accuracy in classifi cation obtained by the networks were 88%, 86% and 79% for FFBP, CFBP and RBFNN, respectively, indicating that the spectral signatures can be determined from images acquired in the fi eld. So, the proposed method could be used to develop a software that aims to monitor the status of N in real time, providing a fast and inexpensive tool for defi ning the time and the amount of N fertilizer, according to the pasture demand.

What are the effects of irrigation rates and cropping systems on the soybean agronomic traits?

The irregularity and uneven distribution of rainfall may restrict the potential productive development of soybeans, causing numerous losses to farmers. The use of irrigation systems in hydrically heterogeneous areas are important measures that should be adopted during the crop cycle. Furthermore, the implementation of conservationist strategies, such as crop rotation or intercropping and no-till (NT) farming systems, can minimize the damage caused by water deficit. Therefore, the present study aimed to evaluate the soybean yield under different irrigation sheets and cropping systems in the extreme west of São Paulo. A completely randomized design was used, with 10 repetitions, in a subdivided plot scheme. The treatments were composed of different cropping systems in the plots, with four levels (conventional system; NT, using Urochloa brizantha cv Paiaguás; U. brizantha cv Piatã; and U. ruziziensis cv Ruziziensis), and different irrigation scheduling in the subplots, with three levels of irrigation scheduling (0%, 70% and 100%) based on reference evapotranspiration (ETo). Irrigation rates of 70% and 100% ETo in the conventional system provided higher grain yields under the climatic conditions in which the experiment was conducted. However, the continuity of long-term research is necessary, since NT is incipient, and have been implemented only two years ago. This is a relatively short period to observe the advantages of this cultivation system and for its consolidation process. Thus, the Brachiaria residual dry mass showed similar behavior in NT at the irrigation levels evaluated.

CROP COEFFICIENT OF MARANDU PALISADE GRASS: AN APPROACH INVOLVING LEAF AREA INDEX AND CANOPY HEIGHT

Determining the evapotranspiration rate enhances our understanding of plant water needs, potentially improving irrigation management. This study aimed to investigate the water consumption of the Marandu palisade grass (Urochloa brizantha) cultivar ‘Marandu’, single cropped and intercropped with black oat and ryegrass, by determining the crop coefficient (Kc) and their correlation with canopy height (CH) and leaf area index (LAI). The experiment was carried out at ESALQ/USP from April 2016 to January 2017. Two weighing lysimeters were used for calculated the Crop evapotranspiration (ETc): one with single-cropped Marandu palisade grass throughout the year and the other intercropped with black oat and ryegrass during autumn and winter (from April to September 2016). Estimated Kc, CH, and LAI were measured every 4-day. Regression equations were generated to determine the correlation between Kc and CH and Kc and LAI in each season. Minimum and maximum Kc values for single cultivation in each season were: 0.61 and 0.97 for spring, 0.45 and 1.10 for summer, 0.47 and 0.74 for autumn, and 0.52 and 0.94 for winter. In the intercropped cultivation, Kc values ranged from 0.62 to 1.04.

Effect of injectable trace mineral at weaning on growth and physiology of Nellore calves under feed restriction

Calves are susceptible to a wide variety of stressors besides the seasoning low forage availability during their weaning phase. Thus, it is ideal if they receive adequate trace mineral supplementation during this period. This study evaluated the effect of injectable trace minerals (ITM) on performance, concentration of oxidative stress enzymes, and biochemical plasmatic parameters in Nellore calves during the weaning phase and under feed restriction. A total of 30 Nellore calves were used at the age of 7 ± 1month and 176.23 ± 21.68kg of initial body weight (BW). These animals were allocated in Urochloa decumbens pasture for 28days and transferred to Urochloa brizantha cv Marandu pasture for another 28days. The treatments were: Saline (saline solution; 0.9% NaCl) and ITM (Multimin®, providing: 15mg Cu/mL, 60mg Zn/mL, 10mg Mn/mL, and 5mg Se/mL). Both treatments were applied subcutaneously in the ratio of 1mL/45kg of BW. At the end of the experiment (d 56), animals were lighter than on d 0 in both treatments (P < 0.05). However, calves that received the ITM treatment presented lower body weight (P < 0.05) on d 56, compared to those in the control group. No significant difference (P > 0.05) was observed on the concentrations of oxidative stress enzymes. Moreover, no significant difference (P > 0.05) was observed in the plasmatic parameters; these were at normal range or slightly below the concentrations described for the species. We concluded that, in a feed restriction condition, the use of ITM in weaned calves did not improve performance, and the concentration of oxidative stress enzymes, and biochemistry variables. Therefore, we do not recommend using injectable trace minerals in the concentrations used in this study in animals under such stressful conditions.

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.

Effects of mineral or protein-energy supplementation and genetic group on metabolism parameters of young beef bulls grazing tropical grass during the rainy season

The objective of this study was to evaluate the effects of mineral or protein-energy supplementation and animal genetic groups on rumen fermentation, digestibility and microorganisms of young beef bulls grazing tropical grass during the rainy season. Twelve (nn = 4 per genetic group) ruminally cannulated beef bulls [16 ± 2-months-old and 411 ± 34 kg initial body weight (BW)] were used in a cross-over design, with 4 periods, in a 2 × 3 factorial arrangement. Factors included: 1) two supplementation strategies (SS; mineral supplement [30 g/100 kg BW per day] and protein-energy supplement [300 g/100 kg BW per day]); and 2) three genetic groups (GG; Nellore [NL], ½Angus½Nellore [AN] and Senepol [SN]). Animals were continuously allocated in twelve paddocks composed of Urochloa brizantha (A. Rich.) Stapf. cv. Xaraés for 126 days during the rainy season. Supplementing animals of all GG with protein-energy supplement resulted in an increase of the intake of DM, OM, CP, EE, NFC and ME, and apparent total-tract digestibility of CP and EE. Additionally, animals fed protein-energy supplement showed highest rumen NH3N concentration, microbial-N synthesis, and retained-N. However, a decrease in rumen pH and acetate:propionate ratio was observed when animals were fed protein-energy supplement. Except for Ruminococcus flavefaciens, the relative abundance of total Archaea and Prevotella.spp. were increased when animals where fed protein-energy supplement. Moreover, a GG effect was observed on the relative abundance of total Archaea, Prevotella.spp. and Ruminococcus flavefaciens, which were highest in NL, SN and AN animals, respectively. SN animals fed protein-energy supplement showed an increase of Streptococcus bovis and Selenomonas ruminantium relative abundance, while Fibrobacter succinogenes and Ruminococcus albus were highest in NL animals supplement mineral and protein-energy supplement, respectively. In conclusion, protein-energy supplementation to beef bulls grazing high-quality tropical grass is an effective strategy to increase rumen fermentation during the rainy season. In addition, it modulated rumen microorganism leading to an increase in the relative abundance of Prevotella.spp., Streptococcus bovis and Selenomonas ruminatium, and a decrease in acetate:propionate ratio in Senepol animals.

Complex polyploid and hybrid species in an apomictic and sexual tropical forage grass group: genomic composition and evolution in Urochloa (Brachiaria) species.

Diploid and polyploid Urochloa (including Brachiaria, Panicum and Megathyrsus species) C4 tropical forage grasses originating from Africa are important for food security and the environment, often being planted in marginal lands worldwide. We aimed to characterize the nature of their genomes, the repetitive DNA and the genome composition of polyploids, leading to a model of the evolutionary pathways within the group including many apomictic species. Some 362 forage grass accessions from international germplasm collections were studied, and ploidy was determined using an optimized flow cytometry method. Whole-genome survey sequencing and molecular cytogenetic analysis were used to identify chromosomes and genomes in Urochloa accessions belonging to the 'brizantha' and 'humidicola' agamic complexes and U. maxima. Genome structures are complex and variable, with multiple ploidies and genome compositions within the species, and no clear geographical patterns. Sequence analysis of nine diploid and polyploid accessions enabled identification of abundant genome-specific repetitive DNA motifs. In situ hybridization with a combination of repetitive DNA and genomic DNA probes identified evolutionary divergence and allowed us to discriminate the different genomes present in polyploids. We suggest a new coherent nomenclature for the genomes present. We develop a model of evolution at the whole-genome level in diploid and polyploid accessions showing processes of grass evolution. We support the retention of narrow species concepts for Urochloa brizantha, U. decumbens and U. ruziziensis, and do not consider diploids and polyploids of single species as cytotypes. The results and model will be valuable in making rational choices of parents for new hybrids, assist in use of the germplasm for breeding and selection of Urochloa with improved sustainability and agronomic potential, and assist in measuring and conserving biodiversity in grasslands.

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.

Understanding the arrangement of Eucalyptus-Marandu palisade grass silvopastoral systems in Brazil

CONTEXTLimited land availability and an increasing global population are challenges faced by the agricultural sector in the coming decades. The silvopastoral system is an efficient alternative to full sun pastures that could be used to sustainably intensify animal and crop production. However, the adoption of this system is being held back by a lack of knowledge on how the trees in such a system should be arranged in order to avoid detrimental effects on pasture growth. OBJECTIVEThe aim of this study was to test different arrangements of trees in the Eucalyptus-Marandu palisade grass silvopastoral system and to evaluate its performance in different regions of Brazil. METHODSA functional-structural plant model was developed to simulate radiation interception by trees and was then coupled to the CROPGRO-Perennial Forage model to simulate the production of forage biomass. Considering solar radiation as the main resource under competition, water interactions that occur under-ground between Eucalyptus and Maranu palisade grass were not considered. The models were calibrated with experimental data collected in silvopastoral systems in Brazil. The silvopastoral systems were selected according to a combination of tree row spacing (15, 30, and 45 m), two row orientations (north-south and east-west), and single or triple rows. Simulations were replicated for different tree ages (2, 4, 6, 8, 10 and 12 years) representing different levels of shading. RESULTS AND CONCLUSIONSOur simulations show that the tree arrangement has a significant effect on the incidence of radiation on the pasture, resulting in different levels of forage production. Row spacing of 30 and 45 m is suitable for providing forage for the animals for several years. In contrast, tree arrangements with a row spacing of 15 m or triple lines demand more careful planning and management, taking into account the soil and climatic characteristics of each region. Lower declines in the forage production were observed in arrangements of 45 m, varying from 1000 and 3000 kg ha−1 after 6 years of system establishment. In this period, the annual production level was lower than 14,000 kg ha−1 for arrangments with row spacing of 15 and 30 m, being recommend pruning and thinning practices aiming to increase the radiation incidence within the system. SIGNIFICANCEThe approach used in this study can be extended to other combinations of species and environments to aid the planning and management of this kind of system.