Brachiaria Brizantha Research Articles

O21 The in vitro degradation of corn and citrus pulp is unrelated to their efficiency of nitrogen use by F1 Angus x Nellore young bulls grazing Urochloa brizantha

O21 The in vitro degradation of corn and citrus pulp is unrelated to their efficiency of nitrogen use by F1 Angus x Nellore young bulls grazing Urochloa brizantha

English

Grass constitutes the nutritional basis for most livestock, whether domesticated or wildlife. The present study evaluates the enhancement of the nutritional value of five different pasture grasses: Palisade grass (Urochloa brizantha), Biscuit grass (Paspalum vaginatum), Giant star grass (Cynodon plectostachyus), Goose grass (Eleusine indica), and Stubborn grass (Sida acuta) for use as animal feeds and xylanase production. The grasses received two different treatments:  Autoclaving and solid state fermentation. Analysis carried out on untreated, autoclaved and solid state fermented grasses showed an increase in pH for all autoclaved grasses and solid state fermented grasses when compared to the control. The total flavonoid content was significantly improved in the solid state fermented grasses (116.7 ±1.4 μg/ml for palisade grass). There was a significant increase (p<0.05) in soluble protein content from 21.86 ± 1.7 to 44.06 ± 1.3 mg g-1 of palisade grass fermented with Rhizopus oligosporus. Similarly, there was a substantial rise (p < 0.05) in glucose concentration of solid state fermented biscuit grass (54.6 ± 3.3 mg g-1) when compared to the control (32.4±1.6 mg g-1). The total flavonoid content was improved in the solid state fermented (73.53 ± 0.35 μg/ml for biscuit grass) compared to the control (64.6±3.35μg/ml). Biscuit grass subjected to solid state fermentation was more potentially active (62.4±1.3μg/ml) when compared to the control (42.2 ± 0.9 μg/ml). For xylanase production, solid state fermented goose grass showed the highest enzymatic activity. These results indicate that solid state fermentation enhanced the nutritional value and antioxidant profile of grasses, which can also be used in livestock feeding and as a substrate for the production of xylanase. Key words: Grasses, animal feeds, solid state fermentation, xylanase, autoclave.

Growth, Nutrient Accumulation, and Nutritional Efficiency of a Clonal Eucalyptus Hybrid in Competition with Grasses

Invasive grasses reduce resource availability, mainly nutrients in the soil, and the growth of eucalyptus plants. Efficient management to increase productivity depends on understanding levels of weed interference in eucalyptus plantations. The nutritional efficiency of eucalyptus plants in competition has been evaluated by plant tissue analysis. The objective was to evaluate the growth, relative accumulation of nutrients, and nutritional efficiency of the eucalyptus clonal hybrid I144 (Eucalyptus urophylla × Eucalyptus grandis), in competition with Megathyrsus maximus cv. BRS zuri, Urochloa brizantha cv. marandu, Urochloa decumbens cv. basilisk and in the control (eucalyptus plants without weed competition). The experiment was carried out with a completely randomized design, with four treatments and ten replications. The height, stem diameter, number of leaves, leaf area, dry matter of leaves and stem, nutrient content in leaves and uptake, transport, and N, P, and K utilization efficiency of the eucalyptus clonal hybrid were evaluated at 110 days after transplantation. The growth parameters and relative contents of macro and micronutrients in the eucalyptus clonal hybrid were lower in competition with M. maximus, U. brizantha and U. decumbens. The efficiency of N, P, and K uptake and transport by the eucalyptus clonal hybrid was 29.41 and 7.32% lower in competition with U. decumbens than in the control treatments, respectively. The efficiency of N, P, and K utilization by eucalypts was 13.73, 9.18, and 22.54% lower in competition with M. maximus, U. brizantha, and U. decumbens, respectively. The reduced growth and nutritional parameters of the eucalyptus clonal hybrid were more evident in competition with U. decumbens. Plant tissue analyses efficiently determined the level of competition for nutrients between species. Crop competition with grasses can decrease the efficiency and use of nutrients, which consequently reduces plant development and productivity.

Leaf Spectra Changes of Plants Grown in Soils Pre- and Post-Contaminated with Petroleum Hydrocarbons

Leaks from accidents or damage to pipelines that transport liquid petroleum hydrocarbons (PHC) such as gasoline and diesel are harmful to the environment as well as to human health, and may be hard to detect by inspection mechanisms alone when they occur in small volumes or persistently. In the present study, we aim to identify spectral anomalies in two plant species (Brachiaria brizantha and Neonotonia wightii) linked to contamination effects at different developmental phases of these plants. To do so, we used spectroscopy and remote sensing approaches to detect small gasoline and diesel leaks by observing the damage caused to the vegetation that covers simulated pipelines. We performed a contamination test before and after planting using gasoline and diesel volumes that varied between 2 and 16 L/m3 soil, in two experimental designs: (i) single contamination before planting, and (ii) periodic contaminations after planting and during plant growth. We collected the reflectance spectra from 35 to approximately 100 days after planting. We then compared the absorption features positioned from the visible spectral range to the shortwave infrared and the spectral parameters in the red edge range of the contaminated plants to the healthy plants, thus confirming the visual and biochemical changes verified in the contaminated plants. Despite the complexity in the indirect identification of soil contamination by PHCs, since it involves different stages of plant development, the results were promising and can be used as a reference for methods of indirect detection from UAVs (Unmanned Aerial Vehicles), airplanes, and satellites equipped with hyperspectral sensors.

Soil Organic Matter and Aggregate Stability in Soybean, Maize and Urochloa Production Systems in a Very Clayey Soil of the Brazilian Savanna

Forage grasses cultivation in production system with soybean and maize is an alternative to improve tropical weathered soils quality in Brazil. The aim of the study was to evaluate the effects in the production systems involving cultivation of Urochloa brizantha cv. Piatã, in monoculture or in succession with soybean and maize crops, on organic matter and structuring of soil in Brazilian savanna. The experiment was implemented in the 2010/2011 season. The treatments consisted of nine production systems and a native forest (savanna) as a reference area. In March 2017, soil sampling was carried out for C and N analysis, physical and chemical fractionation of SOM and aggregate stability. Production systems influenced total organic carbon (TOC) and aggregate stability, mainly in the surface layers, leading to changes in SOM quality. TOC was 31% lower in monoculture soybean production system, when compared to native savanna area, in the 0.00–0.20 m layer. The agricultural production systems influence organic matter quality and soil aggregates stability. For the Brazilian savanna conditions, grain cultivation systems under no-tillage that integrate Urochloa brizantha cv. Piatã contribute to the soil quality improvement. Soybean monoculture generally provides worse soil quality indices compared to other agricultural production systems.

Milk carbon footprint of silvopastoral dairy systems in the Northern Peruvian Amazon.

The objective of this study was to estimate the carbon footprint (CF) of milk production (in kg of CO2 equivalents (CO2e) per kg of fat and protein corrected milk (FPCM)) in dairy farms of the San Martín region, in the Peruvian Amazon. A cradle-to-farm gate characterization and analysis were carried out on eight representative dairy farms. Greenhouse gas (GHG) emissions were estimated using equations, following the 2019 refinement of the 2006 IPCC Guidelines. The results showed an average milk production of 9.7 ± 0.82 L milk/cow/day, Gyr x Holstein crosses as the predominant breed, use of cultivated grasses such as Brachiaria brizantha, living fences (Guazuma ulmifolia Lam) as the predominant silvopastoral arrangement, and low level of external inputs such as feed or grain additives. In relation to CF, an average value of 2.26 ± 0.49kg CO2e/kg FPCM was obtained, with enteric fermentation being the most important source (1.81 ± 0.51kg CO2e/kg FPCM), followed by manure management, land use, and energy/transport (0.26 ± 0.06, 0.14 ± 0.04, and 0.05 ± 0.04kg CO2e/kg FPCM, respectively). Differences were found between farmers, obtaining lower CF values (1.76 vs 3.09kg CO2e/kg FPCM) on farms with better feed quality, higher production levels, and a higher percentage of lactating animals compared to dry cows. It is concluded that dairy farms in the Peruvian Amazon region can reduce their emissions if they improve their current feeding practices.

Establecimiento de gramíneas forrajeras tropicales en el bioma del Cerrado

This study was carried out to evaluate the time for the establishment of tropical forage grasses in the “Cerrado” biome, based on morphogenetic and structural traits. Three Brachiaria brizantha (Syn. Urochloa brizantha) cultivars (Paiaguás, Ipyporã and Marandu) and two Panicum maximum (Syn. Megathyrsus maximus) cultivars (Quênia and Tamani) were distributed in a randomized-block design with four replicates. Morphogenetic and structural traits of the pasture were assessed from d 35 to d 65 after sowing, at seven-day interval. Canopy height rose linearly with the establishment period, in all cultivars. In the Megathyrsus cultivars, tiller density decreased as the experimental period progressed, whereas the number of tillers in the Urochloa cultivars increased. The cultivars Ipyporã and Marandu had the highest leaf appearance rates. The lowest leaf elongation rates occurred in the cultivars Paiaguás, Ipyporã and Tamani, and the highest elongation rates in cv. Quênia. As a result, cv. Quênia showed the highest values of final leaf length (64.9 cm) and leaf blade mass (3,352.9 kg DM ha-1). The higher senescence rate of cv. Tamani (2.1 cm tiller-1 d-1) resulted in the highest percentage of dead material (1,815.5 kg ha-1) being found in the herbage mass of this cultivar. Cultivars Paiaguás, Marandu and Tamani were established at 44 d, whereas cv. Quênia and Ipyporã were established at 51 and 58 d after sowing, respectively, in the Brazilian Cerrado.

Disponibilidad de forraje en praderas de pasto Xaraés en respuesta a fuentes de nitrógeno convencionales y tratadas con N-(n-butil) triamida tiofosfórica (NBPT)

The N-(n-butyl) thiophosphoric triamide (NBPT), a urease inhibitor, has been reported as one of the most promising compounds to reduce losses by volatilization, and to maximize the use of urea nitrogen (N) in agricultural systems. A field study was carried out to examine urease inhibitors' potential about volumetric density and forage mass grass (Brachiaria brizantha cv. Xaraés) to N application. The experiment was carried out from September 2017 to September 2018. The experimental design used was complete randomized blocks in the 3×2×4 factorial array, considering: three periods of the year (wet season, dry season, and the transition), two sources of urea (conventional urea and NBPT–treated urea), and four N rates (0, 80, 160 and 240 kg N ha-1 yr-1), replicated three times. Nitrogen sources promoted a positive effect (P<0.0001) on bulk density, forage mass, and in the grazing stratum during the wet season and the transition season, with increasing N rates in pastures. The leaf: stem ratio decreased linearly (P<0.0045) as increased N rates, and the higher ratio during the wet season and lower in the dry season of the year. For the rates of 80 kg N ha-1 yr-1, there was a significant difference (P=0.0042) between sources, with greater (P=0.0006) forage mass of 0–30 cm, post-grazing forage mass (P=0.0042) and forage volumetric density (P=0.0006), when utilized the conventional urea. The application of N, regardless of the source, provides an increase in forage mass and volumetric density in Xaraés grass pastures up to a dose of 240 kg N ha-1 yr-1, in the transition season and wet season.

Components of seed production and ergot resistance used as criteria for selection of Brachiaria hybrids

Ergot is a fungal disease and causes reductions in seed productivity and quality. We aimed to identify promising genotypes of brachiaria evaluating: (1) seed production potential (number of tillers, racemes per inflorescence, spikelets per raceme, raceme length, weight and number of seeds, and germination) and (2) resistance of seeds to Ergot (infected tillers, infected seeds). Five genotypes of Brachiaria grasses, four non-natural hybrids named BH1619, BH1810, BH1516 and Mavuno Palisadegrass (Urochloa brizantha x Urochloa ruziziensis), and Marandu Palisadegrass (U. brizantha Hoechst cv. Marandu) were evaluated. The BH1619 hybrid, despite the high weight of seeds, produced less viable, pure seeds. The hybrid BH1516 had a lower percentage of flowered tillers (42%) and seeds infected with ergot (8%). Marandu Palisadegrass had a higher percentage of infected tillers (95%) and infected seeds (38%). The hybrid BH1516 was the most resistant to ergot, followed by Mavuno Palisadegras sand BH1619. Among all materials, Mavuno Palisadegrass and BH1516 have a higher potential for seed production due to the higher percentage of flowered tillers and production of pure seeds with high germination capacity. The BH1516 hybrid was resistant to ergot, making it a better choice for use in infected areas used for seed or forage production.

Cover crops biomass yield grown as a 2nd summer crop in relation to sowing periods

The aim of this study was to evaluate cover crop precocity and biomass yield growth as a 2nd summer crop after soybean at different sowing periods (January 2nd; February 2nd and March 2nd at 2019 and January 27th and March 3rd at 2020). Experiment was laid out as a randomized block design in a 3x3 factorial for each sowing period, in the 2019 and 2020 off-seasons, being factor A represented by the cover crops (Urochloa brizantha cultivar Xaraés, Crotalaria juncea cultivar IAC-KR-1 and Pennisetum glaucum cultivar ANm 38,) and factor B by the evaluation periods along cover crops development cycle. There was an interaction between cover crops and evaluation period for plant height and dry matter yield for both years. C. juncea and P. glaucum showed faster growth, regardless of the evaluation period and sowing periods, compared to U. brizantha in both years. Cover crop biomass yield reduced as sowing period is delayed from January to March to an extend that P. glaucum yield dropped from 14.6 to 4.2 t DM ha-1 at 2019 and from 14.4 to 6.9 t DM ha-1 at 2020 as a result shorter photoperiod and lower temperature. The same was noticed to U. brizantha and C. juncea which showed yields of 11.676 and 8.800 and 2.220 and 2.555 kg ha-1 at April 29th of 2019 and 12.507 and 7.812 and 3.041 and 2.346 kg DM ha-1 at June 18th 2020 respectively for January and March sowing periods. U. brizantha and C. juncea are more viable 90 days, while P. glaucum showed the fastest dry matter accumulation rate. All species are viable due to the benefits they provide to the productive system, which becomes more diversified and therefore more sustainable

Effect of different nitrogen fertilizers on nitrogen efficiency use in Nellore bulls grazing on Marandu palisade grass

We evaluated the effects of different sources of nitrogen (N) applied to pastures of Urochloa brizantha cv. Marandu during the rainy season on the efficiency of N use in plants and animals. Continuous grazing with variable stocking rates was employed to maintain 25 cm pasture height, corresponding to 95% light interception. The experimental design consisted of randomized blocks with four treatments and three replications (paddocks per treatment). The applied N sources were urea, ammonium sulfate, and ammonium nitrate, at a respective dosage of 150 kg N per ha, in three treatments, in addition to a control treatment without N fertilization. N recovery by plants differed between fertilizers (p = 0.047) and was highest in the ammonium sulfate treatment. The proportion of retained N was higher in animals kept on fertilized pastures (p < 0.01). Different sources of N in pasture system, or its non-use, affected the efficiency of N use by animals, and ammonium sulfate and ammonium nitrate were more efficient with respect to the N balance.

Seed quality of Brachiaria brizantha by X-ray image analysis using a Bayesian approach

Brachiaria brizantha is the most economically important forage grass in Brazil and is propagated through sowing. Producing high-quality seeds has been a constant challenge due to their uneven maturation. The development and application of precise and non-destructive methods for identifying internal damages to seeds, such as the X-ray test, which quickly indicates the quality of the lots, is of fundamental importance for the seed industry. In this work, the quality of Brachiaria brizantha seeds was analyzed based on the morphological characteristics observed in X-ray images that were related to viability using a mixture model under a Bayesian approach, with the following objectives: i) verify the adequacy of the Bayesian modeling used in the data analysis; ii) associate the efficiency of using radiographs as a way to assess the viability of the seeds; and iii) relate the classifications carried out by evaluators with the probability of originating normal or abnormal seedlings. The methodology applied for the analysis proved to be adequate. Further, the Bayesian estimates for parameters related to internal morphology were established with associated levels of uncertainty, which represents an advantage over usual frequentist methods. Based on the model's estimates, seeds evaluated as potentially unviable by three evaluators had practically no probability of germination and did not germinate in the test applied later. Seeds classified as potentially viable had a high probability of developing into normal seedlings, while 73.27% showed this property in the germination test.

Screening and selection of Brachiaria brizantha accessions for forage values under irrigation at Wondo Genet, Sidama, Ethiopia

The experiment was conducted to evaluate different Brachiaria brizantha accessions at the Wondo genet agricultural research center to identify species/accessions so as to use the better performing ecotype for wider distribution among livestock producer communities in the country. Seven Brachiaria grass accessions (B. brizantha, 13151; B. brizantha, 13368; B. brizantha, 13653; B. brizantha, 16550; B. humidicola, 9222; B. brizantha, 13379 and B. mutica,) were used as treatments in randomized complete block design with three replications. The overall dry matter yield for B. humidicola, 9222 (5.95t/ha), and B. mutica, (5.61t/ha) accessions didn’t show a significant difference (p &gt; 0.05) but significantly (p &lt; 0.05) lower than all other accessions. Mean plant heights for the accessions were significantly different (p &lt; 0.05) throughout the harvesting cycle period and overall yield with a lower plant height of B. mutica (63.2 cm) while non-significant (p &gt; 0.05) overall mean height was recorded among other accessions. B. brizantha, 13151; B. brizantha, 13368; B. brizantha, 13653; B. brizantha, 16550 and B. brizantha, 13379 accessions outperformed in terms of overall dry matter yield. Further studies on agronomic performances of promising B. brizantha accessions under on-farm conditions and nutritional evaluation involving live-animal experiments are recommended.

Dry matter accumulation and nutrient cycling by soil cover plants in an intensive corn silage production system

This study aimed to evaluate dry matter accumulation and nutrient cycling by soil cover plants in an intensive corn silage production system. At the beginning of October, a study consisting of five soil cover plants, plus a control treatment (fallow area vegetation) was installed. The following cover plants were used: brachiaria brizantha, brachiaria ruziziensis, crotalaria juncea, jack bean and velvet bean. At the beginning of February of the year following sowing, we evaluated dry matter and nutrient accumulation in plant shoots. There was a significant effect at 0.1% of the cover plants on dry matter and nutrient accumulation. The average values ​​for dry matter accumulation in plant shoots were 19.88; 18.06; 16.38; 9.66; 8.96 and 4.26 t ha-1 for brachiaria brizantha, crotalaria juncea, brachiaria ruziziensis, jack bean, velvet bean and fallow area vegetation, respectively. The highest nitrogen accumulation was observed in crotalaria juncea (343 kg ha-1), followed by jack bean (269 kg ha-1). For brachiaria brizantha and ruziziensis, N accumulation of 247 and 216 kg ha-1 were found, respectively. Brachiaria brizantha had the highest accumulation of phosphorus and potassium, with average values ​​of 39 and 362 kg ha-1. In the fallow area vegetation, the accumulations of N, P and K were 42; 9.0 and 62 kg ha-1, respectively.

Bioprospecting Fluorescent Pseudomonas from the Brazilian Amazon for the Biocontrol of Signal Grass Foliar Blight

Biological control is considered the only viable integrated disease management practice for controlling the widely distributed and destructive foliar blight and sudden death disease caused by the fungus Rhizoctonia solani AG-1 IA on signal grass (Urochloa brizantha) pastures. Since major signal grass varieties are highly susceptible and fungicide sprays are not labeled for grass pasture cropping systems, biological control is sought as an alternative for managing this fungal disease. In this study, 24 fluorescent Pseudomonas isolates obtained from naturally suppressive soils from the Amazon biome were bio-prospected for their role as biocontrol agents against R. solani AG-1 IA. Based on in vitro antagonism, three isolates (Amana, Poti, and Yara) were selected for further in vivo assays. Multilocus phylogenetic analysis indicated that Amana and Yara were grouped into the Pseudomonas putida group while Poti was grouped into the Pseudomonas asplenii group, and could well constitute a new Pseudomonas species. For in vivo biocontrol assays, the biocontrol agents were applied either via seed-treatment or via foliar spray. All three isolates produced siderophores and solubilized phosphate, while Amana and Poti showed protease and chitinase in vitro activity. Foliar application of P. putida Amana from Amazonian suppressive soils resulted in a significant reduction of the foliar blight disease severity on signal grass. We discuss further steps for the development and labeling of Pseudomonas-based biofungicides for managing the foliar blight disease on signal grass pastures in Brazil.

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 ± 8.18kg 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 [2g.kg‒1 body weight [BW]]); dry season (NP1, nitrogen/energy supplement [1g.kg‒1 BW], and NP2, nitrogen/energy supplement [2g.kg‒1 BW]); and rainy season 2 (NP1, mineral mixture ad libitum, and NP2, nitrogen/energy supplement ([1g.kg‒1 BW]). Total chewing time was longer in NP1 (566.44 vs 528.33min.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.

Performance of soybean crop in response to palisadegrass pasture desiccation and nitrogen fertilization under integrated crop-livestock system

The desiccation (burn down) time of high-biomass pasture in no-tillage system and nitrogen (N) fertilization of pasture and soybean can influence the crop performance under crop-livestock system. The objective of this study was to evaluate the effect of desiccation times of palisadegrass pasture combined with three N fertilization levels of pasture and two N fertilization levels of soybean on crop yield, yield components and grain oil and protein concentration. Three N rates in the U. brizantha cv. BRS Piatã pasture were evaluated (0; 150 and 300 kg ha-1 of N as urea) in three different experiments. In each experiment, five pasture desiccation periods (60; 45; 30; 15 and 1 days before soybean sowing) and two levels of N fertilization of soybean (30 kg ha-1 of N distributed as urea at sowing + a control without urea) were evaluated. A randomized complete block design with five replications was used for each experiment. After statistical analysis of each experiment, a joint analysis of the three experiments was performed, allowing the comparison of the three rates of N in the pasture. The time interval between Urochloa brizantha pasture desiccation and soybean sowing did not influence soybean yield, yield components or the grain oil and protein concentrations, regardless of N fertilization of pasture and soybean. N fertilization of pasture induced a taller soybean plant height, insertion height of first pod, increased lodging, and reduced yield, but did not change the grain oil and protein concentration, regardless of the pasture desiccation time and N fertilization of soybean. Soybean grain yield was negatively affected by N fertilization of the crop, regardless of fertilization levels and desiccation times of the previous pasture

Boron and zinc coating of Brachiaria brizantha cv. MG5 seeds

Brachiaria brizantha cv. MG5 has been increasingly used in pasture establishment to intensify production systems and increase yield and quality of forage. However, Brazilian soils are deficient in Boron and Zinc, which are essential elements for plant growth and development. Thus, to improve physical and chemical quality of brachiaria seeds, doses of boric acid (H3BO3) and zinc sulfate (ZnSO4.7H2O) were added to the calcium silicate and sand coating of the seeds, using a rotary coater. We tested 11 independent treatments in laboratory and greenhouse, where the seeds were evaluated for physical and physiological quality and the initial growth of the plants. At the end of the evaluations, the collected data were submitted to statistical analysis. There was an increase of up to 320% in seed mass with the seed-coating method tested. The treatment with 10 g H3BO3 + 5 g of ZnSO4.7H2O.kg-1/seeds enhanced plant growth and did not affect the physiological quality of the seeds. Thus, the seeds are ready to be tested in the implementation of pastures. The combinations of 25g H3BO3 + 5 g of ZnSO4.7H2O.kg-1 /seeds and 25g H3BO3 + 15g of ZnSO4.7H2O.kg-1 /seeds reduced seed vigor and are not suitable for seed coating of Brachiaria brizantha cv. MG5

Principal component analysis applied to the study of yield and nutritional characteristics of forage cultivars

The objective of this study was to evaluate the importance of various yield and nutritional characteristics for the differentiation of forage cultivars using principal component analysis (PCA). Data were obtained from an experiment conducted with a complete randomized block design (RCBD) with 6 replications. Eleven cultivars of forage grasses of the species Urochloa brizantha, U. ruziziensis, Megathyrsus maximus, Cenchrus ciliaris, Andropogon gayanus and Setaria sphacelata were evaluated. For yield characteristics, PCA revealed that the first 3 components explained 82.0% of total variation between forage cultivars. Similar results were observed for nutritional characteristics with the first 3 components explaining 91.4% of total variation in leaf chemical composition and 83.8% of variation in stem chemical composition. Variables that contributed most to discrimination between forage cultivars were: number of tillers per plant; number of leaves per plant; median leaf width; stem dry matter yield; leaf:stem ratio; % dry matter, % crude protein (CP) and % neutral detergent fiber of leaves; and % CP, % ether extract and % acid detergent fiber of stems. PCA was effective in identifying the key parameters that need to be measured in evaluating grass species and allowed a reduction in the number of yield and nutritional characteristics to be assessed in experiments designed to evaluate forage cultivars. This reduced both the workload and the costs involved while still allowing valid conclusions.

Maintaining grass coverage increases methane uptake in Amazonian pastures, with a reduction of methanogenic archaea in the rhizosphere

Cattle ranching is the largest driver of deforestation in the Brazilian Amazon. The rainforest-to-pasture conversion affects the methane cycle in upland soils, changing it from sink to source of atmospheric methane. However, it remains unknown if management practices could reduce the impact of land-use on methane cycling. In this work, we evaluated how pasture management can regulate the soil methane cycle either by maintaining continuous grass coverage on pasture soils, or by liming the soil to amend acidity. Methane fluxes from forest and pasture soils were evaluated in moisture-controlled greenhouse experiments with and without grass cover (Urochloa brizantha cv. Marandu) or liming. We also assessed changes in the soil microbial community structure of both bare (bulk) and rhizospheric pasture soils through high throughput sequencing of the 16S rRNA gene, and quantified the methane cycling microbiota by their respective marker genes related to methane generation (mcrA) or oxidation (pmoA). The experiments used soils from eastern and western Amazonia, and concurrent field studies allowed us to confirm greenhouse data. The presence of a grass cover not only increased methane uptake by up to 35% in pasture soils, but also reduced the abundance of the methane-producing community. In the grass rhizosphere this reduction was up to 10-fold. Methane-producing archaea belonged to the genera Methanosarcina sp., Methanocella sp., Methanobacterium sp., and Rice Cluster I. Further, we showed that soil liming to increasing pH compromised the capacity of forest and pasture soils to be a sink for methane, and instead converted formerly methane-consuming forest soils to become methane sources in only 40–80 days. Liming reduced the relative abundance of Beijerinckiacea family in forest soils, which account for many known methanotrophs. Our results demonstrate that pasture management that maintains grass coverage can mitigate soil methane emissions, compared to bare (bulk) pasture soil.