Search Results (59)

The objective of this study was to evaluate the effects of potassium (K) on disease severity and the chemical composition of Megathyrsus maximus cultivars. The experiment was conducted in a randomized block design in a 6 × 4 factorial arrangement, consisting of six Megathyrsus maximus cultivars (Massai, Mombaça, Tamani, Tanzânia, Quênia, and Zuri) and four K doses (0, 205, 410, and 820 mg dm⁻³). The severity of the leaf spot complex, caused by Bipolaris maydis and B. yamadae, was assessed using a diagrammatic scale. A significant interaction between K doses and cultivars was observed for all evaluated diseases. At K doses of 0 and 205 mg dm⁻³, the Tanzânia cultivar showed lower leaf spot severity compared with the other cultivars, whereas at higher doses, no disease symptoms were observed in any cultivar. The area under the disease progress curve (AUDPC) for mosaic followed a linear model only for the Tanzânia cultivar, whereas quadratic regression models best described the response for the remaining cultivars, with maximum mosaic severity values of 67.74% for Quênia, 72.34% for Mombaça, 76.99% for Zuri, 74.88% for Massai, and 68.93% for Tamani. Increasing K doses reduced the severity of both the leaf spot complex and mosaic. However, the leaf spot complex did not affect the nutritional value of the evaluated cultivars. Full article

This study evaluated the effects of including palm kernel oil in the diets of pasture-raised sheep on carcass characteristics, meat quality, and fatty acid profiles. A completely randomized design with four treatments was used, consisting of 0, 20, 40, and 60 g/kg of palm kernel oil in the dry matter of the supplement, with eight replicates. Thirty-two uncastrated Santa Inês sheep, with an average initial body weight of 23.2 ± 2.6 kg, were used in this study. The animals were kept on Aruana grass (Panicum maximum (syn. Megathyrsus maximum) cv. Aruana) pastures under continuous stocking for 59 days (preceded by 15 days of adaptation), with each one fed supplements (1.4% of body weight) at 8 am. At the end of the experimental period, the animals were slaughtered in a commercial slaughterhouse for carcass and meat quality evaluation. The inclusion of palm kernel oil had a decreasing linear effect on hot and cold carcass weight (p = 0.0403) (p = 0.0398), but it did not affect hot or cold carcass yields or carcass morphometric measurements, commercial cut weights, pH, or loin area (p > 0.05). However, it affected the color of the L. lumborum muscle, showing an increasing linear effect on yellow intensity (b*) (p = 0.002) and on the centesimal composition, with an increasing linear effect on ether extract content (p = 0.006). Shear force, cooking loss, and water-holding capacity were not affected (p > 0.05). Fatty acid profiles, the atherogenicity and thrombogenicity indices, and the ratio of hypocholesterolemic to hypercholesterolemic fatty acids (h:H) were also unaffected by the inclusion of palm kernel oil (p > 0.05). The inclusion of up to 60 g/kg of palm kernel oil in the diets of pasture-raised sheep had an effect on carcass weight but not yield. It also had an effect on the color and chemical composition of L. lumborum muscle, but these changes did not compromise the overall quality of the meat. Full article

Tropical grasses are increasingly present in farming systems in Brazil. However, a national-scale assessment of this practice’s impact on soil health (SH) and soybean yield has been lacking. In this study, we conducted a meta-analysis of 55 studies published until February 2026, comprising field trials run in 33 locations in Brazil, aiming to assess the effects of deep-rooted tropical grasses as preceding crops on biological indicators of SH and soybean yield. Results showed that grasses (Urochloa spp. and Megathyrsus maximus) promote soybean yield by 15%, representing an average increase of 515 kg ha⁻¹ and an additional revenue of US$198 ha⁻¹. The analysis of forage grass species used, management system (single or intercropped), soybean cultivar (growth habit, life cycle, genetic modification), and edaphoclimatic controlling factors revealed positive effects of tropical grasses on soybean yield under all the study conditions and yield ranges. SH indicators also showed sizeable increment, notably the activity of arylsulfatase (+35%) and β-glucosidase (+31%), followed by acid phosphatase activity (+20%), microbial biomass carbon (+24%), and organic carbon (+11%). The results confirmed the beneficial effects of deep-rooted tropical grasses, highlighting their contribution to sustainable intensification in tropical farming systems due to their ability to enhance SH. This, in turn, leads to increased soybean yield under most agronomic and environmental conditions. Full article

Maize–tropical grass intercropping has been adopted during the dry season as a strategy for soil cover; however, a knowledge gap remains regarding adequate nitrogen (N) supply and the efficiency of this system in degraded pasture areas. The objective of this study was to evaluate dry biomass, grain yield, and macronutrient concentrations in maize–tropical grass intercropping as a function of N rates applied as side-dressing in the dry season. The experimental design consisted of a randomized complete block design in a split-plot arrangement with four replications. Main plots comprised maize monoculture, maize intercropped with Urochloa ruziziensis (Congo grass), and maize intercropped with Megathyrsus maximus cv. Aruana (Aruana Guinea grass). Subplots consisted of N rates (0, 50, 100, and 150 kg ha⁻¹). Maize–Aruana intercropping showed a positive linear response to N rates for grain yield; specifically, the nitrogen rate of 150 kg ha⁻¹ resulted in a 71.71% increase in grain yield compared to the lack of nitrogen supply. Conversely, maize monoculture showed a negative linear response, where the highest N rate (150 kg ha⁻¹) resulted in a 68.83% reduction in grain yield compared to the lack of nitrogen supply. Despite yield potential being capped by seasonal water deficits and frost events, the intercropping systems maintained essential growth dynamics. Aruana grass provided a protective effect for maize development under stress. The findings demonstrate that N side-dressing in the maize–Aruana intercropping system in a minimum of 71.83 kg ha⁻¹ is an adequate strategy to enhance grain yield and biomass production. Full article

Sward height is a practical indicator for defining management targets that reflect pasture structure. The complexity of integrated systems, including the coexistence of trees, crops, and livestock, can modify animal grazing distribution and microhabitat conditions, leading to different degrees of sward heterogeneity and botanical composition. This study investigated sward-height distribution and species composition in four systems: livestock (L), livestock–forestry (LF), crop–livestock (CL), and crop–livestock–forestry (CLF). Data were collected over two years in pastures of black oat (Avena strigosa Schreb.), Aries grass (Megathyrsus maximus cv. Aries), Italian ryegrass (Lolium multiflorum Lam.), and other tropical grasses during summer, transition, and winter. Sward heights were classified into three categories (low, optimal, high) according to seasonal thresholds (winter: <18.0; 18–29.9; >30 cm; summer: <15.0; 15–24.9; >25 cm) and fitted to four probability distributions (normal, log-normal, Gamma, Weibull). Management based on target-height maintained 46% of observations within the optimal class, a satisfactory proportion for continuous stocking systems where structural heterogeneity is inherent. The CL system presented greater species diversity due to a higher frequency of Italian ryegrass and other grasses. Across systems and seasons, the Gamma distribution provided the best fit for sward-height frequencies. These findings offer a practical statistical tool for evaluating grazing management efficiency. Full article

Estimating nitrogen (N) and the corresponding crude protein (CP) content in forage crops is essential for optimizing fertilization and livestock nutrition. However, standard methods such as the Dumas and Kjeldahl techniques are destructive, costly, and impractical for field use in certain regions of developing countries. This study evaluated four non-destructive approaches—morphometric measurements, Pantone^® color scales, smartphone-based RGB analysis (ColorDetector app), and SPAD chlorophyll readings—for predicting N and CP in Megathyrsus maximus (Mombasa grass). A total of 120 samples were collected under three nitrogen fertilization levels and assessed using linear mixed-effects models with cross-validation. Morphometric variables showed poor performance (R² < 0.01), indicating low correlation with nutrient content. Pantone-based RGB models provided slightly better predictions (R² ≈ 0.30) but were limited by subjectivity and discrete data. SPAD-based models demonstrated moderate predictive accuracy (R² ≈ 0.53; RMSE ≈ 0.46%). The highest accuracy was achieved with smartphone-derived RGB data, where full RGB models reached R² = 0.60 and RMSE = 0.45%. Based on these results, a practical green color scale was developed from RGB values to support real-time, in-field nitrogen and crude protein assessment. This study highlights smartphone imaging as a scalable, low-cost, and accurate tool for non-destructive estimation of nitrogen and crude protein in tropical forages, offering an accessible alternative to laboratory methods for producers and field technicians. Full article

Poorly drained pastures in tropical America are recurrently degraded by Marandu Death Syndrome (MDS), affecting beef and dairy production. This study screened genotypes of Megathyrsus maximus and Urochloa spp. for waterlogging tolerance under controlled conditions to identify discriminant, easily measurable morphoagronomic traits suitable for breeding programs. Four experiments were conducted in factorial arrangement (five genotypes × two water regimes, with four replications), where morphoagronomic and physiological variables were analyzed using multivariate techniques. The first two principal components explained 75.17–88.60% of the total variation and stayed above 70% after variable reduction, without significantly altering genotype dispersion. Physiological responses showed a strong correlation with morphoagronomic traits. The most informative traits were the number of yellow and senescent leaves, number of tillers, SPAD index, leaf dry mass, and root dry mass. Genotypes were grouped by tolerance level. Among M. maximus, ‘Mombaça’ was the most tolerant, while PM13 and PM21 were the least. In Urochloa spp., U. humidicola cv. Tully was the most tolerant and ‘Marandu’ the least tolerant. Screening under controlled conditions is an alternative to distinguish genotypes with contrasting tolerance; however, because controlled environments do not fully reproduce the multifactorial nature of MDS, this approach is recommended only for early stages of breeding programs. Nevertheless, field evaluations on poorly drained soils under grazing remain essential to confirm tolerance to MDS. Full article

In the oilseed–cereal–forage system, information on the performance of grasses of the genus Megathyrsus maximus and on the optimal fertilization levels for forage production is still scarce. Therefore, this study aimed to evaluate forage yield (FY) of pastures established in crop succession systems and subjected to two fertilization regimes during the 2020 and 2021 growing seasons, in the municipality of Rio Verde, Brazil. The experiment evaluated four M. maximus cultivars (Paredão, Zuri, Quênia, and Tamani) under two fertilization rates: maintenance (50, 50, 20, and 3.2 kg ha⁻¹ year⁻¹ of N, K, S, and micronutrients, respectively) and enhanced (150, 150, 40, and 6.4 kg ha⁻¹ year⁻¹, respectively). The Zuri cultivar showed a higher daily forage accumulation rate and greater forage leaf mass compared with the other cultivars. In addition, the Zuri and Paredão cultivars achieved the highest FY, reaching 12.80 and 12.10 Mg ha⁻¹, respectively. The Tamani cultivar exhibited a lower neutral detergent fiber concentration and a higher total digestible nutrient concentration, indicating its potential for systems that prioritize higher forage nutritive value. Zuri and Paredão maximize forage yield in crop succession systems, while enhanced fertilization increases yield by 15%, with adoption dependent on economic feasibility. Full article

This study aimed to determine the optimal combination of forage grass and row spacing to maximize the balance between sorghum silage yield and quality in a simultaneous sowing system for integrated crop-livestock production. The experiment evaluated three cropping systems: biomass sorghum (Sorghum bicolor (L.) Moench) in monoculture, and intercropped with Urochloa brizantha cv. Marandu and Megathyrsus maximus cv. BRS Zuri. These systems were tested under two row spacings: 45 cm and 90 cm. The field trial was conducted in Vicentina, Mato Grosso do Sul State, Brazil, using a randomized complete block design in a 3 × 2 factorial arrangement with four replications. Dry matter production, fermentative parameters, and chemical composition were measured. The 45 cm spacing provided higher productivity (23.1 t/ha of TDMY), while the intercropping with Zuri grass showed lower levels of NDF (73.46%) and ADF (49.61%), indicating better nutritional quality. The silages exhibited ideal pH (4.0–4.1) and low levels of butyric acid (<0.33%), with higher total digestible nutrients (TDN) (54.33%) at the 90 cm spacing. The Sorghum + Zuri (ZS) intercropping at the narrower spacing (45 cm) is viable for quality silage production, showing a better balance between overall chemical quality and biomass production. Full article

Nutrients and carbon cycling processes in integrated production systems are essential for agroecological sustainability in the Cerrado of Northeast Brazil. However, quantitative and process-level understanding remains limited. This study aimed to characterize off-season plant residue decomposition under different production arrangements through the assessment of dry biomass, bromatological composition, and litter decomposition kinetics. The experiment was conducted in the off-season of the 2022/2023 agricultural year at Barbosa farm (Brejo, Maranhão, Brazil), in a Yellow Argisol (Ultisol), with Aw prevailing climate. We evaluated residues of soybean, Urochloa brizantha cv. Marandu, maize, maize + Marandu, Megathyrsus maximus cv. BRS Tamani, Eucalyptus, Eucalyptus + Tamani, and native forest, representing crop–livestock integration (CLI), livestock–forestry integration (LFI), no-tillage soybean (Soybean-NT), and native forest (control). For each treatment, 0.20 × 0.20 m, 2 mm mesh nylon litterbags (nº = 4 replicates) were filled with 20 g of oven-dried plant residues cut into ~10 cm pieces. Litterbags were placed on the soil surface and sampled at 0, 30, 60, and 118 days to estimate the decomposition rate (k), C and N mineralization, and macronutrient dynamics. Residues differed in initial composition, with Eucalyptus and Eucalyptus + Tamani showing higher C contents (41–43%), while Marandu and Soybean-NT had greater concentrations of N (37.8–39.2 g kg⁻¹), P (2.37–2.42 g kg⁻¹), and Mg (2.38–2.83 g kg⁻¹). The Eucalyptus + Tamani mixture exhibited the highest decomposition rate (k = 0.0041), which was about 40% greater than Soybean-NT (k = 0.0026), and faster C release, whereas N in maize residues remained immobilized for up to 118 days. CLI and Soybean-NT enhanced nutrient cycling efficiency, with K+ increasing 17.3-fold (1.1 to 18.9 g kg⁻¹) and N 1.2-fold (1.8 to 2.3%) compared to native forest. Overall, residue quality, especially C/N ratio and lignin, regulated decomposition and integrated systems, particularly LFI, which conferred greater resilience and nutrient cycling efficiency in the Cerrado. Full article

The development of an efficient agricultural system depends on the correct choice of crops and the management of nutrient supply and distribution within the system. This study aimed to determine how nitrogen (N) rates applied to rows of maize and tropical grass during the autumn–winter season (previous crop) influence subsequent intercropped plants. Treatments were arranged in a randomized complete block design with a split-plot scheme and four replications. The main plots comprised three cropping systems: soybean monoculture, soybean intercropped with Aruana Guinea grass (Megathyrsus maximus cv. Aruana), and soybean intercropped with Congo grass (Urochloa ruziziensis cv. Comum). The subplots consisted of four N rates (0, 50, 100, and 150 kg ha⁻¹) applied to the rows of maize and tropical grass during the previous crop. Macronutrient accumulation and efficiency indices were determined for intercropped plants. Aruana Guinea grass increased the accumulation of N, phosphorus (P), potassium (K), and sulphur (S) in the soybean crop. N applied to the previous crop negatively affected the accumulation of P, K, and S in soybean monoculture. The maximum physiological efficiency of soybean was related to N supply. The efficiency indices for Aruana Guinea grass highlighted its ability to recover residual N applied to the previous crop. Full article

Gamba grass (Andropogon gayanus Kunth) is a promising forage alternative for Brazil’s Cerrado regions, attracting increasing research interest due to its potential to complement or replace widely planted species such as Urochloa and Megathyrsus. Despite the release of three cultivars, significant improvements in dry matter (DM) yield and forage quality are needed to fully realize its agronomic potential. This study aimed to evaluate genetic variability, estimate narrow sense heritability, and predict expected genetic gains for DM yield and key forage quality traits in two gamba grass populations derived from the cultivars BRS Sarandi and Planaltina. Trials were established in spring 2017 in Planaltina, DF, and evaluated during February–March 2018 and January–March 2019. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose (CEL), and hemicellulose (HEMIC) were quantified alongside DM yield. BRS Sarandi exhibited higher CP (12.3% vs. 9.8%) and lower NDF (57.1% vs. 63.4%), ADF (36.2% vs. 41.5%), CEL (20.8% vs. 23.7%), and HEMIC (20.9% vs. 21.9%) compared to Planaltina, while DM yield did not differ significantly between populations (4.57 t·ha⁻¹ vs. 4.50 t·ha⁻¹ per harvest, p > 0.05). Heritability estimates for individual harvests ranged from 0.31 to 0.68 for DM yield and 0.28 to 0.62 for quality traits, whereas multi-harvest models across years yielded lower estimates (0.07–0.27). Expected annual genetic gains were modest, with the highest predicted increase for CP (0.45% per year) and the largest decrease for NDF (−0.78% per year), reflecting the quantitative nature of trait inheritance and strong environmental influence. This study provides novel insights by simultaneously comparing two populations for multiple harvests and quantifying both yield and detailed forage quality traits, offering practical guidance for gamba grass breeding strategies. Results indicate that breeding programs should prioritize multiple selection cycles, precise phenotyping, genotypic and potentially genomic selection to accelerate improvement in both DM yield and forage quality, overcoming the constraints of low heritability and multi-trait selection. Full article

This study aimed to determine the optimal nitrogen (N) fertilization rate per regrowth cycle for Megathyrsus maximus cv. BRS Tamani by evaluating its effects on forage production, nutrient uptake, bromatological composition, and in vitro degradation kinetics. A randomized complete block design with five N doses (0, 40, 80, 120, and 160 kg N ha⁻¹) and seven replications was conducted over two rainy seasons. From December 2019 to April 2020, canopy height and light interception were measured weekly. When canopy height reached 95% of light interception the grass was harvest and productive and morphological structure were measured. Nitrogen fertilization increased forage mass and yield up to the dose of 40 kg N ha⁻¹, resulting in 1959 and 9798 kg DM ha⁻¹, respectively, while nitrogen use efficiency declined at higher doses. Weed mass was decreased at 0 kg ha⁻¹, and chlorophyll index increased with the N dose. Nitrogen and potassium were the most extracted nutrients, with nitrogen uptake being highest at 80 kg ha⁻¹. Fertilization elevated the levels of crude protein, NDIP, cell content, and cell wall-bound protein, while ash content decreased. In vitro fermentation showed a reduced gas volume at higher N doses and improved degradation and digestibility up to 40 kg ha⁻¹. Nitrogen fertilization enhanced the forage yield and quality of BRS Tamani, with 40 kg ha⁻¹ maximizing efficiency and digestibility. Full article

Foliar fertilizers are low-cost agrochemicals used in pastures, and further research is needed regarding their impact on tropical grasses. Therefore, the objective of this research was to evaluate the effects of foliar fertilization on the development of tropical grasses. Two experiments, consisting of five treatments and four replicates, were carried out. Each experiment was carried out using the following grasses: Zuri grass (Megathyrsus maximus Jacq. cv. Zuri) and ipypora grass (hybrid of Urochloa brizantha × Urochloa zizizensis). In each experiment, ten treatments were evaluated using a 2 × 5 factorial design with four replications. Treatments combined two soil fertilization strategies (with and without nitrogen) and five foliar fertilization strategies, which consisted of a control treatment without foliar fertilization and four application times: immediately after defoliation (0 leaves) and with 1, 2, and 3 expanded leaves. The grass height, tiller population density (TPD), leaf number (LN), forage dry mass (FDM), individual leaf mass (ILM) were evaluated. In the absence of soil fertilization, foliar fertilizer application had no effect on the development of the grasses (p > 0.05). Foliar fertilization did not affect the FDM of Ipyporã and Zuri grass under any of the conditions evaluated (p > 0.05). When applied in the soil fertilize with nitrogen, foliar fertilizer increased LN by 24% for two grasses (p < 0.05). For Zuri grass, foliar fertilization reduced individual leaf mass by 19% (p < 0.05). Thus, foliar fertilizer does not increase the productivity of tropical grasses, with small effects on the leaf’s appearance in Ipyporã and Zuri grass, without altering the forage mass, which necessitates new studies with agrochemicals, new doses, and concentrations of nitrogen. Full article

The main challenge of soybean cultivation in Brazil’s last agricultural frontier is to ensure sustainable production. This study aimed to evaluate the use of cover crops (CC) to improve soil fertility, plant nutrition, and soybeans productivity grown in the Cerrado of Brazil. The study was carried out on a farm located in the state of Maranhão, Brazil, with nine treatments, fallow and CC preceding soybean cultivation: (i) Millet (Pennisetum glaucum L.); (ii) Marandu (Urochloa brizantha); (iii) Ruziziensis (Urochloa ruziziensi); (iv) Tanzania (Megathyrsus maximum); (v) Massai (Megathyrsus maximum); (vi) cowpea (Vigna unguiculata L.); (vii) pigeon pea (Cajanus cajan L.); and (viii) Crotalaria (Crotalaria juncea). An analysis for the characterization of the biomass of cover crops and fallow was carried out. Soil chemical and biological properties, soybean foliar nutrient concentrations, and the soybean seed yield and quality grown in sequence to the CC were also analyzed. Soil microbial carbon was favored by the cultivation of ‘Marandu’, ‘Ruziziensis’, ‘Tanzania’, and cowpea. Nutrient cycling promoted by CC contributed to the maintenance of soil quality and increases in the leaf nutrient concentrations of soybeans. The cultivation of millet, ‘Tanzania’, ‘Massai’, cowpea, and C. juncea increased the soybean yield. Cover crops improved soil fertility while increasing soybean productivity, thus being an effective strategy for the achievement of sustainable soybean production. Full article