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The implementation of more sustainable soil management strategies, such as the use of cover crop for no-till system with crop rotation, can help increase nutrient use efficiency and consequently decrease the use of mineral fertilizers for agriculture. In this context, the objective was to evaluate the efficiency of desiccation, decomposition and release of nutrients in the biomass of forage plants of the genus Brachiaria after intercropping with sorghum in integrated systems for soybean productivity. The experiment was conducted in the field in two agricultural seasons in randomized block design with four repetitions. The treatments consisted of biomass obtained after sorghum intercropping with forage plants of the Brachiaria genus (Brachiaria ruziziensis, Brachiaria brizantha cv. Marandu, Brachiaria brizantha cv. Xaraés, Brachiaria brizantha cv. BRS Piatã, Brachiaria brizantha cv. BRS Paiaguás, Brachiaria cv. BRS Ipyporã), sorghum biomass in monoculture, which after cutting for grain production, remained fallow for one year and an additional soybean treatment without soil cover biomass. The results showed that Cropping systems on sorghum and forage biomass resulted in a 25.64% increase in soybean yields compared to soybeans grown without soil cover. The use of tropical forage as a cover crop in integrated systems proved to be an efficient technique for biomass production, in order to minimize the effect of water deficit during soybean development, and nutrient cycling, which resulted in the replacement of mineral potassium fertilization for the no-till soybean system, by making better use of soil nutrients and contributing to greater sustainability. [ABSTRACT FROM AUTHOR]

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The study aimed at the effect of different regrowth ages on chemical, productive, and morphological characteristics, in addition to the kinetics of gas production and in vitro digestibility of grasses of the genus Brachiaria. The treatments consisted of two regrowth ages (21 and 35 days) and two grass species (Brachiaria brizantha and B. ruziziensis), in plat with a dimension of 10 × 10 with four replications, totaling 16 plats in a completely randomized design. The regrowth age did not change the leaf:stem ratio of the grasses. Ruziziensis-grass had higher crude protein (CP) content in leaves than Marandu-grass (14.0% versus 10.9% respectively). Marandu-grass leaf had higher NDF content than Ruziziensis-grass (65.0 and 58.3%, respectively) and ADF content (39.6 and 33.2%, respectively). The accumulation rate is high in Marandu-grass regardless of the age of regrowth; however, the in vitro digestibility of dry matter of Ruziziensis-grass is better both in the leaf and in the stem. The regrowth age did not influence the dry matter (DM) and neutral detergent fiber (NDF) in vitro digestibility (ivD) of the leaves. The ivDNDF of leaves of both types of grass were similar. There was an increase in the ivDDM of stem when the regrowth age was 21 days. The DM degradation rate was higher in Marandu-grass at both regrowth ages, and the total gas production was higher at 21 days. The parameters evaluated in the dual-pool logistic model showed interaction for age and cultivar, except for fractions λ (lag time) and total gas production. Marandu-grass presented a greater volume of gas for the rapidly degradable fraction and a lower degradation rate. There was a significant interaction for the parameters evaluated in the models between ages and grasses. The exponential model showed interaction in all fractions. Grasses had reduced CP content and increased fibrous fraction as a function of age, with no reduction in leaf DM and NDF digestibility. The Ruziziensis-grass has higher digestibility at the regrowth ages evaluated, while Marandu-grass has higher yields. We recommend adjusting the in vitro degradation kinetics by the dual-pool logistic model. [ABSTRACT FROM AUTHOR]

We aimed to measure the efficiency of visual selection of plant vigor for green biomass production of U. ruziziensis using single- and multitrait approaches to maximize the predictive accuracy of the genetic value. The green biomass production and plant vigor of 254 U. ruziziensis clones were measured over nine evaluation cuttings to determine the efficiency of these approaches for production improvement. Individual and multicutting analyses were performed under single-trait and multitrait approaches using mixed models. The efficiency of visual selection was assessed by measuring plant vigor based on direct and indirect genetic gains. Plant vigor showed a high genetic association with green biomass and could be selected for production, especially in the initial phases of breeding programs. The multitrait approach was superior to the single-trait approach in predicting the genetic value of the clones, and it can be used in U. ruziziensis breeding programs. [ABSTRACT FROM AUTHOR]

Background: Brachiaria humidicola (Bh) has the ability to produce biological nitrification inhibitors (NIs) and release NIs from the root to the soil. Aims: To compare the effects of growing Bh with Brachiaria ruziziensis (Br, which is not able to produce NIs) on soil nitrogen (N) dynamics, N gases and carbon dioxide (CO2) emissions and nitrifiers and denitrifiers following sheep urine application, a laboratory incubation was conducted in a He/O2 continuous flow denitrification system (DENIS). This incubation was conducted in the absence of light. Hence the measured effects of Bh and Br on N cycling were the residual effect of biological NIs released into the soil prior to the incubation and released via root death. Methods: The treatments were: (1) Bh with water application (Bh + W); (2) Bh with sheep urine (Bh + U); (3) Br with water application (Br + W); (4) Br with sheep urine (Br + U). Results: Results showed that soil NO3– concentration increased significantly in the soil with sheep urine application after the incubation. Soil nitrous oxide (N2O) and nitric oxide (NO) emissions increased immediately after the sheep urine application and peaked twice during the incubation. Cumulative emissions for the first peak were significantly lower from the Bh + U treatment (0.054 kg N ha–1) compared with the Br + U treatment (0.111 kg N ha–1), but no significant differences were observed in the total cumulative N2O and NO emissions between the Bh + U and Br + U treatment at the end of the incubation. Sheep urine addition did not affect the AOA, nirS and nosZ gene copies, but significantly increased the AOB gene copies after the incubation. Conclusions: We conclude that the residual effect of Bh to mitigate N2O emissions in a highly nitrifying soil is short‐lived. [ABSTRACT FROM AUTHOR]

Se planteó la hipótesis de que es posible que el inóculo de diferentes especies de rumiantes con capacidades digestivas diferentes que se alimentan de un determinado forraje puede mostrar diferentes utilizaciones de alimento en comparación con otras especies de rumiantes. Se evaluaron cinco gramíneas Brachiaria: B. decumbens cv. Basilisk, B. decumbens acceso D70, B. humidicola cv. Tupi, B. humidicola cv. Común, y B. ruziziensis acceso R124, en dos edades de rebrote (21 y 42 d). Se analizó la producción, el contenido bromatológico, la digestibilidad de materia seca in vitro (DMSiv) y la digestibilidad de la fibra detergente neutro in vitro (DFDNiv) utilizando inóculos bovinos u ovinos. El experimento utilizó un diseño factorial de 5 × 2 × 2 y encontró efectos significativos para la variedad de gramínea y la edad de rebrote. Además, se encontraron interacciones significativas de gramínea × edad en la materia seca, la proteína cruda, la fibra detergente neutro y la fibra detergente ácido de la muestra total y lamina de la hoja. Hubo un efecto significativo de la variedad de gramínea y la edad de la gramínea en la masa del forraje, la relación lámina de la hoja/tallo, lámina de la hoja, tallo, material senescente y crecimiento. En los ensayos de la digestibilidad in vitro, el origen del inóculo mostró un efecto significativo en algunas variedades. Debido a las diferencias en los ensayos in vitro, se recomendó el uso de inóculos específicos de las especies para las evaluaciones de alimentos según el animal al que se destina. Asimismo, B. decumbens cv. Basilisk presentó la mejor digestibilidad in vitro (DMSiv y DFDNiv) en inóculo bovino, mientras que B. humidicola cv. Tupi tuvo mejor digestibilidad in vitro (DMSiv y DFDNiv) en inóculo ovino.

It was hypothesized that i t is possible that inoculum from different ruminant specie s with different digesti ve abilities feeding from a certain forage may show different feed utilization s comparing to other ruminant specie s . Five Brachiaria grass es were evaluated : B . decumbens cv . Basilisk, B . decumbens access D70, B . humidicola cv . Tupi, B humidicola cv . Common, and B . ruziziensis access R124, at two regrowth ages (21 and 42 d) . Production, bromatological content, in vitro dry matter digestibility ( iv DMD ) and in vitro neutral detergent fiber digestibility ( iv NDFD ) were analyzed using bovine or ovine inoculums . The experiment use d a 5 × 2 × 2 factorial design and found significant effect s for grass variety and regrowth age . In addition, significant interaction s from grass × age on dry matter, crude protein, neutral detergent fiber and acid detergent fiber of total sample and leaf blade were found . There were significant effect of grass variety and grass age on forage mass, leaf blade / stem ratio, leaf blade, stem, senescent material and growth. I n vitro digestibility assays of inoculum source showed significant effect i n some varieties . Due to differences in in vitro assays, it was recommended t he use of specie s - specific inoculums for feed evaluations according to the animal it is intended for . Also, B. decumbens cv . Basilisk presented the best in vitro digestibility ( iv DMD and iv NDFD ) in bovine inoculum, whereas B. humidicola cv . Tupi had better in vitro digestibility ( iv DMD and iv N D FD) in ovine inoculum. [ABSTRACT FROM AUTHOR]

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BACKGROUND: Corn intercropped with ruzigrass is common in Brazil, and it can improve the physicochemical features of soils, increase water retention, and suppress the emergence of resistant weeds and soil nematodes. As both corn and ruzigrass are hosts to Spodoptera frugiperda (the main corn pest in South America), the cultivation of both these plants in the same place at one time motivates investigation into the pest population dynamics. We hypothesize that the intercropping system influences S. frugiperda pressure and leaf injury in corn. Considering that if corn hybrids with high dose toxin expression are used, ruzigrass may be a potential host to susceptible S. frugiperda larvae, consequently an alternative refuge and be included as a tool for the resistant management of Bt corn. To test these hypotheses about the use of ruzigrass as an alternative host of S. frugiperda in an intercropping system with corn, we conducted field trials in three seasons to verify S. frugiperda population dynamics and leaf injury to crop systems. In addition to phenotypic evaluation, we also characterized molecularly S. frugiperda strains collected in corn and ruzigrass to identify strain differences. RESULTS: The insects collected in both corn and ruzigrass were identified as corn strains. Ruzigrass was used as a S. frugiperda host during all crop cycles. The intercropped system did not increase the S. frugiperda population or leaf injury on Bt corn. CONCLUSION: The results suggest that the intercropped system is not prejudicial to Bt corn cultivation since high dose concept applies to all larvae instars. The results also suggest that ruzigrass may be used as a promising alternative refuge in Bt corn agroecosystems, if compliance with management strategies is followed. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Soil tillage and cover crops impact spontaneous vegetation in agrosystems. Soil tillage destroys seedlings and can affect the soil seedbank. Cover crops compete with naturally occurring spontaneous species. Our aim was to gain insight into how soil tillage (here, the false seedbed technique) and cover crops impact the spontaneous vegetation in fallows preceding banana crops. In a fallowed field in Guadeloupe (French West Indies), two factors were combined in a split-plot design: the soil tillage modality before cover crop sowing (with or without the false seedbed technique) and the cover crop species (Crotalaria spectabilis, Pueraria phaseoloïdes, a 50/50 mix of Brachiaria decumbens + Brachiaria ruziziensis, a spontaneous vegetation control). On a monthly basis, in three permanent quadrats per sub-plot, all spontaneous species were identified and their numbers counted, while calculating the species richness and Shannon's diversity index. The spontaneous vegetation dynamics contrasted depending on the treatment. From 7 months post-sowing the species density, richness and Shannon index were significantly lower in treatments with B. decumbens + B. ruziziensis and P. phaseoloïdes, while in treatments with C. spectabilis, the species density and richness were significantly higher with than without the false seedbed technique. These effects were probably related to differences in the competitive ability of the cover crop used and, to a lesser extent, to the false seedbed effects on the soil seedbank. This is the first study to show that under a tropical climate, sown cover crop species combined with different soil tillage modalities have substantial impacts on the species density, richness and diversity of the spontaneous plant community over a 1-year period. These results could help farmers in their weed control strategies by providing them with a deeper understanding of the effects of practices on the spontaneous plant community. [ABSTRACT FROM AUTHOR]

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Abstract New approaches based on image analysis can assist in phenotyping of biological characteristics, serving as support for decision-making in modern agribusiness. The aim of this study was to propose a method of high-throughput phenotyping of free access for processing of 2D X-ray images of brachiaria grass (Brachiaria ruziziensis cv. Ruziziensis) seeds, as well as correlate the parameters linked to the physiological potential of the seeds. The study was carried out by means of automated analysis of X-ray images of seeds in which a macro, called PhenoXray, was developed, responsible for digital image processing, for which a series of descriptors were obtained. After the X-ray analysis, a germination test was performed on the seeds and, from this, variables related to the physiological quality of the seeds were obtained. The use of the macro PhenoXray allowed large-scale phenotyping of seed X-rays in a simple, rapid, robust, and totally free manner. This study confirmed that the methodology is efficient for obtaining morphometric data and tissue integrity data in Brachiaria ruziziensis seeds and that parameters such as relative density, integrated density, and seed filling are closely related to the physiological attributes of seed quality.

Forage plant breeders often use visual scores to assess agronomic traits because of the costs associated with in-depth phenotyping in the initial stages of breeding cycles. The aim of this study was to investigate the impact of the number of graders on the effectiveness of indirect selection of high-yielding genotypes and determine an optimal number of graders in the early-stage trials of Urochloa ruziziensis. For that purpose, five graders assessed 2.219 U. ruziziensis genotypes in an augmented block design. Biomass production and vigor scores were evaluated in two cuts and were analyzed using a linear mixed model approach. Vigor scores were analyzed considering each grader's score and the combinations of two, three, four, and five graders. Genetic variance was significant for both traits. Visual evaluation was effective in identifying productive genotypes based on the statistical criteria. The optimal number of graders for indirect selection of high-yielding U. ruziziensis genotypes is three. [ABSTRACT FROM AUTHOR]

Much of soybeans area cultivated in Brazil uses the no-till system, where the residues produced by crops remain over the soil, reducing its temperature, increasing its moisture and providing a better development of the plant. However, the excessive amount of residues can cause problems, reducing the germination of seeds and growing smaller plants. That said, the aim of this study was to determine the wheat (Triticum aestivum) and braquiária (Brachiaria ruziziensis) straw volumes that enable better soybean plant growth, increase moisture and reduce soil temperature, and to minimize the negative effects on emergence plants in a sandy Ultisol of Sandstone Caiuá region of Northwest Paraná state. The experiment was conducted in vases, using a 2x6 factorial with two sources of residues, Brachiaria ruziziensis and Triticum aestivum and 6 doses of residues, 0, 2, 4, 8, 16 and 32 t ha-1, with 4 repetitions. It was evaluated the seedling emergence at 14 days after sowing, the fresh and dried mass of the aerial part of plants and plant roots, and the average height of the plants at 45 days after sowing. It was also evaluated the gravimetric soil moisture, the minimum and maximum temperature of the day on the ground, as well as the thermal range due to the doses and straw sources. The increase in straw doses resulted in an increase of soil moisture, average height and dried mass of plants, there was a reduction in maximum temperature and thermal soil range. However, there was a reduction in seedling emergence percentage as was increased the dose of residues. It was determined the 2.52 (± 0.33) t ha-1 of residues of braquiária and wheat deposited over the soil as the optimum range for the development of soybean plant.

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This study aimed to evaluate the control and susceptibility of signalgrass and ruzigrass in initial growth under different rates of glyphosate and fluazifop-p-butil. The treatments were distributed in a 2 × 6 factorial design, with five repetitions, being two grasses: Brachiaria decumbens cv. Basilisk (signalgrass) and B. ruziziensis (ruzigrass) with six doses of herbicides: 0.00; 0.25; 0.50; 1.00; 1.5 and 2.00 times the commercial dose recommended by manufacturers. At 7, 15, 21, and 30 days after herbicide application (DAA) were evaluated the intoxication in signalgrass and ruzigrass, visually. The glyphosate toxicity was of 100% in both plants, signalgrass and ruzigrass, even at the lowest dose (90 g ha-1), so it can control effectively these species in early growth stage. It was observed that the plants exposed to fluazifop-p-butil showed regrowth only in the doses to 100 g ha-1 and 50 g ha-1 for signalgrass and ruzigrass, respectively. These results confirm the effectiveness of this herbicide molecule in the control of these two species from doses of 200 g ha-1 and 100 g ha-1 for signal grass and ruzigrass, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT The objective of this study was to evaluate the effects of soil cover with sugarcane residue on weed emergence of four weeds from the genus Brachiaria. The study was conducted in an area whose soil was classified as Red Nitosol. Seven different amounts of sugarcane residue (0, 3, 6, 9, 12, 15 and 18 ton ha-1) were used as soil cover. The residue of variety SP832847 was used upon four weed species: Brachiaria decumbens, B. brizantha, B. ruziziensis, and, B. humidicola. The experimental design was a randomized block with four replications. The weeds were sown 1 cm deep and covered by the residue. The seeding rate in use was 1,200 plants m-2. The study was comprised of two phases: the first phase was an evaluation of plant emergence (more than 1 cm for shoots) at 9, 12, 19, 34 and 43 days after sowing (DAS), and in the second phase, plant emergence was evaluated after removal of the straw residue at 89, 130, 175, 196, 217 and 234 DAS. The amount of sugarcane residue used as soil cover influenced the emergence pattern of Brachiaria spp. Minor germination was noticed after residue removal. Amounts greater than 9 ton ha-1 decreased the total number of seedlings in all species, except for B. ruziziensis, whose emergence decreased at 12 ton ha-1.

The agriculture expansion at Brazil is turning to lower clay index soils and consequently, less organic matter content and cation exchange capacity. To overcome those deficiencies, an intense organic matter addition in these soils may be a solution, and this solution is positive when using a crop-livestock integration with corn-pasture dual crop planted on winter. However, to establish this dual-crop system, there is a need to study the behavior of seeds and seedlings of Brachiaria ruziziensis sown in greater depths than normally recommended. Thus, this work aimed to determine the best depth of sowing B. ruziziensis in sandy and loamy soils of Umuarama region, studying the germination and early development of seedlings. The work was held in pots of 12 cm diameter x 12 cm deep, filled with 2 types of soil, a sandy and clay ones with 30 B. ruziziensis seeds sown each pot in five sowing depths: 0, 2, 4, 6 and 8 cm. After 16 days, the number of emerged seedlings was evaluated to set up the germination rate of each treatment, after that, the plants where leveled to 4 each pot, those were cultivated for another 45 days to evaluate the fresh and dried masses of plants and roots, the height of the plants and average length of roots. The sowing depth with higher percentage of germination estimated was 2.65 cm to sandy and 3.02 cm to clay soil. At seedlings development, there was a standard, with better development seedling at lower sowing depths on clay soil and better developments at higher sowing depths in sandy soil.

Resumo: O objetivo deste trabalho foi avaliar o acúmulo de forragem e o valor nutritivo do híbrido de Urochloa 'BRS RB331 Ipyporã' (Urochloa brizantha x Urochloa ruziziensis) submetido à pastejo intermitente. Os tratamentos corresponderam às combinações entre as condições de pré-pastejo, interceptação de 95% da luz incidente e máxima interceptação de luz, e as de pós-pastejo, 10 e 15 cm de altura de resíduo, em delineamento de blocos ao acaso, em arranjo fatorial 2x2, com quatro repetições. Pastos manejados com 95% de interceptação da luz apresentaram maior taxa de acúmulo de forragem, proporção de folhas, relação folha:colmo, teor de proteína bruta e densidade populacional de perfilhos basilares (DPPb), em comparação àqueles manejados com máxima interceptação da luz. Pastos manejados com 15 cm de altura do resíduo apresentaram maior DPPb do que os manejados com 10 cm e apresentaram pequena variação de DPPb entre as estações do ano avaliadas, independentemente do tratamento. Pastos do híbrido interespecífico de Urochloa 'BRS RB331 Ipyporã' apresentam maior acúmulo de forragem e maiores teores de proteína bruta e digestibilidade in vitro da matéria orgânica e menores teores de fibra em detergente neutro na fração folha, quando manejados com 95% de IL nas condições de pré-pastejo, com 30 cm de altura do dossel, associada com 15 cm de altura de resíduo.

Forages of the genus Brachiaria stand out among those used in integrated systems. Little is known about the potential value of new species and cultivars when intercropped with sorghum and planted in the second crop season. The objective of this study was to evaluate the performance (agronomic characteristics) of grain sorghum and the production and nutritional characteristics of forage plants of the genus Brachiaria in an integrated agricultural production system in the second season. The experiment had a randomized block design with four replicates. The treatments consisted of the intercropping of sorghum with forage plants of the genus Brachiaria (Ruziziensis grass, Marandu, Xaraes, Piata, Paiaguas palisadegrass and Ipypora grass), in addition to an extra treatment with sorghum in monoculture. The results showed that sorghum intercropping with Ruziziensis grass, Paiaguas palisadegrass, Piata, and Ipypora grass did not cause a reduction in grain yield. The Xaraes, Piata, and Paiaguas palisadegrass showed higher forage production. However, the Paiaguas, Piata palisadegrass, and Ipypora grass showed better nutritional value. The sorghum intercropping with forage plants of the genus Brachiaria were promising alternatives for grain and forage production in the off-season. The right forage grass combined with sorghum in an integrated system can intensify agricultural production, optimizing the use of the area and increasing sustainability.

ABSTRACT: This research aimed at investigating which sowing method is more suitable for the deployment of Urochloa ruziziensis to suppress the weed community in no-tillage. The design was a randomized block ones, with a 3 x 2 factorial design, in which the first factor was composed of three sowing methods (broadcast, broadcast with incorporation or line sowing) and factor B consisted in the application and non-application of the herbicide 2,4-D. On day 30 and 60 after sowing (DAS), the relative importance of the present plant species was determined. On day 120 and 180 DAS, the accumulation of biomass and the plant cover percentage on the soil provided by the cover crop and weed species were determined. Moreover, on day 180 DAS, the density of the existing weeds was determined. The weed with the highest occurrence in the area was Conyza canadenses, and the lowest percentage of soil covering by signalgrass and the greates occurrence of weeds occurred with broadcast seeding. It is possible to conclude that the broadcast seeding with the incorporation of signalgrass seeds and line sowing methods provide enough plant cover to suppress weed species, avoiding the application of the herbicide 2,4-D in order to suppress the infesting community.

Resumo: O objetivo deste trabalho foi avaliar a sobressemeadura de soja com Urochloa ruziziensis, quanto à capacidade de produção de matéria seca pela forrageira, à infestação de plantas daninhas e ao desenvolvimento da cultura do milho em rotação, no sistema plantio direto. O experimento foi desenvolvido em delineamento de blocos ao acaso, com quatro repetições, em arranjo fatorial 2 x 5 + 1. Avaliou-se a sobressemeadura com U. ruziziensis, em dois estádios de desenvolvimento da soja (R6 e R8) e cinco quantidades de sementes: 200, 400, 600, 800 e 1.000 pontos de valor cultural (PVC). Como testemunha, manteve-se um tratamento sem sobressemeadura. A sobressemeadura de 200 PVC de U. ruziziensis, nos estádios R6 ou R8 da soja, resulta na formação de palha em quantidade suficiente para o sistema plantio direto, além de beneficiar o controle de plantas daninhas na cultura do milho em rotação. Porém, em quantidade elevada, a palha de U. ruziziensis sobre o solo afeta a altura e a produção de grãos de milho.

ABSTRACT Perennial forage crops used in crop-livestock integration (CLI) are able to accumulate large amounts of straw on the soil surface in no-tillage system (NTS). In addition, they can potentially produce large amounts of soluble organic compounds that help improving the efficiency of liming in the subsurface, which favors root growth, thus reducing the risks of loss in yield during dry spells and the harmful effects of “overliming”. The aim of this study was to test the effects of liming on two models of agricultural production, with and without crop-livestock integration, for 2 years. Thus, an experiment was conducted in a Latossolo Vermelho (Oxisol) with a very clayey texture located in an agricultural area under the NTS in Bandeirantes, PR, Brazil. Liming was performed to increase base saturation (V) to 65, 75, and 90 % while one plot per block was maintained without the application of lime (control). A randomized block experimental design was adopted arranged in split-plots and four plots/block, with four replications. The soil properties evaluated were: pH in CaCl2, soil organic matter (SOM), Ca, Mg, K, Al, and P. The effects of liming were observed to a greater depth and for a long period through mobilization of ions in the soil, leading to a reduction in SOM and Al concentration and an increase in pH and the levels of Ca and Mg. In the first crop year, adoption of CLI led to an increase in the levels of K and Mg and a reduction in the levels of SOM; however, in the second crop year, the rate of decline of SOM decreased compared to the decline observed in the first crop year, and the level of K increased, whereas that of P decreased. The extent of the effects of liming in terms of depth and improvement in the root environment from the treatments were observed only partially from the changes observed in the chemical properties studied.

Chromium toxicity affects redox reactions within plant cells, generating detrimental reactive oxygen species. Glutathione is an antioxidant peptide and also a substrate for the production of phytochelatins, which are chelating peptides reported to mitigate Cr3+ toxicity in plants. In this study, Brachiaria brizantha (B. brizantha) and Brachiaria ruziziensis (B. ruziziensis) seedlings were evaluated for physiological responses and glutathione production following the addition of zero or 5 mg L-1 Cr3+ to the nutrient solution. Glutathione levels were determined by colorimetric analysis at 412 nm using 5,5'-dithio-bis(2-nitrobenzoic acid) as a chromophore reagent and recovery with glutathione reductase (with evaluations at days 10 and 20 of continuous growth). The assessments were carried out in a completely randomized design with 2 authentic replications, and arranged in a 23 factorial. Cr3+ caused an average increase of 0.76 mg g-1 in the initial glutathione content. However, by day 20 there was an average reduction of 3.63 mg g-1. Chromium-affected physiological detrimental responses, albeit detected in both species, were less-pronounced in B. ruziziensis, along with a much higher level of glutathione. This study indicates that B. ruziziensis has a greater tolerance for chromium toxicity than B. brizantha, and that glutathione is likely to be involved in the mitigation of chromium stress in B. ruziziensis.

Resumo: O objetivo deste trabalho foi avaliar o efeito do manejo de plantas de cobertura na floração e na maturação fisiológica sobre a produtividade do milho cultivado em sucessão. O experimento, em delineamento de blocos ao acaso com parcelas subdivididas, foi realizado em Latossolo Vermelho, em sistema plantio direto, com nove espécies. Foram avaliados: produtividade de matéria seca; tempo de ciclagem dos resíduos vegetais; teores de N das plantas de cobertura; e produtividade de grãos e teores de N nas folhas do milho. As espécies Pennisetum glaucum, Mucuna aterrima, Cajanus cajan e Canavalia brasiliensis apresentaram as maiores produtividades de matéria seca na floração. Na maturação fisiológica, Sorghum bicolor, P. glaucum, C. brasiliensis, Crotalaria juncea e C. cajan apresentaram produtividades mais elevadas de fitomassa. Não houve efeito da época de corte e da interação planta de cobertura e época de corte sobre a produtividade do milho. As maiores produtividades de milho foram obtidos após cultivo de Urochloa ruziziensis, C. juncea, C. brasiliensis, C. cajan, P. glaucum e Raphanus sativus, e estão relacionadas ao maior acúmulo de matéria seca e ao menor tempo de ciclagem dos resíduos vegetais das plantas de cobertura.

Soil aggregation and the distribution of total organic carbon (TOC) may be affected by soil tillage and cover crops. The objective of this study was to determine the effects of crop rotation with cover crops on soil aggregation, TOC concentration in the soil aggregate fractions, and soil bulk density under a no-tillage system (NTS) and conventional tillage system (CTS, one plowing and two disking). This was a three-year study with cover crop/rice/cover crop/rice rotations in the Brazilian Cerrado. A randomized block experimental design with six treatments and three replications was used. The cover crops (treatments) were: fallow, Panicum maximum, Brachiaria ruziziensis, Brachiaria brizantha, and millet (Pennisetum glaucum). An additional treatment, fallow plus CTS, was included as a control. Soil samples were collected at the depths of 0.00-0.05 m, 0.05-0.10 m, and 0.10-0.20 m after the second rice harvest. The treatments under the NTS led to greater stability in the soil aggregates (ranging from 86.33 to 95.37 %) than fallow plus CTS (ranging from 74.62 to 85.94 %). Fallow plus CTS showed the highest number of aggregates smaller than 2 mm. The cover crops affected soil bulk density differently, and the millet treatment in the NTS had the lowest values. The cover crops without incorporation provided the greatest accumulation of TOC in the soil surface layers. The TOC concentration was positively correlated with the aggregate stability index in all layers and negatively correlated with bulk density in the 0.00-0.10 m layer.

O nematoide reniforme (Rotylenchulus reniformis) tem se tornado crescente problema fitossanitário da cultura da soja. Considerando a limitada disponibilidade de cultivares de soja que aliem resistência ao nematoide a outras características agronômicas desejáveis, estuda-se a possibilidade de utilização de manejo cultural para seu controle. Este trabalho visou avaliar o efeito da rotação de culturas no verão com milho, Crotalaria ochroleuca ou soja; e o manejo de entressafra, com Brachiaria ruziziensis como espécie de cobertura ou pousio. O experimento foi implantado em solo naturalmente infestado pelo nematoide reniforme (1245 nematoides/200cc de solo) em delineamento experimental de blocos ao acaso, com quatro repetições, em esquema fatorial 3x2 (cultivos de verão x manejo de entressafra). Foram avaliadas a densidade populacional do nematoide no solo e sua variação durante as safras e entressafras, bem como a produtividade da soja na safra subsequente à rotação de culturas. Não houve efeito do manejo da entressafra com braquiária sobre o nematoide. A rotação de culturas com milho ou crotalária no verão propiciou redução da densidade populacional do nematoide reniforme em comparação ao monocultivo de soja, com reflexos positivos sobre a produtividade de soja na safra seguinte

Objective: The preference evaluation of cattle is an important factor for estimation and improvement of the grazing amounts of newly introduced or bred grasses or cultivars in barn. This study was performed to assess the grazing behavior (the amount of grazing and/or the grazing speed) of cattle as indirect method using newly bred Brachiaria ruziziensis tetraploid strain 'OKI-1'(BR) hay as treatment group and Cloris gayana 'Callide' (CG) hay as control group. It also compared the feasibility of using behavioral differences between two groups as one criteria for evaluating preference by Japanese black cattle in barn. Methods: Three experiments were carried out using 12 growing Japanese Black cattle including 6 males and 6 females. In each experiment, the four Japanese Black cattle (2 males and 2 females) were placed in separated stall and allowed to graze BR and CG in manger that was separated into two portions for about 30 min. The position and behavior of the cattle were recorded, and weighed the residual of each gay at 15 and 30 minutes after experiment start. Results: The BR was superior to CG in chemical composition such as protein, fibers and non-fibrous carbohydrate. The cattle, over all, tended to prefer BR over CG in the first half 15 minutes in terms of the time spent and amount of grazing. Additionally, growing cattle exhibited neophilia for BR bred newly. Conclusion: These findings indicated the current approach could be applied for one of criteria to evaluate the preference of hay by Japanese black cattle under indoor housing environment. [ABSTRACT FROM AUTHOR]

ABSTRACT This study was conducted in order to evaluate the selectivity of signal grass and congo grass, submitted to post-emergence herbicide application. The experiment was conducted under greenhouse conditions, in Diamantina, Minas Gerais state, and it was arranged in a randomized block design, with five replications. Treatments were set in factor scheme (8 x 2) + 2. Eight herbicides (nicosulfuron; clomazone; glyphosate; fluazifop-p-butyl + fomesafen; lactofen; fomesafen; fluazifop-p-butyl and mesotrione) were applied in doses recommended by the manufacturer on two fodder species: Brachiaria decumbens cv. Basilisk (signal grass) and Brachiaria ruziziensis (congo grass); in addition, there were two control samples without herbicide application, for a total of 18 treatments. The evaluated herbicides showed less intoxication on signal grass when compared to congo grass. Nicosulfuron and glyphosate promoted higher intoxication on both species when compared to the other herbicides. Glyphosate, fluazifop-p-butyl + fomesafen, fluazifop-p-butyl, mesotrione and nicosulfuron affected the ratio variable / maximum fluorescence (Fv/Fm) in both species, indicating an effect provided by these herbicides on the electron transport chain. Results demonstrated that signal grass and congo grass have higher susceptibility to glyphosate, fluazifop-p-butyl + fomesafen, fluazifop-p-butyl, mesotrione and nicosulfuron. congo grass shows higher susceptibility to the studied herbicides when compared to signal grass.

Phosphorus fixation in tropical soils may decrease under no-till. In this case, P fertilizer could be surface-spread, which would improve farm operations by decreasing the time spend in reloading the planter with fertilizers. In the long term, less soluble P sources could be viable. In this experiment, the effect of surface-broadcast P fertilization with both soluble and reactive phosphates on soil P forms and availability to soybean was studied with or without fertilization with soluble P in the planting furrow in a long-term experiment in which soybean was grown in rotation with Ruzigrass (Brachiaria ruziziensis). No P or 80 kg ha-1 of P2O5 in the form of triple superphosphate or Arad reactive rock phosphate was applied on the surface of a soil with variable P fertilization history. Soil samples were taken to a depth of 60 cm and soil P was fractionated. Soybean was grown with 0, 30, and 60 kg ha-1 of P2O5 in the form of triple phosphate applied in the seed furrow. Both fertilizers applied increased available P in the uppermost soil layers and the moderately labile organic and inorganic forms of P in the soil profile, probably as result of root decay. Soybean responded to phosphates applied on the soil surface or in the seed furrow; however, application of soluble P in the seed furrow should not be discarded. In tropical soils with a history of P fertilization, soluble P sources may be substituted for natural reactive phosphates broadcast on the surface. The planting operation may be facilitated through reduction in the rate of P applied in the planting furrow in relation to the rates currently applied.

Considerando o crescimento da produção de forragem no sistema integração lavoura-pecuária e a possibilidade de consorciação de milho com forrageiras semeadas em diferentes profundidades, ainda são necessárias mais pesquisas para entender o desenvolvimento das principais forrageiras. Objetivou-se neste trabalho avaliar o perfilhamento e a produtividade de matéria seca de duas espécies de braquiárias submetidas a profundidades de deposição das sementes em consórcio com milho, em sistema de integração lavoura-pecuária, na região do Cerrado. O experimento foi conduzido em sistema plantio direto no município de Selvíria - MS, num LATOSSOLO VERMELHO Distroférrico, textura argilosa. O delineamento experimental foi o de blocos ao acaso, em esquema fatorial 2x3, com quatro repetições. Os tratamentos foram duas espécies de braquiárias (Brachiaria brizantha cv. 'Marandu' e Brachiaria ruziziensis), cujas sementes foram misturadas ao fertilizante do milho, e três profundidades (8, 10 e 16cm) de deposição do fertilizante + sementes. A deposição das sementes de braquiárias a 16cm de profundidade resultou em menor número de perfilhos e produtividade de matéria seca. O perfilhamento das forrageiras foi influenciado pelo ciclo do milho, com tendência de estabilização no fechamento das entre linhas da cultura e retomada na emissão de perfilhos no final do ciclo

Em regiões de clima tropical, as principais limitações na manutenção de palhada na superfície do solo são a dificuldade de sua implantação e as suas elevadas taxas de decomposição. Visando identificar o potencial produtivo dos capins xaraés e ruziziensis, bem como a posterior formação de palhada para continuidade do sistema plantio direto, avaliou-se a produtividade de massa seca, a relação lignina/N total, o acúmulo de macronutrientes e a decomposição da palhada em duas safras agrícolas. Os tratamentos foram constituídos por duas espécies de braquiária (Brachiaria brizantha cv. Xaraés e Brachiaria ruziziensis), implantadas em consórcio com a cultura do milho e adubadas com as mesmas doses de N (0, 50, 100, 150 e 200 kg ha-1), durante e após o consórcio com a cultura do milho. O tempo de decomposição da palhada durante o período de 120 dias foi avaliado pelo método das sacolas de decomposição (litter bags). A adubação nitrogenada não influenciou a produtividade de massa seca dos capins xaraés e ruziziensis, a relação lignina/N total e a quantidade de palhada depositada sobre a superfície do solo após o consórcio com milho, porém elevou os acúmulos de N, K, Mg e S. Os capins xaraés e ruziziensis apresentaram potencial de produção de palhada acima de 4.000 kg ha-1 na entressafra, com a manutenção de 15 a 60 % dessa quantidade aos 120 dias após o manejo.

Brachiaria species, particularly B. humidicola, can synthesize and release compounds from their roots that inhibit nitrification, which can lead to changes in soil nitrogen (N) dynamics, mainly in N-poor soils. This may be important in crop-livestock integration systems, where brachiarias are grown together with or in rotation with grain crops. The objective of the present study was to determine whether this holds true in N-rich environments and if other Brachiaria species have the same effect. The soil N dynamics were evaluated after the desiccation of the species B. brizantha, B. decumbens, B. humidicola, and B. ruziziensis, which are widely cultivated in Brazil. The plants were grown in pots with a dystroferric Red Latosol in a greenhouse. Sixty days after sowing, the plants were desiccated using glyphosate herbicide. The plants and soil were analyzed on the day of desiccation and 7, 14, 21 and 28 days after desiccation. The rhizosphere soil of the grasses contained higher levels of organic matter, total N and ammonium than the non-rhizosphere soil. The pH was lowest in the rhizosphere of B. humidicola, which may indicate that this species inhibits the nitrification process. However, variations in the soil ammonium and nitrate levels were not sufficient to confirm the suppressive effect of B. humidicola. The same was observed for B. brizantha, B. decumbens and B. ruziziensis, thereby demonstrating that, where N is abundant, none of the brachiarias studied has a significant effect on the nitrification process in soil.

The objective of this work was to evaluate the effectiveness of ruzigrass (Urochloaruziziensis) in enhancing soil-P availability in areas fertilized with soluble or reactive rock phosphates. The area had been cropped for five years under no-till, in a system involving soybean, triticale/black-oat, and pearl millet. Previously to the five-year cultivation period, corrective phosphorus fertilization was applied once on soil surface, at 0.0 and 80 kg ha-1 P2O5, as triple superphosphate or Arad rock phosphate. After this five-year period, plots received the same corrective P fertilization as before and ruzigrass was introduced to the cropping system in the stead of the other cover crops. Soil samples were taken (0-10 cm) after ruzigrass cultivation and subjected to soil-P fractionation. Soybean was grown thereafter without P application to seed furrow. Phosphorus availability in plots with ruzigrass was compared to the ones with spontaneous vegetation for two years. Ruzigrass cultivation increased inorganic (resin-extracted) and organic (NaHCO3) soil P, as well as P concentration in soybean leaves, regardless of the P source. However, soybean yield did not increase significantly due to ruzigrass introduction to the cropping system. Soil-P availability did not differ between soluble and reactive P sources. Ruzigrass increases soil-P availability, especially where corrective P fertilization is performed.

O objetivo deste trabalho foi avaliar a necessidade de bordadura e estimar o tamanho ótimo de parcela em experimentos para avaliação de Urochloa ruziziensis. Foram avaliadas a altura das plantas e a produção de massa verde de oito progênies de meio-irmãos de U. ruziziensis, em dois cortes. Utilizou-se o delineamento de blocos ao acaso, com quatro repetições e parcelas de 16 m². Cada parcela foi subdividida em 32 estratos de 0,5 m², sendo cada estrato considerado como uma unidade básica. Para determinar a necessidade de bordadura, foi realizada análise de variância, tendo-se considerado a posição da unidade básica na parcela. As estimativas do tamanho ótimo da parcela foram realizadas pelo método da máxima curvatura do coeficiente de variação e pelo método da reamostragem. O uso de bordaduras não altera o desempenho médio e a classificação das progênies de meio-irmãos avaliadas. O emprego de parcelas com 3 m² é suficiente para obter boa precisão experimental em experimento com progênies de meio-irmãos de U. ruziziensis.

The use of cover crops in no-tillage systems (NTS) increases the levels of organic matter and could increase the nitrogen content of the soil, contributing to reduce fertilizers costs. The knowledge of these processes is fundamental for deciding whether cover crops can be effectively incorporated into the agricultural production system. The objective of this study was to evaluate the effect of cover crop species on the levels of nitrate and ammonium in the soil in early upland rice development, as well upland rice yield. A field experiment was performed and treatments consisted of growing rice on five cover crops (Panicum maximum, Brachiaria ruziziensis, Brachiaria brizantha, millet and fallow) in an NTS and two control treatments (Brachiaria brizantha and fallow) under a conventional tillage system, CTS, (one plowing and two disking). The experimental design was a complete randomized block with three replications. The soil samples were collected during a period of six weeks (0, 7, 14, 21, 28 and 35 days in relation to upland rice sowing). The cover crops Brachiaria brizantha, Panicum maximum and Brachiaria ruziziensis in the NTS and B. brizantha fallow incorporated into the CTS favored higher levels of nitrate in the soil. In contrast, B. brizantha and fallow in the CTS and millet and P. maximum in the NTS favored the buildup of high levels of ammonium in the soil. The treatments under the plowed cover crops millet and fallow allowed for a higher upland rice yield. The tillage system and nature of the cover crops could be used to achieve the desired levels and forms of nitrogen in soil. O uso de plantas de cobertura no sistema plantio direto (SPD) aumenta os níveis de matéria orgânica e pode ajudar a aumentar os teores de nitrogênio no solo contribuindo para reduzir os custos de fertilizantes. O conhecimento desse processo é fundamental para que as plantas de cobertura possam ser efetivamente incorporadas aos sistemas de produção agrícola. O objetivo deste estudo foi avaliar o efeito de espécies de plantas de cobertura nos níveis de nitrato e amônio no solo durante o desenvolvimento inicial do arroz de terras altas, bem como a produtividade do arroz. Um experimento de campo foi realizado e os tratamentos consistiram de cultivo de arroz sobre cinco plantas de cobertura (Panicum maximum, Brachiaria ruziziensis, Brachiaria brizantha, milheto e pousio) no SPD e mais dois tratamentos controle (Brachiaria brizantha e pousio) no sistema de plantio convencional, PC (uma aração e duas gradagens). O delineamento experimental foi em blocos completos casualizados com três repetições. As amostras de solo foram coletadas por seis semanas (0, 7, 14, 21, 28 e 35 dias em relação à semeadura do arroz). As culturas de cobertura B. brizantha, Panicum maximum e B. ruziziensis no SPD e B. brizantha incorporada e pousio incorporado no PC tiveram os níveis mais elevados de nitratos no solo. Por outro lado, B. brizantha e pousio no PC e milheto e P. máximo no SPD tiveram os níveis mais elevados de amônio no solo. Tratamentos com a planta de cobertura milheto e pousio incorporado proporcionaram as maiores produtividades do arroz. Sistema de cultivo e espécies de plantas de cobertura podem ser usadas para atingir os níveis desejados e a forma de nitrogênio no solo.