J. C. B. Dubeux

The future of warm-season, tropical and subtropical forage legumes in sustainable pastures and rangelands

Forage legumes have the potential to contribute substantially to warm-season, subtropical and tropical pastures and rangelands. Compared to grasses, they have advantages in accessing subsoil nutrients and moisture; legumes typically concentrate protein in forage, even in infertile soils, and they can also provide ruminants with plant proteins and soluble carbohydrates that increase digestibility of grasses when consumed in legume–grass mixtures. Yet their inclusion in warm-season, subtropical or tropical pasture seed mixes or rangeland rehabilitation is minimal considering the percentage of grasslands coverage in these regions. Why have past diligent attempts failed to develop the germplasm, agronomic techniques, dissemination and ultimate widespread acceptance by land managers in regions where these legumes are widely adapted? Successful forage legume reports indicate that farmers’ participation in technology development, persistence with minimal management, adequate seed supply following release of new varieties, meeting recognised needs, delivery of clear benefits and profits, and communication among researchers, extension and stakeholders are crucial. Current and future research and development programs based on limited past successes and widespread failures should enhance successful commercial use of warm-season, subtropical and tropical forage legumes.

Environmental impacts and nutrient recycling on pastures grazed by cattle

Grasslands are being replaced by urbanization and more profitable agricultural activities around the world. Producers may be faced with land constraints and need to consider intensification of the remaining grasslands as a means of maintaining overall production on a decreasing land resource. However, intensification of the grazing system is usually associated with greater nutrient inputs, including those from commercial fertilizers and supplement fed to animals. Excessive loading of nutrients in intensive grazing systems via fertilizer and animal wastes can cause nutrient buildup in the soil and subsequent water quality problems. Surface runoff and leaching of nutrients are the two major process affecting water quality. Nitrogen and P represent major nutrient concerns as related to water quality. Increased nitrate concentrations render groundwater unsuitable for drinking and can cause serious health issues for humans. Excessive N and P concentrations may contribute to eutrophication of streams and lakes. Maximizing efficiency of nutrient recycling through the soil-forage-animal system minimizes off-site nutrient transport and decreases production costs by reducing the quantity of commercial fertilizer needed. Management strategies to reduce soil and water contamination include refining the balance of nutrient inputs from feeds and fertilizers as well as accounting for the nutrients recycled through the decomposition of plant litter and animal wastes. Current interest in the development and adoption of efficient and sustainable agriculture systems has led forage researchers to amplify the scope of grasslands research by increasing multidisciplinary efforts. There is an increased interest in quantifying the impacts of forage-animal management strategies on the environment, with the goal of developing economically viable best management practices that result in optimum forage production and profitability, while protecting the environment. Furthermore, these best management practices will supply reliable information for future environmental policies that may be adopted by governmental agencies.

Aspectos agronômicos e bromatológicos de leguminosas forrageiras no Nordeste Brasileiro

EnglishThe aim of this work was to evaluate the agronomic and bromatologic aspects of nine herbaceous forage legumes. Legumes studied included C. ternatea L., D. heterocarpon (L.) DC. subsp. ovalifolium (Prain) Ohashi cv. Itabela, A. pintoi Krap and Greg. cv. Amarillo, Pueraria phaseoloides (Roxb.) Benth, S. guianensis (Aubl.) Sw. cv. Bandeirante, cv. Cook and cv. Mineirao and Stylosanthes macrocephala Ferreira e Sousa Costa cv. Pioneiro. The following response variables were measured: soil cover, plant height, fresh matter production, stand, seed production, FDN, FDA, hemicellulose, lignin, PB and MM concentrations of leaves and stems. Four cuts were performed during the experimental period. Cutting intensities were at the ground level for the first cut and 5 cm for the following cuts. It was used a complete randomized block design with three replications per treatment. C. ternatea showed the greatest fresh matter yield summed along the four cuts (45.6 t/ha/432 d). This same legume showed one of the greatest PB concentrations, both for leaves (27.4%) and for stems (11.5%). At 43 days after transplanting, C. mucunoides showed the greatest soil coverage. During the 432 days of experimental period, the S. guianensis cultivars did not flower, however, C. mucunoides, C. ternatea, and S. macrocephala presented the greatest seed production. A. pintoi, C. ternatea and C. mucunoides showed greater potential for forage production in this region, and with C. ternatea presenting the most promising results in terms of chemical composition. portuguesO trabalho objetivou avaliar aspectos agronomicos e bromatologicos de nove leguminosas forrageiras herbaceas na zona da Mata Seca de Pernambuco. As leguminosas estudadas foram: Calopogonium mucunoides Desv, Clitoria ternatea L., Desmodium heterocarpon (L.) DC. subsp. ovalifolium (Prain) Ohashi cv. Itabela, Arachis pintoi Krap e Greg. cv. Amarillo, Pueraria phaseoloides (Roxb.) Benth, Stylosanthes guianensis (Aubl.) Sw. cv. Bandeirante, cv. Cook e cv. Mineirao e Stylosanthes macrocephala Ferreira e Sousa Costa cv. Pioneiro. Foram avaliadas as seguintes variaveis: cobertura do solo, altura da planta, producao de materia verde, stand, relacao folha/caule, producao de sementes, teores de fibra em detergente neutro (FDN), fibra em detergente acido (FDA), hemicelulose, celulose, lignina, proteina bruta (PB) e materia mineral (MM) das folhas e caules. Foram realizados quatro cortes, sendo utilizada intensidade de 0 cm para o primeiro corte e 5 cm para os demais. O delineamento foi blocos casualizados com tres repeticoes. A maior producao de MV acumulada foi de 45,6 t/ha/432 dias apresentada pela C. ternatea que tambem apresentou um dos maiores teores de PB, tanto para a folha (27,4%) quanto para o caule (11,5%). Aos 43 dias apos o transplantio, o C. mucunoides foi a leguminosa que apresentou a maior porcentagem de solo coberto. Durante o periodo experimental (432 dias) nao foi observado florescimento dos S. guianensis, enquanto que C. mucunoides, C. ternatea e S. macrocephala apresentaram maior potencial de producao de sementes. A. pintoi, C. ternatea e C. mucunoides mostraram grande potencial para producao de forragem nesta regiao, com a C. ternatea apresentando os resultados mais promissores quanto a composicao quimica.

Soil-Fertility Principles for Warm-Season Perennial Forages and Sustainable Pasture Production

Pasture fertilization plays a vital role in the biological and economic successes of forage-based livestock systems. Sustainability of productive, warm-season perennial forage systems depends, to a major extent, on management–utilization strategies and pasture fertilization. As soil nutrient reserves are exhausted, forage production and nutritive value are reduced proportionally. Despite the vast scientific literature suggesting that warm-season forage crops can respond favorably to high levels of N fertilization, the increasing costs of commercial fertilizers and environmental concerns have prompted the need to reexamine optimumefficient fertilizer levels, sources, and methods of application that can sustain economic pasture production. Because the fate of fertilizers applied to grassland systems is extremely complex and is affected by several factors, including application rate and timing, fertilizer source, and soil and environmental characteristics, it is critical to implement management strategies for soil fertility that integrate all the factors that affect fertilizer efficiency, sustainable forage production, and protection of natural resources. The primary objective of this review paper is to present some of the basic principles of soil-fertility management for warm-season perennial forages and fertilization strategies for sustainable

Sustainable intensification of cultivated pastures using multiple herbivore species

Demand for animal products is growing faster than for any other agricultural product. As a result, pressure for greater output from cultivated pastures is expected to increase. Assuming cultivated pasture area will decrease with land degradation, conversion to grain crops or urban expansion, the only alternative is to increase productivity per area. We suggest an underutilised solution: increase herbivore diversity on cultivated pastures. We review multiple herbivore species (MHS) ecology in natural ecosystems (rangeland and wildlife parks) for guidelines to implementing this approach in cultivated pasture. In rangeland or natural grassland systems, sequential or simultaneous introduction of MHS results in greater productivity, diversity and resilience of plant as well as animal populations. Replacing historical mono-ruminant systems with MHS or classes on cultivated pasture is currently beyond landowner experience and will stretch cultivated pasture science. This approach becomes more feasible, however, as cultivated pastures increase in plant biodiversity and canopy complexity. We enumerate research and demonstration topics that might promulgate MHS in cultivated pastures.

Avaliação de métodos para recuperação de pastagens de braquiária no agreste de Pernambuco: 1. aspectos quantitativos

The experiment was performed to evaluate the productive response of a degraded B. humidicola pasture to different pasture recovery methods. It was used a split-plot within a confounded randomized block design. The main plot was represented by the combination among managements and fertilization levels and the sub-plot by the deferred periods. The experimental treatments were four recovery managements (no-tillage, harrowing, harrowing + corn as a companion crop, no-tillage + corn as a companion crop), two levels of nitrogen (0 and 100 kg/ha of N), two levels of phosphorus (0 and 100 kg/ha of P2O5) and, different periods of deferment (113, 156, 200 and 240 days), totalizing 64 treatments with three replications each one. It was found a significant interaction between recovery managements and P fertilization. The average dry matter accumulation (DMA) was 7.52; 1.68; 1.10 and 4.43 t/ha of B. humidicola for no-tillage, harrowing, harrowing + corn as a companion crop, no-tillage + corn as a companion crop, respectively. The highest deferment period increased DMA, plant heigth and B. humidicola participation in the botanical composition, as well reducing percentage of other species in the DMA and percentage of uncovered soil. Brachiaria humidicola pastures at the initial degradation stage, grown in low available phosphorus soils, may be recovered using a deferment period associated to a phosphorus fertilization.

Decomposition of cattle dung on grazed signalgrass (Brachiaria decumbens Stapf) pastures in monoculture or intercropped with tree legumes

Livestock excreta is one of the major nutrient sources in natural grasslands. Understanding how livestock diet and season affects the decomposition dynamics is critical to nutrient cycling models. We hypothesised that livestock diet and season of the year affect dung decomposition. This study evaluated the decomposition and release of N, P, K, Ca, Mg, and Na from faeces of cattle collected in dry and wet seasons. Treatments were signalgrass (Brachiaria decumbens Stapf) in monoculture or mixed with sabiá (Mimosa caesalpiniifolia Benth.) or gliricidia (Gliricidia sepium (Jacq.) Kunth ex Walp.). Excreta samples were incubated in nylon bags for 0, 2, 4, 8, 16, 32, 64, 128 and 256 d. The single negative exponential mathematical model was adequate (P < 0.0001) to explain the decomposition. The relative rate of dung decomposition (k) was greater for samples that originated from cattle grazed on signalgrass (k = 0.00284 g g−1 d−1), followed by sabiá (k = 0.00233 g g−1 d−1), and gliricidia (k = 0.00200 g g−1 d−1) pastures. The rate of nutrient release showed a time effect for all variables and interaction between time and season for Ca (P = 0.0042) and Mg (P = 0.0013). Faeces collected from cattle grazing/browsing intercropped pastures tended to have lower decomposition rates.

Avaliação de métodos para recuperação de pastagens de braquiária no agreste de Pernambuco: 2. valor nutritivo da forragem

The research was carried out to evaluate qualitative aspects of a B. humidicola degraded pasture managed under different recovery methods in Bezerros-PE. A confounded split-plot randomized block design was used. The main plot was formed by the factorial arrangement between managements and fertilization levels. The splitplot model consisted of the different deferment periods. The factors were represented by four recovery managements (no-tillage, arrowing, arrowing + corn, no-tillage + corn), two N levels (0 and 100 kg/ha of N), two P levels (0 and 100 kg/ha of P2O5) and four deferment periods (113, 156, 200 and 240 days), with three replications. CP, NDF, ADF, P, ashes contents and IVDMD were determined. Significant interaction among management systems and P fertilization was observed when NDF, ADF and P concentration of braquiaria were evaluated. B. humidicola deffered for 113, 156, 200 and 240 days showed the following ADF and IVDMD values, respectively: 40.36 and 61.92%; 43.89 and 56.58%; 44.52 and 31.35%; 46.25 and 30.07%.

A New Red Clover 2,4-D-Resistant Cultivar to Improve Broadleaf Weed Control and Elucidate the Molecular Mechanism of Resistance

Using recurrent phenotypic selection we have developed a red clover (Trifolium pratense L.) cultivar (FL24D) resistant to 2,4-Dichlorophenoxyacetic acid (2,4-D) after six cycles. Approximately 20,000 seeds were broadcast seeded into metal flats and sprayed with 1.1 kg a.i. ha-1 2,4-D at 4 week (3 trifoliate leaf stage). One month later, 385 (1.95 %) plants were selected for intercrossing. Selection criteria were based on survival and regrowth. Following cycles were based on recurrent half-sib selection. While standard red clover cultivars (susceptible to 2,4-D) died after the recommended 2,4-D application rates, FL24D established a stand with no decrease in total yield relative to the unsprayed treatment. Under unsprayed conditions, FL24D presented one of the highest yields compared to commercially available cultivars. Additionally, FL24D is earlier in spring growth than any other known cultivar in the market. Despite the economic importance of 2,4-D and its use for more than 60 years, remarkably little is known about the underlying genetic architecture or the genetic process by which resistance is acquired in plants. Using remnant seed from the cultivar development, cycle 0 (susceptible) through cycle 6 (resistant), we are studying both the process of acquired resistance and the molecular mechanism involved in such resistance.

Repetibilidade de variáveis produtivas e qualitativas da forragem e da excreta bovina em pastagem de braquiária

The objective of this work was to determine the repeatability and the number of the required evaluations to obtain determination coefficient greater than 90% in the productive and qualitative variables of forage and cattle excreta on a signal grass (Urochloa decumbens) pasture. The utilized variables were: fecal production, feces mineral composition, herbage mineral composition around dung pads, feces biometry, herbage mass and herbage rejection around dung pads, urinary volume, and urine chemical composition. A fixed rotational stocking was used, with three days of occupation and 32 or 67 days of resting period, during the rainy and dry seasons, respectively. Repeatability analyzes were obtained with the software Genes, using the principal component method based on the covariance. The repeatability coefficients (r) had high estimates, and the R2 were equal to or greater than 90%, except for herbage mass at 20-40 cm, for the difference between pre-and post-grazing herbage height of herbage grown on dung pad, and for nitrogen concentration in the urine for the treatment with 3,2 animal units per hectare (r<0.50). For R2 above 90%, the number of evaluations required would be 11, 9, and 9, for the variables forage, feces, and urine, respectively.