Root growth and nutrient accumulation in cover crops as affected by soil compaction

Crop rotation using cover crops with vigorous root systems may be a tool to manage soils with some degree of compaction. Root and shoot growth as well as nutrient accumulation by summer species suitable for crop rotation in tropical areas were studied at different subsoil compaction levels. Crotalaria juncea (Indian hemp), Crotalaria spectabilis (showy crotalaria), Helianthus annuus (sunflower), Pennisetum americanum (pearl millet) and Sorghum bicolor (guinea sorghum) were grown for 40 days in pots 33.5 cm high with 10 cm internal diameter. Soil in the pots had uniform bulkdensity of 1.25 Mg m-3 for the top and bottom 15 cm sections. Bulk densities of 1.31, 1.43, 1.58 and 1.70 Mg m-3 Were established in the 3.5 cm middle section. H. annuus and P. americanum had the highest early macronutrient accumulation. The grasses S. bicolor and P. americanum yielded twice as much shoot dry matter as the other species. Root growth generally decreased with increasing soil bulk density with C. spectabilis less affected than other species. Although the grasses were more sensitive to high soil penetration resistance, they showed higher root length densities at all compaction levels. P. americanum had the highest potential to be used as cover crop due to its high root density at high soil penetration resistances, vegetative vigour and ability to accumulate macronutrients. © 2002 Elsevier Science B.V. All rights reserved.

Métodos de coleta de fezes e determinação dos coeficientes de digestibilidade da fração protéica e da energia de alimentos para o pacu, Piaractus mesopotamicus (Holmberg, 1887)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Potencialidades da utilização de taninos na conservação de forragens e nutrição de ruminantes-revisão

This review present a discussion abouth the tannins. The tannins are compounds that have the ability to bind other macromolecules, reducing their availability to animal metabolism. This characteristic can be benefic or deleterious, depending on the tannin concentration degree in the plant and its structure. Positive effects are mainly related with a better use of the dietary protein and an increased efficiency of microbial protein synthesis in the rumen. The use of tannins to reduce ruminal methane emission has been subject of current researches, firmly indicating a decrease of ruminal methanogenesis. However, many of these studies, carried out to evaluate the effects of tannins on forage fermentation and animal metabolism, are based on legume plants, so their results can not be surpassed to studies concerning tanniniferous grasses. By improving the characterization of the profile and reactivity of tannins in tanniniferous forages, such as some sorghum hybrids, as well as conducting experiments to demonstrate the effects of tannins on animal metabolism and performance, the real potential of forages with tannin will be enlightened.

Degradação ruminal e síntese de proteína microbiana em bovines alimentados com silagem de sorgo contendo tanino suplementado com concentrado ou uréia

This work aimed to determine ruminal parameters of dry mater (DM), neutral detergent fiber (NDF) and protein synthesis in the rumen of animals fed diets based on sorghum with different tannin levels. In situ degradation was evaluated by rumen incubation of level 1 (L1) and level 2 (L2) sorghum silages during 0, 6, 24, 48 and 96 hours. A duplicated 4 × 4 Latin Square was used. Potential degradability (PD) of DM was similar among silages, whereas the effective degradability (ED) decreased when the diets were supplemented with concentrate. Microbial nitrogen flux and microbial synthesis efficiency were not affected by roughage source. The synthesis efficiency, expressed in organic matter and crude protein digested in rumen, was higher in L1 tannin diets supplemented with concentrate. There was not relationship between the presence of tannins and the parameters of ruminal degradation.

Resposta plasmática de glicose e insulina em eqüinos alimentados com diferentes fontes de amido

This study was aimed to measure the plasmatic response of glucose and insulin of horses fed diets containing different starch sources, like corn, oat, sorghum and a mix of corn and oat in equal parts. Four standarbred gelding 36 month old an weighing average of 350 kg were used in a Latin Square 4 x 4 (four animals, four treatments and four period) trial design. No statistical differences were observed in plasmatic glucose levels either before or after ingestion between treatments. Maximum plasmatic level of glucose was observed in all diets two and a half hours post ingestion. Insulin plasmatic level was significantly lower before ingestion in horses treated with the mixed corn and oat diet, when compared with the other treatments. In the other hand, the insulin plasmatic level in horses fed corn-formulated diet was statistically higher than the others treatments at three hours and a half after ingestion. Diets containing different sources of starch had no effect in time neither quantity of glucose absorbed in small intestine. Variation observed in insulin plasmatic levels indicate that a proper feeding can have a regulatory effect of this hormone, avoiding undesirable's behaviors.

Atividade rizosférica de solo tratado com herbicida durante processo de remediação por Stizolobium aterrimum

This study aimed to evaluate the soil microbiota activity associated to S. aterrimum rhizosphere, during the phytoremediation process of a soil contaminated with trifloxysulfuron-sodium. S. aterrimum was cultivated in vases (6, 0 L) filled with soil, after trifloxysulfuron-sodium, at 7.5 g ha -1, was applied or not. Every 15 days after sowing (DAS), rhizospheric soil was collected for soil microbial respiration (amount of evolved CO 2) and microbial biomass carbon (MBC) analysis. To determine herbicide residues in the soil samples, after phytoremediation, Sorghum bicolor L. was cultivated as an indicator species, in addition to high performance liquid chromatography (HPLC) analysis. The microbiota associated to S. aterrimum rhizosphere showed to be sensitive to trifloxysulfuron-sodium and may be used as a microbiological indicator of disturbances caused by this herbicide in the environment. Regarding time for remediation, 45 days of development is enough for S. aterrimum to reduce residual trifloxysulfuron- sodium to a level not able to cause toxicity to the indicator plant.

Determinação da massa seca, teor de nutrientes e cobertura do solo de espécies semeadas no outono-inverno

Culture options for the autumn-winter season are a major problem for production systems under low rainfall. The aim of this study was to evaluate the effect of the sowing season on dry matter yield, nutrient content of the shoot and soil covering percentage of coverage plants on the soil on the intercrop: grain sorghum, rattlepods, pearl millet brachiaria grass and an area with weeds (fallow). The experiment was conducted under field conditions on an Oxisol (Haplustox), clay texture, in Selvíria, Mato Grosso do Sul, Brazil. The experimental design was a randomized block design with eight replications, two sowing seasons and five coverage treatments. When the sorghum culture of the first sowing season reached the harvest stage, the dry matter yield on the other treatments was evaluated. Results showed that sowing in March results in higher dry mass yield and higher soil coverage percentage in the studied species. In the first sowing season, Brachiaria brizantha presents higher dry matter yield and macronutrients extraction.

Degradabilidade ruminal da matéria seca de grãos de milho e de sorgo com alto ou baixo conteúdo de tanino processados

This work evaluated the effects of high moisture silage, extrusion and corn and sorghum drying with and without tannin, on the chemical composition and ruminal digestion of dry matter. The experimental design was completely randomized in 3x3 factorial scheme (kinds of grains: processing), for the chemical composition and degradability and three blocks (animals) through in situ method. It was verified significant difference between kinds of grains and processing in relation to the chemical composition, except for crude protein and mineral matter. The contents of etherextract in the three types of grains, were reduced significantly with the high moisture silage, extrusion and drying in relation to the humid material. For the contents of phenols, total and condensed tannin there was effect of hybrid, processing and interaction, and the most elevated contents were found in sorghum with tannin. Although grain composition has been similar, the interaction in ruminal ambient associated to the tannin, promoted differences in the dry matter degradability. It was concluded that sorghum without tannin may be ensiled or extruded, while the sorghum with tannin, must be extruded to improve the degradability and availability of nutrients.

Gene Content Analysis of Sugarcane Public ESTs Reveals Thousands of Missing Coding-Genes and an Unexpected Pool of Grasses Conserved ncRNAs

Sugarcane is the most important crop for sugar industry and raw material for bioethanol. Here we present a quantitative analysis of the gene content from publicly available sugarcane ESTs. The current sugarcane EST collection sampled orthologs for ~58 % of the closely-related sorghum proteome, suggesting that more than 10,000 sugarcane coding-genes remain undiscovered. Moreover the existence of more than 2,000 ncRNAs conserved between sugarcane and sorghum was revealed, among which over 500 are also detected in rice, supporting the existence of hundreds of conserved ncRNAs in grasses. New efforts towards sugarcane transcriptome sequencing were needed to sample the missing coding-genes as well as to expand the catalog of ncRNAs. © 2012 Springer Science+Business Media, LLC.

Características morfogênicas e estruturais de híbridos de sorgo submetidos a adubação nitrogenada

The effect of two topdressing nitrogen doses was evaluated on the morphogenetic and structural characteristics of sorghum hybrids (Sorghum bicolor (L.) Moench) BRS 801 and 0734006, cultivated in vases in open-air conditions. A completely randomized design was used with four treatments arranged in factorial outline 2x2 (two sorghum hybrids and two nitrogen doses, 50 and 100 kg ha-1), with eight replications per treatment. There was a significant effect of interaction hybrid x fertilization on the leaf appearance rate, the hybrid BRS 801 being more responsive to the increased nitrogen dose. The phyllochron, the total number of leaves and leaf elongation rate, were influenced both by nitrogen doses and by hybrids. The leaf senescence rate was not influenced by factors fertilization and hybrids. These variations in morphogenetic and structural characteristics between the hybrids and/or nitrogen doses, probably indicate that hybrids respond in a different way to topdressing.

Phosphorus and potassium budget in the soil-plant system in crop rotations under no-till

Soil management and crop rotations can affect P and K budget in soil, decreasing losses, and increasing fertilizer use efficiency. The P and K budget in the soil-plant system at depths up to 60. cm was studied for different soil managements and crop rotations under no-till for three years in Botucatu, São Paulo, Brazil. The investigated crop rotations were: triticale (X Triticosecale) and sunflower (Helianthus annuus) cropped in autumn-winter; pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor), and Sunn hemp (Crotalaria juncea) were grown in the spring, as well as an additional treatment with chiseling followed by a fallow period; and soybean (Glycini max, L., Merril) was cropped in the summer. Each year triticale and sunflower were grown in plots and pearl millet, forage sorghum, Sunn hemp and of chisel/fallow in sub-plots. The triticale/millet rotation led to the largest decrease in available P within the 0-0.60. m layer of the soil profile and the largest K increase within the 0-0.05. m layer. Potassium mobility in the soil profile and the increases in the available K content in the 0.40-0.60. m layer were independent of the management system. Crop rotations with or without chiseling are not effective in preventing soil P losses. There is considerable K leaching below 0.60. m, but chiseling and the use of high K accumulating plants as triticale results in lower K losses. © 2012 Elsevier B.V.

Teor de ácido cianídrico e taxa de crescimento do híbrido de sorgo x capim sudão durante o outono

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Methane emissions and estimates of ruminal fermentation parameters in beef cattle fed different dietary concentrate levels

Using sorghum silage, the effect of roughage/concentrate ratios was evaluated on nutrient intake, digestibility, ruminal parameters and methane production by beef cattle. Three treatments (0, 30 and 60% of concentrate in DM of the diet) were distributed in three Latin squares, with nine animals and three periods. Dry matter intake increased as the grain concentration in diet increased; pH showed opposite behavior. Methane emissions were lower for animals fed the diet exclusively with sorghum silage as compared with those fed 30% of concentrate, but was similar to that of animals receiving 60% of concentrate. Losses of ingested gross energy as methane were reduced by 33% when grain concentration was increased in the diet. Concentrations of propionic and butyric acids were greater in diets with grain concentrate; acetic acid concentration was not affected. Concentrate in diet increases available energy for the metabolism, measured by lower losses of ingested gross energy as ruminal methane. © 2013 Sociedade Brasileira de Zootecnia.

Soil organic matter and physical attributes affected by crop rotation under no-till

Growing cover crops in systems under no tillage affects different pools of soil organic matter, and eventually soil physical attributes are modified. The objective of this study was to evaluate changes in soil organic matter and their relationship with soil physical attributes as affected by plant species grown in rotation with soybean [Glycine max (L.) Merr.] under no-till for 3 yr. Crop rotations included grain sorghum [Sorghum bicolor (L.) Moench], ruzigrass [Urochloa ruziziensis (R. Germ, and CM. Evard) Crins] and sorghum mixed with ruzigrass, all grown in fall/winter, followed by pearl millet [Pennisetum americanum (L.) Leeke], sunn hemp (Crotalaria juncea L.) and sorghum-sudangrass [S. bicolor × S. sudanense (Piper) Stapf] grown during the spring, plus a fallow check plot. Soybean was grown as the summer crop. Millet and sorghum-sudangrass cropped in spring showed higher root and shoot production as spring cropping. In fall/winter, sorghum mixed with ruzigrass yielded higher phytomass compared with sole cropping. Soil physical attributes and organic matter fractioning were positively affected by cropping millet and sorghum-sudangrass whereas intermediate effects were observed after sunn hemp. Maintaining fallow in spring had negative effects on soil organic matter and physical properties. Ruzigrass and sorghum mixed with ruzigrass cropped in fall/winter resulted in better soil quality. Spring cover crops were more efficient in changing soil bulk density, porosity, and aggregates down to 0 to 10 cm; on the other hand, fall/winter cropping showed significant effects on bulk density in the uppermost soil layer. Total C levels in soil were increased after a 3-yr rotation period due to poor initial physical conditions. Fractions of particulate organic C, microbial C, and C in macroaggregates were the most affected by crop rotations, and showed high relation with improved soil physical attributes (porosity, density, and aggregates larger than 2 mm). © Soil Science Society of America, All rights reserved.

Sistemas de manejo e efeito residual do potássio na produtividade e nutrição do feijão-caupi

Cowpea [Vigna unguiculata (L) Walp] have great social and economic importance for the Para State. It grows well in areas with low precipitation and two crop cycles can be obtained annually. This study aimed to assess the effect of the residual fertilization from a previous culture (Sorghum bicolor L. Moench) and crop systems on cowpea yield and macronutrient concentration on leaves of three cowpea cultivars (BRSMilênio, BRS-Urubuquara e BRS-Guariba). The study was conducted at the UFRA. The treatments were two crop systems (minimum tillage and conventional), four levels of potassium (50, 100, 200 e 300 kg de KCl ha-1 applied to a previous sorghum culture) and the three cowpea cultivars. Treatments were organized as a three (4 x 2 x 3) factor experiment on a randomized complete block design. The soil was a yellow latosol. In each experiment plot five plants were selected to determine shoot dry matter and foliar nutrient concentration. Grain yield was determined after harvesting all plants on the experiment plot. The residual KCl fertilization affected foliar nutrient content, but did not affect shoot dry mass or yield of grain. Yield was higher in the minimum tillage system. Highest yield (1590 kg ha-1) was recorded int the cv. 'Guariba' when 100 kg of KCl ha-1 had been used in the previous crop. The highest content of leaf N and K was found in cowpea under minimum tillage system. The amount of P and Mg were higher in the conventional system whereas the amount of Ca did not change.