Resumo em Inglês:

A finite element method-based model of a substrate heated by an electric heating cable buried in a thermal isolated container was experimentally validated with root mean square error values of root zone temperature ranging 0.25 to 0.62 ºC. The two-dimensional transient model allowed variations in the physical properties of the substrate with temperature, water content and depth. The operation of nine configurations of a heating cable buried in sand at different depths (50 to 450 mm, at 50 mm intervals) at 200 mm spacing was simulated and assessed. The validated model was used to perform 24-h simulations applying boundary conditions, and substrate moisture content was experimentally obtained at a mean substrate surface temperature of 13.98 ºC. Such simulations reproduced the operation of the heating system by setting a reference temperature of 20 ºC at the control point in the root zone. Burying the heating cable in the surface layers of the substrate caused large temperature gradients and high heat losses through the substrate surface. Accordingly, average temperature in the root zone increased with heating cable depth, up to the 200 mm depth. For greater depths, temperature in the root zone was constant. The ON/OFF control was most effective with the heating cable buried in the root zone and at control point temperatures of 20 ± 1 ºC. Burying the heating cable in the surface layers required higher energy consumption, up to 28 % at 50 mm. The most efficient heating cable depth was 350 mm, with a daily energy consumption of 6750 kJ m-2.

Resumo em Inglês:

Non-symbiotic diazotrophic bacteria are amongst the most important functional groups of soil-dwelling microorganisms. These bacteria contribute to plant growth predominantly through biological N2 fixation. Here, we evaluated the density and diversity of non-symbiotic diazotrophic bacteria in soils taken from diverse land use systems (LUS) in Amazonia using nitrogen-free media. A total of 30 soil samples were collected from the following LUS: pristine forest, young secondary forest, old secondary forest, agroforestry, agriculture and pasture. Bacterial density was evaluated by the most probable number (MPN) method utilizing N-free semi-solid media with varied compositions (JNFb, NFb, LGI and Fam). Individual isolates were characterized by colony and cellular morphology as well as total protein profiles and nitrogenase activity. Isolate genotypes were determined by partial 16S rDNA sequences. No typical diazotrophic growth in the JNFb medium was observed. Bacterial densities in the NFb medium were higher in the agriculture and agroforestry soil samples. In LGI and Fam media, bacterial densities were highest in the pasture soil samples. Overall, 22 isolates with high phenotypic diversity were obtained. Eleven isolates exhibited nitrogenase activity. Sequences of 16S rDNA genes of 14 out of 19 isolates had similarities below 100 % with known nitrogen-fixing species. Isolates were identified as belonging to the Burkholderia, Enterobacter, Serratia, Klebsiella, and Bacillus genera. A higher number of isolates from pasture soil samples were isolated, with the majority of these belonging to the Burkholderia and Bacillus genera. Among the isolates, unknown sequences were obtained, possibly indicating new species. Taken together, these data demonstrate that Fam, NFb, and LGI semi-solid media allowed the growth of diazotrophic bacteria belonging to different phylogenetic lines.

Resumo em Inglês:

Silicates can be used as soil correctives, with the advantage of being a source of silicon, a beneficial element to the grasses. However, high concentrations of silicon in the plant would affect the digestibility of the forage. To evaluate the influence of the substitution of the calcium carbonate by calcium silicate on the nutrition, biomass production and the feed quality of the palisade grass [Urochloa brizantha (C. Hochstetter ex A. Rich.) R. Webster], three greenhouse experiments were conducted in completely randomized designs with four replications. Experimental units (pots) contained a clayey dystrophic Rhodic Haplustox, a sandy clay loam dystrophic Typic Haplustox and a sandy loam dystrophic Typic Haplustox. Each soil received substitution proportions (0, 25, 50, 75 and 100 %) of the carbonate by calcium silicate. The increase in the proportion of calcium silicate elevated the concentrations and accumulations of Si, Ca, Mg, and B, reduced Zn and did not alter P in the shoot of plants. The effects of the treatments on the other nutrients were influenced by the soil type. Inclusion of calcium silicate also increased the relative nutritional value and the digestibility and ingestion of the forage, while the concentration and accumulation of crude protein and the neutral detergent and acid detergent fibers decreased. Biomass production and feed quality of the palisade grass were generally higher with the 50 % calcium silicate treatment.

Resumo em Inglês:

Studies regarding seed maturation are important to determine the ideal fruit development stage for harvesting in order to obtain high-quality seeds. Changes in sweet pepper (Capsicum annuum L.) seed quality were monitored during seed development in order to identify the stage of maximum quality of the seeds and the optimum harvest date. Fruits harvested from 20 to 75 days after anthesis (DAA) with step of five days were grouped according to maturity stage (green, yellow, red and intense red color outside). Before seed extraction, the fruit weigh, diameter and length were determined. Seed water content, seed dry weight, 1.000-seed weight, germination, first count, speed emergence index, seedling length, accelerated aging and electrical conductivity tests were performed. Mass maturity of the seeds was attained at 75 DAA, when seed water content was 47.3 % and the fruits were red. Sweet pepper seeds with high germination and vigour should be harvested when fruits are completely red outside, at 75 DAA.

Resumo em Inglês:

Upland rice (Oryza sativa L.) production is basically concentrated in four central Brazilian States, Mato Grosso, Goiás, Rondônia and Tocantins. To reduce the genotype and environment (G × E) interactions, the classification of environment groups was proposed. The goal of this study explores possibilities to adjust the upland rice regional breeding systems to optimally fit to the range of environments they are targeting, based on a historical yield data set of the Brazilian Geographic and Statistics Institute (IBGE, www.ibge.gov.br/home/) from 54 microregions. The specific objectives of this study were: (i) to identify and classify environmental groups in the Brazilian upland rice production area; (ii) to validate these environmental groups using yield data set from the upland rice multi-trial experiments (MTEs); (iii) and to identify the most representative site for each environmental group. For this the historical upland rice yield data from 54 microregions were detrented from the effects of technological advances and adjusted to the reference year, 2006. The adjusted yield data were used to build a matrix, which was submitted to a cluster analysis allowing the identification of three different environmental groups. These groups were classified as: highly favorable environment (HFE); favorable environment (FE); and less favorable environment (LFE). The HFE is less affected by inter-annual rainfall variability than the other two groups. The upland rice breeding programs must take into account the differences among the environmental groups to conduct their trials and suggest genotypes for the upland production area.

Resumo em Inglês:

Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.] and Cleopatra mandarin (C. reshni Hort. ex Tan.) are the most important rootstocks used in Spain, but they are problematic and it is necessary to search for new rootstocks with better all-round performance. The performance of 'Lane Late' navel orange [Citrus sinensis (L.) Osb] on ten rootstocks was determined in the South of the province of Alicante (Spain). They are Carrizo citrange, Cleopatra mandarin and eight new hybrids obtained at the Instituto Valenciano de Investigaciones Agrarias in Valencia (Spain): 020324 [Troyer citrange (C. sinensis × P. trifoliata) × Cleopatra mandarin], Forner-Alcaide 418 (F&A 418) [Troyer citrange × common mandarin (C. deliciosa Ten.)], Forner-Alcaide 13 (F&A 13), 030118, 030127 and 030131 (Cleopatra mandarin × P. trifoliata) and 030212 and 030230 (Cleopatra mandarin × Troyer citrange). Soil is clay loam, with pH 8.5 and electric conductivity in the saturation extract at 25ºC of 5.79 mS cm-1. Yield was weighed during the first nine harvests, fruit quality was determined in the last three. Pre-harvest fruit-drop was controlled for the 4th until 9th harvests. The trees of 'Lane Late' navel budded on Cleopatra mandarin were the tallest (2.5 m) and F&A 418 (1.6 m) the shortest of all rootstocks tested. Trees on 030131 hybrid and Carrizo citrange rootstocks had the highest mean yield (81.2 and 80.3 kg per tree per year respectively), while trees on F&A 418 produced the lowest mean yield (22.3 kg per tree per year). Trees on 030131, 020324 and 030212 had the highest yield efficiency as total cumulative yield per cubic meter of canopy volume (62.1, 58.7 and 55.9 kg m-3 respectively) whereas trees on 030127, F&A 418 and Cleopatra mandarin had lower yield efficiencies (45.0, 44.4 and 38.6 kg m-3, respectively). Pre-harvest fruit-drop was lower in trees grafted on Cleopatra mandarin (24.62 %) and on 030212 (26.61 %), and was also low on F&A 418 (27.76 %), 020324 (28.14 %) and 030230 (29.18 %) rootstocks. Trees on Carrizo citrange and 030127 experienced important fruit-drop (40.24 % and 38.27 % respectively). Trees on F&A 418 had the highest fruit weight and fruit size whereas trees on 030118 induced the lowest ones. The ripeness index was the highest on F&A 13 (18.3) and lowest on F&A 418 (15.3), 030212 (15.3).

Resumo em Inglês:

Despite the agronomic, economic and food values of soybean (Glycine max L. Merrill), there is still dearth of information on the tillage need and the implications of surface mulch for the crop in the eastern part of the forest-savanna transition zone of Nigeria. This study was therefore carried out on a sandy loam Ultisol at Nsukka with a sub-humid climate, during 2006 and 2007 cropping seasons. Our objective was to devise an appropriate tillage method for the crop from evaluated effects of no-till (NT), conventional tillage (CT) and mulch on selected key agronomic indices. Each of the NT and the CT was either unmulched (U) or mulched (M) in a split-plot, giving four treatments/tillage methods (NTU, NTM, CTU and CTM) randomized in four blocks. Rainfall was more favorable in the first than in the second season. The mean seasonal soil water storage (range, 99-109 mm) within 0.5-m soil layer differed among the treatments (NTU < CTU < NTM = CTM). However, for the first and second seasons, both water use (582-616 and 667-709 mm respectively) and grain yield (0.71-0.81 and 1.22-1.91 Mg ha-1 respectively) were not different. Mulch lowered the crop water use but had no influence on grain yield. Water use efficiency was enhanced with mulch only in the second season. Although either of the two mulch treatments (NTM/CTM) would be suitable for growing soybean especially in years of unfavorably distributed rainfall, NTM is a more rational choice than CTM. Rainfall adequacy at the critical reproductive stage of the crop showed to be a more important yield factor than the tested tillage methods.

Resumo em Inglês:

Citrus Variegated Chlorosis (CVC) caused by Xylella fastidiosa is one of the most important diseases for Brazilian citriculture. The CVC is a vascular disease with a long incubation period and symptoms similar to other disorders, and this factors difficult the CVC quantification in the field. Two methods of CVC assessment were compared in this study. The first method was based on a descriptive rating scale with four ratings, commonly used for the disease quantification. The second one was based on the incidence of symptomatic branches. The quantification of CVC through these two methods was carried out in a 10-year-old 'Natal' sweet orange orchard. The descriptive scale considered the symptoms of the entire plant. The disease incidence was evaluated in 36 branches in each plant. The assessments were conducted by three raters in 144 plants in July 2006 and July 2007 as well as in March and November 2008. The descriptive scale did not allow an accurate assessment and resulted in a moderate strength of agreement among the raters. On the other hand, the incidence quantification of CVC through the symptomatic branches showed high repeatability among the raters. We suggest the use of incidence of symptomatic branches as variable for CVC quantification.

Resumo em Inglês:

The growth and developmental characteristics of grasses and their high biodiversity make such plants suitable for remediation of areas contaminated by heavy metals. Nevertheless, heavy metal toxic effect on the plants may cause alteration in their metabolic pathways, such as photosynthesis, respiration, and growth, modifying plant anatomy. This work aimed to evaluate the effect of levels of soil contamination (0, 7.5 % and 15 % m³ m-3) on biomass production, on photosynthetic characteristics and on anatomical changes in roots and leaves of brachiaria (Brachiaria decumbens Stapf.). After seeds were planted, seedlings were uprooted and replanted in vases containing soil at different contamination levels, being left to rest for 120 days. At the end of that time, plants presented reduced yield of root and shoot dry matter, contents of chlorophyll a, chlorophyll b, total chlorophyll and potential photosynthesis with increased of soil contamination. The cell layers of endodermis and exodermis in the root tissues and the cell walls of the xylem and cortical parenchyma all thickened as contamination increased. In the leaf tissues, the adaxial and abaxial epidermis presented increased thickness while the leaf blade presented reduced thickness as contamination increased with consequent change in the root growth rate. In general, the effects of heavy metal increased with the metal concentration. Some results indicate that B. decumbens seems to have some degree of heavy metal tolerance.

Resumo em Inglês:

The growing demand of world food and energy supply increases the threat of global warming due to higher greenhouse gas emissions by agricultural activity. Therefore, it is widely admitted that agriculture must establish a new paradigm in terms of environmental sustainability that incorporate techniques for mitigation of greenhouse gas emissions. This article addresses to the scientific demand to estimate in a fast and inexpensive manner current and potential soil organic carbon (SOC) stocks in degraded pastures, using remote sensing techniques. Four pastures on sandy soils under Brazilian Cerrado vegetation in São Paulo state were chosen due to their SOC sequestration potential, which was characterized for the soil depth 0-50 cm. Subsequently, a linear regression analysis was performed between SOC and Leaf Area Index (LAI) measured in the field (LAIfield) and derived by satellite (LAIsatellite) as well as SOC and pasture reflectance in six spectra from 450 nm - 2350 nm, using the Enhanced Thematic Mapper (ETM+) sensor of satellite Landsat 7. A high correlation between SOC and LAIfield (R² = 0.9804) and LAIsatellite (R² = 0.9812) was verified. The suitability of satellite derived LAI for SOC determination leads to the assumption, that orbital remote sensing is a very promising SOC estimation technique from regional to global scale.

Resumo em Inglês:

Using scaling methods, a single solution of Richards' equation (RE) will suffice for numerous specific cases of water flow in unsaturated soils. In this study, a new method is developed to scale RE for the soil water redistribution process. Two similarity conditions are required: similarity in the shape of the soil water content profiles as well as of the water flux density curves. An advantage of this method is that it is not restricted to a specific soil hydraulic model - hence, all such models can be applied to RE. To evaluate the proposed method, various soil textures and initial conditions were considered. After the RE was solved numerically using the HYDRUS-1D model, the solutions were scaled. The scaled soil water content profiles were nearly invariant for medium- and fine-textured soils when the soil profile was not deeply wetted. The textural range of the soils in which the similarity conditions are held decreases as the initial conditions deal with a deeply wetted profile. Thus, the scaling performance was poor in such a condition. This limitation was more pronounced in the coarse-textured soils. Based on the scaling method, a procedure is suggested by which the solution of RE for a specific case can be used to approximate solutions for many other cases. Such a procedure reduces complicated numerical calculations and provides additional opportunities for solving the highly nonlinear RE as in the case of unsaturated water flow in soils.

Resumo em Inglês:

Cytogenetic analysis of the Amazon stingless bee Melipona seminigra merrillae, by conventional Giemsa staining and C-banding, revealed a different chromosome number for Melipona: 2n = 22 for females and diploid drones while the haploid drones present n = 11. There is no evidence of B chromosomes. This result contrasts with previous studies, in which the chromosome number of 19 Melipona species was determined as 2n = 18 for females and n = 9 for haploid males. Based on cytogenetic information available for other Melipona species, we propose that M. s. merrillae has a more derived diploid number. This indicates that chromosome number is not a conservative characteristic within the genus as previously thought. Cytogenetic data for stingless bees are scarce, especially in Amazon region. Additional studies will be very important in order to promote Melipona karyoevolution discussion and consequently a taxonomy review.

Resumo em Inglês:

The Berkshire pig (Sus domestica L.) breed has thin muscle fibers and excellent water-holding capacity. The Berkshire meat makes it widely accepted in the Japanese premium pork market. This study evaluates the accuracy of improving carcass quality with the use of live animal records of Berkshire pigs. Traits analyzed in live animals were: body weight at 60 days of age (W60), age at finish (AGF), daily weight gain from birth to finish (DG), back fat thickness at finish (BFTF), and loin eye area at finish (LEAF), and in carcasses were: carcass weight, loin eye area (LEA), and subcutaneous fat thickness (SCF) at some points, using the records of 4,773 purebred Berkshire pigs. Variance components for the traits were estimated according to the animal model by the Restricted Maximum Likelihood (REML) procedure using the VCE6 program (Neumaier and Groeneveld, 1998). Correlated responses were also calculated. Genetic correlations of back fat thickness (BFT) in live animals with SCF in slaughtered animals were strong, whereas that of LEA between live and slaughtered animals was low. The expected gains by actual selection including W60 and BFTF as selection criterion were superior to other selections. Therefore, selection of live animals at an early stage of growth would be conducive to the production of high quality meat.

Resumo em Inglês:

Seed priming with hormones has been an efficient method for increasing seed vigor as well as seedling growth under stressful conditions. These responses have in the past been attributed to the activation of antioxidant systems in a range of crops. The results described in this work show that hormonal priming with methyl jasmonate, salicylic acid or CEPA (chloroethylphosphonic acid), an ethylene (ET) releaser, does not induce the antioxidant activity of superoxide dismutase, catalase, ascorbate peroxidase or glutathione reductase in maize seedlings subjected to salt stress. The enhanced biomass of maize seedlings under salt stress that was observed only from ET priming indicates that the stress tolerance in maize from ethylene priming is a fundamental process for stress tolerance acquisition, which is explained, however, by other biochemical mechanisms but not by changes in the antioxidant system.

Resumo em Inglês:

Microbial solubilisation of low soluble inorganic phosphates is an important process contributing for the phosphorus available to plants in tropical soils. This study evaluates the ability of inoculant strains for tropical legumes to solubilise inorganic phosphates of low solubility that are found in tropical soils. Seven strains of Leguminosae nodulating bacteria (LNB) were compared with one another and with a non-nodulating positive control, Burkholderia cepacia (LMG 1222T). Four of the strains are used as inoculants for cowpeas (Vigna unguiculata) (Bradyrhizobium sp. UFLA 03-84; Bradyrhizobium elkani INPA 03-11B and Bradyrhizobium japonicum BR3267) or for common beans (Phaseolus vulgaris) (Rhizobium tropici CIAT 899T). Rhizobium etli UFLA 02-100 and Rhizobium leguminosarum 316C10a are also efficient nodulators of beans and Cupriavidus taiwanensis LMG 19424T nodulates on Mimosa pudica. Two experiments, with solid and liquid media, were performed to determine whether the strains were able to solubilise CaHPO4, Al(H2PO4)3 or FePO4.2H2O. On solid GELP medium none of the strains dissolved FePO4.2H2O, but LMG 1222, UFLA 03-84 and CIAT 899 solubilised CaHPO4 particularly well. These strains, along with LMG 19424 and BR 3267, were also able to increase the solubility of Al(H2PO4)3. In liquid GELP medium, LMG 1222 solubilised all phosphate sources, but no legume nodulating strain could increase the solubility of Al(H2PO4)3. The strains CIAT 899 and UFLA 02-100 were the only legume nodulating bacteria able to solubilise the other phosphate sources in liquid media, dissolving both CaHPO4 and FePO4.2H2O. There was a negative correlation between the pH of the culture medium and the concentration of soluble phosphate when the phosphorus source was CaHPO4 or FePO4.2H2O. The contribution of these strains to increasing the phosphorus nutrition of legumes and non-legume plant species should be investigated further by in vivo experiments.