Scientific Journals of INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria)
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Aplicabilidad del método de elementos finitos al análisis de las tensiones producidas en soleras de hormigón debido a las cargas transmitidas por los neumáticos de los tractores agrícolas
No full textThere are several methods to dimension concrete slabs due to vehicle loads, most of them based on Westergaard theory. These methods have been developed for industrial vehicles (cars, trucks and forklifts). Considering agricultural buildings one of the most used vehicles is the agricultural tractor whose characteristics (tires of great dimensions but with a reduced contact surface) are different to those of the industrial vehicles. The goal of this research was to analyze the applicability of the finite element method (FEM) to estimate the stresses generated on the concrete slabs considering the loads transmitted by agricultural tractors. To achieve this objective, the effect of the loads transmitted by the rear axle tires of three agricultural tractors has been considered. In parallel, the same study has been carried out using the Westergaard theory. As a preliminary step, to validate the FEM, a numerical analysis has been made to obtain the stresses generated on a concrete slab considering three forklifts. The numerical analysis results have been compared with those obtained by mean of validated methods (Portland Cement Association) and the classical theory of Westergaard. For each agricultural tractor, the actual geometry of the contact surface of tires has been measured on a concrete slab and discretized by the FEM. As a result of the research process developed, it is possible to conclude that the FEM is a valid tool to analyze the tensions generated by the loads transmitted by the tires of agricultural tractors on concrete floors supported on the ground.En relación con el dimensionado de soleras de hormigón apoyadas sobre el suelo, existen metodologías rigurosas para el cálculo de las tensiones de trabajo, basadas en la teoría de Westergaard, pero desarrolladas para vehículos industriales (coches, camiones y carretillas elevadoras). En las soleras de edificios agrícolas, el vehículo más utilizado es el tractor agrícola, que dispone de neumáticos de elevada anchura y diámetro, pero con una superficie de contacto reducida. En este artículo se ha abordado el estudio de las tensiones generadas en las soleras de hormigón por las cargas transmitidas por los neumáticos de los tractores agrícolas utilizando el método de elementos finitos (FEM). Para ello, se han estudiado las cargas transmitidas por los neumáticos del eje trasero de tres tractores. En paralelo, se ha realizado el mismo estudio utilizando la metodología de cálculo clásica de Westergaard. Como paso previo se ha justificado la utilización del FEM realizando una validación de cálculo de soleras para vehículos tradicionales industriales (carretillas elevadoras) en comparación con métodos validados para ese tipo de vehículos (Portland Cement Association, PCA) y con la teoría clásica de Westergaard. Como resultado se puede concluir que el FEM es una herramienta válida para analizar las tensiones generadas por las cargas transmitidas por los neumáticos de los tractores agrícolas sobre soleras de hormigón apoyadas sobre el terreno
Estudio comparado del crecimiento, la fenología y la producción de varios cultivares de ciruelo japonés manejados desde su plantación en agricultura ecológica y convencional
No full textThe growth, phenology and fruit yield of 14 Japanese plum cultivars (Prunus salicina Lindl) were studied in two newly established experimental orchards under organic and conventional management. The experiment was conducted during 2005-2011 in the province of Seville (SW Spain), an important region of Japanese plum culture. Trunk cross-section areas (TCSA), flowering, yield and tree defoliation before winter dormancy were analysed over several years. After one year, TCSA were larger in the organically managed orchard (OMO) for most of the cultivars, in the next two years they were equal, and from the fourth year, several cultivars showed significantly larger TCSA in the conventionally managed orchard (CMO). Flowering in the conventional orchard started from 2 to 6 days before and lasted for 3 to 5 days more than in the OMO. Several cultivars produced significantly more fruit in the CMO, being the average fruit yield in the organic orchard about 72% of the conventionally managed orchard. Autumn defoliation was significantly advanced in the organic orchard, especially in cultivars highly susceptible to rust (Tranzschelia pruni spinosae), a disease not adequately controlled in the organic orchard.Se ha realizado un estudio comparado del crecimiento, la fenología y la producción de 14 cultivares de ciruelo japonés, cultivados desde su plantación en agricultura convencional o ecológica. El estudio se ha realizado durante el periodo 2005-2011 en la provincia de Sevilla, en el suroeste de España, región con una superficie importante de este frutal. Tras un primer año de crecimiento se observó que el área de la sección transversal de tronco (TCSA) fue mayor para la mayoría de los cultivares en la parcela ecológica. Tras el segundo y tercer año de crecimiento los valores de TCSA fueron similares con ambos tipos de manejo agronómico y partir del cuarto año varios cultivares tuvieron siempre valores de TCSA significativamente mayores en la parcela convencional. Varios cultivares han tenido una producción de fruta significativamente superior en la parcela convencional, suponiendo el rendimiento promedio de la parcela ecológica aproximadamente un 72% de la producción convencional. Se ha evaluado varios años la floración y la defoliación previa a la parada invernal. En general se ha observado que los árboles de la parcela convencional han manifestado una floración adelantada de 4 a 6 días con respecto a la parcela ecológica. La duración de la floración en la parcela convencional ha durado de 3 a 5 días más. Se ha observado una defoliación otoñal prematura en la parcela ecológica, más acusada en los cultivares susceptibles a la roya (Tranzschelia pruni spinosae), enfermedad que no se controla bien en manejo ecológico
Estimation of soil coverage of chopped pruning residues in olive orchards by image analysis
Get PDFResidue chopping from orchard pruning is becoming a common practice in conservation agriculture after the establishment of eco-conditionality policies in the European Union. This type of residue is used to protect the soil from erosion and improve the water balance and fertility of soils by improving the organic matter content. However, no studies have evaluated the influence of pruning residues and size on soil coverage. This study examines the effect of different treatments on pruning residue soil coverage in an olive orchard (cv. Picual). Treatments consisted of two quantities of pruning residues, specifically, high (2.04 kg m-2) and low (1.02 kg m-2), and two chopping speeds, low (2.4 km h-1) and high (3.2 km h-1). The different treatments were evaluated by image analysis and pixel counting to determine the soil cover percentage, size, number and distribution of the pruning residues after chopping. After chopping, the soil cover percentage was 39% higher in the high quantity pruning residue treatments but was not significantly influenced by the chopping speed. The size and number of lignified residues was quantified via pixel counting. In the high quantity pruning residue treatments, the number of large lignified residues (> 6 cm2) was higher, and the number of pruning residues smaller than 2 cm2 was lower, when compared with low quantity pruning residue treatments. The high chopping speed treatments produced more smaller-sized pruning residues
Hindgut fermentation in pigs induced by diets with different sources of starch
No full textA proportion of dietary starch reaches the hindgut, being fermented there. The characteristics of in vitro caecal fermentation and microbial community in pigs given different sources of starch were studied. Twenty-four Duroc × (Landrace × Large White) gilts given diets based on barley (B), broken rice (R), maize (M) or peas (P) (n=6) for five weeks were slaughtered with 93.6 ± 6.41 kg. No differences (p>0.10) were recorded in caecal pH, total short chain fatty acid (SCFA) and total bacterial concentration, nor in in vitro gas production from caecal contents, indicating the lack of a quantitative dietary effect on caecal environment. This could be partly due to the length of fasting time before slaughter (around 10 h). Molar SCFA proportions did not differ among diets; however, relative proportion of Lactobacillus sobrius/amylovorus as the species-type in starch digestion in hindgut of pigs, was highest with P diet (p = 0.010), and gas production from potato starch as substrate with P diet was highest at 2 h incubation (p = 0.012), and higher than B and R diets at 4 (p = 0.055) and 6 (p = 0.10) h incubation. Caecal bacterial biodiversity was higher for M and R diets than for P and B diets (Shannon index, p = 0.003). Sources of resistant or slowly digestible starch such as peas promote a microbial community with a different profile and higher capacity to ferment the starch arriving to the organ than other sources which are mostly digested in the small gut
Effect of weeding management on the performance of local maize populations
Get PDFOne of the most important stress factors in maize (Zea mays L.) fields is weed competition, which reduces the crop yield. Weeds chiefly interfere with maize and establish considerable competition for light, water and nutrients. To avoid these harmful effects, there are different agronomic measures and factors among which, the most relevant are the interactions between crop and weed, weed management practices and type of germplasm. This study attempts to evaluate maize germplasm for tolerance to weed competition in order to achieve competitive ability and suitability for farming. Ten genotypes of maize, classified into two groups, i.e. improved populations and traditional cultivars, were grown under four types of weed management practices (mechanical harrowing control, chemical control, combination of harrowing and chemical control and untreated control as check) for three years (from 2009 to 2011) in Zaragoza (Spain). We found that the effect of weed management practices was not significantly different, whereas the genotype effect was highly significant, with genotype EZS34 (mean yield of 7.7 Mg ha-1) showing the highest yield. Other traits, such as earliness, displayed a good behaviour under weed competition. On the other hand, harrowing management proved to be the most effective method of weed control although it did not show a significant response. The best results are associated with some maize genotypes that have a specific adaptation to local conditions, according to their genetic background
Experimental results and modelling of humidity control strategies for greenhouses in continental and coastal settings in the Mediterranean region. II: Modelling of strategies
Get PDFStrategies for humidity control —with and without heating— were evaluated via simulations performed with apreviously developed model (see accompanying paper, this issue, part I). With heating, the best strategy combined theuse of a humidity setpoint with step control of the roof window, increasing the ventilation in line with the outsidetemperature. Without heating, the best strategy again combined the use of a humidity setpoint with step control of theroof window, but required ventilation to be increased in line with the inside air temperatur
Arbuscular mycorrhizal fungi (AMF) as bioprotector agents against wilt induced by Verticillium spp. in pepper: a review
Get PDFVerticillium dahliae Kleb. is a vascular pathogen that alters water status and growth of pepper plants and causes drastic reductions in yield. Its control is difficult because it can survive in field soil for several years. The application of arbuscular mycorrhizal fungi (AMF) as bioprotector agents against V. dahliae is an alternative to the use of chemicals which, in addition, is more respectful with the environment. The establishment of the mutualistic association of plant roots and AMF involves a continuous cellular and molecular dialogue between both symbionts that includes the preactivation of plant defense responses that may enhance the resistance or tolerance of mycorrhizal plants to soil-borne pathogens. Some AMF can improve the resistance of Capsicum annuum L. against V. dahliae. This is especially relevant for pepper cultivars (i.e. cv. Piquillo) that exhibit high susceptibility to this pathogen. Compared with non-mycorrhizal plants, mycorrhizal pepper can exhibit more balanced antioxidant metabolism in leaves along the first month after pathogen inoculation, which may contribute to delay both the development of disease symptoms and the decrease of photosynthesis in Verticillium-inoculated plants with the subsequent benefit for yield. In stems, mycorrhizal pepper show earlier and higher deposition of lignin in xylem vessels than nonmycorrhizal plants, even in absence of the pathogen. Moreover, AMF can induce new isoforms of acidic chitinases and superoxide dismutase in roots. Mycorrhizal-specific induction of these enzymatic activities together with enhanced peroxidase and phenylalanine ammonia-lyase in roots may also be involved in the bioprotection of Verticillium-induced wilt in pepper by AM
Short Communication. Application of Meta-Analysis if Forestry Related Topics.
Get PDFAim of study: Provision of the necessary knowledge to foresters in order carry out objective literature research, through meta-analysis.Area of study:MediterraneanMaterial and Methods: We describe in detail the methodology of meta-analysis. Then, we apply a meta-analysis in a set of independent studies of density of Aleppo pine (Pinus halepensis Mill.), a common forest species of theMediterranean.Research highlights: Making high quality meta-analyses, can help foresters in making the most of individual forest studies by synthesize them. In this work:We provide details on approaches for undertaking a meta-analysis.We use a silvicultural example to demonstrate our idea.We show how the method of meta-analysis could be applied to forestry also (besides the classical medical study reviews).We have as ultimate goal the use of this article as a reference from other researchers as regards the application of meta-analysis to their area of expertise.Keywords: Literature research; Systematic review
A quantitative and molecular examination of Tuber melanosporum mycorrhizae in Quercus ilex seedlings from different suppliers in Spain
Get PDFAim of study: The aim of the work was to determine the degree of mycorrhization of Quercus ilex L. subsp. ballota (Desf.) Samp. by the black truffle fungus T. melanosporum Vittad. by quantitative and molecular analyses.Area of study: seedlings inoculated by different Spanish suppliers.Material and methods: The internal transcribed spacers (ITS) of mycorrhizae from different plants were amplified by nested PCR involving fluorescently-labelled primers, and the amplicons either directly sized by ARISA or analysed by TRFLP following their digestion with restriction endonucleases. TRFLP analysis distinguished between mycorrhizae of T. melanosporum, T. indicum Cooke & Massee and T. borchii Vittad., as suggested possible by virtual (in silico) TRFLP analysis and real TRFLP analysis of the ascomata of these species.Main results: Significant differences between suppliers were detected in terms of the mean number of mycorrhizae established per plant and percentage mycorrhization. These results allowed the following quality standards for 2 year-old plants to be proposed: a) good quality: >3000 mycorrhizae/plant, >40% mycorrhization, b) medium (acceptable): >3000 mycorrhizae/plant, >30% mycorrhization, c) low quality: <3000 mycorrhizae/plant or <30% mycorrhization, always supposing the mycorrhizae counted represent the species of interest as confirmed by the presence of its DNA and the absence of DNA belonging to contaminating species. Finally, a new microsatellite allelic map obtained from the analysis of several T. melanosporum populations across Spain was used to provide a tool capable of determining the geographic origin of the fungi used to inoculate plants.Research highlights: The proposed quality standards can be useful for the evaluation and certification of commercialized Q. ilex plants mycorrhized with T. melanosporum.Keywords: mycorrhiza; certification; truffle; TRFLP; fungi
Field performance of a pneumatic row crop planter equipped with active toothed coulter for direct planting of corn in wheat residue
Get PDFIn this research effects of active toothed coulter on planter penetration in semi-dried soils covered with previous wheat (triticum aestivum) residue was studied. Therefore, effects of three levels of speed ratio (coulter peripheral speed/tractor forward speed; 1.22, 2, 3) at two previous residue levels (baled and non-baled) and two modes of planter attachment (with and without row cleaner) on the corn (zea mays) planting depth and its uniformity, amount of surface residue, emergence rate index and seed spacings indices were investigated. Results showed that planting depth and its uniformity increased significantly with increasing speed ratio, so that desired planting depth was obtained at speed ratio of 2. The emergence rate index decreased with increase in speed ratio mainly due to increase in seeding depth at higher speed ratios. Miss and precision indices decreased in a significant manner with increase in the speed ratio. Other results showed that planting with row cleaner attachment into baled-out residue plots at speed ratio of 2 resulted in 31% decrease in miss and 30% decrease in precision indices as compared to control (inactive coulter). Quality of feed index at same conditions was 72%, the increase was up to 11% as compared to control. No significant difference was found between speed ratios of 2 and 3 for all the parameters studied. The results suggests that the row crop planter equipped with active toothed coulter and row cleaner attachment can be satisfactorily used for direct corn planting in hard soils covered with previous crop residues