Scielo RSS <![CDATA[Engenharia Agrícola]]> vol. 38 num. 5 lang. en <![CDATA[SciELO Logo]]> <![CDATA[WOOD UTILIZATION OF <em>Eucalyptus grandis</em> IN STRUCTURAL ELEMENTS: DENSITIES AND MECHANICAL PROPERTIES]]> ABSTRACT Over the years, the species of eucalyptus has become a multipurpose raw material. In addition, the most relevant aspect of the use for various purposes is related to the production of a high quality wood, coming from short duration plantations, which is fundamental to the current demand of the industries. However, its use in civil construction has not yet reached a level of importance, due to the low knowledge of many of its resistance properties and the consequent popular fear in the use of reforestation woods, in particular the Eucalyptus grandis. This research investigated its main mechanical properties, aiming to reinforce its constructive applications in wood structures. For this, two physical properties and fourteen mechanical properties, in two different moisture conditions of the samples were evaluated, according to the norm NBR 7190 (1997). In the first moisture content, the samples were stabilized at 30%, while the second level considered the content of 12%. It was obtained 3580 determinations for the sixteen properties. From the 14 mechanical properties, only 7 had significant increases with the moisture reduction (30% to 12%), consisting of the rupture modulus in the parallel and normal compressions, normal traction and static bending; modulus of elasticity in normal compression and static bending and in shear strength. <![CDATA[PHYSIOLOGICAL RESPONSES OF COFFEE TREE UNDER DIFFERENT IRRIGATION LEVELS]]> ABSTRACT The plant water potential and the leaf temperature are physiological responses of the coffee tree that can be used as indicative of the irrigation management of this crop. There is a dependence between the leaf water potential with the potential matrix of the soil solution, however, the water potential levels found for the coffee tree show divergent relationships in the literature regarding the matrix potential. The objective of this study is to verify the water potential and leaf surface temperature in the coffee tree when submitted to different irrigation levels. The study was conducted in Piracicaba, SP, Brazil, using Coffea arabica species from Red Catuaí IAC 144 variety, the drip irrigation system was adopted and the management done by tensiometry. The relationships among these physiological responses and the treatments of actions presented high determination coefficients (R2 of 0.84, 0.90 and 0.65 for the leaf water potential, leaf temperature measured with the portable infrared sensor and the thermal camera respectively). The estimated values for leaf water potential were −0.23, −0.56, −0.89 and −1.22 MPa for irrigation treatments L130%, L100%, L70% and L40%, respectively. The calculated leaf temperature values were 31.7, 32.4, 33.0 and 33.7°C in average, for treatments L130%, L100%, L70% and L40% in proper order. <![CDATA[WATER AVAILABILITY AND POTASSIUM DOSES IN CHERRY TOMATO QUALITY]]> ABSTRACT The quality of cherry tomato fruits is directly related to the management strategies used in the production system, such as irrigation and fertilization. This study aimed to assess the quality of cherry tomato fruits cultivated under water availability and potassium fertilization. The experiment was carried out in a greenhouse in pots of 12 dm3 of an Oxisol. The experimental design was a randomized block design in a 52 fractional factorial arrangement with five water availabilities in the soil (4, 14, 24, 34, and 44 -kPa), five potassium doses (0, 125, 250, 375, and 500 mg dm−3) and with four blocks. Irrigation was performed with a semi-automated drip irrigation system with soil moisture monitoring by the Diviner 2000® capacitance probe. The assessed variables in fruits were longitudinal and transversal diameter and pulp thickness, fruit shape index, total soluble solids (SS), titratable acidity (TA), the SS/TA ratio, and vitamin C. The data were submitted to statistical analyses at 5% probability error, with analysis of variance by the F-test and polynomial regression. Fruit size presents a reduction as water availability decreased. The total soluble solids have a higher concentration at a potassium dose of 326 mg dm−3. The quality of cherry tomato fruits cultivated in an Oxisol is influenced by water availability and potassium doses. <![CDATA[TRACTOR PERFORMANCE IN SOWING WITH FURROWER CONFIGURATIONS IN AREAS WITH CONTROLLED TRAFFIC OF MACHINES]]> ABSTRACT The controlled traffic of machines is a technique that performs the standardization of machine wheel gauges and width of implements, allowing them to move in predetermined places. The objective of this study was to evaluate the performance of an agricultural tractor, pulling seeder with configurations of furrows, in an area with controlled traffic of machines in various intensities. The study was developed in an agricultural area located in the municipality of Carazinho, RS. The experimental design was 3 × 3 randomized blocks, with traffic conditions (tractor traffic, tractor and harvester traffic, other tractor traffic, harvester and sprayer) and three configurations of furrows (double disk, double disk in the rows without traffic and rod in the traffic and double disk in the rows without traffic and without furrower in the lanes of traffic). The variables analyzed were traction force, power in the drawbar, maximum power, speed, skidding, operational capacity and efficiency of the engine. It was concluded that the absence of furrows in controlled traffic lanes provides reduction of traction force. The power demand of the seeder decreases when the rod-type furrow is replaced by double disc and this reduction is even greater when removed from the traffic lanes in situations of higher traffic intensity. <![CDATA[INSECTICIDE SPRAYING IN SOYBEAN PLANTS: DIFFERENT NOZZLES MODELS AND AGROMETEOROLOGICAL CONDITIONS]]> ABSTRACT The aim of the experiment was to evaluate the quality of the spraying by the spray volume deposit provided by different nozzles models in two agrometeorological conditions of application. Four parameters related to spray quality were evaluated: spray volume deposit, droplet size, surface tension and contact angle. The treatments consisted of three nozzle models (AXI Twin 12002, TTJ 110015 and JAI 120015) and two application times (between 02:00 p.m. and 04:00 p.m. and between 08:00 a.m. and 09:30 a.m.). The spray volume deposit in the upper portion of the soybean plants was similar, but the JAI 120015 nozzle model produces more uniform droplet spectra and is safer than the AXI Twin 12002 and TTJ 110015 due to the highest drift risk. It is necessary to study alternatives that increase spray deposits in the lower portion of the crop, since in this study the distribution uniformity of the mixture in the portions of the soybean plant was low and the agrometeorological conditions interferes in the deposits of the sprayed mixture but is dependent on the selected nozzle model. <![CDATA[COIL SPRING FOR TORQUE REDUCTION IN TRACTOR FOLDABLE ROPS]]> ABSTRACT Studies conducted by the international labor organization have shown that operations involving agricultural machinery are among the three activities with the highest risk of accidents to workers. Among the possible causes, rollover is the most common, accounting for 33% of fatal accidents. Despite this, there are standards that provide for the use of safety devices to ensure the physical integrity of the operator, among these equipment stand out rollover protection structures, which can be foldable or not. In this sense, the objective of this study was to perform an ergonomic study in order to analyze the torque required for lowering and lifting a foldable rollover protection structure attached to an agricultural tractor, developing instrumentation for validation of the efforts required to operate the structure and comparing the results obtained with the values recommended by the Standard (CODE 6 - OECD). When torque values were above those recommended by the standard, a set of torsion springs was used as solution to torque reduction. After further testing, the effectiveness of the solution was verified. Furthermore, it was observed that the angular speed of the bar does not have a significant influence on the torque required to lift the bar. <![CDATA[SPATIALIZATION OF SOIL RESISTANCE TO PENETRATION FOR LOCALIZED MANAGEMENT BY PRECISION AGRICULTURE TOOLS]]> ABSTRACT Soil resistance to penetration is an indicator of easy measurement which can be used to make scarification / subsoiling recommendations in areas that work with localized management. The objective of this study was to evaluate the spatial variability of soil resistance to penetration (RP) in the area of direct sowing system, and to carry out the recommendation of scarification / subsoiling in a localized way through precision agriculture. The research was conducted in commercial area, in a field of 49.12 ha. The RP collection was with an electronic penetrometer in a sample mesh of 47 points distributed regularly in the area, with georeferenced points. The data were analyzed every 0.10 m being collected up to 0.40 m depth, in addition to obtaining the mean and maximum RP values in the profile (0 – 0.40 m), and the depth value of the maximum RP in the profile. Soil samples were collected randomly in the area to characterize the water content at the time of RP collection. Data were analyzed using descriptive statistics and geostatistics. The resistance to penetration (RP) presents moderate to strong spatial dependence in the evaluated layers. The RP is in most of the area below the critical limits which demonstrates that there is no need to perform a scarification / subsoiling in the total area, only in a localized way. <![CDATA[SPATIAL VARIABILITY OF SOIL RESISTANCE TO PENETRATION IN NO TILLAGE SYSTEM]]> ABSTRACT In areas of no tillage system where there is intense traffic of machines and minimal soil mobilization, the periodic monitoring allied on localized soil compaction represent important strategies aiming agricultural sustainability. Thus, the objective of this study was to evaluate the spatial variability of soil resistance to penetration (RP) in no tillage system. Data collection took place in an experimental area of 7.65 ha using a sample grid composed of 40 points. At each point the RP was determined by three replications from which was obtained the mean RP, the maximum RP, and the depth of the maximum RP in the 0-0.40m layer. Deformed samples were randomly collected in the area to determine the water content in the soil (θ). Then the RP data were analyzed using descriptive and geostatistical statistics techniques for spatial variability maps. The RP presents spatial variability detected by means of spherical semivariogram in all soil layers. There was spatial variability in the area with the appearance of intermediate values for RP (2.00-3.00 MPa) due to no ploughing and continuous traffic of agricultural machines. There were greater reaches and critical levels of compaction on the layers 0.10-0.20 and 0.20-0.30 m where there is predominance of the maximum RP. <![CDATA[TEMPORAL DYNAMICS OF CLIMATOLOGICAL PARAMETERS AND HYDRIC BALANCE IN THE MANAGEMENT OF AGRICULTURAL CROPS]]> ABSTRACT One of the main factors that determine the success of decision-making in the fields is the climatic factor. This way, the geostatistical techniques have been used to represent and understand the spatial or temporal dynamics of meteorological parameters. Therefore, the aim of this research was to represent temporally through thematic maps, the average daily behavior for meteorological variables and the hydric balance for the municipality of Patos de Minas - MG. The climatic data were acquired from the automatic station INMET from the years 1990 to 2015. Later, it was calculated the evapotranspiration and the hydric balance for different capacities of available water in the soil (CAW): 24 mm, 48 mm, 80 mm and 112 mm. The climate variables showed temporal dependence, and through the thematic maps, derived from the ordinary Kriging, it was possible to identify the seasons of the year that are favorable for the production for the different crop groups. <![CDATA[SAMPLING DENSITY FOR CHARACTERIZING THE PHYSICAL QUALITY OF A SOIL UNDER COFFEE CULTIVATION IN SOUTHWESTERN MINAS GERAIS]]> ABSTRACT The elaboration of maps to characterize the spatial variability of soil attributes assists in the strategic planning and decision making of agricultural managers. Precision and accuracy of maps are related to the ideal sampling density to characterize the variability pattern. This study was conducted with the aim of identifying the sampling density to represent the variability of soil physical quality using attributes with different magnitudes of variation in an area cultivated with coffee. Three approaches were used to find the most adequate sampling density (geostatistical analysis, percentage of error associated with the sampling density, and coefficient of variation). A total of 145 soil samples were collected at a depth of 0-0.20 m at the crossing points of a regular grid with a spacing of 50 m. The percentage of clay, silt, and sand, macroporosity, microporosity, total pore volume, and soil density were determined. The data were submitted to descriptive statistical analysis. For elaborating the variability maps with up to 15% error and soil attributes with a coefficient of variation close to 50%, a sampling density of 3 points ha−1 is suggested. <![CDATA[TOPOGRAPHYC SHADOW INFLUENCE ON OPTICAL IMAGE ACQUIRED BY SATELLITE IN THE SOUTHERN HEMISPHERE]]> ABSTRACT During image acquisition, is usually chosen scenes with a lesser cloud cover to avoid loss of spectral information. However, when training samples are collected for image classification, the user finds shadowed areas. Such situation is similar to the presence of clouds since spectral information of these classes is the same in all optical bands of the sensor. This fact becomes more pronounced in mountainous relief areas due to shadow projection on the terrain, which can vary among all seasons during the solar year. With the goal to obtain images with a lower presence of shadow, it was simulated, under the same relief conditions, shading variation in function of latitude (0° to 40° S). Solar radiation models were processed for the days and times passages of the Landsat TM and ETM+ satellite on the Southern Hemisphere. It was verified that over 30° S and 40° S latitudes, a loss of shading area varying between 27% to 91 % and that images should be preferentially taken between October and February. For latitudes comprising 0° and 10° S, the loss was considered negligible, when we set a 10% threshold of loss in the total valid area in an image. According to the amount of radiation in a terrain, South and West areas received less direct solar radiation over the year for all analyzed latitudes in the modeling. <![CDATA[MICROBIOLOGICAL ACTIVITY DURING THE COMPOSTING OF WASTES FROM BROILER PRODUCTIVE CHAIN]]> ABSTRACT The quality of the carbon used as bulking agent in the composting process directly affects the dynamics of the waste degradation, which is governed by an active and diversified microbiota. The monitoring of the basal respiration and enzymatic activities during the composting of broiler agro-industrial wastes with different carbon sources as bulking agents was the aim of this study. The microbiological activities were more intense in the thermophilic phase of the process. The dynamics of the enzymatic activities were affected by the different carbon sources used as bulking agent in the composition of the windrows. When the milled sugarcane bagasse was used as carbon source, the windrow presented the highest amount of P in its constitution and presented, in the evaluation averages, a greater intensity of the alkaline phosphatase enzyme (842 μg g−1 h−1 p-nitrophenol compost); the highest intensities of β-glucosidase and cellulase enzymes were observed when fresh and ground napier grass was used as the main source of carbon (6.1 μmol g−1 h−1 p-nitrophenol compost and 35.2 μmol g−1 16h−1 glucose compost, respectively); the highest intensity of the urease enzyme was also observed in the windrow where napier grass was used as the main carbon source and bulking agent (205,890 μmol g−1 2 h−1 N-NH4+ compost). It can be concluded that napier grass when used as the main source of carbon and bulking agent in the composting of the wastes from broiler chicken production chain promotes greater intensity of most of the enzymatic activities of interest. The enzymatic activity of urease presented the highest values due to the high nitrogen content of the composted wastes. <![CDATA[ESTIMATION ON THE CONCENTRATION OF SUSPENDED SOLIDS FROM TURBIDITY IN THE WATER OF TWO SUB-BASINS IN THE DOCE RIVER BASIN]]> ABSTRACT Knowing the relationship between the total suspended solids concentration (TSS), turbidity in the waters, and that turbidity analysis can be done faster and in less expensive way, this study aimed to obtain mathematical model to estimate the total suspended solids (TSS) concentration from the turbidity values for waters of Doce river basin. For this purpose, it was used the water quality database of the Minas Gerais Institute of Water Management (IGAM). The data were pre-treated using the adjusted boxplot technique followed by adjustment of curves for the different management units and rainfall regime period. It was verified the possibility of a single curve through the dummy variable technique, subsequently. With the results it was observed that the adjusted boxplot technique proved to be useful for environmental data. Linear relationships with R2 values, as a rule, were higher than 0.6, however, it was not possible to develop a single model. It is concluded that the generated models presented good adjustments being able to be used for predicting the concentration of TSS as a function of turbidity. However, each management unit in each period of rainfall regime presents particularities that were reflected in the prediction models. <![CDATA[MERCURY IN THE SEDIMENT OF THE UPPER PARNAÍBA RIVER]]> ABSTRACT The contamination of aquatic environments with chemical trace elements can be evaluated by their accumulation in sediments of the water body. Studies on mercury require the use of exclusive extraction techniques that have relatively high costs when compared to the analysis of other trace elements. This study was conducted aiming at determining the mercury concentration in sediments of the Upper Parnaíba River basin, located in a region of agricultural expansion between the states of Piauí and Maranhão. The sediment was collected at 12 sites in the basin. After drying, the quantification of total mercury was performed by the Zeeman atomic absorption spectrometry coupled to a pyrolysis reactor. Mercury concentrations in sediments of the Parnaíba River ranged from 4.2 to 58.5 ng g−1 and presented a low probability of adverse effects on biota. Mercury had no correlation with the variables clay, silt, sand, total organic carbon, iron, and aluminum, demonstrating its possible anthropogenic origin. Although mercury concentrations have a low probability to disturb the balance of the local ecosystem, there is a need for monitoring the region in order to quantify the risks to biota and human health. <![CDATA[BIOHYDROGEN PRODUCTION IN AnSBBR IN FED-BATCH FROM STARCH EFFLUENT: INFLUENCE OF ORGANIC LOAD]]> ABSTRACT The hydrogen is a fuel with a high energy density. Studies have sought to verify the potential of different residues and configurations of reactors in the production of biohydrogen. This study evaluated the influence of the organic loading rate on the production of biohydrogen from cassava starch wastewater (CSW) in anaerobic sequencing batch biofilm reactors (AnSBBR) operated in a fed-batch. In the tests, the organic loading rates of 9.0; 13.5 and 18.0 gCT L−1 d−1 were used, at cycle times (CT) of 4; 4 and 2 h (tests I, II and III, respectively). The reactor was inoculated with sludge from a pilot anaerobic reactor used in the treatment of CSW, heat treated (heated at 90°C for 15 min). With the increase of the organic load (condition I to II) with the same cycle time (CT: 4 h), there were increases in the hydrogen molar productivity (PrM) and hydrogen yield in relation to applied total carbohydrate (RMCA) and removed (RMCR). However, with the increase in the organic loading rate in which the CT was reduced from 4 to 2 h (condition II to III), there was a decrease in PrM and RMCA and RMCR. The best performance of the reactor was verified in condition II (organic loading rate: 13.5 gTC L− 1 d−1; CT: 4 h), in which the PrM was 35.8 molH2 m−3 d−1 and RMCA and RMCR were 2.24 and 3.67 molH2 kgTC−1, respectively. <![CDATA[DEVELOPMENT OF A TRANSFER FUNCTION FOR WEIGHT PREDICTION OF LIVE BROILER CHICKEN USING MACHINE VISION]]> ABSTRACT The objective of this study was to process digital images to investigate the possibility of broilers body weight estimation based on the dynamic model. For this experiment, 2440 images were recorded by a top-view camera from 30 birds. An ellipse fitting algorithm was applied to localize chickens within the pen, by using a generalized Hough transform. Chickens’ head and tail were removed efficiently using the Chan-Vese method. After that, using image processing, six body measures were calculated. Next, they were used to design a Transform Function (TF) model with weight measurements as output. Second-order dynamic models were used to predict the weight of life broiler chicken, without delay, stable and with the highest R2 were predominantly selected according to the Young Identification Criterion (YIC) criterion chosen models. It was observed that predicted values rigorously follow the real values. Moreover, the relative body weight errors of chickens in the early days of grow-out was much more than last days. The accuracy of TF for body weight prediction from a comparison between measured (absolute) and predicted total life body weights were estimated for all studied broiler chicken (R2=0.98). <![CDATA[IDENTIFICATION OF NAVEL ORANGE LESIONS BY NONLINEAR DEEP LEARNING ALGORITHM]]> ABSTRACT It is difficult for humans to recognize recessive diseases in navel oranges. Therefore, deep neural networks are applied to plant disease identification. To improve the feature extraction ability of convolutional neural networks, the Parameter Exponential Nonlinear Activation Unit (PENLU) is proposed to replace the activated function of the neural network. This function not only adds multiple parameters but also brings better generalization ability to the neural network. In addition, the proposed function parameters can be updated by the inverse Stochastic Gradient Descent (SGD) algorithm, which has unparalleled advantages over the existing activated functions. The Residual Network (ResNet), improved by PENLU, is applied to navel orange lesion recognition and achieves the most advanced accuracy compared with traditional lesion recognition methods. It is worth mentioning that the data set of navel orange leaf images proposed in this paper will provide samples for subsequent research. The code and model are available at the website <![CDATA[PARTICLEBOARDS PRODUCED WITH EPOXY INK WASTE AND BTH POLYMER AS ADHESIVES]]> ABSTRACT The aim of this research was to analysis the feasibility of production of wood particleboard with two alternative adhesives: epoxy ink waste and polyhydroxybutyrate polymer (BTH). Particleboard were produced with Pinus sp. wood specie wastes from sawmill process. For each alternative adhesive was proposed different combinations of parameters: time and temperature of press, pressure; alternative adhesive content and mass of wood particles. Two alternative adhesive contents were adopted, 10% and 20% replacing ureaformaldehyde adhesive. Mechanical properties (perpendicular tensile strength, pullout strengths of screw on face and top; modulus of elasticity and rupture) were determined according to ABNT NBR 14810:3 Brazilian Standard Code. The obtained results were compared to ABNT NBR 14810:3 and ANSI A.2018:1 Standard Codes requirements values. Particleboards produced with epoxy ink waste showed perpendicular tensile strength according to the minimum Standards requirements values. All proposed combinations to manufacture BTH polymer particleboards didn't show satisfactory mechanical properties in comparison to the Standard Codes values. Other combinations of wood species, time, pressure and temperature, epoxy ink waste and BTH polymer contents should be studied so that the requirements can be met. <![CDATA[SIMULATION OF DISTANCE BETWEEN FIELD AND REPLENISHMENT PUMP IN MECHANIZED SPRAYING OF SUGARCANE (<em>Saccharum</em> spp.)]]> ABSTRACT Brazil is the world's largest producer of sugarcane destined for mills. Spraying in sugarcane plantations is carried out in extensive cultivation areas and with self-propelled, tractor-driven, and aerial hydraulic equipment. For this, a good positioning of the replenishment pump of agricultural defensives close to the field where the spraying is carried out is necessary. However, it is desirable that the replenishment be carried out at short distances between the field and replenishment pump. This study aimed to assess the impact of the distance between the field and replenishment pump on the operational cost of hydraulic sprayers for sugarcane farming practices. Due to the difficulty in accomplishing the work and meeting the objective under field conditions, we decided to develop a computational model called “TratoCana” in a spreadsheet and programming language. The model was verified for possible routine errors, validated, and used in the analysis of factors and in the generation of scenarios. The results showed that the increased average distance between the field and replenishment pump has a negative impact on the operational and economic performance of the machine.