Scielo RSS <![CDATA[Engenharia Agrícola]]> vol. 41 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[PHYSICAL AND MECHANICAL PROPERTIES OF THE <em>BAMBUSA VULGARIS</em> AS CONSTRUCTION MATERIAL]]> ABSTRACT The fabrication of traditional construction materials consumes a large amount of energy, emits pollutants, and utilizes nonrenewable raw materials. Therefore, it is important to reduce the environmental impact of construction through the use of eco-friendly materials, such as bamboo. This work presents the characterization of Bambusa vulgaris, which is widely available in Brazil. The aim is to employ this raw material as a construction material. The geometric and physical properties were obtained. The results showed that, when bamboo is soaked in water, dimensional variations up to 7% were observed along the radial direction. The mechanical properties depend on the moisture content. The compressive strength can exceed 60 MPa with approximately 7% moisture content, while the tensile strength can exceed 100 MPa. <![CDATA[IRRIGATION WATER MANAGEMENT TECHNIQUES FOR LOWLAND FURROW-IRRIGATED SOYBEAN IN SOUTHERN BRAZIL]]> ABSTRACT Different water management strategies should be investigated to ensure adequate water supply to furrow-irrigated soybean plants in lowlands. This study examined the performance and efficiency of furrow irrigation techniques and related them to the soybean yield potential in lowland fields of Southern Brazil in the 2017/18 growing season. An experiment was conducted on raised seedbeds to evaluate furrow irrigation techniques: full irrigation with cutback, irrigation during the advance phase with low inflow, irrigation during the advance phase (cutoff), surge irrigation, and no irrigation. The design parameters, efficiency of the techniques, agronomic characteristics, and the grain yield of the soybean crop, were evaluated. The overall performance of the cutback technique in furrow irrigation was superior, followed by the surge irrigation, cutoff, and low inflow techniques. Furrow irrigation increased soybean yield in lowlands, and the cutback technique was the best to guarantee the soybean yield potential in lowlands, resulting in a 29% yield increase compared to non-irrigated. <![CDATA[SEWAGE PERFORMANCE OF A NEW TYPE OF FLAP FILTER]]> ABSTRACT The drainage performance of a mesh filter determines the water consumption degree of the filter and the efficiency of the next work cycle. Through analysis, we found that the influent flow rate and the sediment content of the influent were important influencing factors. This experiment focused on the drainage time, pressure difference, and cleanliness to investigate the drainage performance of a new type of flap filter. The results showed that with increasing inlet flow rates, the time to discharge the effluent decreased, and the time required for the difference between the primary and secondary sewage pressures to reach a constant level was shorter. The cleanliness and drainage effects were improved. To verify this, we established mathematical models of sewage discharge time, sewage pressure difference, and sewage cleanliness based on the mass conservation law. The results showed that the relative error between the fitting calculation results and the experimental results was small, and the formula fit was over 95%. In the actual work, to achieve efficient sewage discharge under the condition of low sewage discharge and low water consumption, the discharge flow rate was set to 180 m³ h-1, and the sewage discharge time was set to 50 s. Under this condition, the sewage cleanliness reached above 97%. <![CDATA[EFFECT OF THE DISTANCE BETWEEN THE CUTTING DISC AND FURROW OPENERS EMPLOYED IN ROW CROP PLANTING ON SOIL MOBILIZATION]]> ABSTRACT The objective of this study was to determine the effect of the longitudinal distance between a cutting disc and a fertilizer furrow opener on the operational performance of the furrow opener working at different forward speeds during soil mobilization. The soil in the experimental area was classified as Typic Hapludalf with a loam soil texture. The experiment involved 24 treatment combinations in a 2 × 3 × 4 factorial scheme. These combinations were formed by the interaction of the following factors: furrow opening mechanisms, longitudinal distance from the center of the cutting mechanism to center of the furrow opener, and forward speeds. The effects of the tools on the soil mobilization variables were characterized in three phases: analysis of the natural profile and elevation and mobilization of the soil using a microprofilometer. A statistical analysis of variance was performed on the acquired data and the significance of the factors was verified using an F test. The furrow opener factor significantly substantially influenced all variables, whereas the distance significantly modified only the soil swelling and elevated soil area, with a reduction of approximately 30% in this variable when separating the mechanisms by an additional meter. Likewise, for a hoe furrow opener, the speed significantly influenced only the maximum depth of the furrow. Hence, we recommend the installation of fertilizer furrow openers close to the cutting mechanisms to increase the quality of the furrows produced in seeding operations using the direct planting system. <![CDATA[SELECTION OF EFFECTIVE SOFTWARE FOR THE ANALYSIS OF THE FRACTIONAL COMPOSITION OF THE CHAOTIC SEED LAYER USING THE EXAMPLE OF OILSEED RADISH]]> ABSTRACT This article generalises the peculiarities and efficiency of the use of three software packages, Digimizer image analysis software (v. 4.2), ImageJ2 version 2.0.0-rc-64 and WipFrag These packages were used in studying the fractional composition of oilseed radish seeds for scanning in the mode of single-layer inseparable placement. The generalisation of the main caveats and features of the effective use of each of the software packages is made on the basis of detailed analysis of the features of each of package in the use to the features of the scan and the obtained scanned image The above-mentioned aspects are illustrated in detail and reservations about the options for the effective use of each package are represented. The efficiency and expediency of using the program, ImageJ2 version 2.0.0-rc-64, with a level of identity to the standard method of determination of 75.9% and the program, WipFrag, with a similar efficiency index at 89.3% for laboratory determination of seed fractional composition were also established. <![CDATA[PHYTOREMEDIATION OF FLUORIDE-CONTAMINATED WATER BY <em>Landoltia punctata</em>]]> ABSTRACT Fluorine is released into the water environment naturally or by anthropogenic activities. Fluorine promotes health benefits at low concentrations, but it promotes adverse effects ranging from fluorosis to carcinogenic problems at high concentrations. Although fluorine removal from environment can occur through processes such as adsorption, reverse osmosis, and electrodialysis, the phytoremediation emerges as an accessible and environmentally friendly treatment. This research aimed to study the phytoremediation potential of Landoltia punctata for treating water contaminated with fluorine ion (fluoride). The central composite rotatable design was used to assess the effect of three variables in the process: pH ranging from 5 to 9; phosphate concentration from 0 to 10 mg L−1; and nitrate concentration from 0 to 800 mg L−1. The plants were exposed to a fluoride initial concentration of 5 mg L-1 in 3L-vessels that also included Clark's solution for a period of 10 days. Experimentally, removal of up to 21% was observed for the supplied fluoride. Values of the order of 30% for the removed fluoride mass can be predicted by the obtained model. Landoltia punctata is a promising candidate for the phytoremediation of fluoride-contaminated waters. <![CDATA[PEACH PIT CHEMICALLY TREATED BIOMASS AS A BIOSORBENT FOR METFORMIN HYDROCHLORIDE REMOVAL: MODELING AND SORPTION MECHANISMS]]> ABSTRACT In this work, the potential of peach pit biosorption in the removal of the drug metformin hydrochloride from water is evaluated. Experiments are carried out in a closed batch system to evaluate the effect of the solution pH (2–10), temperature (25, 35 and 45 °C), stirring (100, 150 and 200 rpm) and chemical treatments. During the study, biosorbent characterization, kinetic tests, equilibrium tests and thermodynamic parameter calculations are performed. The operating conditions that show the best results for both the raw biosorbent and the biosorbent submitted to acid, basic and acid followed by basic treatments with removal capacities of 3.17, 10.83, 18.10 and 49.14 mg g−1, respectively, are pH 7, 25 °C and 100 rpm, which result in an equilibrium time of 12 h. In the kinetic study, the pseudo-second-order model represents the best fit for the experimental data, while the Langmuir model best represents the equilibrium data. The biomasses submitted to chemical treatments show a significant increase in drug removal capacity related to the raw biosorbent, with the best maximum absorption of 82.54±1.34 mg g−1 achieved after the application of the acid followed by basic treatment. These results show that peach pit has potential to be used as a low-cost biosorbent to remove drugs from water. <![CDATA[CROP MODELING WITH LESS DATA: THE FAO MODEL FOR SOYBEAN YIELD ESTIMATION]]> ABSTRACT Crop growth simulation models such as WOFOST and DSSAT are useful, but require several inputs that sometimes are not available, especially in developing areas. In addition, measured data is usually time and labor-intensive. In search of faster and easier methods for soybean estimates, this study presents a lower input requiring methodology for yield estimation. This study combines the FAO-33 yield model with the agro-ecological zone approach for soybean yield estimations using mostly indirect data. Sowing and harvest dates and yield were collected from 74 soybean commercial farms. Agrometeorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF) were used. Fifty farms (66%) were used to calibrate the model and 24 farm areas (33%) were used for evaluation purposes. Two methodologies (FAO-56 and Thornthwaite and Mather) for water balance and actual evapotranspiration (ETa) estimations were used. The comparison of yield estimations and observations showed that the use of low data input to obtain reasonable accuracy, with a mean error of −310 kg ha−1 and a mean absolute percentage error of 23.3%. <![CDATA[FUZZY MODELING IN ORANGE PRODUCTION UNDER DIFFERENT DOSES OF SEWAGE SLUDGE AND WASTEWATER]]> ABSTRACT The present work aimed to develop mathematical fuzzy models to evaluate the effects of different doses of sewage sludge and irrigation with wastewater and potable water. Such models were elaborated from an experiment carried out at the Faculty of Agronomic Sciences, in the Department of Soil and Environmental Resources, from the Sao Paulo State University, in Brazil. The experiment was carried out in a randomized block design, in a 6 × 2 factorial scheme, with 6 doses of sewage sludge (0, 25, 50, 75, 100 and 125 of the recommended dose of N), and in the presence and absence of wastewater. In the development of the fuzzy model, the Mamdani method was used for the defuzzification. As input variables, the doses of sewage sludge and the types of water were used. For the output variables, it was sought to evaluate the biometric and developmental components of the culture. It can be inferred that the model developed presented a good fit when compared to the regression model, and that the use of sewage sludge may prove to be a potential future replacement of mineral nitrogen. <![CDATA[CONTRIBUTION OF SOIL ATTRIBUTES AND MORPHOLOGICAL VARIABLES TO YIELD OF IRRIGATED GARLIC]]> ABSTRACT This study aimed to investigate relationships between the soil attributes that most affect garlic yield, which can be useful to choose a new area for the growing of this vegetable. We also aimed to study the effects of irrigation deficit at bulb formation stage (cloves) on final garlic quality and yield. The variables evaluated were garlic yield, irrigation, nitrogen, lateral shoot growing, plant water potential, bulb volume, leaf area index, soil electrical conductivity, soil mechanical resistance to penetration, and volumetric soil moisture content. Initially, the Pearson's correlation was estimated for the phenological indexes, and a correlation network was used to graphically express the results and to correct multicollinearity between variables. A track analysis was performed considering yield as the main dependent variable. The analyses showed that, of the primary garlic yield components, bulb volume is the phenological index with the greatest potential for selection and identification of garlic production. Moreover, soil resistance to penetration impaired garlic yield. Finally, irrigation deficit at clove formation stage has a negative relation with lateral shoot growing and bulb volume. <![CDATA[DAILY RAINFALL DISAGGREGATION COEFFICIENTS FOR THE DOCE RIVER BASIN, BRAZIL: REGIONAL APPLICABILITY AND THE RETURN PERIOD INFLUENCE]]> ABSTRACT Alternative methods to the intensity-duration-frequency equations have been used for intense rainfall study in places with no pluviographic data. A pioneering study, by CETESB (1986), established rainfall disaggregation coefficients for Brazil; however, the use of these coefficients take into account neither the rainfall characteristics of the interest locality nor the return period influence in obtaining the precipitation intensities. This study aimed to determine rainfall disaggregation coefficients for Doce river basin; to verify the validity of the regional coefficients use for the entire basin; and to evaluate the return period influence on these coefficients. Data from 19 gauges located in the basin, with rainfall associated with durations of 10 to 1440 min and return periods of 2, 5, 10, 20, 50 and 100 years, were used to obtain the coefficients. Student's t-test was used to assess the regional applicability of these coefficients and the return period influence. The coefficients do not provide regional validity for the entire basin; therefore, regional coefficients were estimated for five hydrologically homogeneous regions, confirming the validity of these coefficients use and the influence of the return period. We conclude that the disaggregation coefficients must be specific for the homogeneous regions and for each return period. <![CDATA[EFFECT OF THE DOWNWASH FLOW FIELD OF A SINGLE-ROTOR UAV ON DROPLET VELOCITY IN SUGARCANE PLANT PROTECTION]]> ABSTRACT Protecting against the main sugarcane diseases and insect pests requires good control at the base of the plant; therefore, higher droplet penetration is required during plant protection. The objectives of this research were to explore the movement mechanism of droplets in a sugarcane protection operation using a single-rotor unmanned aerial vehicle (UAV) and establish the connection between the UAV downwash flow field and droplet penetration. By considering the downwash flow field of a single-rotor UAV in layers, a theoretical model of the vertical velocities of droplets was established, and verification experiments were carried out in a sugarcane field. The results showed that the velocity of the UAV downwash flow was the main factor affecting the final vertical velocity of the droplets, the final vertical velocity of a droplet was positively correlated with the droplet diameter, and the initial droplet velocity had no significant effect on the final droplet velocity. In the transportation of droplets, the droplet velocity quickly approached the velocity of the airflow, and the smaller the droplet diameter was, the higher the acceleration. These research results can provide guidance for the theoretical study of droplet deposition effects in sugarcane protection operations using single-rotor UAVs. <![CDATA[USE OF REMOTELY PILOTED AIRCRAFTS FOR THE APPLICATION OF PLANT PROTECTION PRODUCTS]]> ABSTRACT The use of remotely piloted aircrafts (RPAs) to apply plant protection products has grown a lot in agriculture worldwide. However, little research data are available regarding the efficiency and safety of this method, especially in Brazil. Thus, this review aimed to present the current scenario of scientific research involving RPAs in the application of pesticides. Several factors interfere with the quality of this type of application. Among them are height and flight speed, droplet generator elements, application rate, and spray solution properties. In general, applications have been performed between 1.0 m and 3.0 m of height and 1.0 m s-1 and 7.0 m s-1 of speed. As for the droplet generator element, there is still no clarity as to the ideal system. Efficacy studies involving RPA applications demonstrate the potential of this method in replacing applications performed mainly by using knapsack equipment in an effort to reduce occupational risks. However, it is essential to observe the advantages of RPA use, while also taking into account the risk of drift. The aerodynamic effect in the droplets, qualified personnel, appropriate formulations, regulations, and details in labels are challenges that still need to be addressed for this new technology to be successful. <![CDATA[SPATIAL AUTOCORRELATION OF PHYSICAL ATTRIBUTES OF AN OXISOL]]> ABSTRACT Studies that seek to identify a smaller number of soil attributes that represent others can generate less expenditure of time and financial resources for monitoring cultivated areas. Thus, this study aimed to analyze the spatial distribution and spatial autocorrelation of physical attributes of an Oxisol (Latossolo Vermelho Amarelo, Brazilian Soil Classification System). The evaluated attributes consisted of soil density (SD), total porosity (TP), free porosity (FP), field capacity (FC), permanent wilt point (PW), and total water availability (TW). Semivariogram adjustments and semivariance estimates were performed to characterize the structure and magnitude of the spatial dependence of soil attributes. The attributes were distributed on thematic maps and the spatial autocorrelation was estimated by the Moran index, which quantifies the degree of autocorrelation. TP showed a high positive correlation with PWP. Soil TW showed a high positive correlation with SD and a high negative correlation with FP. In turn, FP showed a high negative correlation with SD. The results showed spatial dependence for all attributes, standing out the apparent soil density and permanent wilt point, which were good evaluators of strong spatial dependence.