Resumo em Inglês:

ABSTRACT Sugarcane is considered one of the main alternatives for biofuel production and an important product of Brazilian agriculture, so it is indispensable to adopt new techniques for its cultivation and management. Thus, the present study aimed to evaluate the effect of the quality of supplemental lighting, based on light-emitting diode (LED), on the acclimation of pre-sprouted sugarcane seedlings in a protected environment. The experimental design was completely randomized, consisting of three supplemental LED lighting systems, with light proportions of 90% red + 10% blue (R:B 90/10), 80% red + 20% blue (R:B 80/20) and 70% red + 30% blue (R:B 70/30), and a control, with natural solar radiation, with 5 replicates. Multivariate principal component analysis was used based on the matrix of correlation between all variables (meteorological, physiological and biometric). It was found that the different LED lighting systems increased the photosynthetically active radiation; however, until 20 days after planting, the seedlings were little influenced by the supplemental lighting systems. At the end of the acclimation period, the R:B 80/20 lighting system was the most associated with the growth and size of sugarcane seedlings.

Resumo em Inglês:

ABSTRACT A comparative test of water heating between the hybrid system - solar collector with heat pump - and a system with conventional supplementary heating - with high electric power - was performed. For this, a small capacity heat pump was installed, which was later installed together with a solar heating system, composed of a 250 L thermal reservoir and three thermoplastic collector plates. Tests were carried out to evaluate the COP of the heat pump and the energy consumption of the solar heating system operating with the heat pump and with an electrical resistance of 3000 W. In the laboratory tests, the heat pump presented an average COP of 2.15. In the field tests, the energy consumption of the solar system with heat pump was 54.9% lower when compared to the tests in which electrical resistance was used as a source of supplementary heating.

Resumo em Inglês:

ABSTRACT The aim of this study was to evaluate the energetic potential achieved by the application of phyto-regulators to sweet sorghum cultivars. A randomized complete block design was used. Experiments were conducted using two sweet sorghum cultivars (BRS 508 and BRS 509), fourphyto-regulators (ethephon, ethyl-trinexapac, glyphosate, and sulfometuron-methyl), and a control; four replicates were performed 70 days after sowing, at the beginning of the flowering phase of the plants, with the aid of a CO2-pressurized coastal sprayer. The plants were harvested after 40 days, with the stems being cleared at the height of the apical bud, and were subjected to grinding for the extraction of broth. The following analyses were carried out: chemical (total extractives, lignin, and holocellulose contents), proximate (volatile matter, fixed carbon, and ash contents), and energetic (higher heating value). Multiple comparison (Tukey) and linear correlation (Pearson) analyses were carried out at a 5% significance level. The phyto-regulators positively and significantly influenced the chemical attributes and contents of lignin and fixed carbon. It was concluded that glyphosate, sulfometuron-methyl, and ethephon enhanced the biomass/bioenergy potential of sweet sorghum cultivars.

Resumo em Inglês:

ABSTRACT Potato (Solanum tuberosum L.) cultivation has a high demand for management and treatments during the vegetative cycle in the field. Among these requirements, water management is a limiting factor of tuber productivity and quality. This study aimed to determine the most appropriate soil water depletion depth for irrigation management in potato crops of Ágata cultivar, under the edaphoclimatic conditions of Guarapuava-PR, considering its influence on crop vegetative development. The study was conducted using four water depletion depths in the soil (12, 24, 36, and 48 mm). The different irrigation treatments promoted differences in shoot dry mass, leaf area index (LAI), number of tubers per plant, and productivity. The highest yield was observed for 27.62 mm depletion. When irrigation depth was increased to 48 mm, tubers showed individual mass reduction and hence productivity, affecting commercial classification. A cumulative depletion of about 27 mm between irrigations proved to be the most adequate management to supply the water demand of Ágata potato cultivar.

Resumo em Inglês:

ABSTRACT The least limiting water range (LLWR) is a soil physical quality indicator that receives much attention. It has been criticized and put to the test regarding mathematical models that compose it since they describe the behavior of soil physical attributes in a simplified way. This study aimed to assess the efficiency of some pedofunctions proposed in the literature and artificial neural networks on the accuracy in predicting soil water retention at potentials equivalent to field capacity (θFC) and permanent wilting point (θPWP). In other words, to apply the best models to LLWR of two soil types (Oxisol and Ultisol) and verify changes in their structure. The results indicated that pedofunctions using sand, silt, clay, bulk density, and soil organic matter contents are more efficient in estimating θFC and θPWP. However, the use of multiple linear regression models to predict θFC values below 0.20 m3 m−3 may present a slight tendency to overestimate it, which is not observed in the neural networks. As in R2, equations from neural networks were more efficient in estimating θFC and θPWP. Pedofunctions used to calculate LLWR differ in the establishment of the critical soil bulk density, exposing the limitations of the model.

Resumo em Inglês:

ABSTRACT The inadequate agricultural management in the semiarid region of northeastern Brazil, associated with the fragility of most soils, has caused degradation of the quality of this resource. This study aimed to evaluate the quality of Quartzipsamments under different uses through the multivariate analysis of chemical and physical attributes. Five areas were selected: four of them with agricultural use (onion, banana, cassava, and corn) and the other with Caatinga. Soil samples were collected at depths of 0.00–0.10, 0.10–0.20, and 0.20–0.40 m for chemical and physical analyses. The data were submitted to descriptive analysis and then to the multivariate analysis using the principal component analysis (PCA) technique and Ward’s clustering method. PCA and clustering techniques allowed the identification of different production systems in subsurface layers, suggesting the effect of fertility on the differentiation of areas with onion and banana, as well as the clustering of cassava and corn cultivations. Physical attributes and sodium content of the surface layer of the area with onion showed a tendency of compaction and salinization process of this environment. In general, fertility was the main responsible for the improvement of soil quality with agricultural use when compared to the Caatinga.

Resumo em Inglês:

ABSTRACT The objective of this study is to evaluate spatial and temporal variations in rainfall aggressiveness in southern Brazil. A total of 181 rain gauge stations located in southern Brazil with rainfall time series from 1976 to 2015 were used. Seasonal and annual rainfall aggressiveness values measured according to the Modified Fournier Index (MFI) were analyzed. The trends in the data series were evaluated using the Mann-Kendall test at a level of significance of 5%. Maps on spatial and seasonal variations in rainfall aggressiveness were prepared. The percentage of rain gauge stations with significant decreasing trends, significant increasing trends, and no significant trends in rainfall aggressiveness between years was 3.3%, 7.7%, and 89.0%, respectively. Moreover, 90% of stations had no significant trends between seasons. There were seasonal differences in rainfall aggressiveness between the three southern states in Brazil caused by rainfall factors. Rainfall aggressiveness was comparatively higher in the west of Santa Catarina and southwest of Paraná due to the rains originating from the mesoscale convective systems predominant in autumn, and in the north coast of Santa Catarina and east coast of Paraná due to convective and orographic precipitations predominant in the summer.

Resumo em Inglês:

ABSTRACT Knowledge of droplet spectra generated by spray nozzle tips is important to ensure the quality of applications of plant protection products. However, there are different methods for this evaluation, which can cause difficulty in interpreting the results. This study aimed to evaluate the droplet spectra produced by the flat fan spray tip AD 11002 operated under different pressures and using different techniques and equipment. The volume median diameter (VMD), percentage of spray volume in droplets smaller than 100 µm diameter and relative spam (RS), considering pressures of 200, 300, and 400 kPa were determined using two direct measurement equipment (Spraytec and Shadow Sizer), based on laser diffraction and image analysis, respectively, and a measure based on indirect analysis, through the digitization of water-sensitive paper. Thus, the use of different analysis techniques led to variations of the analyzed parameters. Among the direct measurement equipment, a difference of up to 58% was observed in VMD. The use of water-sensitive paper to characterize droplet spectra must be carried out with great discretion because there is an underestimation of fine droplets. Pressure variations of 200 to 400 kPa did not influence VMD and RS.

Resumo em Inglês:

ABSTRACT Soybean has significant economic importance in Brazil despite high production costs, making it necessary to increase the efficiency of mechanized harvest through the reduction of losses. Thus, this study aimed to evaluate the total losses in the mechanized soybean harvest as a function of the combination of header types, operating speeds, and geometry of collection frames. The study was carried out in a commercial farm in a randomized block design arranged in a 2 × 3 × 3 factorial with 10 replications, totaling 180 replications. The data were analyzed by descriptive statistics, analysis of variance, and quality control. The square frame can be used instead of the rectangular frame for the determination of the total losses. The increasing operating speed increased total losses in the auger header. On the other hand, the lowest losses at the highest operating speed were observed in the belt header. The harvester with belt header was more efficient when compared to that with auger header at the highest operating speed.

Resumo em Inglês:

ABSTRACT The way the soil is managed can influence its structuring and, consequently, crop yield. Thus, this study aimed to evaluate the effect caused by the management systems plowing followed by two intermediate harrowing operations, intermediate harrowing, chiseling, chiseling followed by intermediate harrowing, cross chiseling followed by intermediate harrowing, and non-tillage on soil and agronomic attributes of the soybean crop. A randomized block design with four replications was used. The percentage of soil cover, soil resistance to penetration, number of plants per meter, longitudinal distribution of seedlings, and soybean yield were evaluated. The data were submitted to analysis of variance by the Tukey test at 5% probability, and use of geostatistics for soil resistance to penetration. The system without soil tillage provides the best straw preservation but affects the longitudinal distribution of soybean seedlings. The use of intermediate harrowing for managing crop residues or soil tillage leads to the greatest compaction problems. Chiseling is efficient in maintaining compaction values below critical values up to a depth of 0.20 m when working at 0.35 m. Soil yield is not affected by soil management systems when the pluviometric regime is adequate to crop requirements.

Resumo em Inglês:

ABSTRACT The mechanized harvesting of sugarcane has increased exponentially in recent years because of the gradual prohibition of burning on the cane fields in mechanizable and non-mechanizable areas. This study aimed to evaluate the wear of the basal cutting knives in two different mechanized sugarcane harvesters, through statistical process control. The experiment was conducted in Cravinhos, São Paulo, in an agricultural area, on July 25, 26, and 27, 2016. Two harvesters with different basal cutting mechanisms were evaluated: harvester A—Model BE1035e (conventional type knife), and harvester B—Model A8800 (racket type knife). The experimental design was completely randomized with two treatments. The wear was quantified by measuring the thickness increase and width losses of each knife, and it was evaluated for each harvester every 2 hours, during 3 days of operation. Data were evaluated using descriptive statistics and statistical process control. The harvester B model (racket knife) presented lower variability in the cutting width and stability in the cutting width of the knives. The harvester A model (conventional knife) presented greater wear in the width, but less variability in the thickness of the cutting wire.

Resumo em Inglês:

ABSTRACT Product deposition and foliar surface cover are highly impacting factors on the efficiency of foliar fungicides applied to soybean cultivars, due to their low mobility, with side effects on Asian soybean rust (ASR) control. Spray bar support systems, such as the air curtain (Vortex®) and the use of nozzles along the bar (Dropleg®), stand out as an alternative to obtain a better distribution of fungicide throughout the plant. In this study, two spray bar support systems (Vortex® and Dropleg®) were, therefore, evaluated and compared with the conventional spraying method based on the biological efficacy in ASR control. In order to do this, two harvests, with three spacing between rows and two cultivars were employed. Vortex® and Dropleg® spray bar support mechanisms do not effectively contribute to the optimization of Asian soybean rust control or to the grain crop yield, regardless of cultivar and row spacing. Decreasing the row spacing did not influence the level of control of Asian soybean rust, as the highest grain yield was obtained with the smallest spacing. The cultivar with genetic resistance to Asian rust showed lower levels of this disease, thus, greater control against the use of fungicides.

Resumo em Inglês:

ABSTRACT Integration of forage grasses with grain crops, such as maize, allows maintaining soil cover. The objective of this study was to evaluate the tensile strength, friability, and stability of soil aggregates in the maize and forage grass intercropping under no-tillage system. The study used a completely randomized block design with seven treatments and three replications. Undisturbed soil samples were collected in two seasons (2015 and 2016) at 0–0.10 m and 0.10–0.20 m soil depth. The following properties of soil aggregates were measured: tensile strength (TS), friability (F), gravimetric moisture (GM), weighted mean diameter (WMD), geometric mean diameter (GMD), and aggregate stability index (ASI). The intercropping of maize with Urochloa ruziziensis presented higher WMD and GMD at 0.10–0.20 m soil depth. Moreover, TS at 0.10–0.20 m soil depth was lower in maize without intercropping. The effects of the intercropping system on soil aggregates were better detected by aggregate stability than by TS or F. The intercropping of maize and U. ruziziensis improved soil aggregation to a higher extent than those systems with other forage grasses.

Resumo em Inglês:

ABSTRACT Peeling of crambe fruits, besides increasing the yield of mechanical oil extraction, can increase its apparent specific mass from about 330 to 700 kgm−3, reducing transport and storage operating costs, as well as increasing cake protein content. However, there is no information on the quality of the oil extracted from the stored unpeeled crambe. This study aimed to assess the possible effects of peeling fruits submitted to different storage systems. For nine months, peeled and unpeeled crambe fruits were stored in conventional (permeable) and hermetic packages and water content, fatty acid, and acidity and oil peroxide indices were monitored. The experimental design was a completely randomized design in a 2 x 2 x 3triple factorial, with three replications. After analysis of variance, the mean data were compared by the Tukey’s test, being considered significant when p<0.05. The results showed that peeled crambe had better conservation in relation to that unpeeled, mainly when submitted to the hermetic storage system.

Resumo em Inglês:

ABSTRACT Knowledge on sorption isotherms is important for predicting drying and storage processes of a product. A sorption isotherm can be generated from two processes: desorption and adsorption. The lag between these two curves is called hysteresis. Static method was used to obtain the equilibrium moisture content of paddy rice grains, in different temperature (10, 20, 30, 40 and 50 ± 1°C) and relative humidity (between 11 and 76% ± 2%) conditions. Equilibrium moisture content data were correlated with eight mathematical models and. The Chung Pfost model had the best fit to the experimental data. Desorption and adsorption isotherms, represented by the Chung Pfost model, showed a sigmoidal shape, characteristic of type II curve. Equilibrium moisture content values obtained by desorption were higher than those obtained by adsorption, evidencing the hysteresis phenomenon.

Resumo em Inglês:

ABSTRACT According to the ABNT NBR 7190: 1997 standard, tensile strength of wood samples shall be defined as the ratio between the ultimate strength from a stress test and the specimen cross-sectional area (350 mm2). However, due to the complex wood anatomy and experimental difficulties, the fractured surface in tested samples are not perpendicular to the loading direction; therefore, such fractured surface becomes larger than the sample cross section, overestimating tensile strength by this method. Using an alternative approach, we aimed to determine the approximate fracture surface of wood specimens subjected to tensile test. For this purpose, we used the least square method to estimate tensile strength of four hardwood species, which were equally divided into strength classes. Then, we determined the relationship between the cross-sectional areas of intact and fractured specimens. The results showed that the approximate area of a fractured surface was 2.14 higher than that of an intact sample. As a result, tensile strength estimates were 47% lower than those currently estimated, which is unfavorable for the safety of construction structures.

Resumo em Inglês:

ABSTRACT The largest energy losses and voltage variations from electricity suppliers occur at times of peak demand. Daytime peaks are mainly influenced by large industrial and commercial consumers. The installation of photovoltaic systems without energy storage to supply part of the demand can contribute to stabilize the voltage and reduce losses. These and other benefits constitute the so-called externality of the decrease in off-peak demand due to photovoltaic generation. The objective of this study was to investigate the role of this externality in agroindustry, as a consumer of electrical energy, in order to better understand its effects on the consumer and the utility. The implementation of photovoltaic systems was simulated with the objective to reduce the off-peak contracted demand by agroindustries. Both the energy balance and the economic viability of the photovoltaic system implantation were analyzed. It was concluded that the photovoltaic system contributed to the reduction in energy costs, improved the load factor by about 47%, and reduced the off-peak contracted demand by about 20.2% and 54.2% for the small and medium-sized agroindustries considered, respectively.

Resumo em Inglês:

ABSTRACT For the purpose of achieving the distribution of the potato-soil mixture and the appropriate parameters of the swing separating sieve, we conducted experiments using the 4SW-170 potato digger. The experiments consisted of two parts. In each part, the experimental factors were crank rotational speed, sieve inclination and machine forward speed. The difference is that the first part involved a single factor test, which selected the coverage of the potato-soil mixture as the evaluation indicator. In contrast, the second part involved an orthogonal test, which selected the obvious rate and damage rate as evaluation indexes. In the first part, it was observed that the coverage of the potato-soil mixture on the separating sieve reduced gradually with the increase in crank rotational speed and sieve inclination. Inversely, as the machine forward speed was raised, the coverage of the potato-soil mixture gradually increased. In the second part, when the crank rotational speed was 230 rpm, the sieve inclination became 21.1°, and the machine forward speed was 2.03 km . h-1; the optimal parameter combination was obtained. Under such conditions, the obvious rate of potato harvest could reach as high as 99.49%, and the damage rate of potato harvest could reach as low as 0.87%. The reported results may be of help in providing a reference for the design of the swing separating sieve on potato diggers.