Resumo em Inglês:

ABSTRACT Pneumatic seed metering devices are widely used in high-speed and precise corn seeding operations. The objective of this study was to analysis the high-speed seeding performance of a pneumatic precision seed metering device at seeding speed ≥12 km/h. In this study, full-factor experiments were conducted of an air-suction rotary-hub corn precision seed metering device at the early stage of development. Seed leaking was the primary failure mode, and the experimental factors had no evident regular influence on the repeat index. The negative pressure of 3-7 kPa had significantly positive and negative correlations with the qualified index and the leak index, whereas the seeding speed of 12-20 km/h was significantly negatively and positively correlated with the qualified index and the leak index, respectively. The leak index reached its greatest value of 32.48%, 15.61% and 66.77% when the negative pressure was 3 kPa, and it was always less than 10% when the negative pressure was greater than 6 kPa for the three corn seed varieties. The corn seed varieties with smaller sizes and regular shapes were more suitable for high-speed precision seeding operations above 12 km/h, and the negative pressure could be increased to improve the qualified index and reduce the leak index.

Resumo em Inglês:

ABSTRACT Hyperspectral sensors and regression analysis have been used to analyze the most important spectral ranges for biophysical parameters of target crops, aiding in management decision-making. This study aimed to analyze the spectral response of Brachiaria brizantha cv. Marandú leaves to increasing rates of urea fertilization and predict leaf nitrogen content (LNC). Four rates of urea fertilization (0, 25, 50, and 75 kg of N ha-1) were applied. Eight leaves were collected per plot seven times at monthly intervals and subjected to hyperspectral analysis. Leaf spectral responses differed statistically within the visible region, particularly at 550 nm (green). The regression models achieved moderate to good R2 values (0.53 to 0.83) for predicting LNC and identified important wavelengths in the red edge region (715 to 720 nm). These findings demonstrate the potential of spectral analysis to detect changes and forecast leaf nitrogen content in B. brizantha cv. Marandú crops at different fertilization levels.

Resumo em Inglês:

ABSTRACT Various problems are encountered during the screw feeding process of chopped cornstalk. Therefore, it is important to deeply analyze and understand the relationship between conditions and productivity of screw conveyors. This study reveals the influence of air velocity, pitch, rotational speed, and feeding rate on productivity, power consumption, specific power consumption and pressure of material for a coupled screw-pneumatic conveyor. Through a theoretical analysis, a mathematical model is established that simultaneously considers the compression characteristics of the material, material pressure from the change in pitch and centrifugal force of the screw axis, productivity of the coupled screw-pneumatic conveyor, power consumption and specific power consumption. Then, experiments are conducted to investigate the influence of the structural and working parameters of the conveyor on its performance. Finally, the correctness of the theoretical calculation is verified through a comparison with experimental results. The results of the theoretical analysis are in good agreement with the experimental results, and the relative deviations fall within 10%, 13%, 14% and 11% for the productivity, energy consumption, specific consumption and material pressure of the conveyor, respectively. With increasing airflow speed, pitch, rotational speed and feeding volume, the power consumption increases, and the other parameters have their own trends.

Resumo em Inglês:

ABSTRACT The paddy field machine uses excessive power during paddy field preparation because of the high distribution density of rice straw. In this study, a rotary blade is created to address this problem. The structural parameters of the rotary blade were designed and the dynamic analysis of the rotary blade's soil-cutting process was completed to establish a model of the rotary blade's power consumption. Through the model, the primary factors influencing the rotary blade's power consumption were identified. A composite soil bin model of rice straw‒muddy layer‒bottom soil was established in EDEM software, with the bending angle of the front blade, the working width of a single blade, and the thickness of the blade as the test factors. The straw burying rate, power consumption, and surface flatness after rotary tillage were used as evaluation indicators to conduct multi-factor simulation tests on the composite soil bin model. The optimized analysis of the test data showed that the optimal geometric parameters for the rotary blade were 49 mm working width, 108° front blade bending angle, and 4 mm blade thickness. A field verification test was carried out on the optimized rotary blade, and the test results showed that the surface flatness after rotary tillage was 3.25 cm, the qualified rate of rotary tillage depth was 93.3%, and the degree of mud mixing was 3.41 kg/dm3, which was suitable for the land preparation requirements of paddy fields.

Resumo em Inglês:

ABSTRACT The aim of this study is to simplify the difficult excavation that is caused by the root-sand complex in the process of harvesting Cyperus esculentus in the desert of Xinjiang by performing mechanical tests and analysis of the interaction between the vibrating excavation shovel and the rotary blade on the root-sand complex. The rotary blade number, rotary blade speed and digging depth were used as the test parameters, and the Cyperus esculentus breakage rate, root-grass crushing rate, and soil carrying rate were used as the test indicators. The characteristics of the influence of various factors and their interaction on the crushing and separation of the root-sand complex were explored. A parameter combination optimization model is verified by experimental data. The test results showed that the optimal combination was as follows: the number of rotary blades was 20, the rotational speed of the rotary blade was 373 r/min, and the digging depth was 12 cm. At this time, the Cyperus esculentus breakage rate, root-grass crushing rate, and soil carrying rate were 2.62%, 63.68% and 55.40%, respectively. This study can support the development of a Cyperus esculentus harvester suitable for deserts in Xinjiang.

Resumo em Inglês:

ABSTRACT In the process of rice harvesting, the passability of the track combine harvester is often limited by the state of the soil. Meanwhile, wet and soft paddy soil is compacted under the rolling of harvesting machinery, which also affects the soil function and the ecological environment. Therefore, the relationship between the physical and mechanical properties of wet and soft paddy soil was studied in this paper. In addition, compaction from a track combine harvester on field soil with and without rice stubble was studied. The density and gradation of wet and soft paddy soil were positively correlated with cohesion and negatively correlated with the internal friction angle. In paddy soil with a moisture content of 16–36%, the soil moisture content was negatively correlated with cohesion and internal friction angle. Additionally, the plastic deformation of soil with rice stubble under compaction was greater than that without rice stubble, and the plastic deformation of the field with rice stubble mainly occurred in the second rolling stage. Increasing the speed of the track combine harvester effectively reduced the compaction risk of rice stubble soil.

Resumo em Inglês:

ABSTRACT The structural parameters of a grain dryer are directly related to the its energy consumption and quality formation. Therefore, based on the Ergun model, air state parameters and uniformity evaluation method, the effect of changes in the ventilation area on grain airflow resistance, drying energy consumption, drying efficiency and uniformity are theoretically and experimentally studied in this work under the same initial grain weight and air flux. The results show that under the conditions of air temperatures 35℃ and 70℃, the weight of paddy 8.547 kg and the air flux 12.3 m3·h-1, hot air introduced into the drying chamber with cross-sectional areas of S1 and S2 respectively, the ventilation area enlarged by 2.328 times, the grain airflow resistance decreased by 7.17 and 6.99 times. Enlarging the ventilation area effectively improved the drying rate of paddy, especially at 70℃, while the unit energy consumption was the opposite. It also accelerated the moving speed of the saturated humidity line in the drying layer and improved the drying uniformity of the paddy. These experimental results are in agreement with the theoretical analysis, which provides a reference for the design of grain drying equipment and technology.

Resumo em Inglês:

ABSTRACT Two-stage harvesting is the main method for performing the mechanized harvesting of peanuts, and the picking device is a core part of the combined harvester in China. In order to solve the problem of pod loss caused by the "stacking", "impact" and "throwing up" of peanut plants by a traditional cam-slide spring-finger cylinder picking device, the shovel-finger and cylinder peanut-picking device was developed and used in a picking-up performance test based on the study of peanut-plant strip-picking characteristics. The mathematical model of the mechanism was established by analyzing the structure of the mechanism and the peanut-plant strip-picking characteristics, and the parameters of the mechanism were optimized using the objective function method. The prototype was developed and tested. The experiments in which the prototype was used to collect peanut plants indicated that the phenomenon of peanut plants being stacked and thrown disappeared. Through a response surface analysis and prototype test, the optimal working parameters of the picking device were obtained: the forward speed V was 48.0 m/minute, the rotational speed N was 45.3 r/minute and the ground height H was -18 mm. The peanut-plant picking rate was 98.9% and the fruit loss rate was 2.8% under two different harvesting conditions for which the peanut-plant moisture content was 15~17%.

Resumo em Inglês:

ABSTRACT The goal of this paper was to apply a method for the delineation of vegetation homogeneous zones (HZs) to map the profitability of cotton ( Gossypium sp.) using NDVI (Normalized Difference Vegetation Index) data from RPA imagery. Two irrigated cotton crops, at the FAU (103 ha) and FRP farms (106 ha), located in the western region of Bahia State, Brazil, were studied. The NDVI images were classified into three HZs: “high”, “medium” and “low” plant vigor; using the k-means clustering method. In each HZ the yield was measured, and the profitability estimated. In FAU we found that the lower the HZ’s NDVI values, the lower its profitability, because there was profit in the “high vigor” HZ, of US$ 829.40 ha-1, and loss in the “low vigor” HZ, of about US$ ‒1.256.09 ha-1 (‒251.44% compared with the “high vigor”). In the FRP plantation, the lower the NDVI values, the lower the loss of the plantation, as there were losses in all HZs: from “high” to “low vigor” HZ, the percentage difference in profitability was ‒343.43%. Thus, the use of a low-cost modified near-infrared Canon S100 on an RPA enabled the mapping of crop profitability, aiding the search for the factors behind yield variability.

Resumo em Inglês:

ABSTRACT The study aimed to determine the evapotranspiration (ETc) of the mango cv. ‘Palmer’ over two productive cycles, analyzing water-use efficiency (WUE) and crop water productivity (CWP) to propose average crop coefficient (Kc) values for improving irrigation management under cultivation conditions in the Low-Middle São Francisco Valley. The study was conducted from July 2019 to May 2021 in a commercial ‘Palmer’ mango orchard in Petrolina, State of Pernambuco, Brazil. Micrometeorological data was collected throughout the experimental period. The crop evapotranspiration (ETc) was determined using Bowen ratio energy balance (BREB), and then the Kc, WUE, and CWP were determined. The highest ETc values occurred during the floral induction phase (5.14 ± 0.85 mm day-1), with a Kc of 0.85; however, the lowest values were observed during the fruit maturation phase (3.60 ± 0.73 mm day-1), with a Kc of 0.91. Average water consumption per cycle was 1445 mm, with a daily average of 4.39 mm day-1. WUE and CWP were 16.9 and 24.5 kg ha-1 mm-1, respectively. Average Kc values of 0.81, 0.76, 0.85, 0.90, 0.95, and 0.91 are recommended for the vegetative growth, rest period and shoot maturation, floral induction, flowering, fruit development, and fruit maturation phases, respectively.

Resumo em Inglês:

ABSTRACT To address the low efficiency and high flower bud damage rate in camellia-fruit-picking machines, a multichannel camellia-fruit-picking device was designed. Three factors and levels of the quadratic orthogonal rotation combination test method were used in the test. The experimental results show that the fruit picking and bud damage rates were affected most by the roller speed, followed by the distance between rollers, and, finally, the roller diameter. The optimal parameter combination was determined to be the roller speed of 130 mm/s, distance between rollers of 21 mm, and roller diameter of 30 mm, as verified by outdoor experiments. The average camellia-fruit-picking and bud damage rates were 95.68% and 3.92%, respectively. Compared with a rotating rubber roller picking device, the average flower bud damage rate of the multichannel camellia-fruit-picking device was reduced by 14.71 percentage points.

Resumo em Inglês:

ABSTRACT Sugarcane requires planning aimed at maintaining production levels, technological quality, and longevity of the sugarcane field, as it is a semi-perennial crop. To this end, the adoption of soil management systems associated with the maintenance of remaining straw are some of the strategies aimed at protecting the soil structure and its properties vital to the sustainability of agricultural systems. In this context, this study aimed to evaluate the influence of soil management systems and remaining straw with and without ratoon chiseling on the optimum water range (OWR) and load-bearing capacity (LBC) of the soil. The experimental design consisted of randomized blocks in a split-plot scheme, with four replications. The plots were composed of no-tillage and conventional tillage, the subplots consisted of three levels of remaining straw (0, 50, and 100%), and the sub-subplots consisted of the use or not of chiseling. Samples with preserved structures were collected at depths of 0.05 and 0.15 m for the analysis of the physical indicators OWR and LBC. Maintaining 100% straw associated with the use of chiseling resulted in an increase in OWR in both soil management systems and depths. Maintaining straw at 50 and 100% also led to lower LBC values in the evaluated soil management systems and depths, suggesting an improvement in soil physical quality. The use of chiseling of ratoons in conventional tillage promoted higher LBC values, indicating possible additional soil compaction in these areas.

Resumo em Inglês:

ABSTRACT In this study, a device was designed for tillage of compacted soil in wheel ruts formed by the repeated passage of agricultural machines.[Ed1] Soil parameters were measured, and then the wheel rut tillage device was divided into two parts, the soil lifting unit and the soil breaking unit, for separate simulation tests to study the tillage process. EDEM[Ed2] simulations were applied to the soil lifting device to compare and analyze the microscopic movement of the simulated soil particles and the operational resistance of the device. Analysis of variance (ANOVA) was performed using Design-Expert10 [Ed3] software to obtain the optimum combination of parameters of 125 mm device offset distance, 43.6° entry angle and 28° lifting angle. A full-factor test was conducted on the soil crushing device using EDEM coupled with RecuDyn multi-body system dynamics simulation software. The number of bond breaks and the traction resistance of the soil crushing device were used as the test indicators, and the optimum parameters were obtained for a soil crushing knife blade thickness of 6 mm and a cutting edge angle of 30° for the largest number of bond breaks and least traction resistance. The results of this study will provide technical support for the reduction of compaction zones in wheel ruts after tire travel on agricultural machinery in real time.

Resumo em Inglês:

ABSTRACT In rural areas, the electricity supply is affected by problems such as low quality and limited access in some regions. The use of renewable sources, with decentralized generation, can offer an alternative to the existing scenario. The objective of this work is to perform a technical and economic analysis of off-grid photovoltaic systems, without energy storage, intended for irrigation. Photovoltaic systems from different irrigation systems were sized, with power ratings from 0.736 to 29.44 kW. Their technical feasibility was determined based on the energy supply period and the availability of solar radiation as restriction variables. Economic feasibility was determined by the indicators of net present value (NPV), internal rate of return (IRR), benefit/cost ratio (B/C) and profitability index (PI). Feasible operation was found for irrigation systems with motors up to 11.04 kW; however, for systems that required higher powers, the number of operating hours available was less than the minimum required. NPV, IRR, B/C and PI showed increasing values as a function of increasing power. Thus, off-grid photovoltaic systems without energy storage are technically and economically feasible for systems with power of up to 11.04 kW.