Resumo em Inglês:

ABSTRACT Sugarcane is grown in several countries and environmental conditions, and production increases should not only be based on the expansion of the cultivated area. As water is a limiting factor for sugarcane yield, irrigation is crucial to increase its yields. Thus, this study aimed to evaluate the agronomic performance of five sugarcane cultivars under irrigated and rainfed conditions and compare yields in each treatment with those of previous cycles. The experiment was carried out from July 2017 to July 2018, which stands for the fourth sugarcane harvest. It consisted of two irrigation factors (irrigated and rainfed conditions), and five sugarcane cultivars (CTC4, IACSP93-3046, RB86-7515, IACSP95-5000, and IAC91-1099). Irrigation was applied to supply 100% of crop evapotranspiration. Irrigation increased sugarcane yields, and such increases varied with the genotype and crop cycle evaluated. In general, the cultivars most responsive to irrigation were IACSP93-3046 and IACSP95-5000, regardless of the evaluation cycle, and CTC4 from the fourth harvest onwards. Irrigation did not interfere with sugarcane technological quality if harvested after the middle of the crop season (June). Cultivars with higher tillering capacity, such as CTC4, had improved yield stability throughout the cycle when under irrigated conditions.

Resumo em Inglês:

ABSTRACT For the synergistic improvement of soil fertility and rice yields in a cold region, we investigated the effects of plastic mulching with different straw incorporation rates on the rice yield and nitrogen use efficiency in a rice growing area of a cold region. The field experiment was conducted using the Jijing 88 rice cultivar, and set up four straw incorporated treatment: 20% (S1), 40% (S2), 60% (S3) and 100% (S4) under two conditions: mulching (M) and without mulching (NM). The results showed that under the same straw incorporation rates: (1) Plastic mulching increased the total soil nitrogen and organic matter contents while improving the grain yield; the yield increases were 2.8–14.9% in 2016 and 1.4–12.3% in 2017. (2) The mulched treatment improved the net photosynthetic rate, the maximum tiller number, the crop growth rate of the later growth stages, and the shoot dry weight. (3) The recovery efficiency, agronomic efficiency, and partial factor productivity of the nitrogen applications were all higher under the mulched treatment than under the non-mulched treatment. In a comparison of the different straw incorporation treatments, above three indicators consistently increased before they decreased, and significantly higher levels were reached under the 40% straw incorporation treatment with mulching than under the other treatments.

Resumo em Inglês:

ABSTRACT The growing demand for gladiolus, especially at peaks of consumption, requires efficient scheduled production and good quality of floral stems. The objective of this study was to understand how water deficit affects the growth and development of gladiolus and, consequently, the quality of the floral stems produced. Plant development, quantitative parameters of the floral stems, and dry mass partitioning were evaluated in two field experiments with four gladiolus cultivars, with and without irrigation. The development cycle was longer in the non-irrigated treatment, whereas its duration under no water deficit was similar to that predicted by PhenoGlad, which is a gladiolus phenology model. As PhenoGlad predicts gladiolus development only for scenarios without water deficit, the inclusion of a water-stress submodel in the model would allow its application to any water supply scenario and help decision makers and farmers to plan gladiolus production more accurately. Water deficit also reduced gladiolus growth and flower stem size, but did not affect dry mass partitioning. As the development and quality of the floral stems of gladiolus were negatively affected by water stress, irrigation is essential for producing high-quality gladiolus floral stems and enabling production planning for peaks of consumption.

Resumo em Inglês:

ABSTRACT In El Oued, southern Algeria, the traditional Mini-Centre Pivot System (MCPS) is widely used for the irrigation of agricultural crops, and its use has been growing continuously. However, these systems have a constant nozzle diameter along the lateral pipe, which affects productivity directly, besides decreasing both the quantity and quality of agricultural products by irrigation heterogeneity. Therefore, optimising the design of the MCPS nozzles is linked strongly to the desired uniform irrigation. This study aims to determine the optimal configuration of nozzles for high irrigation uniformity. To achieve this goal, a genetic algorithm was used for maximising the uniformity of MCPS-mediated irrigation. The optimisation is carried out according to water distribution modelling, calculation of the Heermann and Hein uniformity coefficient (CUH), and existing nozzle diameters. To verify the accuracy of the proposed model, three existing MCPS (60 m, 50 m, and 46 m in length) are investigated experimentally. The developed code findings in terms of CUH are in agreement with those obtained by experimental tests. The analysis indicated that the nozzle diameter should vary from 5 to 15 mm along the lateral pipe. In these optimal conditions, the CUH was improved by 29.77%, 33.99%, and 19.36%, respectively, for the existing 60, 50, and 46 m irrigation systems. The most obvious findings to emerge from this study is that using a genetic algorithm to optimise the design based on the nozzle size improves water application uniformity by more than 19% in terms of the CUH.

Resumo em Inglês:

ABSTRACT Aiming at addressing the uneven pesticide distribution when spraying high-spindle apple trees, the parameters of a homemade profiling boom sprayer were analysed, and the optimal parameter combinations of the profiling sprayer were determined. Fluent was used to simulate the spray for various parameter values. The goodness of fit (R2) with experimentally measured data was 0.9270, which verified the accuracy of the numerical simulations. The response surface methodology (RSM) method was used to obtain optimal parameter values from the simulations, and the effective collection rate and spray distribution coefficient of variation were introduced as response values. A sprayer prototype was manufactured based on the optimal parameters determined by RSM analysis, and the results were verified by vertical droplet distribution tests. The results showed that the spray quality increased by 0.7%, 0.9%, and 0.3% for the three best parameters combinations, the droplet distribution was more uniform, and the effect of the profiling spray was better than that of the control tests. The results can provide guidance for the design of sprayers for orchards, and the optimal combination of parameters can provide a basis for subsequent research on precision modelling of profile spraying.

Resumo em Inglês:

ABSTRACT In order to provide the basis for the design and control of a citrus picking robot clamp and cutter, and find the optimal combination of cutting parameters, this study used a self-made citrus stem cutting test-bed to study the effects of the citrus stem diameter, blade cutting speed, blade cutting clearance, and tool sliding cutting angle on the peak cutting force of citrus stems through a single-factor experiment. Based on the single-factor test, the blade cutting speed, blade cutting clearance, and tool sliding angle are selected as the influencing factors, and a multi-factor test is carried out with the target of the peak cutting force, and the regression model is established. The results showed that the peak cutting force increased linearly with the diameter of the fruit stalk, decreased with the increase of the blade cutting speed and sliding cutting angle, and first decreased and then increased with the increase of the blade cutting clearance. Through the optimisation analysis of the regression model, it is found that the optimal cutting parameter combination is the blade cutting speed of 40 mm/min, blade cutting gap of 1 mm, tool sliding cutting angle of 20°, and the peak cutting force under this combination is 168.23 N. The deviation between the predicted value of the peak cutting force and the measured value is less than 2%, and the optimisation result of the cutting parameters is reliable. This study provides a theoretical basis for the optimal design and control of the clamping and cutting mechanism of the citrus picking robot.

Resumo em Inglês:

ABSTRACT To improve the working performance of hammer mill, cutting-edge hammer and oblique hammer were designed in this study. The advantages of new hammers were theoretically analyzed. The grinding process of corn grain with different hammers was studied by discrete element method (DEM) and experiments. Discrete element simulation results showed that under same rotor speed conditions, the cutting-edge hammer had highest bond-breaking efficiency in corn grain model. The oblique hammer could reduce the incident angle of corn grain and improve sieving efficiency. The motion trajectory of corn grain in grinding chamber was relatively dispersed and similar when using common hammer and cutting-edge hammer, and the motion trajectory was more concentrated when oblique hammer was used. The experimental results showed that both cutting-edge hammer and oblique hammer could improve the working performance of hammer mill. The productivity of hammer mill could be improved by using cutting-edge hammer, electricity consumption per ton and temperature rise of feed could be reduced by using oblique hammer, and the experimental results were consistent with simulation results and theoretical analysis results. The research results can provide references for the design of new hammer and the grinding process simulation of other agricultural materials.

Resumo em Inglês:

ABSTRACT Brazilian flora has more than 12 thousand tropical wood species, which can be the raw material for the construction industry. Chromated copper borate (CCB) and chromated copper arsenate (CCA) are wood preservative chemicals, which can generate toxic waste. Particleboards are usually produced from Pinus sp. and Eucalyptus sp. wood particles and a polymeric matrix (often formaldehyde-based), and they are used as raw material mainly for the furniture industry. This study aimed to investigate the technical feasibility of particleboard production using caixeta wood (Simarouba amara Aubl.) particles and bicomponent castor oil-based polyurethane resin for tropical wood waste management, as well as study the impact of CCA/CCB treatments on the performance of these panels according to NBR 14810 standards. Analysis of variance (ANOVA) tests was performed to compare ten physical and mechanical properties of the panels produced with CCA, CCB, and non-treated caixeta wood particles. The performance of caixeta wood panels was similar to the usually produced boards (using Pinus sp. and Eucalyptus sp. wood). Furthermore, preservative treatments did not change significantly the mechanical performance of panels. However, water absorption increased and thickness swelling decreased in CCA/CCB treated samples.