As an essential element, the effect of Phosphorus (P) on plant growth is very significant. In the early growth stage of maize, it has a high sensitivity to the deficiency of phosphorus. The main ...purpose of this paper is to monitor the maize status under two phosphorus levels in soil by a nondestructive testing method and identify different phosphorus treatments by spectral data. Here, the Analytical Spectral Devices (ASD) spectrometer was used to obtain canopy spectral data of 30 maize inbred lines in two P-level fields, whose reflectance differences were compared and the sensitive bands of P were discovered. Leaf Area Index (LAI) and yield under two P levels were quantitatively analyzed, and the responses of different varieties to P content in soil were observed. In addition, the correlations between 13 vegetation indexes and eight phenotypic parameters were compared under two P levels so as to find out the best vegetation index for maize characteristics estimation. A Back Propagation (BP) neural network was used to evaluate leaf area index and yield, and the corresponding prediction model was established. In order to classify different P levels of soil, the method of support vector machine (SVM) was applied. The results showed that the sensitive bands of P for maize canopy included 763 nm, 815 nm, and 900–1000 nm. P-stress had a significant effect on LAI and yield of most varieties, whose reduction rate reached 41% as a whole. In addition, it was found that the correlations between vegetation indexes and phenotypic parameters were weakened under low-P level. The regression coefficients of 0.75 and 0.5 for the prediction models of LAI and yield were found by combining the spectral data under two P levels. For the P-level identification in soil, the classification accuracy could reach above 86%. These abilities potentially allow for phenotypic parameters prediction of maize plants by spectral data and different phosphorus contents identification with unknown phosphorus fertilizer status.
Extensive research has been conducted on the effects of pollen activation temperature, cultivation temperature, and ambient temperature on germination rates and fruit sets. Yet, the influence of the ...temperature (pre-germination temperature) at which the pollen suspension is prepared within the storage container (tank) remains unexplored. In this study, we initially established the optimal time for pollen activation. Subsequently, pollen suspensions at varying temperatures were prepared, and their germination rates were analyzed using microscopy. Pollen suspensions of different temperatures were then sprayed onto Fojianxi pear flowers, and parameters such as flower fruit set rate, inflorescence fruit set rate, fruit longitudinal dimension, fruit transverse dimension, and fruit shape index were evaluated. The findings revealed that the optimal pollen activation duration was 6 h. A pollen suspension temperature of 30 °C resulted in the highest germination rate (72.06 ± 6.87%). However, a suspension temperature of 25 °C achieved the highest flower fruit set rate (57.29 ± 5.58%) and inflorescence fruit set rate (87.50 ± 4.84%). The fruit longitudinal dimension (68.12 ± 3.94 mm), transverse dimension (73.77 ± 4.04 mm), and fruit shape index (108.42 ± 6.02%) were most favorable at a suspension temperature of 15 °C. Our study concludes that the pollen in lower pollen suspension temperatures (15~25 °C) has higher germination energy and have higher stigmatic capacity. Thus, we advocate for a pollen suspension temperature range of 15~25 °C when employing liquid spray pollination techniques with Xuehuali (Pyrus bretschneiderilia) pollen.
Under the rapid development of unmanned aerial vehicle (UAV) plant protection products (PPP) application in Asian countries, the drift risk of UAV sprayer operation in orchard or vineyard is fairly ...high because of the much finer droplets generated and the higher height than ground sprayers, increasing threats to non-targeted crop, human and environment. However, there is few of comprehensive experimental study on the effects of UAV type and nozzle type on spray deposition and drift from UAV sprayer. The objectives of this study were to compare the spray performance of three different typical commercial UAV types (helicopter, 6-rotor and 8-rotor) with two nozzles types (hollow cone nozzle, HCN and air-injector flat fan nozzle, AIN) in vineyard. An artificial vineyard and three vertical collection frames, designed and built by ourselves, were applied for collecting droplets together with PVC collectors, petri dishes and rotary samples. The characteristics of deposition, drift and mass balance of UAV aerial spraying in vineyard were analyzed. As a result, under the crosswind speed of 3.11–3.79 m/s, AIN promoted spray deposition and uniformity and reduced drift significantly compared to HCN for all tested UAVs, improving of the utilization of PPP. The fitted regression functions of the sedimenting and airborne drift were obtained, respectively, and the drift percentage reduction values of AIN compared to HCN determined based on those functions varied from 81% to 95%. With HCN, 49.3%–73.4% of measured droplets drifted into non-targeted area and the highest proportion of drift loss was found for the airborne spray drift. According to the principle of more deposition and less drift, the spray performance of the three UAVs can be ranked in an order of 6-rotor, 8-rotor and helicopter, and two main reasons causing the difference in spray performance were the vortex airflow and the nozzle arrangement.
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•Experiments were focused on the influence of UAV designs on spray deposition and drift in a vineyard scenario.•Deposition, sedimenting and airborne drift and mass balance of UAV sprayer were evaluated using an artificial vineyard.•Air-injector nozzle was an effective technique for promoting deposition distribution and reducing drift from UAV spraying.•With hollow cone nozzle, over half of measured droplets drifted and the highest proportion of drift was from airborne loss.
Traditional plant protection machinery cannot apply pesticides according to the actual growth demand of crops, which causes a lot of pesticide waste and serious environmental pollution. Based on ...this, an intelligent variable-rate application system based on 3D LiDAR (light detection and ranging) scanning and PWM (pulse-width modulation) control for maize canopy was developed in this paper. After completing the performance testing, the system was mounted on a lightweight high-clearance self-propelled sprayer by remote controlling with an operating width of 6.0 m, and a ground gap of 2.0 m. And the actual operational performance of the sprayer showed that the prediction error of LiDAR for plant height was within 10%, which illustrated the accuracy of the detection system and the reliability of the variable application based on the plant height change. And the variable-rate system could adjust the spray volume in real-time according to the plant height change. The penetration rate of the upper, middle, and bottom layers maintained a relatively stable state (upper > middle > bottom) at variable-rate application and could reach the normal application level. This study can provide new ideas for efficient pests and diseases control of high stalk crops, especially suitable for small fields, and gives a reference for the structural design of new precise variable-rate application machinery and performance optimization of efficient application technology.
•A complete intelligent application system has been developed.•A reliable decision model of application quantity is established.•The intelligentsprayer meets the spraying technology requirements.
Fruit tree frost, an agricultural meteorological disaster primarily occurring in spring, severely impacts the growth and development of trees and fruit set. Therefore, exploring the temperature ...change rules of fruit trees during frost events is of considerable importance. This study used a T40 unmanned aerial vehicle (UAV) as the test vehicle based on the air disturbance frost prevention principle. The airflow field change pattern of the UAV was explored using the computational fluid dynamics simulation method, and the reliability of the multi-rotor UAV in frost prevention was verified using field tests. Setting the UAV height at 6.0 m above the ground and the rotor speed at 1000 r min−1, it was found that under the conditions of the inverse temperature phenomenon, the temperatures of different altitude layers will eventually converge to a stable value when the UAV down-rotating airflow is disturbed, which could be completed rapidly within 20 s. The results of the field test also showed that when the fruit trees reached the critical temperature of frost at the flowering stage, UAV intervention could have a substantial effect on the warming of the near-surface layers, whose warming amplitude was in the range of 2.5 °C–3 °C. This study provides a reliable method for mitigating frost, which serves as an important theoretical and guiding basis for improving agricultural frost disasters in China.
•A multi-rotor UAV is used to test frost protection performance on fruit trees.•The temperature field characterizations are obtained.•The anti-frost effectiveness of UAV intervention is confirmed.
•An economical and feasible method is proposed to analyze the droplet deposition behavior (DDB), which can intuitively show the process of DDB and reveal some invisible laws.•The models established ...in this paper reveal the general laws of DDB, which can guide pesticide spraying with different liquid properties and operating parameters and provide a reference for the pesticide configuration and parameters optimization in actual operation.•The micro mechanism analysis and macro phenomenon explanation of the DDB is helpful to deeply interpret the atomization phenomenon and laws so as to optimize the spray process and improve the operation efficiency.
The variation of relevant parameters during the spraying process will affect the droplet deposition behavior (DDB) on the plant leaf surface. Hence, a comprehensive analysis and modeling are the basis for model-based control design and performance optimization of spraying efficiency. This paper adopted the method of computational fluid dynamics (CFD) to conduct real-time visualization analysis and numerical modeling establishment of the DDB from the micro and macro perspectives, aiming to obtain the quantitative deposition laws of relevant parameters in the deposition process. The micro results showed that the droplet had different degrees of deposition, bouncing, and diffusion at different blade inclination angles (IAs) and contact angles (CAs). The system’s total pressure presented a consistent trend, while there was a sharp increase of about 2–3 times at the moment of impact on the leaf surface. Numerically, the droplet diffusion speed was basically at 5–7 mm/ms. And it presented an exponential function between the diffusion time and the diffusion velocity of the droplets, whose coefficient of determination (R2) equaled 0.73. The DDB of macro analysis clearly explained the change laws of droplet size, residence time, shear stress, and spreading speed. And the mathematical models of the droplet deposition thickness (DDT) on the target surface about time, spraying speed, liquid density, and fluid viscosity were established, which showed a trend of string functions. The growth rate of DDT reached a maximum of 13331% at 40 ms, which could be considered as an economic spraying time. The study achieved a comprehensive dynamic visualization and model-building of relevant spraying parameters and provided an actual reference for the spraying deposition control design and the parameters selection.
Extensive research has been conducted on the effects of pollen activation temperature, cultivation temperature, and ambient temperature on germination rates and fruit sets. Yet, the influence of the ...temperature (pre-germination temperature) at which the pollen suspension is prepared within the storage container (tank) remains unexplored. In this study, we initially established the optimal time for pollen activation. Subsequently, pollen suspensions at varying temperatures were prepared, and their germination rates were analyzed using microscopy. Pollen suspensions of different temperatures were then sprayed onto Fojianxi pear flowers, and parameters such as flower fruit set rate, inflorescence fruit set rate, fruit longitudinal dimension, fruit transverse dimension, and fruit shape index were evaluated. The findings revealed that the optimal pollen activation duration was 6 h. A pollen suspension temperature of 30 °C resulted in the highest germination rate (72.06 ± 6.87%). However, a suspension temperature of 25 °C achieved the highest flower fruit set rate (57.29 ± 5.58%) and inflorescence fruit set rate (87.50 ± 4.84%). The fruit longitudinal dimension (68.12 ± 3.94 mm), transverse dimension (73.77 ± 4.04 mm), and fruit shape index (108.42 ± 6.02%) were most favorable at a suspension temperature of 15 °C. Our study concludes that the pollen in lower pollen suspension temperatures (15~25 °C) has higher germination energy and have higher stigmatic capacity. Thus, we advocate for a pollen suspension temperature range of 15~25 °C when employing liquid spray pollination techniques with Xuehuali (Pyrus bretschneiderilia) pollen.
Although the internal jugular vein (IJV) is the most widely used puncture site in hemodialysis catheter insertion and central vein angioplasty, the external jugular vein (EJV) offers an alternative ...vascular access point in cases when the IJV is inaccessible. The present study aims to observe the efficacy and safety of sharp recanalization of the brachiocephalic vein occlusion through the EJV in hemodialysis patients.
This retrospective study enrolled a cohort of hemodialysis patients who received sharp recanalization of occlusive brachiocephalic vein through the EJV at a university-affiliated hospital between January 2017 and January 2019. The demographic information and clinical outcome data of the patients were collected and analyzed.
A total of 16 hemodialysis patients who received right brachiocephalic vein sharp recanalization through the EJV were analyzed. The technical success rate was 100%. Twelve patients (12/16, 75%), whose EJV-subclavian vein angle (E-S angle) was 60-80 degrees, were successfully recanalized on the first attempt. With the other 4 patients (4/16, 25%), whose E-S angle approached 90 degrees, the brachiocephalic vein was recanalized on the second attempt by elevating the ipsilateral shoulder, therefore decreasing the E-S angle to align the course of the EJV with the brachiocephalic vein. Three minor complications were recorded, including 1 patient with blood continuously oozing from the EJV at the puncture site and 2 patients with mild chest pain. After an average of 10 months of follow-up, the clinical patent rate was 81.25% with no procedure-related complications reported.
Sharp recanalization through the EJV could be an effective and safe alternative treatment for right brachiocephalic vein occlusion in hemodialysis patients if performed by an experienced practitioner. Measuring the angle formed by the EJV and the subclavian vein might provide helpful information for selecting patients.
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