Evaluation of Variable Rate Technology for Fertilizer Application in Permanent Pastures

This paper describes the field tests carried out to evaluate the new Vicon RS-EDW centrifugal fertilizer spreader, to be used in Precision Agriculture. The results of initial dynamic calibration tests showed a significant and systematic difference between the application rates of the two discs （about 20%）. This difference had to be corrected by the manufacturer that carried out the necessary changes to the electric actuators. The fertilizer spreader had good distribution homogeneity, considering different working velocities and different positions in the parcel. The pattern distribution curve for 18% super phosphate fertilizer led to an effective working width of 28 meters, with a coefficient of variation of 15%. The longitudinal test, under experimental working conditions led to a machine delay time of 6-7 seconds. The results show an actual fertilization application density between 74%-90% of that determined for each location. These results confirm that the spreader can be used to spread fertilizer differentially in the field.

Approach for improving precision of regression analysis of single-replication fertilization experiments in rice

The field experiment designs with single replication were frequently used for factorial experiments in which the numbers of field plots were limited, but the experimental error was difficult to be estimated. To study a new statistical method for improving precision of regression analysis of such experiments in rice, 84 fertilizer experiments were conducted in 15 provinces of China, including Zhejiang, Jiangsu, Anhui, Hunan, Sichuan, Heilongjiang, etc. Three factors with 14 treatments (N: 0—225kg/ha, P: 0 —112. 5kg/ha, K: 0—150kg/ha) and two replications were employed using approaching optimun design. There were 2352 (84×14×2=2352) Yield deviations (d) between the individual treatment yields and its arithmetic mean. The results indicated that:

Structure optimization of cam executive component and analysis of precisely applying deep-fertilization liquid fertilizer

Since there are some problems in the previous cam of deep-fertilization liquid fertilizer applicator,such as poor precision and low-fertilization performance,a method of the contour line of a cam was proposed based on Matlab GUI development platform.Bernoulli’equation between the liquid fertilizer and the pressure valve of the fertilizer-spraying needle was founded.Moreover,the motion angles of a rise travel and return travel were corrected and the corresponding parameters of the contour line of the cam were obtained.Equations of cam moving from rise travel to return travel were derived according to the simple harmonic motion.In addition,3D model of cam was established by applying the Pro/E software and the rationality of the cam design was verified.The static analysis of the cam was carried out under working conditions and the corresponding dynamics analysis was performed based on D’Alembert’s principle.And then relationships between the binding force and the drag torque were obtained.A bench test indicates that when the pressure of a hydraulic pump is 0.5 MPa and the velocity of a output shaft is 50 r/min,the average consumption of the fertilizer is 19.7 mL for each measurement,which meets the corresponding agronomic requirement,i.e.20 mL.When the rotation angle of the cam is 8.6°and the rise displacement of a plunger is 0.84 mm,the mouth of the fertilizer-spraying needle sprayed liquid fertilizer as soon as it got into the soil and stopped spraying as soon as it got out of the soil.The results show that the designed contour line of the cam meets the requirement,that is,the mouth of the fertilizer-spraying needle should spray liquid fertilizer as soon as it gets into the soil and stop spraying as soon as it gets out of the soil,which meets the agronomic requirements,that is,fertilizer should be sprayed deeply and precisely.And this study lays a theoretical foundation for designing the cam of intermittent type distributor and provides relevant parameters.

Structural design and parameter determination for fluted-roller fertilizer applicator

The instability of the motion layer of fertilizer particle influences the precision and the accuracy of the amount of fertilizer application in the working process of fluted-roller fertilizer applicator.The characteristics of the motion layer were investigated,and a systematic scheme was proposed for designing the structures of fertilizer-filling cavity,fertilizer-filling surface and fertilizer-delivery cavity.The key parameters of the structure were studied by discrete element method.It was figured out that to ensure the smooth operation of fertilizer applicator,the fertilizer-filling angle was 105°,fertilizer-contact angle should be large than 100°,and the fertilizer-resistance angle should be smaller than 35°.Moreover,the stability of fertilizer motion morphology was investigated to verify the design.The results showed that when the roll rotational speed was larger than 120 deg/s,compared with the conventional design the CV of the amount of fertilizer application was reduced from 1.5%-3.5%to 0.5%-1.0%,and the accuracy of the fertilizer discharge was improved with the square of the correlation coefficient between the amount of fertilizer application and the roll rotational speed was larger than 0.999.It was deduced from the results that the precision and accuracy of the amount of fertilizer application are improved via eliminating the driving layer and enhancing the stable filling and conveying of the forced layer.

Design and experiment of centralized pneumatic deep precision fertilization device for rice transplanter

To improve the precision of deep fertilization of paddy fields,a six-row centralized pneumatic deep precision fertilization device for a rice transplanter was designed.This device included a spiral fertilizer distribution system,centralized pneumatic fertilizer delivery system,an opener system,and a fertilization control system.The centralized airflow distribution method was used in the fertilizer delivery system to ensure that the airflow in each fertilizer pipe was evenly distributed.The rotational speeds of the power take-off(PTO)and fertilizer shaft were measured synchronously using photoelectric sensors and matched proportionately in real-time using PID closed-loop control algorithms to achieve precise fertilization rates at each working speed of the rice transplanter.There were two key considerations in the design of the control system to ensure precise fertilization.Firstly,a photoelectric sensor was used to measure the speed of the PTO;the high rotational speed of the PTO could provide a high signal frequency and improve the precision of the measurement of the transplanter’s working speed.Secondly,the fertilizer shaft speed measurement subprogram was set to sleep for a short period to reduce the vibration caused by the engine.During the tests of pneumatic fertilizer delivery system,single-factor tests on airflow distribution methods were conducted.The results showed that the coefficient of variation of the airflow speed for the centralized airflow distribution method was 1.67%,which was the least among the coefficients of the three distribution methods.In the bench tests,the rotational speeds of the fertilizer shaft were set at 10 r/min,20 r/min,30 r/min,and 40 r/min.The maximum coefficient of variation of the fertilization consistency in different rows was 1.49%at the rotational speed of 20 r/min.The maximum coefficient of variation of the fertilization stability was 2.86%at the rotational speed of 40 r/min,while the average fertilizer amount per lap for each distributor was 26.25 g/r.The results of the dynamic fertilization tests showed that the maximum relative error of the fertilizer distribution amount was 2.00%when the target fertilizer rates were 20,30,and 40 kg/667 m2.The results of the field tests showed that the average relative error of the fertilization amount was 3.53%,which satisfies the design standard.This research provides a reference for optimizing pneumatic fertilizer delivery systems and improving fertilization control systems and other pneumatic precision fertilizer application devices.

Design and experiment of vertical pneumatic fertilization system with spiral Geneva mechanism

In the traditional fertilization method,a large amount of fertilizer is applied,which causes congestion easily.It is not conducive to the sustainable development of agriculture.In this work,a vertical pneumatic fertilization system with a spiral Geneva mechanism was designed according to the operational requirements of variable-rate and smooth fertilization.The uniformity in discharging fertilizer with different spiral angles was simulated and analyzed by extended discrete element method(EDEM)based simulation software,from where the spiral angle of the fertilizer discharge wheel was determined to be 45°.The fertilization system includes a fertilizer apparatus with a spiral Geneva mechanism,whose optimal performance parameters were obtained from the bench experiment.The accuracy and uniformity of the fertilizer application system were taken as the evaluation indicators.The linear relationships of the discharged amount of fertilizer with the rotational speed and the opening of the fertilizer discharging wheel were verified by both static blowing fertilization and field experiments.The static blowing experimental results show that the discharged amount of fertilizer has a high linear correlation and accuracy with both the opening and rotational speed,and the highest correlation occurs with the rotational speed.The rotational speed and opening have significant effects on the discharged amount of fertilizer and the average coefficient of variation.The effect of the rotational speed was the most significant.According to the model obtained by multiple regression fittings,the optimal parameters were determined when the average coefficient of variation was small,the rotational speed was 15.9 r/min and the opening was 34.4 mm.Therefore,the purpose of precise fertilization can be achieved by adjusting the opening or rotational speed in a way to get the exact amount of fertilizer discharged as required by the corresponding crops.The field experiment showed that the variation coefficient of each fertilizer discharged decreases first and then increases with an increasing opening under different rotational speeds,which is consistent with the theoretical value.When the opening was 40 mm or 50 mm,the variation coefficient reached the minimum value,which is far less than the qualified index of 7.8%.In the static blowing experiment and the dynamic field experiment,the stability of the fertilizer discharging device can be significantly enhanced with the utilization of the pneumatic conveying fertilizer.This study can provide a theoretical reference for parameter selection and optimization of vertical spiral fertilization systems.

Design of variable-rate liquid fertilization control system and its stability analysis

Variable-rate technology(VRT)has been paid more attentions by farmers in an attempt to match inputs to local growing conditions efficiently.Farmers in every country are highly encouraged to adopt this practice rather than uniform-rate application(URA).However,the standard methods and design used to quantify application accuracy for VRT remain lacking.Therefore,a variable-rate liquid fertilization control system was designed to meet accurate fertilization demand.The designed control system could enable the real-time proportion and mixture of three kinds of liquid fertilizers,namely,N,P and K,in accordance with decision support subsystem.The task controller reads related information and sends such data to the control system,which is responsible for fertilization operation.The controller could realize liquid fertilizer adjusting through the electromagnetic flow control valves.A high-precision flow meter could measure the fertilization amount,which is sent as feedback to the controller to form a closed-loop control system based on the improved proportional-integral-derivative(PID)control algorithm that could enhance the stability and accuracy of precision variable-rate liquid fertilization control systems.Comparisons between the actual and planned application rates indicated good performance for both static and field experimental trials.Mathematical models and transfer functions for some functional modules were then constructed by classical theories to derive a system characteristic equation.To verify the static and dynamic performances,the control system was simulated using the Simulink module on Matlab.Results showed that the variable-rate fertilization was in accordance with the planned data and that the signal trace effect was good.The error was less than 5%for fertilization amount and fertilizer proportion,respectively,and the control response time was 6 s.

Development of the peanut precision fertilization control system based on threshold velocity algorithm

In view of the fact that the current ground wheel velocimetry of the peanut precision fertilizer control system cannot solve the phenomenon of ground wheel slippage,and signal interference and delay loss cannot be excluded by BeiDou positioning velocimetry,a set of peanut precision fertilizer control system was designed based on the threshold speed algorithm.The system used STM32F103ZET6 microcontroller as the main controller,and touch screen for setting the operating parameters such as operating width,fertilizer type,and fertilizer application amount.The threshold speed algorithm combined with BeiDou and ground wheel velocimetry was adopted to obtain the forward speed of the tractor and adjust the speed of the DC drive motor of the fertilizer applicator in real time to achieve precise fertilizer application.First,through the threshold speed algorithm test,the optimal value of the length N of the ground wheel speed measurement queue was determined as 3,and the threshold of the speed variation coefficient was set to 4.6%.Then,the response performance of the threshold speed algorithm was verified by comparative test with different fertilization amounts(40 kg/hm^(2),50 kg/hm^(2),60 kg/hm^(2),70 kg/hm^(2))under two speed acquisition methods of ground wheel speed measurement and threshold speed algorithm(combination of Beidou single-point speed and ground wheel speed measurement)in different operation speeds(3 km/h,4 km/h,5 km/h).The response performance test results showed that the average value of the velocimetry delay distance of the BeiDou single-point positioning velocimetry method was 0.58 m,while the average value of that with the threshold velocity algorithm was 0.27 m,which decreased by 0.31 m and indicated more accurate with the threshold velocity algorithm.The field comparison test for fertilizer application performance turned out an over 96.08%accuracy rate of fertilizer discharge by applied with the threshold speed algorithm,which effectively avoided the inaccurate fertilizer application caused by wheel slippage and raised the accuracy of fertilizer discharge by at least 1.2%compared with that of using the ground wheel velocimetry alone.The results showed that the threshold speed algorithm can meet the requirements of precise fertilizer application.