The Study Of High Arch Precise Fertilization Machinery Based On Maize Leaf Chlorophyll Detection

The mechanized maize intertillage fertilization production technology mainly involves nutrient condition during topdressing stage,topdressing model,supporting operation machinery,variable control technique and so on.According to the characteristics of maize planting agronomy in Huang-Huai-Hai Region,on the basis of diffuse reflectance testing technique for maize leaf chlorophyll,the topdressing model is built by field experiment,and a kind of tri-wheel high arch field operation vehicle and its variable fertilization system are designed.Thus,the study of mechanized maize intertillage fertilization technology is conducted,which mainly covers the following three aspects:(1)The study of maize leaf chlorophyll detection technology is carried out using diffuse reflection spectroscopy technique.The construction of detection system mainly includes the design of light path,circuit,software and so on.The light path design mainly uses light source dispersion stereo setting and sensor-in-the-center methods to realize the purification of diffuse reflection light;the detection circuit design mainly uses constant current source circuit and photoelectric conversion circuit to deliver stable and reliable light intensity data calculation.Then on this basis,the reflective maize leaf chlorophyll detector is developed.And the detection experiment and calibration of potted maize and field maize chlorophyll are conducted respectively.For two consecutive years,the reflective maize leaf chlorophyll detector,SPAD chlorophyll meter and Greenseeker canopy analyzer are used to conduct chlorophyll detection contrast test,which shows that three-wavelength diffuse reflection is an effective and feasible method for maize leaf chlorophyll content detection.The average determination coefficient of measured value(KM value)and the truth value of chlorophyll content derived by this method is 0.95.As for the leaf chlorophyll of certain maize varieties,the detection precision by this method is higher than that of SPAD chlorophyll meter and Greenseeker canopy analyzer.(2)According to fertilizer effect function,using maize leaf chlorophyll detector as the detection tool,the linear intertillage topdressing model for maize is built.In topdressing model experiment,the Lianchuang 808 maize variety is chose as the object.According to relative soil NO3—N content and recommended summer maize base fertilization and topdressing solution for target yield,testing solutions for maize planting,base fertilization and topdressing are designed.Using maize leaf chlorophyll detector as the detection tool,according to the KM value of maize leaf and corresponding optimumtopdressing amount during topdressing stage,linear fitting and polynomial fitting are completed to generate the KM value based topdressing solution for test plot.Besides,the linear top dressing model for Lianchuang 808 is built with determination coefficient of 0.9206,which is intended for guiding intertillage topdressing of maize,providing fertilization plan for high-clearance intertillage fertilization operation vehicle and eventually realizing variable rate fertilization for different rows of maize.(3)According to the agronomic requirements for mechanized operation of maize topdressing operation,a kind of straddle-rowtri-wheel high arch field operation vehicle is developed and the supporting variable fertilization system is designed.The fertilization system consists of hydraulic drive system,electronic speed control system,and mechanical fertilization device and so on.The intertillage fertilizer applicator is capable of 6 rows' fertilization at once.By simulation analysis of its opener lift,the rear wheel track adjustment(1.8~2.4 m)requirement of the operation vehicle is met;by multi-way valve,the rear wheel track adjustment in hydraulic system and its features like machinery lifting and ejecting fertilizer by drive hydraulic motor is realized;the closed-loop control is adopted by electronic speed control system;by utilizing the setting fertilization parameters and the tested speed signal,and the digital incremental PID algorithm,the proportional flow valve opening in hydraulic system is adjusted to control motor speed and realize variable rate fertilization.With the combination of trial-and-error method and critical proportioning method,the PID parameter setting test is conducted;the motor speed and the relationship between the fertilizer sowing amount and the motor speed under different fertilizer tank lengths are calibrated.Through test and research,the relationship between fertilizer amount and motor speed under 10 mm and 20 mm opening of fertilizer tank,the proportionality coefficient(1.2),the integral coefficient(0.04)and the differential coefficient(0.2)of PID parameter are defined;according to the state standards of dressing cultivator,the tilling depth consistency,fertilizer amount consistency and total fertilizer amount stability experiments against high clearance topdressing machine are conducted.By field experiment,all of the coefficients of variation of tilling depth consistency are verified to be less than 18%.The coefficients of variation of fertilizer amount in each row are less than 8%,and the average variation coefficients of total fertilizer amount stability is 2.01%,which all meet the national standard requirements and the fertilizer amount requirement of 150-750 kg/hm2.In order to further promote the modular design of precise maize topdressing control,the Hall sensor is replaced by GPS signal speed to extract the speed of operation vehicle.And the GPS speed and Hall sensor based comparative test of fertilizer amount by operation vehicle is conducted.In conclusion,according to the agronomic characteristics of summer maize planting in Huang-Huai-Hai region,this thesis realizes the maize chlorophyll detection in reflection method and builds the corresponding topdressing model on the basis of field experiment.At the same time,the variable fertilization system on tri-wheel high arch field operation vehicle is designed,and the field operation experiment is carried out.The primary mechanized maize topdressing technology system is constructed,which provides technical foundation for mechanized maize field management in Huang-Huai-Hai area.There are still deficiencies in this thesis in terms of topdressing model,PID control algorithm,GPS velocity filtering and some other aspects.Therefore,further experiments and studies are needed to be conducted.