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Design And Development Of A Handheld Instrument In Nitrogen Nutrition Diagnostic For Plant Leaf

Posted on:2018-09-10Degree:MasterType:Thesis
Country:ChinaCandidate:M C LiuFull Text:PDF
GTID:2310330536971340Subject:Agricultural Electrification and Automation
Abstract/Summary:PDF Full Text Request
The optical properties of plant leaves are closely related to their chemical components,it can be used to detect the nitrogen nutrition status of plants by detecting the optical parameters of the leaves which are closely related to the nitrogen content.The SPAD-502 chlorophyll meter which based on the principle of spectrum absorption was generally used when the situation of needing for real-time,rapid and quantitative measurement leaves nitrogen contents.Since the instrument was used to measure the chlorophyll content of the leaves with higher or lower chlorophyll content,as the result of the measurement value was low or high.In order to solve this problem,we need to use the NDVI(Normalized Difference Vegetation Index)value which based on the principle of spectral reflectance,and combined the two parameters to reflect the nitrogen nutrition status of the plant.Both of the two instruments do not have GPS positioning function and data storage function,It's been a long haul because you can only copy them with your hands and write down them in a paper after these meters display,which caused the follow-up work great inconvenience,and more bulky to carry these two kinds of instruments.this instrument was designed in this paper which based on the shortcomings of the above equipments,and finally developed a handhold measuring instrument that can measure both the chlorophyll relative content and NDVI at the same time by using of plant physiology optoelectronic principle,combining with sensors and precision instrument design technology,optimizing core optoelectronic components,designing of electronic circuits,projecting instrument shell,making PCB board,not only completed the whole instrument building and commissioning,but also testing and verify the instrument's accuracy through arrange experiment.Meanwhile the instrument also has the function of GPS positioning and data storage.The power of the whole system was supplied by lithium battery.This instrument is convenient and portable.The main contents and results of this study were as follows:Firstly,the relationship between the spectra and plant nitrogen nutrition was introduced,got characteristic wavelength 660 nm is more suitable than 650 nm to measure accurately the status of plant nitrogen nutrition.Expounded the origin of the chlorophyll content calculation formula in theory,and explained the reason why putting 940 nm as the reference wavelength which based on the basis of Bill's law.Similarly,the measurement principle of NDVI was also introduced.Finally,this instrument established 660 nm and 940 nm,660nm and 780 nm as the characteristic wavelengths to detect the relative content of chlorophyll and NDVI.Designed the whole system scheme and the shell appearance of the instrument which aiming at achieving functions of the instrument,established by the ATmega2560 microcontroller as the core,which the hardware circuit system were composed of constant current source light emitting circuit,photoelectric conversion circuit,AD circuit,LCD display circuit,GPS circuit,clock circuit,memory circuit,power supply circuit and alarm circuit etc.effectively avoided the design complexity which caused by optical fiber coupling by optimizing selecting the dual band light emitting tube,usefully reduced the received light loss through selecting a large area photovoltaic cell,and increased the measurement accuracy.Built the constant current light emitting circuit and the photoelectric conversion circuit by means of using bread boards,the optical properties of the light emitting devices were tested.By testing the optical characteristics of the light emitting device which under different light intensities of the red and infrared lights,the relationship were linear,and the linear imitation R2 were 0.999 and 0.997.Secondly,the instrument has been completed the PCB production.The meter has been welded electronic components.We also have finished the programming and system debugging.PCB was often found problems in debugging situation.Programming platform was based on Arduino IDE,the program was written by C language,through using of interrupt nesting and sub-module call design.We not only debugged the main measurement functions,but also tested GPS positioning and micro SD card Storage function.As the experiment shown,the various functions of the test equipment are normal.Finally,the measuring accuracy of the instrument has been verified,which was divided into two parts: the accuracy of the chlorophyll relative content verification and the precision of NDVI validation.After measuring different chlorophyll of plants relative values,compared with classical color value and make a correlation.It shown that corn and holly's chlorophyll a,b and chlorophyll total content were highly positive correlation,R2 values were 0.759,0.75 and 0.77,0.8055,0.771 and 0.7964(p <0.01).In the measurement of high chlorophyll content of the leaves,made a correlation analysis between this instrument and the actual content of chlorophyll.The result was shown that R2 value was 0.7964.bulid a correlation analysis between SPAD-502 and the actual content of chlorophyll.The result was shown that R2 value was 0.7716.It's easy to find that this instrument was better than SPAD-502 in measuring.Through measuring the total nitrogen of Chemical determination of the maize leaves that the two kinds of instruments measured,build the correlation analyses respectively with this instrument measured NDVI value and Greenseeker measured NDVI value.Got their R2 were 0.599 and 0.4021.The results showed that the measured effect of this instrument was better than GreenSeeker.The research of this paper provided a basis for diagnosing the nitrogen nutrition status of plants,and had a positive effect on the diagnosis of nitrogen fertilizer,on the quantifying of nitrogen level and on the improving of nitrogen use efficiency.
Keywords/Search Tags:plant, nitrogen nutrition, photoelectric detection, precision agriculture, diagnosis
PDF Full Text Request
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