Evaluation And Modelling Of Portable Crop Nitrogen Monitoring Instrument

Information agriculture is the advanced development stage of agriculture information industrialization.Information agriculture which bases on collection technology of information,decision support technology and intelligent equipment to carry out quantitative decision and variable investment for agricultural production with executing in accurate position is the production management technical system of modern agriculture.Furthermore,farmland collection technology of information and equipment are basic and sustain of accurate agriculture and important guarantee of realization high efficiency,high yield and high quality agriculture.The inevitable development trend of agriculture will be intelligent,precise digital and internet in future.non-destructive monitoring technique of crop nitrogen nutrition is not only an urgent need for the key technology for accurate diagnosis and dynamic regulation of crop nitrogen nutrition based on spectral information,but also a technology foundation of nitrogen nutrition non-destructive monitoring equipment development in digital agricultural research.A self-developed non-destructive monitoring instrument to measure crop growth information based on crop canopy reflectance spectral is presented from three parts includes structure,operation principal and measure method.This equipment is portable,simple with less cost and low power assumption.Crop nitrogen nutrition and growth information were real-time assessed by crop canopy spectral reflectance values with four special bands acquired by 8 specially designed interference filters in that instrument using the sun as a passive source together with relatively agriculture mathematical model.The performance of photoelectric detection significantly affect the measure accuracy and precision of entire detection system,spectral response is not only the most important parameter in photoelectric detection instrument,but also one of the important bases of the calculation of other parameters.spectral response of battery light and the light pipe includes photocell,different lens,filter,and window mirror or cosine diffuser were investigated by detector spectral response measurement system and which was used to calculate Integral responsivity,then response parameters were used to check the whole photoelectric detection system,and making the output response standard by calibration the entire photoelectric detection system of monitor instrument.The information of wheat canopy spectral reflectance in field experiment was obtained by nitrogen nutrition non-destructive monitoring equipment.The work performance of nitrogen nutrition non-destructive monitoring equipment was elevated by studying the pattern of canopy spectral reflectance under varied nitrogen rates.Results showed that the sequence of canopy reflectance spectrum of four characteristic bands included in the instrument was R810>R546>R710>R660.With increasing nitrogen rates,the spectral reflectance of 810 and 546nm increased and 710 and 660nm decreased,respectively.Reflectance at visible band(546,660 and 710nm)decreased gradually with the increase in soil water content,whereas reflectance in near infrared(810nm)increased.Compared with the same band of Cropscan MSR-16 and Fieldspec Pro FR2500,there was a remarkable difference in spectral reflectance,and variation coefficients of canopy reflectance under different N fertilization levels was smaller integrally.Field experiment involving two wheat varieties and four nitrogen rates were conducted,and the information of wheat canopy spectral reflectance in field experiment was obtained by self-developed portable non-destructive nitrogen nutrition monitoring equipment and field samples and the nitrogen content were also investigated.Then the work performance of portable nitrogen nutrition monitoring instrument was measured and evaluated by analyzing the correlation and relationship between leaf nitrogen content(LNC)and canopy spectral reflectance and vegetation indexs(VI)in wheat.The results showed that portable non-destructive nitrogen nutrition monitoring equipment made a good performance on nitrogen monitoring and field work.The correlations between spectral reflectance in 660,710 and 810nm and LNC were all exceed 0.5(P>0.01);the fitting coefficients between the whole VI and LNC were all exceed 0.7 during different growth stages,and reached the highest in flowering and maturing stage(>0.83).