Research On Variable Rate Fertilization Control Technology In Precision Agriculture

As one of the kernel techniques in the precision agriculture, the variable rate fertilization is a new technical architecture and production mode. It can input fertilizer as necessary according to the soil fertility and crop demands in the certain field. The variable rate fertilization is developed for improving fertilizer utilization efficiency, reducing the damage of ecological environment caused by unreasonable fertilization and realizing agricultural sustainable development. Foreign variable rate fertilization has formed a comparatively mature technique system as a result of the earlier study and has developed some variable rate fertilization application systems for practical application. In recent years, the domestic research on the variable rate fertilization technique has made some achievements, however, the application systems of variable rate fertilization were developed slowly. Developing the variable rate fertilization system which is applicable to the actual needs and low cost in China is the subject worth being studied. Meanwhile, it is of great significance to build the related technique system and technological framework.This paper mainly focuses on the research of the fluted roller fertilizer distrib-utor. According to the characteristics of the model, we analyze the relationship between the fertilizer application rate of the fluted roller and the structure pa-rameters. We conclude two variable fertilization control strategies based on the fluted roller fertilizer distributor:adjusting the active feed-roll length of the fluted roller and adjusting the rotating speed ratio between the fluted roller and ground wheel. The pneumatic seeder (Maxima 2) produced by Kuhn Company and the air cart seeder (model 1910) produced by John Deere Company are chose as the experimental mechanical platforms to realize the construction of variable rate fer-tilization application system based on the two control strategies. We expounds the general methods of designing the variable rate fertilization systems with the two variable rate fertilization control strategies, respectively. According to the fertilization mechanical structure and experimental data, we realize the hardware construction of the variable rate fertilization system in the two platforms by in-ferring the variable rate fertilization relation model and designing the precisely control for fertilization actuator.This paper utilizes the Android and ArcGIS framework to construct the soft-ware system of variable rate fertilization. A variable rate fertilization system based on prescription map is built for the embedded vehicle control terminal which is used to achieve the visualization of working flow and working state of variable rate fertilization. In order to realize the offline recognition of spatial grid, two spa-tial grid offline recognition schemes are proposed is this paper. A multi-layered nesting method is put forward for grid recognition, which solves the low efficiency of grid recognition. The ZigBee technology is adopted to achieve the wireless communication between the embedded vehicle control terminal and the variable rate fertilization actuator, avoiding the wiring inconvenient on the agricultural machinery.The generation of the variable rate fertilization prescription map based on the spatial variability data is studied in this paper. The soil nutrient data is obtained by soil sampling and testing. The methods of Shapiro-Wilk test, Q-Q graph and histogram are used to conduct the normal distribution test of the collected soil nutrient data. The spatial distribution map of soil nutrient is generated by spa-tial interpolation based on analyzing the spatial correlation and variation of the soil. The yield data is collected by using our developed yield data collector. A spatial distribution map of yield is generated by interpolation method after error processing. The fertilization model of soil nutrient-target yield is used to make the fertilizer prescription map for the field grid cells. For the constructed vari-able rate fertilization system based on adjusting the active feed-roll length of the fluted roller, we evaluate the fertilization uniformity performance and analyze the response time of variable rate adjustment. The experiment results indicate that our system has good uniformity fertilization performance and the response speed of variable rate adjustment meets the design requirement. For the variable rate fertilization system based on adjusting the rotating speed ratio between the fluted roller and ground wheel, we conduct the fertilizer calibration experiment and ana-lyze the control error caused by the variable rate controller, the result shows that the system can satisfy the demand of variable rate fertilization application.