| Abstract: With the development of agricultural modernization, in order to ensure the environmental and economic sustainability, precision agriculture has emerged. The variable rate fertilizing and seeding technology is an important component of the precision agriculture based on field spatial variability. The slope land of the black soil gentle hilly regions of the northeast China cultivated for many years formed their own characteristics, combined with agronomic research and large-scale production of soybean accurate product demand, research work carried out including spatial variability of slope farmland, land three-dimensional topographic mapping technology, variable control hardware systems research and development of variable control software, the traditional soybean planter be modified, soybean variable rate fertilizer application and seeding experiments in fields. The variable rate fertilizing and sowing techniques are explored, which is suitable of black soil hilly areas soybean production. The main contents and results in the following areas:1. Study on the the black soil gentle hilly regions spatial variability of slope land. Using the SPSS Statistics 17.0, MATLAB R2009a, AFS 5.02 software and other tools, elevation, available N, available P of experimental field in the Hongxing Farm were descriptive statistics analysis, normality test, correlation analysis, found that the land elevation and soil available N showed a significant positive correlation. GPS positioning and soil sampling conducted on experimental field in Nenjiang County, available N, P, K, pH, OM were basic statistical analysis, normality test, made a Q-Q probability plots and frequency distribution histograms. The correlation analysis indicated that soil OM and available N was strong positive correlation (r = 0.498, P <0.01), land elevation and soil available N was positively correlated (r = 0.253, P <0.05). Experimental field elevation map, available N, P, K, pH, OM distribution were produced. The results show that slope farmland's elevation in the black soil gentle hilly regions and the distribution of soil available N is correlated, the topography of slope farmland correlate with distribution of soil water and fertilizer.2. Three-dimensional topographic mapping conducted techniques. Through needs analysis that the elevation data of sloping land terrain in the sub-meter accuracy can meet the demand, the choice of the AgGPS 332 receiver which free receive MSAS2 satellite differential signal and achieve sub-meter positioning accuracy. The UTM projection was used for coordinate transformation. The vehicled 3D-terrain measuring system was developed, straight line navigation algorithm was given, a navigation light bar was produced. The software was developed to meet the needs of the field mapping navigation. The wavelet transform was used for 3D-terrain survey data processing, research shows using a db6 wavelet 5 level decomposition denoising for elevation data measured by DGPS continuously was suitable for the 3D-terrain farmland surveying and mapping in black soil hilly area which farmland have the more moderate wavy. Farmland can be a good response to topography features.3. The variable control system's hardware architecture was designed for variable rate fertilizer planter. Select a on-board computer which equipped GPS module was tested for dynamic positioning. Select the U34-0.75 type mechanical impulse stepless speed variator as the main working parts, and modified it for the electronic control. The variables controller was design by using a closed-loop control scheme and the dual H bridge DC motor driver module, using AT89C52 micro-controller as the master chip. Experimental test was conducted and regression curve equation was obtained for electronically controlled CVT transmission ratio and instruction, the linear regression equation between output shaft speed and the return value. The new hardware solution was proposed for variable fertilizing and seeding of precision farming.4. The design of variable control software. The control instruction algorithm and example were studied. Simple methods for accurate variable rate fertilizer control have been proposed that the use of average fertilizer of field and set the variable range, accurate control variable rate fertilizing based on control value of fertilizer prescription map. The real-time fertiling algorithm was analysised. According to the characteristics of the system speed signal, multi-level complex digital filter is designed which can get a better filtering effect for the fast-changing signals and a pulse interference signal. The variable rate fertilizer seeding software for precision agriculture is developed. Software developed using VB6.0 programming language and MSComm serial communication control and MO2.2 geographic information control and Access2000 database. The shape file format is used which is widely form in Prescription map. Software can automatically generate operating records. When sowing machine normal operation, every two seconds record one set of data, real-time display length of operation and operating area since the job beginning. The record showing and operations playback function is designed, which will help users to use record information and production traceability.5. The experiment of variable rate fertilizing and seeding was implemented in the field. Variable rate fertilizer planter was modified and debuged. The transmission ratio of the seeding system was calculated for the actual amount of the check and adjustment of planting. The transmission of fertilizer system was designed that add a electric continuously variable transmission in the planter, the total ratio of fertilizer transmission system can be changed beween 1.89 to 3.77, which can be variable rate fertilization and the quantitative amount of fertilizer can be quickly adjusted. The fertilizer of planter was modified, so that average value of agricultural decision-making fertilizer could be around the median of the planter maximum and minimum fertilizer, to ensure reliable control of variable rate fertilization. According to soybean cultivation agronomic demand and soil nutrient relevance, the elevation data is processed by positive linear related dimensionles, the OM data is processed by negative linear related dimensionles, with the average of the two data as a prescription decision values to produce a mixed fertilizer prescription map to achieve the variable rate fertilization based on field spatial variability. The scope variable is±5% of experiment of field fertilization, fertilizer ranged from 213.75 to 236.25 (kg/hm2). The field experiments show that variable rate fertilizer control system developed easy to use, stable, variable control reliable, have a good effect.
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