| Precision fertilization is a symbol technology for precision agriculture. Taking the precision fertilization in flue-cured tobacco cultivation as the research object, this paper developed some key technologies in different topography conditions, which included soil sampling, establishment of fertilization indicators system, the site specific nutrient management under the mode of diversified operation, precision fertilization management in scale agriculture, and the design of the variable rate fertilizer applicator machinery. It can provide scientific basis for the application of precision agriculture technology. The main conclusions were showed as follows:1. The nugget effect of soil nutrients and pH is for the strong to moderate. The structural Variation is the main source of variation, which meet the basic conditions analysis of statistics and interpolation and is suitable for precise nutrient management. The order of the effective range of4kinds of terrain is for pH value> organic matter> n> P> k, which is consistent with the rule for P, K excess investment. The same soil test index in different terrain conditions is not exactly the same for data distribution and the best fitting model. The data distribution and the best fitting model is not the same for the same index the same place in2010and2013. Because temporal stability of the model is poor, which limit its ability to guide the application of fertilizer, so it needs re-sampling when time and space change.2. Based on the Cochran formula, when the confidence level was90%and the permissible error was15%, the soil samples can meet the demands of fertilizer recommendations which represented tobacco acreage of0.73hm2,1.01～1.56hm2, and1.92hm2in gentle slope, plateau and plain fields, respectively. By using geo-statistical analysis, the maximum intervals of grid sampling for the3topographies that gentle slope, plateau and plain fields were58.2m,134.4～177.5m,234.0m, respectively.3. The main problems in nutrient absorption and dry matter accumulation of the flue-cured tobacco in yellow soil included that:the uptake of P and K nutrients before the fast growing period was lower (i.e.,4%and4%), the N absorption during mature period was higher (35.5%), and dry matter accumulation was later than that of high quality flue-cured tobacco. The demands of tobacco leaf per100kilograms for N, P2O5, and K2O were4.51kg,0.29kg, and5.31kg, respectively. The time of N, P and K nutrient absorption mainly concentrated on40～80d; the relatively low absorption rates of P and K (6.1%,3.7%) were the main problems before fast growing stage for paddy soil. The nutrient needs of N, P2O5, K2O for tobacco were4.25kg,0.41kg, and6.29kg per one hundred kilograms tobacco, respectively. Household survey showed that:nitrogen, phosphorus, potassium fertilizer is higher than the growth of flue-cured tobacco demand and lack of organic manure. The N、P2O5、K2O had surplus for35.7kg/hm2、103.5kg/hm、169.5kg/hm2, respectively, but SOC showed a deficiency of438.0kg/hm2.4. Based on the field experiment, household survey, the distribution of soil nutrient and nutrient classification literature in North Guizhou province, an index system was set up for tobacco fertilization. Through combining the nutrient conditions of tobacco soils in Zunyi with the index system, it calculated the average recommend nutrient needs of tobacco in Zunyi. That was, the amounts of N、P2O5、K2O as basal fertilizer were recommended as64.58kg/hm2、75.1kg/hm2、157.65kg/hm2, with a formula of10-11-24(N-P2O5-K2O); the additional fertilizers were27.68kg/hm2、0kg/hm2、55.35kg/hm2, with a formula of15-0-30(N-P2O5-K2O).5. On condition of diversified management, the basic steps of soil nutrient precise management and partition were put forward without the support of variable machine equipments, which included soil nutrition interpolation, soil nutrient statistics taking the separate plot as a unit, fertilizer formula recommended according to the fertilizer model, plot nutrient management based on cluster analysis of fertilizer nutrient. With the support of the variable rate fertilization machinery under the condition of the scale operation, the mode of flue-cured tobacco nutrient management can be summarized as "big formula, small adjustment", that is, to use the same fertilizer formula in an area, and to adjust the rate of fertilizer application according to the recommended N nutrient. The recommended nutrient rate can be calculated by the soil nutrient interpolation and be directly executed using the variable fertilizer machinery, which was different from the nutrient management by the artificial fertilization.6. A variable rate fertilizer applicator machine was designed based on the formula fertilization map. It mainly included two components, i.e., fertilizer formula generated module and execution module. The generated module can automatically calculate the recommended fertilizer rate based on soil testing data, map boundary and nutrient fertilization model and then generate digital geospatial formula; The execution module was composed of some core hardware, such as the control terminal combining GPS data acquisition, scientific computing, variable rate fertilization control, and the fertilizer applicator comprising vortex rod, shell, and motor parts; the execution software was responsible for driving GPS, motor, speed sensor, and monitoring each part’s status, and executing the fertilizer formula according to the location information of the fertilizer applicator.7. For diversified management, the application of the steps in gentle slope fields showed that, compare with farmers’conventional fertilizer, N and P fertilizers through the precise nutrient management could be decreased by10.7%,10.3%, the production would be increased by5454.63yuan/hm2, and the net benefit would be increased by5140.9yuan/hm2taking off0.5%of K fertilizer amendment and soil test cost. For the scale operation, the variable rate fertilization management with machinery can play a great effects on the economic and social benefits, such as saving fertilizer input rate4.6%f, narrowing the difference of crop growth caused by variable farmland nutrient management, reducing the coefficient of variation of crop plant agronomic traits29.6%, increasing crop yield and improving the quality of agricultural products by13.05%, and improving production efficiency per unit farmland for4310.65yuan/hm2. |
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