| The rice planting area in china is about 30 million hm2, which make up nearly30 percent of national grain planting, and also capture almost 20 percent of the world's rice planting. Fertilization in paddy field is an effective way to improve the per unit yield,stabilize the total harvest, increase the efficiency of rice production, and also an inevitable choice to ensure food security, achieve agricultural production, and to increase the farmers' income as well. Domestic and foreign have been doing long-term fertilizer experiments,and the results showed that the sustained, reasonably and effectively fertilization would have a positive impact on soil fertility, in the same time, the unit yield showed an increasing trend. Different fertilization methods are one of the important reasons that affect the utilization rate of fertilizer, and the supply position of root nutrients significantly affects the growth of roots and the absorption of nutrients. fertilizing on the surface of the field is a traditional way, which causing a mass of loss on fertilizer, low utilization rate of nutrient,and a poor effect of it. Mechanical fertilization has a stable depth and quantity, prosperity growth of rice.At present, one of the main reasons for the low utilization rate of fertilizer in rice field is the long distance between nutrients and the rice roots, which made the nutrient move a far distance, and lower the efficiency, in other words,the existing fertilizing device can hardly cast the fertilizer nearby rice roots. In addition, traditional rice ditching and fertilizing device always have fertilizer conveying pipes, which are easily been adhered by the solid fertilizer and lead to blockage of the pipeline. These devices also have the disadvantages of complicated structure, difficult maintenance, and poor stable fertilization.Therefore, synthesized the characteristics of absorption of nutrients in the soil this study proposed a method to fertilize without furrowing nearby the root zone by using the water jet technology, it also designed a jet of liquid fertilizer in rice fertilization, simulated and analysed its cavity structure, optimized design, and determined the different combinationsof working parameter to meet the different needs of fertilization in rice growing seasons in the soil-bin. The specific contents and conclusions are as follows :(1) Study on jet fertilization methods by using water jet technology.On basis of high-pressure water jet cutting and crushing technology and low-pressure water jet cutting technology in animal soft tissue, a preliminary experiment to cut the soil with high-speed and low-pressure water is been tested on the CNC water cutting platform.This test explored some operating parameters of water jet shoot into the soil at a certain depth, analysed the distribution of rice seedling roots at the same time, ascertained the feasibility of water jet technology in rice fertilization.(2) Build the low pressure testbed and design the fertilization architecture.Firstly analysed the structure of the jet, obtained the calculation formulas of jet velocity and flow by analyzing the mathematical relations, then work out the operating parameters of the components of low-pressure testbed. High-pressure water jet system is reference for build of low-pressure jet fertilization test platform, which is mainly consists of water supply system, filtration system, and pressure charging system. Refer to the structura l of high-pressure water tool bit, a fertilizer device including dead lever, gem knife head, fe rtilizer and water mixing chamber, fertilize suction pipe, spray unit and the like is prelimina ry designed.(3) Using Fluent fluid simulation technology to simulate the cavity structure of the fertilizer device, and optimize parameters of the structural.The water jet fertilizer device exists intense energy exchange and turbulent diffusion between water and liquid fertilizer when working, that involves complex problems in many disciplines. Using a conventional analytical method to calculate the characteristics of water flow and liquid fertilizer flow and the structural parameters of the inner cavity will be difficult, so we chose Fluent simulation to analysis different factors of velocity losing rate.Result showed that: the higher of system pressure, the shorter of spray pipe, and the less length of mixing chamber comes with the lower loss of velocity. Radial orthogonal various factors simulation results show that: the rate of losing speed increasing comes with system pressure increases, decreasing comes with inlet diameter increases, and increasing comes with increases of diameter of fertilize suction pipe; the sequence of factors inaffecting the interaction stress is: inlet diameter>outlet diameter>system pressure>fertilize suction pipe diameter.(4) Inquiring the different combinations of working parameter of fertilizer device to meet the different needs of fertilization in rice growing seasons.In the soil rest tank, a repeated orthogonal experiment was made to fertilize liquid nitrogen by one side in different velocities of paddy field tractor; system pressure, inlet diameter, outlet diameter and fertilize suction pipe diameter was selected as four factors;depth of the water jet, amount of per acre fertilizer nitrogen was selected as the two targets of this repeated orthogonal experiment. ascertained the suitable combinations appropriate parameters. Results showed that: as shown in Table 4.6 in Chapter IV, the increasing in running speed of paddy field tractors reduced the working ability of the fertilizer device;when the system pressure stayed at 5Mpa, jet fertilizer device would have a weaker capacity, and treatment group 5 had a relative strong ability to fertilize when it was 10 Mpa,and a stronger synthetical fertilization ability showed up as the pressure rose to 15 Mpa,treatment group 6 can not suck out the liquid nitrogen by its own vacuum. When the paddy field tractors was moving forward at speed of 0.25 m / s, treatment group 2 applied to fertilize the base fertilizer on both sides with two devices, while treatment group 3?4 and 7applied to fertilize the base fertilizer too, but on unilateral side, group5? 8 and 9 applied to fertilize the tillering fertilizer. When the paddy field tractors was moving forward at speed of 0.4m / s, treatment group 1,2,3, and 4 could not meet the requirements on depth for the jet fertilizer device, treatment group 7 could fertilize the base fertilizer with a working tractor; treatment group 5 could meet the unilateral side tillering fertilizer requests,treatment group 9 applied to the amount of tillering fertilizer when using two fertilize device on both sides. When the paddy field tractors was moving forward at speed of 0.4m /s, one fertilizer device could only have a week ability, and treatment group 7 can be appropriate for working with a moving tractor for the base fertilizer fertilizing; treatment group 5 and 9 can be appropriate for the requirements of amount for tillering fertilize. |
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