| Fertilizer amount reduction has been listed as the main content of the action plan of tackling agro-rural pollution in China.In view of the serious nutrients loss,low utilization rate of fertilizer and environment pollution in the process of fertilizer application of winter wheat,mechanized deep placement fertilization can effectively reduce nitrogen volatilization and improve utilization rate.In order to achieve the goal of fertilizer deep application,this paper proposed a method of fertilizer deep placement application in a fixed row based on autonomous navigation technology,studied the key technology of accurate fertilizer application,realized quantitive and accurate fertilizer amount control based on working speed Which provide reference for mechanized fertilization application in narrow row.The main research contents and conclusions are as follows:1.To meet the requirements of mechanized deep fertilizer application for wheat,the effects of pointed furrower and double-disc opener on soil disturbance were analyzed by discrete element simulation method.The micro-movement processes of soil action of the pointed furrower and the double-disc openers were obtained.When the pointed furrower opereted on soil,the soil disturbance was greatly affected by the tine part of the furrower,soil hilling was observed at the connection position of tine and handle.When the double-disc opener operated on soil,due to the rolling action of the disc,the effect of the disc front part on the soil disturbance was effectively reduced,thus reducing the soil congestion.Meanwhile,the rolling action reduces the disturbance effect on the soil layer.The effects of disc diameter,the included angle of two dics and the deflection angle of disc on soil disturbance were analyzed,it was concluded that the selected disc diameter and deflection angle of disc parameters had no significant effects on soil disturbance,the included angle of two dics had significant effect on soil disturbance,when the disc diameter is 350 mm,included angle is 10° and the deflection angle is 25°,the range of soil disturbance was significantly smaller than the other two kinds of disc,the soil backflow mass was greater,which provides reference for the parameters determination of deep fertilizing furrow opener.2.The accuracy of row-following operation was studied for two types of traction navigation system.Motor driven turning navigation system and hydraulic driven turning navigation system were selected to analyse,machine track was measured by single point GNSS receiver and antenna.Row-following accuracy and reverse pick up line accuracy were selected as evaluation indexes,the experiments were conducted to analyse the influences of operation speed,operation condition and navigation system on row-following operation deviation.The results showed that the navigation deviation of the two navigation systems were within ±3cm and had a high repeatability.The deviation of machine row-following operation was stably distributed on both sides of the zero value under forward and reverse condition.The deviation of each row did not accumulate with the increase of the subsequent rows.Under the flat ground condition,the deviation obtained by motor driven turning navigation system was close to the normal distribution,while the deviation distribution regularity obtained by hydraulic driven turning navigation system was relatively poor.With the acceleration of operation speed,the row-following deviation of two navigation systems increased from ±3cm to ±5cm under flat ground conditions.Under field conditions,the deviation obtained by motor driven turning navigation system increased from ±4cm to ±6.5cm,the deviation obtained by hydraulic driven turning navigation system was basically maintained within ±7cm,there is no significant difference with the operating speed.It turns out that hydraulic driven turning navigation system has a good stability and adaptability.3.A precise-rate control system based on PID was developed.Electro-hydraulic proportional valve control hydraulic motor system was developed to realise accurate control of fertilizer feed shaft rotate speed.The simulation was developed to analyse the speed control accuracy and adjust PID parameters,under the static and dynamic conditions,the modification experiments were conducted to verify PID control accuracy.The results illustrated that the biggest rotate speed control error under static and dynamic conditions were 6.5% and 10.2%,respectively.Take fertilizer amount variation coefficient as the optimization index,a openning length of outer-fluted fertilizer apparatus paremeter coordinate match method based on tractor speed and target fertilizer amount was proposed.The regression models of fertilizer amount per revolution,fertilizer amount,the coefficient of variation of fertilizer amount with fertilizer apparatus openning length and rotate speed were established,respectively.A quadratic and cubic equation of rotate speed related to target fertilizer amount,operate speed and openning length was established,the equation was solved by using shengjin formula,the combinations of opening length and rotate speed corresponding to the operation speed and target fertilizer amount were obtained by traversal method.The model was verified under field experiments,the results showed that,besides the the operation speed and target fertilizer group of(3,200),the fertilizer amount deviation was less than 4%,the maximum deviation of motor rotate speed between the measured average value and predicted value was 2.74%,which indicated that the regression model of fertilizer amount per revolution and fertilizer amount has a good fitting accuracy.4.Field mechanized topdressing fertilizer application experiments for wheat were conducted to analyze the performance of precisely row-following deep fertilizer applicator,the influence of deep fertilizer application on grain yield and yield components.The results showed that the whole fertilizer amount deviation was less than 8.92%.The variation coefficient of inter-row fertilizer rate was about 2%,which showed good uniformity of inter-row fertilizer application.The row-following deviation of 5 working widthes were analyzed,the results showed that under the guidance of autonomous navigation system,the row-following deviation of machine was basically within the range of ±5cm.Comparison experiments between the fertilizer deep application of 10 cm and the surface broadcasting application under(10+20)cm wide and narrow row spacing cropping pattern were conducted,the results showed that deep topdressigng fertilizer application can promote the SPAD value and plant height during growing period,which also increased the kernel number per spike,thousand kernel weight of grain and crop yield. |
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