| Precision agriculture is the focus of agricultural science research in recent years.Precision fertilization is an important part of precision agriculture,which mainly includes variable rate fertilization automatic control technology and mechanical equipment.Variable rate fertilization technology has great practical significance for improving fertilizer utilization rate,improving soil environmental quality,reducing environmental pollution caused by chemical fertilizer and increasing crop yield.At present,the precision fertilization equipment developed and applied at home and abroad is mainly for field fertilization operation,and the research on variable rate fertilization device suitable for hilly and mountainous orchards is less,which can not take into account the quantitative fertilization of a small amount of nitrogen fertilizer and a large amount of organic compound fertilizer in orchards at the same time,which affects the promotion and application of precision fertilization in Hilly and mountainous fruit industry.In this paper,according to the actual production needs,a variable rate fertilization device combining ditch fertilization and sprinkling fertilization was developed.The device can not only adapt to the application of quantitative fertilizer discharge in hilly orchards,but also meet the requirements of quantitative ditch fertilization and quantitative sprinkling fertilization in hilly orchards.The main research work of this paper is as follows:(1)By consulting the domestic and foreign literatures about the quantitative fertilization device and orchard fertilization method,investigating the current situation of fertilization and the demand of fertilization equipment in hilly orchards in China,the overall structure,technology and overall objectives of the fertilization device were analyzed and determined.The variable rate fertilization device can realize two modes of variable rate fertilization.In the orchard furrow fertilization mode in Hilly and mountainous areas,the external grooved wheel structure with adjustable notch volume and grooved wheel speed is adopted;in the sprinkling fertilization mode,the air blowing structure is adopted for quantitative sprinkling of fertilizer.The variable rate fertilization device can adjust the fertilization speed of the device according to the target fertilization amount and vehicle speed,so as to achieve the goal of quantitative and uniform fertilization.(2)The structure design and fertilization performance of variable rate fertilizer discharge device for furrow application were studied.Combined with the actual production demand of hilly orchard,the structure of the device was designed.For granular fertilizer,the volume of fertilizer discharged by external groove wheel was designed as a continuous variable structure,and the theoretical fertilizer discharge and the maximum working space were designed and calculated.The theoretical maximum volume of fertilizer discharge in a circle is 534.07 According to the target amount of fertilizer and vehicle speed,the control system can select the volume of single circle fertilizer from 0 to 534.07cm3;the maximum volume of single circle fertilizer is532.28cm3,the error is 0.34%,the maximum error between the control volume and the actual measurement volume is 0.67% in other cases;the relationship between the rotating speed of Geneva and the filling rate is tested When the rotation speed of fertilizer wheel is 30-120 r / min,the filling rate shows a stable linear relationship,and the correlation coefficient is 0.9995,which has a good effect of fertilizer discharge control;the relationship between vehicle speed and fertilizer discharge speed is established.The indoor simulation test shows that when the vehicle speed is 0.5 km / h,2.0 km / h and 4.5 km / h,the maximum error between the actual fertilizer discharge and the theoretical fertilizer discharge is 3.8%.(3)The structure and performance of variable rate fertilizer discharging device were studied.Based on the principle of air blowing,the mechanical and kinematic analysis of granular fertilizer movement in the fertilizer discharge pipe,pneumatic channel and air was carried out,and the relationship between the initial velocity of fertilizer discharge,the physical characteristics of fertilizer,the wind speed and air volume at the outlet,the air parameters and the fertilizer dispersion distance was established.The radius of the far end is 3.0 m,the radius of the near end is.8 m,the swing angle is 600,the zhf283502 double leaf centrifugal fan is selected as the wind source,the wind speed is 6.5 m / s,the test shows that when the vehicle and the fertilizer throwing mouth are static,the actual fertilizer throwing area is rectangular,the width and length are 0.35 m and 2.2 m respectively,which is suitable for ridge planting of sweet potato and cabbage During the movement,the actual fertilizing area is a circular area with a radius of 2.85 m at the far end and 0.82 M at the near end,and the central angle of the circle is 60 degrees.Under the condition of a certain amount of fertilizer,the uniformity of throwing fertilizer is related to the swing frequency,and the swing frequency can be controlled according to the actual fertilizer demand.(4)The simulation experiment was carried out in greenhouse.The accuracy and stability of the device were verified.When the vehicle speed was 0.5 km / h,2.0 km / h and 4.5 km / h,the maximum error between the target fertilizer discharge and the actual fertilizer discharge was 7.4%.When the fertilizer requirement of a single fruit tree in orchard is different,the fertilization prescription diagram can be imported into the system to realize variable fertilization according to demand;the coefficient of variation and broken strip rate under the condition of continuous quantitative furrow fertilization are tested.When the vehicle speed is 0.5 km / h,2.0 km / h and 4.5 km / h,the coefficient of variation and broken strip rate of the device meet the requirements of the industry standard of less than 7.8% and 2% respectively In static state,the best width of fertilizer spreading device is 2.08 m,and the maximum coefficient of variation of fertilizer spreading operation is 11.81%;in dynamic state,the coefficient of variation increases with the increase of the rotation speed of the fertilizer discharging wheel under the same swing frequency;in the same rotation speed of the fertilizer discharging wheel,the coefficient of variation decreases with the increase of the swing frequency;in dynamic state,the coefficient of variation increases with the increase of the rotation speed of the fertilizer discharging wheel When the rotation speed is 30 R / min,the coefficient of variation is less than 40% when the swing frequency is greater than or equal to 0.5r/s;when the rotation speed of the fertilizer wheel is 60 R / min,the coefficient of variation is less than 40% when the swing frequency is greater than or equal to 0.7r/s;when the rotation speed of the fertilizer wheel is 90 r / min,the coefficient of variation is less than 40% when the swing frequency is greater than or equal to 0.9r/s;when the rotation speed of the fertilizer wheel is 120 r / min,the coefficient of variation is reduced by the swing frequency of 0.5-1.0r/s More than 40%.According to the test results,the regulation rules were optimized,and the modified regulation rules were used to verify the uniformity of fertilizer application.The maximum coefficient of variation was 23.24%,which was in line with the provisions of the agricultural industry standard of the people’s Republic of China(nyt1003-2006)that the coefficient of variation should be less than 40%.This paper provides an effective solution to the problem that the device can not accurately quantify and adapt to different fertilization methods in the process of orchard mechanical fertilization in China,and provides a reference for the development of orchard precision fertilization machinery. |
PDF Full Text Request