Design and experiment of horizontal pneumatic screw combination adjustable quantitative fertilizer feeding device for granular fertilizer

Abstract: Nutrients including the elements of N, P and K are?beneficial?to the growth and yield of crops. Reducing the application amount of chemical fertilizer and increasing the utilization rate have become the important ways and means of high quality and high efficiency green agriculture. Granular fertilizer has been widely used in agricultural production because of its low fluidity, strong?hygroscopicity and cohesion. Meanwhile, the amount of fertilizer applied depends on the crops, the fertilization application time, and the fertilizer varieties. In order to adjust the requirements of fertilization and precision fertilization, the horizontal pneumatic centralized feeder of fertilizer was developed. The fertilizing device is the core part of the horizontal pneumatic centralized feeder. According to the mechanical and physical properties, and fertilizer requirements of granular fertilizers, the inclined screw-type model-hole and combined fertilizer feeding unit was designed. The main structural parameters of the inclined screw-type model-hole and the fertilizing unit were determined. The bottom width, upper width and depth of model-hole were 12.0 mm, 30.0 mm and 18.0 mm, respectively. The left inclined angle, right inclined angle and number of screw-type model-hole was 24°, 37° and 6, respectively. The helical pitch, helix?angle and length of fertilizer feeding unit were 450 mm, 60° and 40 mm, respectively. The number of fertilizing unit could be adjusted from 1 to 4. The amount of fertilizer applied varied with the number of fertilizing units and the rotational speed. The mechanical models of fertilizer combination in fertilizer filling and feeding zone were established. The results showed that filling and feeding performance of fertilizer could be improved significantly by tilting angle between left and right. The fertilization performance experiments were performed in the bench test. The effects of fertilization unit number of and rotation speed on fertilizer application and coefficient of variation were studied using Zhushang Fertilizer. Furthermore, the fertilizer adaptability of fertilization device was studied with Zhushang Fertilizer, Sanning Fertilizer and Yunding Fertilizer. The results showed that: 1) When the fertilization unit number and rotational speed were 1-4 and 10-40 r/min, respectively, the fertilization amount increased with the increase of number of fertilization unit number and rotational speed. The range of fertilizer feeding rate was 912.67-13 164.26 g/min. 2) The amount of fertilizer application was significantly affected by the fertilizer types, rotation speed and interaction between fertilizer types and rotation speed. With the same rotation speed of 10-30 r/min, the fertilizer feeding rate of Sanning Fertilizer was the largest, while that of Yunding Fertilizer was the lowest. The difference of fertilizer feeding rate among three fertilizer types was less than 5%. It indicated that the fertilizer feeding device could be applied to different compound granular fertilizer. 3) The quadratic regression predicted model of fertilizer amount was established with the factors of fertilization unit number and rotational speed. The determination coefficient of the regression prediction model was 0.995 8, which indicated that the prediction model was feasible. The fertilizer feeding rate was studied under the condition of target fertilizer application range of 150-750 kg/hm2 and tractor velocity of 2.52-5.88 km/h. The deviations between the experimental value and the predicted?value of fertilizer feeding rate were not more than 3%. In addition, the coefficients of variation of fertilizer feeding rate in each treatment were less than 1.0%. The results showed that the model can accurately predict the fertilizer feeding rate and calculate the fertilizer feeding unit number and rotational speed. The field experiment showed that the relative error between the fertilizer feeding amount and the theoretical value was 3.54%. The structure of the inclined screw-type model-hole and combined fertilizer feeding unit can realize the adjustment of fertilizer feeding rate in a wide range for granular fertilizer. The fertilizer feeding performance of fertilizer feeding device could meet the requirements of fertilizer application amount and fertilizer feeding stability. This research can provide the basis for the structue design of horizontal pneumatic centralized feeder and variable-rate precision fertilization.