Design and test of vertical spiral organic fertilizer spreading device

China has ranked first in the total output and use of chemical fertilizers in the world, as the increase of grain production. Generally, the single nutrient element of chemical fertilizer makes the fertilizer effect short and fast. If using for a long time, the fertilizer can cause soil hardening, soil fertility decline, even to decrease the quality of agricultural products. Alternatively, the organic fertilizer can be used to increase the soil organic matter and the permeability of soil, and thereby to ensure the high and stable yield of crops. However, the chemical fertilizer by adding more organic fertilizer behaves a high viscosity and fluidity, which makes it difficult to spread. In this study, a vertical spiral spreading device for the organic fertilizer was designed, in order to automatically crush organic fertilizer, and then to spread it wide. The specific processes were as follows: Firstly, the overall structure of device was preliminarily optimized. The vertical spiral spreading device for the organic fertilizer was mainly composed of the fertilizer spreading disc, spiral axis, beam, balance block, spiral blade, fertilizer spreading and crushing blade. The latter three were the key components of crushing organic fertilizer. Meanwhile, the fertilizer spreading and spiral blade were the key components of spreading organic fertilizer. A kinematic model of organic fertilizer in air was established to determine the influencing factors in the process of fertilizer spreading. The test factors included the rotational speed of spiral axis, inclination angle of fertilizer spreading disc, and screw pitch of spiral blade. The coefficient of variation and the fertilizer spreading width were set as the test indicators to evaluate the operation effect of the device, according to the fertilizer application standards. A field test was conducted at the Northeast Agricultural University in July, 2020. A rectangular area with the size of 10 m×8 m was set on the ground for data collection, and then the whole area was divided into many small squares with the size of 0.5 m×0.5 m for measurement. During the test, the fertilizer spreading width was first measured, and then the organic fertilizer was weighed, finally, where all test dataset was recorded. A Design-Expert 8.0.6 software was used to analyze the influence of each test factor and their interaction on each test indicator, and then a relationship was established between each test indicator and the regression equation of each test factor. An optimal combined range of all test factors was achieved via balancing the stability of the device and its economic considerations. A dataset was selected in the optimal range for the verification test: When the rotational speed of spiral axis was 385 r/min, the inclination angle of fertilizer spreading disc was 16°, and screw pitch of spiral blade was 360 mm, indicating that the coefficient of variation was 14.0%, and the fertilize spreading width was 8.1 m. The values were basically consistent with those of software calculation, indicating that can meet the national standards and the requirements of organic fertilizer application. The vertical spiral spreading device has good performance on spreading organic fertilizer, providing for a sound reference for the design and optimization of organic fertilizer spreader. © 2020, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.