Objective  In order to improve the mechanization level of organic fertilizer application in the greenhouse and solve the problem of low fertilizer discharge stability of the existing organic fertilizer discharging device, an organic fertilizer discharging device with scraper conveyor for greenhouse was designed.

Method  Taking the strawberry planting greenhouse in southern Jiangsu area as an example, the main requirements for the design of the fertilizer discharging device were determined according to the basic size parameters of the greenhouse and the agronomic requirements of strawberry planting. The key structure and parameters of the designed fertilizer discharging device were analyzed and determined by combining the bulk mechanics theory, and the main factors affecting the stability of the fertilizer discharging volume were determined to be the rotational speed of the fertilizer discharging shaft and the opening degree of the fertilizer discharging device. An indoor organic fertilizer discharging test platform was built, and single-factor test and two-factor five-level response surface test of rotational speed and fertilizer discharging volume were conducted.

Result  The results of the correlation test between rotational speed and fertilizer discharging volume showed that within the range of rotational speed and opening degree set in the test, the rotational speed and fertilizer discharging volume had a good linear relationship under the conditions with different opening degree. The overall coefficient of determination was above 0.9857, and the fertilizer discharging volume could be adjusted by adjusting the opening degree and rotational speed in real time. The results of the response surface test showed that the stability of fertilizer discharging volume within the set range was good, and the rotational speed of the fertilizer discharging shaft had a greater influence on the coefficient of variation of the fertilizer stability compared with the opening of the fertilizer discharging device. The coefficient of variation of fertilization stability was optimal (1.84%) when the opening degree of fertilizer discharging device was 30.42 mm and the rotational speed of fertilizer discharging shaft was 51.5 r/min. The comparison test showed that the average value of the coefficients of variations of the commonly used spiral organic fertilizer discharger was 6.12%, and the organic fertilizer discharger with scraper conveyor designed in this paper effectively improved the stability of organic fertilizer discharging.

Conclusion  The designed fertilizer discharging device with scraper conveyor has good fertilizer discharging performance and meets the requirements of organic fertilizer application in greenhouse.