Development of the fertilizer applicator for promoting ratoon rice buds

Abstract: A more harsh accuracy of fertilizer amount and uniform discharge can be highly required for the ratoon rice in the regeneration season. There is a relatively small amount of bud-promoting fertilizer at present. However, current fertilization machinery for the ratoon rice can hardly meet the control demand of accurate and uniform fertilization. Here, a pneumatic fertilizer applicator was designed to promote ratoon rice budding. The fluted and toothed fertilizer apparatus were combined with the guiding plate for excellent air distribution properties. A ratoon rice harvester was used coordinately to increase the fertilization width, as well as the control accuracy of fertilization amount and homogeneity. Two-stage fertilizer apparatus was also used to perform the fertilization operation. There were the above-fluted roller and the below-toothed fertilizer discharging roller in the fertilizer applicator. During the fertilization, the fluted roller was responsible for the quantified discharge of fertilizer, while the toothed fertilizer discharging roller was to reduce the breaking rate of fertilization strips for better continuity of fertilization. The main structural parameters were then determined for the fluted roller and toothed fertilizer discharging roller, according to the shape and size of common bud-promoting fertilizers. An appropriate transmission ratio was also determined to adjust the speed of the fluted roller and toothed fertilizer discharging roller. As such, the upper fertilization mass was consistent with the lower fertilization mass. The theoretical calculation and discrete element method were finally utilized in the simulation test. It was found that the optimal transmission ratio of the two rollers was determined as 1:1.8, which reduced the breaking rate of fertilization strips and the heaping phenomenon of fertilizer. Afterward, the atmolysis performance of the air distributor was tested by the CFD simulation. The CFD simulation revealed that the variation coefficient of the consistency of airflow in each outlet decreased first and then increased with the increase of the opening angle of the guiding plate. The minimum variation coefficient was 5.65% at the opening angle of 48°. The optimal air distribution was achieved under the least difference in the air flow among different outlets. Simultaneously, the average air flow rate of the outlets was 19.37 m/s, which fully met the design requirement. Therefore, the optimal opening angle of the guiding plate was determined to be 48°. Subsequently, the fertilizer discharge performance of the two-stage fertilizer apparatus was examined by the discrete element simulation tests. Once the rotating speed of the fluted roller ranged from 10 to 20 r/min, the variation coefficient of the consistency of fertilization mass in each outlet decreased first and then increased with the maximum of 2.57%, which was fully meet the requirement of a variation coefficient lower than 7% in each fertilization row. Finally, a bench test of the fertilization performance was carried out with the small-particle-size urea as the test material, the rotating speed of the discharge wheel as the test factor, while the discharge rate, the variation coefficient of fertilizing mass of each row, and the variation coefficient of the discharge uniformity as the evaluation indices. The results demonstrate that the rate of fertilizer discharge increased with the increasing rotating speed of the fertilizer discharge wheel, and the fertilizer discharge rate ranged from 672.9 to 1447.6 g/min at the rotation speed of 10-20 r/min. There was a better match with the driving speed of the harvester. Moreover, the largest variation coefficient of the consistency of fertilization mass in each row was 3.09%, and that of the discharge uniformity of each discharge port was 27.01%, all of which satisfied the requirements of the NY/T1003-2006 fertilization machinery standards. The findings can provide an important reference to design the fertilization machinery for the ratoon rice.