Optimized Design and Experiment of a Spatially Stratified Proportional Fertilizer Application Device for Summer Corn

In this study, a spatially stratified proportional fertilizer application device was designed, which was mainly composed of a fertilizer equalization and stirring structure, fertilizer guide plate, and fertilizer plate. This was aimed at solving challenges presented by current fertilizer devices that include a poor layering effect due to untimely return of soil, excess nutrients in the early stages of plant growth, and insufficient quantities in the later stages. The "seed fertilizer + chasing fertilizer" is time-consuming and laborious; seed and fertilizer (without layering) are applied to the soil at once, which tends to cause too much nutrients for plants in the early stage and not enough nutrients in the later stage; and the layered fertilizer machines currently on the market have a poor layering effect due to untimely soil return. Through theoretical analysis and calculation, the structural parameters of the device were determined, and the main influencing factors of the movement law of fertilizer in the device were analyzed. Through simulating soil tank tests, the main factors affecting the effect of fertilizer spatial stratification were designed by quadratic regression orthogonal rotation combination designs. The optimal parameters including the length of the first fertilizer plate was 100 mm, the installation angle of the fertilizer plate was 80°, the spacing of the fertilizer port was 30 mm, and the uniform stirring speed was 650 r/min. The results of the bench test showed that the fertilizer granules could be uniformly stirred at the optimized stirring speed, with average values of 74.56, 76.56, and 105.19 g, which met the agronomic fertilizer application requirements, and the coefficient of variation of fertilizer application amount in each layer was less than 1%. The field test results showed that the stratified proportional fertilizer application device could achieve the stratified proportional application of fertilizer in the soil in ranges of 80.2-95.4, 150.3-180.2, and 230.3-250.4 mm for the upper, middle, and lower layers, respectively, with an error within 10 mm from the designed theoretical application depth. Compared with the conventional fertilizer application method, this fertilizer application method had a more obvious promotion effect on the 100-grain weight and yield of corn.