Design and experiment of targeted hole-pricking and deep-application fertilizer applicator between corn rows

Abstract: Corn is a kind of important food crop and feed source, which is of great significance for solving the grain problem of human. Practices have proved that reasonable topdressing especially nitrogen (N) fertilizers in corn growth period can promote the corn growth effectively and improve the corn yield. Huge bellbottom period for corn is the most important period for applying topdressing, during which vegetative growth and reproductive growth occur at the same time. Meanwhile, it is the fertilization habit to apply topdressing in corn's huge bellbottom period in China. However, with the trend of rural labor transferring to the town in recent years, as well as the main fertilization machinery in the domestic market being handheld, the operation has low working efficiency and great labor intensity. For these reasons, it is more difficult to apply topdressing in the middle and later stage of corn growth, which can't meet the requirement of high yield and high efficiency for corn cultivation. A targeted hole-pricking and deep-application fertilizer applicator, which worked between corn rows with 500-600 mm row spacing, was designed to deal with the difficulties in applying topdressing during the middle and later growth stage of corn, and the fertilizer applicator could fertilize 2 rows in a single pass. The corn plant position detection mechanism and ratchet clutch mechanism were used to determine the position of pricked holes, and the motion locus of hole-pricking and fertilization mechanism was synergistically controlled by a horizontal displacement compensator and a crank-link mechanism, which was aimed to realize the vertical movement in the processes of targeted hole pricking and the fertilizing with zero speed. Key parameters of corn plant position detection mechanism and hole-pricking and fertilization mechanism were determined based on the theoretical calculation and empirical design, the theoretic position of pricking point was calculated at the ideal conditions, and the motion locus of drill point of hole-pricker was simulated using MATLAB. Meanwhile, the structure and working principle of the main working parts of the fertilizer applicator were introduced. The field experiment verifying the working performance of the fertilizer applicator was conducted in July, 2016 in Qingyuan County, Fushen City, Liaoning Province. As indicated in the field experiment results, the fertilizing amount of per hole was 2.3 g when the fertilizer cavity was 20 mm long; the coefficient of variation for total fertilizing amount was 3.2%; the average fertilizing depth was 91.3 mm; the average fertilizing distance was 127.5 mm; the unfinished topdressing rate was 2.7%; and the qualified rates of fertilizing depth and fertilizing distance were 88.3% and 96.7%, respectively. All the related indicators met the technological requirements. The maximum amplitude at vertical direction was 16.2 mm, and side-slip phenomenon was not observed during the field experiment. The fertilizing amount was less than 52.5 kg·hm2 when using the targeted hole-pricking and deep-application fertilizer applicator. In the forward process of fertilizer applicator, the hole-pricking and fertilization mechanism pricked holes vertically, the position of the pricked holes was one-to-one corresponding to the corn plant, and there was small soil disturbance. This study provides reference for the design of precise inter-row fertilizer applicator for corn.