Precision planting technologies developed by China Agricultural University (CAU) for no-till and minimum-till corn systems
Precision planting is gaining popularity in row crop systems such as corn. However, existing precision planters have difficulties of maintaining uniform seed spacing at high field speeds. While overcoming these difficulties, we are also facing challenges in achieving uniform seeding depth and dealing with heavy crop residue in conservation tillage systems.
In solving the aforementioned problems, the China Agricultural University (CAU) has developed modern technologies for precision planting in no-till or minimum-till cereal-corn systems.
For seeding corn on cereal residue, a row cleaner featuring an upright roller driven by residue (Fig. 1). The roller is self-cleaning and capable of guiding residue flow to avoid plugging the openers. For seeding corn on corn residue, a powered rotary tool that breaks corn stubbles and cleans the seed row at the same time.
The precision seed metering mechanism is either a vacuum-type meter (Fig. 2) or a mechanical spoon-type meter. In a traditional precision metering system, seeds tend to settle at the bottom of the meter, forming a dense pile that resists being fed into the seed cells. In the CAU technology, the seed pile is loosened to improve the feeding. For the vacuum-type meter, this loosening is achieved through introducing an air stream into the meter to suspend the seeds. In the spoon-type meter, separate feeding and un-feeding zones are designed, and seeds in the feeding zone are loosened to a greater extent to facilitate feeding. In addition, the geometry of the seed cell is specially designed to prevent seeds from falling before being discharged from the meter.
In traditional precision planting, maintaining uniform seed spacing becomes more difficult as the planter travel speed increases. Thus, the traditional precision planters are suitable only for low speed field operations. For high speed operations, the CAU planter uses a transfer wheel located underneath the seed disc. As it rotates, the transfer wheel “grabs” the seeds discharged from the meter, then carries and delivers the seeds to the bottom of the furrow. The transfer wheel ensures a stable transfer of seeds from the seed disc to the furrow by reducing the dropping height of seed relative to the furrow bottom. This allows the CAU planter to produce uniform seed spacing at any field speeds.
For any opener design, challenges include the variations of field surface, seeds bouncing on furrow bottom, and lack of backfilling soil to cover the seeds. One of the CAU openers is double-disc opener that works with double gauge wheels on the sides (Fig. 3). The assembly is attached to the toolbar through a parallel linkage, which enables it to follow the contour of soil surface and therefore, to achieve a uniform cutting depth. The other opener consists of a shank, a wedge, and two small wings, which loosen the soil and guide soil flow to enhance soil backfilling into the furrow. The opener is followed by two rollers, which follow the contour of the field surface, controlling the cutting depth of the opener while simultaneously firming the seedbed.
The double press wheels are tilted to a V shape, which ensures a proper soil cover on the seeds and appropriate amount of compaction for good soil-seed contact.
Fig. 1. Planter showing the row cleaning devices (upright rollers).
Fig. 2. Planter showing the vacuum-type precision meters.
Fig. 3. Planter showing the gauge and press wheels.