Modern planters now offer multiple devices and options to close and firm the seed furrow. Here are some thoughts:
The V-angles of rubber-tired closing wheels closes the seed furrow by directing pressure at an angle toward the seeds at the bottom of the seed furrow, leaving loose soil directly over the seeds. In wet conditions the pinching action of the closing wheels may not be enough to close the furrow at normal down-pressure setting. Increasing down-pressure to close the seed furrow under those conditions may over-compact the soil at seed depth and interfere with shoot and root development. Tined closing wheels may be an option if it’s not possible to wait for the soil to dry enough to close the seed furrow properly.
Opinions vary on tined closing wheels. Long, straight-tined wheels loosen soil while closing the seed furrow, but if set too deep or with too much pressure, can actually dig up seeds. Plastic wheels with U-shaped serrations are less prone to digging seeds, but their wider cross-section can pack soil like a sheep-foot roller if too much down-pressure is used.
Some planter manufacturers use a multi-part seed furrow closing system that mechanically closes the furrow with some type of small concave disk, then uses a wheel to smooth and firm soil over the furrow. The ability to adjust furrow-closing and soil firming independent of each other allows fine-tuning to match soil conditions.
Judge the performance of closing systems by digging in several areas of a field. If you have to use a screwdriver to pry seeds out of the furrow, there’s either too much down-pressure, or the soil is too wet for optimum planting.
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