Seed tubers are planted in small holes or shallow planting furrows made by a planting machine.
Generally, planting depth should be such that seed tuber sprouts are at medium soil level. Growers are planting deeper some varieties with shallow tubers or varieties that are sensitive to greening and also grow in soil that cracks easily. Subsequent hilling provides a sufficient bed for the growth of newly formed tubers.
If the goal is to get full soil cover as soon as possible after emergence to capture as much solar radiation as possible for a high yield, the optimal planting pattern is square. If the goal is 4 plants per square meter, the spacing is 50 cm x 50 cm. Keep the same spacing between rows and between plants in a row. This scheme, however, has several drawbacks: there is not enough space between the plants to form a proper ridge, and quite little space for the mechanical operations of the tractor. This method is used on wide beds in the tropics.
A more common row spacing is 75 cm in Continental Europe, for example, or 90 cm between rows in the UK and USA. To get 4 plants per square meter, the distance between plants in a row should be 35 cm and 28 cm, respectively.
Narrow row spacing is beneficial for early potatoes, which are harvested prematurely to sell more profitably and are not stored. Longer row spacing allows for larger machines with wider tires and larger ridges, which reduces the chances of tubers being exposed to rain and sun. But the crop takes longer to completely cover the soil and intercept all solar radiation. Narrower row spacing increases competition between plants.
Another way of planting is in ridges with a distance between centers of 150 or 180 cm in two or three rows with alternating placement of tubers. The benefits of planting in beds are more even plant distribution across the field, closer to a square planting pattern, and somewhat better water utilization.
Other types of beds are "lazy beds" which are sometimes used in vegetable gardens where the seed potatoes are covered with a mulch of straw or other organic material. Raised beds are often used in tropical mountainous areas with high rainfall. Such ridges are about 150 cm wide and 50 cm high with a rounded top. They are separated by small paths about 50 cm wide. Such ridges prevent flooding of the crop and facilitate the access of the hoe for planting, hilling, weeding and harvesting.
At the same seeding rate, narrower row spacing means wider plant spacing, earlier row closure, and less competition for soil resources, resulting in higher yields. Differences decrease with increasing growing season. On the other hand, a wider row spacing allows for larger ridges, which better protect the tubers and make the tractor's mechanical operations more efficient. The wider the row spacing, the fewer hours of work per hectare required. Wider rows with larger ridges result in warmer soil in spring and less fluctuation in temperature throughout the day.