Raised Beds

Raised beds provide an optimum environment for germination and growth, especially when used with the stale seedbed technique (See Stale Seedbed in the Cultural Weed Management section). They can be formed with special bed shapers mounted to tractors and walk-behind tractors and to some extent with hand tools. Raised beds improve drainage and hasten the drying of soil, which facilitates faster soil warming and early seeding. They can increase yields of vegetables where root length is important, such as carrots and parsnips, because the depth of friable soil is greater. Raised beds can also reduce the incidence of some root and crown diseases favored by wet soils, such as Phytophthora blight and damping-off, as well as feeding by slugs.

Wind damage is reduced with raised beds. Level soil has a more pronounced airfoil effect, and with the wind passing over them, this allows for a partial vacuum effect. Soil particles are more easily lifted and seedlings more often twisted in flat bed systems. The resulting abrasions on the plant surfaces allow for easier disease introduction if conditions are favorable to the pathogens. Raised beds break up the airfoil effect and reduce the twisting of seedlings and the number of airborne soil particles. Wheel traffic is also restricted to a narrow zone between the beds.

Without irrigation, bed height should be restricted to 4". When irrigation is available, bed height can be increased.

Herbicides are often incorporated into the soil at the time of or just after bed formation. It is important that the herbicides are incorporated to the proper depth for the greatest efficacy. For best results, do not incorporate an herbicide before the beds are made; it will likely end up too deep and cause crop injury, or the concentration may increase when soil is piled up during bed formation.

Growers should consider bed direction and the slope of the bed. During cool, spring days, maximum warming of the bed is needed to provide suitable conditions for plant growth. When the days are short and temperatures are low, orient the beds north and south if two rows per bed are used (when soil erosion is not a consideration). If beds are set in an east-west orientation, the rows planted on the south side of the bed get more heat and grow faster than rows planted on the north side of the bed. This can lead to a lack of uniformity at harvest time. However, beds that are oriented across the slope following the contour of the land minimize soil erosion. For instance, on south-facing slopes, beds of spring crops should be oriented east-west.