Performance of late-spring forced asparagus rotated with normal spring harvest under temperate climate conditions.

摘要

Asparagus (Asparagus officinalis L.) is typically harvested for up to 6 weeks in spring, but cultural techniques can be used to extend the harvest. To force spear production beyond the normal harvest season, asparagus plants are allowed to grow undisturbed in spring and then are mowed later in the season, resulting in a flush of harvestable spears. Repetitive off-season forcing of asparagus does not appear to be a viable production practice in the temperate climate conditions of the Midwestern United States because the growing season is not long enough to permit adequate replenishment of energy reserves after even a brief forced harvest. An experiment was conducted in southwest Missouri to determine whether a system of rotating late-spring forced asparagus harvests with typical spring harvests would allow plants to recover sufficient vigor to establish a sustainable extended asparagus harvest regimen in the region. "Jersey Knight" asparagus was planted in 1999 and harvested in eight different 3-year rotations involving late-spring forcing and normal spring harvest from 2001 to 2004. Though yield from normal spring harvests increased during the study, plants that were forced one or more times within a rotation produced less marketable yield and did not recover enough vigor to sustain a satisfactory harvest when subsequently rotated back to spring harvest. Initially, late-spring forced plants yielded roughly half that of normal spring-harvested plants. Though forced plants produced good, marketable spears, they were significantly smaller, with mean weight of 8.1 g compared with 10.3 g for normal spring-harvested spears. There appears to be a need for a longer period of recovery for forced asparagus plants under temperate conditions of the Midwestern United States