Planting Materials Affect Asparagus Performance in a Replant Situation

Replant suppression is one of the major threats to asparagus (Asparagus officinalis) production worldwide. This is a phenomenon which prevents asparagus from establishing well in a site that has previously been planted in asparagus. Unfortunately, virgin land is limited in most asparagus-growing regions in the U.S.  Traditionally, new asparagus fields in Michigan and other regions are established with one-year-old crowns.  If the crown nursery is infested, then the cowns may spread diseases, and wounds created during the crown digging process may serve as entry ports for soilborne diseases. Alternative planting materials that are diseases-free could be used as a component of disease management for improved plant performance.  Therefore, the goal of this research was to compare the performance of asparagus fields established with one-year-old crowns (CR) with that of fields established with greenhouse grown transplants (TP) in a replant situation. Field experiments were established at the Asparagus Research Farm in Oceana County, MI, in 2005 and 2007 using asparagus cultivar Guelph Millennium.  Based on preliminary studies, the transplants were produced in the greenhouse using trays with 72 cells.  One-year-old crowns were provided by a commercial crown grower.  After three years of harvest (2005 trial) and two years of harvest (2007 trial), asparagus yield was consistently higher in TP treatments compared to CR treatments.  The average yield increase was greater than 50% for the 2007 study.  Differences in yield were mainly attributted to a greater number of spears in the TP treatments.  During the fern growth stage, the TP treatment also produced more shoots than the CR treatment.  These preliminary results suggest that TP should seriously be considered as an alternative planting material for the establishment of new fields.  However, the use of TP will require significant changes in the production system, especially during the first years of field establishment, since biotic and abiotic stresses have more impact on TP than CR.  Transplants will need be hardened off adequately and irrigated immediately after transplanting.  They should not be sprayed with potentialy phytotoxic products.