Assessing How Cultural Practices Influence Long-term Productivity in Asparagus

Abstract

Asparagus producers have reported a decrease in plant longevity and plant productivity in asparagus fields. Eleven commercial sites (6 in California and 5 in Washington) were monitored starting in Spring 2003. The purpose in monitoring was to evaluate how long-term growth dynamics are affected by harvest pressure. Sites were planted as crowns in Spring 2002 and farm irrigation methods included furrow, sprinkler, and drip. Most sites were harvested starting in Spring 2003 at varying pressures. Harvest yields ranged from 0 to 1300 kg·ha-1. Carbohydrate (CHO) levels in the roots were sampled over the entire growing season and assessed with AspireUS (www.aspireus.com). At the last sampling in Oct. and Nov. 2003, CHO levels ranged from 438 mg·g-1 to 712 mg·g-1 (97% to 158% of the ideal). This resulted in a root CHO load of 2.6 to 6.3 megagrams/hectare. Root mass and distribution was sampled in Spring 2003 and again at the end of the growing season. Root biomass increased by 18% to 487% of the previous year's growth. Fern number, fern mass and plant population were also sampled. Fern number ranged from 3.2 to 6.4 stems per plant and total fern weight ranged from 8.9 to 36.2 megagrams/hectare. Plant populations were reduced by 3% to 19% when compared to the initial planted population. Findings suggest that excessive harvest pressure in the year after planting adversely affects storage CHO accumulation and root growth. Additional site monitoring will occur through 2005.