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  • Author or Editor: R. Seth Peterson* x
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Asparagus producers have reported a decrease in plant longevity and plant productivity in asparagus fields. Irrigation methods and amounts and early harvest pressure are thought to be some factors affecting asparagus longevity and productivity. The objectives of this study were to determine how irrigation method (sprinkler/drip), amount (0, 75, 150% ET), and harvest pressure (yes/no) modify asparagus growth in the year after planting. In April 2002, plots were planted with as-paragus cultivar Jersey Giant. All plots were treated the same during the establishment year. Each plot was 6.1 m long by 2 rows wide. All plots were separated by a guard row. There were 5 replications. Each irrigation method and amount was divided into two harvest treatments. One row was harvested for three weeks in 2003 (952 kg/ha) while the other was not harvested. Irrigation treatments began after harvest. In 2003, 100% ET from 10 June 10 to 14 Sept. was 55 cm. After correcting for precipitation and crop coefficient, the 75% ET treatment received a total of 28 cm of water while the 150% treatments received 47 cm. There was no difference in fern fresh weight between 150% and 75% ET for the drip irrigates asparagus, but both were significantly greater than non-irrigated treatment. In contrast, fern fresh weight decreased linearly as irrigation amounts decreased in the sprinkler treatments. Yield differences are not expected between drip and sprinkler in 2004. Yield reductions are expected relative to irrigation amounts.

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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.

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