Sustainable Water Management for Irrigated Asparagus
A comparison of irrigation amounts, irrigation systems and harvest pressure demonstrates that all contribute to asparagus productivity. As irrigation amount increased from 0% to 150% of ET, asparagus fern growth increased linearly. In addition, drip improved growth more than sprinkler irrigation. Harvest in the year after planting negatively affected asparagus growth during the summer. Results were conveyed to growers in Washington, California and Michigan. Growers should carefully consider the type of irrigation system and the amount applied to optimize early plant performance. Yield findings in 2004 will determine the full extent of water on spear yield.
Objective 1: To develop irrigation application guidelines that optimize productivity:
A replicated randomized trial comparing irrigation method (sprinkler and drip), harvest pressure (yes/no in 2003) and irrigation amount (0, 75 and 150% of evapotranspiration) was conducted in 2003 on asparagus plants planted in 2002. We periodically monitored fern and root growth and regularly monitored soil moisture content. Objective 2: To assess on-farm water use on asparagus growth and productivity: 6 fields in California (2 drip, 4 furrow irrigated) and 5 fields in Washington (2 furrow, 3 sprinkler irrigated) planted in 2002 were monitored for fern (fern weight, number and stand loss) and root growth (root length, biomass and carbohydrate content) during 2003. Average fern counts and weights did not vary greatly between fields or within irrigation types. Plant stand losses were greatest in sprinkler irrigated fields and least in drip and furrow irrigated fields. This correlated well with irrigation amount and frequency. Root biomass increased in all fields regardless of the irrigation system. However, the percentage change in root mass varied greatly and the rate of increase was least in fields where spear harvested in the spring of 2003 was greater than 600 lb/A. Work in this area is continuing through 2005. Objective 3: To provide asparagus industry water recommendations that ensure optimal production. Preliminary information gathered in 2003 conveyed to growers in California, Washington and Michigan illustrating the effects of irrigation amount, irrigation system and harvest pressure on plant productivity.
Objective 1. Early findings indicate that fern number and weight increases as irrigation application rate increases. In addition, asparagus irrigated with drip had greater number and weight of fern when compared to sprinkler irrigated asparagus. Root biomass will be collected in late March of 2004 to compare the different treatment effects on root distribution and weight throughout the rooting profile. Yield data will be collected beginning in April. Half the plots were harvested in the spring of 2003 with a harvest equivalent to 850 lb/acre removed. In all irrigation systems and amounts, plants harvested in 2003 had fewer and shorter fern that weighed less than plants that were not harvested. This work is continuing in 2004 with additional spear harvest, continued plant growth monitoring and additional soil moisture measurement being collected.
Objective 2. Average fern counts and weights did not vary greatly between fields or within irrigation types. Plant stand losses were greatest in sprinkler irrigated fields and least in drip and furrow irrigated fields. This correlated well with irrigation amount and frequency. Root biomass increased in all fields regardless of the irrigation system. However, the percentage change in root mass varied greatly and the rate of increase was least in fields where spear harvested in the spring of 2003 was greater than 600 lb/A. Work in this area is continuing through 2005.
Objective 3. By the end of 2004, better soil water recommendations can be given to asparagus growers based on the field and research plot information.
Impacts and Contributions/Outcomes
In August 2003, growers in Washington State were exposed to some of our research findings in a presentation at the annual asparagus field day. 45 growers participated in discussions on water use in asparagus, the impacts of shortages on productivity and the effect of over-irrigation on root development and carbohydrate accumulation.
In December 2003, the research findings from our California project were presented to the California Asparagus growers at their winter meetings. 40 growers were in attendance and the findings were discussed with them.
Our final reports for 2003 were presented to the California and Washington Asparagus commissions for their review and comment. Recommendation related to irrigation method and plant growth indicates that over or under irrigation affects plant development. We are continuing to assess asparagus performance. Yield in 2004 will further help us see the impact of these treatments on longevity.
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