Sustainable Water Management for Irrigated Asparagus

View the project final report

• 2003 annual report

Commodities

• Vegetables: asparagus

Practices

• Crop Production: continuous cropping, fertigation, nutrient cycling
• Education and Training: demonstration, extension, farmer to farmer, focus group, on-farm/ranch research, participatory research
• Production Systems: holistic management, permaculture

Improvements in asparagus productivity (spear yield and stand longevity) require a better understanding of present farming practices and how best to manage irrigation. Detailed farm evaluations were conducted on working asparagus farms in California and Washington, two major asparagus producing regions in the western U.S. Current production practices and on-farm plant evaluations were conducted over several years in asparagus fields planted in 2002. Growers employed different harvest strategies, irrigation methods, and amounts which had a significant impact on asparagus fern development, root growth, and crop yield. Growers employing more harvest pressure in the year after planting tended to have less root growth and higher plant stand reductions than those taking smaller harvests during the first harvest season. Irrigation method also appears to influence plant stand reduction with higher plant losses in commercial sprinkler- and drip-irrigated fields when compared to furrow-irrigated asparagus.
In a replicated experiment, we assessed the role harvest strategy, irrigation method and amount had on asparagus plant growth and productivity during the first 3 years of growth. Plants were harvested in the first or second year after planting and were watered at 0, 75, or 150% of evapo-transpiration with drip or sprinkler irrigation systems. While early harvest had little significant effect on yield, plants harvested one year after planting had fewer stems and stem dry weight than those harvested in the second year. Irrigation method had a greater impact on root growth than on fern growth or yield. Plants grown with drip irrigation had greater root mass than those grown with sprinkler irrigation. Although yields were not different between drip- and sprinkler-irrigated asparagus, drip-irrigated plants had a higher percentage of large and very large spears. Fern growth (number and weight of stems) increased when more frequent and higher applications of water were applied during the summer. However, the yield difference between the 150 and 75% ET treatments was not significant while a further reduction in applied water to 0% of ET reduced spear yield by more than 50% when compared to the 75% ET treatment. Growers need to pay more careful attention to harvest pressure and use carbohydrate monitoring to assess the changes in root carbohydrate content as a means of assessing when to stop harvest. These approaches will ensure that plants have sufficient energy reserves to grow enough fern and have adequate time to recharge the root system after harvest. Our farm and research findings suggest that asparagus growers should seriously consider their choice of irrigation system, should monitor soil water to avoid over irrigating, and not over-harvest young plantings. With these improvements, stand longevity should be improved, water resources will be conserved, and long-term yields should be maintained.

Objective 1: Assessing growth and productivity in commercial asparagus fields

Objective 2: To develop irrigation application guidelines that optimizes productivity

Objective 3: To provide asparagus industry water recommendations based on observations gathered in commercial settings and research conducted under controlled conditions and to use this information to ensure optimal production