Annual Report of Cooperative Regional Project, W-128, for California (UCD, Ken Shackel, Larry Schwankl, Jan Hoppmans, Patrick Brown).
January 1, 2001 to December 31, 2001.
Progress of Work and Principal Accomplishments.
Objective 1: To evaluate and refine microirrigation management strategies to promote natural resource protection and optimal crop production.
CA: In prunes, grower demonstration plots continued to confirm that water savings could be achieved by allowing mild to moderate deficits in SWP (to -15 bar by harvest) with only positive effects on economic yield. In almonds, grower demonstration plots were established to use plant-based RDI as a strategy to reduce hull rot and improve nut harvestability.
Objective 2: To improve, modify, and evaluate microirrigation system design and components for natural resource protection and optimal production
Objective 3: To assess and develop decision criteria for adoption of microirrigation technologies
CA: A study was conducted to determine the minimum leaf equilibration time needed for valid measurements of midday stem water potential (SWP) in a number of tree crops (walnut, prune and almond). It was found that leaves equilibrated rapidly (within 10 minutes), allowing a much more convenient and time-efficient protocol to be established for monitoring SWP on a routine basis.
Objective 4: To promote appropriate microirrigation technologies through formal and informal educational activities.
Usefulness of findings.
Objective 1:
CA: Plant-based RDI has allowed substantial reductions (40%) in irrigation water applied to prune trees, while maintaining or improving economic yields.
Objective 2:
Objective 3:
CA: Reducing the leaf equilibration time requirement from 1 hour to 10 minutes for SWP measurements has substantially improved the practical usefulness of SWP as a monitoring and irrigation scheduling tool for growers.
Work Planned
Objective 1:
CA: Prune and almond RDI demonstration plots will be continued in 2002, and a yield and fruit quality summary for the 3-4 year prune sites will be compiled to evaluate any medium-term effects.
Objective 4:
CA: Presentations will be made informing growers of the benefits of site-specific management of deficit irrigation at the annual meetings of a number of industry groups, including the California almond board and the California prune board.
Publications
Shackel, K., B. Lampinen, S. Sibbett, W. Olson. 2000. The relation of midday stem water potential to the growth and physiology of fruit trees under water limited conditions. Acta Hort. 537:425-430.
Fulton A., R. Buchner, B. Olson, L. Schwankl, C, Giles, N. Bertagnia, J. Walton, K. Shackel. 2001. Rapid equilibration of leaf and stem water potential under field conditions an almonds, walnuts and prunes. HortTechnology 11:609-615.