Author: James Adolph Radawich

Publisher:

Published: 2018

Total Pages:

ISBN-13: 9780438929869

Alfalfa producers in many irrigated regions must develop strategies to maximize water productivity (kg/ha per mm of water), given the reality of water supply variations caused by periodic droughts, environmental regulations, or water transfers to cities, to transfer to other crops, or for environmental needs. Climate variability and change further exacerbates these uncertainties. Partial yields may be feasible for alfalfa under deficit irrigation, unlike other crops where complete failure is likely, or fallowing is required. Summer deficit irrigation or mid-season water cut-off utilizing irrigation systems with greater efficiency, such as subsurface drip irrigation (SDI) may be practical solutions to easing seasonal water supply fluctuations and restrictions. Breeders have developed cultivars with putative drought tolerance which could play an important role in a future with unreliable water supply. The objective of this research was to determine the possible interaction between cultivar and deficit irrigation when water was applied using SDI technology. Fifteen commercial or newly released alfalfa cultivars were established in fall 2014 at Davis, CA using a split plot design with four replications with four different irrigation regimes utilizing SDI. Irrigation treatments were: 1) Applications of the full water requirements of the crop -100% of seasonal ET[subscript c], supplied 2) 75% of seasonal ET[subscript c] with an August cutoff, 3) 75% of seasonal ET[subscript c], -fully irrigated to 50% of seasonal ET[subscript c], then 1⁄2 of full ET[subscript c] supplied for the remainder of the season, and 4) 50% of ET[subscript c] –with a July cutoff. Over three years of data collection (2015-2017), yields averaged 80% of fully-irrigated plots when receiving 50% water application and averaged of 96% of the fully-watered yields at 75% of water applications to fully match ET[subscript c]. The results showed that varieties differed significantly in yield potential (P