Field Performance of 21 Alfalfa (Medicago sativa) Varieties Under Saline Irrigation: Dry Matter Yield and Mineral Composition.

As irrigation water becomes scarce in many parts of the world, saline waters will increasingly be used for crop production.   Alfalfa and almonds are the highest acreage crops in California, using approximately 15% and 10% of the state’s water supply, respectively.  Utilization of saline water supplies for alfalfa irrigation could free up a considerable volume of high quality water to irrigate more salt-sensitive crops. This research was initiated to compare 21 new alfalfa varieties, selected for salt tolerance, under field conditions characteristic of the western San Joaquin Valley of California. Two different irrigation water salinities were applied: low saline irrigation water (1.5 dS/m) and high saline irrigation water (8-10 dS/m). Performance of the varieties will be assessed based on shoot dry matter yield and Na and K concentrations in shoots will be assessed in order to correlate the accumulation of salts with the yield response.  In-season EM-38 soil surveys will be conducted to relate the yield response to a season-averaged soil salinity.    Preliminary data suggest that newer, salt tolerant varieties of alfalfa can maintain yields under saline conditions to a greater degree than indicated by published salinity tolerance thresholds (Maas and Grattan, 1999).