Yield and Quality Response of Alfalfa Varieties to High Salinity Irrigation

Abstract

Salinity is an increasing problem in many areas of the world due to the effects of climate change and long-term use of irrigation. We sought to determine the effects of high salinity irrigation water (EC_w 8.0-11.0 dS/m) on the yield and quality of non-dormant alfalfa (Medicago sativa L.) varieties in a Mediterranean environment. The field study was conducted over two years in Five Points, California, utilizing a split plot design with salinity as the main plot and variety as the sub plot. The trial was established in the spring of 2017 with yield and quality measured in 2018 and 2019. Forage quality was determined using Near Infrared Spectroscopy (NIRS) method. Salinity and variety both had a significant effect on quality and yield in alfalfa. The average yield loss due to high salinity irrigation was 21%, but yield levels under high salinity were still economically viable in this location. Few interactions were seen between variety and salinity for yield or forage quality parameters, indicating that varieties generally responded similarly when low and high salinity levels were compared, although the severity of the responses differed by variety. However, the large number of varieties included in this trial may have drowned out small changes. The CP, NDF, ADF, and NFC quality factors were reduced or increased by salinity, depending on the variety and the few significant variety x salinity interactions suggest unique variety responses. We determined that “salinity tolerance” should not be solely determined by the relative yields under saline vs. non-saline conditions, but also by the absolute yields under saline conditions; in addition to the ability to exhibit high yields under non-saline conditions. Performance under both high and low saline conditions should be taken into account to utilize areas of both low salinity and high salinity that are likely to occur within each field.