The effect of saline irrigation on lucerne production: shoot and root growth, ion relations and flowering incidence in six cultivars grown in northern Victoria, Australia

Abstract

The effect of irrigation with saline (0.1–7.6 dS m^–1) water on the growth of six cultivars of lucerne was assessed over four irrigation seasons at Tatura, Victoria, Australia. Measurements made in the study included shoot dry matter production, shoot ion concentrations, flowering incidence, root distribution and soil salinity and sodicity levels. After four seasons, soil EC_e levels had risen to 4.2 dS m^–1 at the beginning of the irrigation season and this increased to around 6 dS m^–1 at the end of the season for the highest salinity irrigation treatment (7.6 dS m^–1). The soils in the two most saline irrigation treatments also became sodic (SAR_1:5>3) by the third and fourth seasons. By the second season, cultivars differed significantly in salt tolerance as defined by the rate of decline in dry matter production. The cultivars CUF 101 and Validor were consistently the most salt-tolerant cultivars, although cv. Southern Special produced the greatest amount of dry matter over all salinity treatments. Root densities at depths from 0 to 60 cm were greater under saline (2.5 and 7.6 dS m^–1) than under non-saline conditions (0.1 dS m^–1). Flower production was increased by salinity. It was concluded that, despite the presence of intraspecific variation for salt tolerance, it is detrimental to irrigate lucerne with water at electrical conductivities greater than 2.5 dS m^–1 on a red-brown earth in southern Australia.