| Popis: |
Lucerne is being widely promoted as a means of salinity prevention, due to its ability to grow roots deeper into the soil and use more water than annual crops or pastures. This helps to reduce groundwater recharge. Direct groundwater use would also help to lower water tables, but lucerne’s role in this regard is poorly understood. In this research, lucerne plants growing in 2 landscape positions (one position with access to moderately saline groundwater, and one without access to groundwater) at similar plant densities were compared in terms of their pre-dawn leaf water potentials and evapotranspiration (ET) rates during summer. Soil analysis (pH, EC, texture, and water content) indicated that soil water content below a depth of 0.9 m was the only major difference between the 2 landscape positions. Plants with access to groundwater were larger (55 v. 13 kg dry matter/ha), less stressed (–0.71 v. –1.16 MPa pre-dawn leaf water potential), and exhibited 2–3 times higher ET rates early in the morning than plants without access to groundwater. ET rates in the afternoon were similar. Total ET from plants in both landscape positions was very low relative to potential ET. We conclude that lucerne plants with access to groundwater are able to use the water to maintain lower stress levels, but not for active growth under conditions of dry topsoil and high vapour pressure deficit. Direct groundwater uptake by lucerne is likely to be low, but may be significant for salinity control in the longer term. |
