Drought stress and alfalfa production in a mediterranean environment

Summary

Plots with alfalfa (Medicago sativa L.) were exposed to water deficit during two consecutive summers. Drought stress treatments which lasted between 2 and 8 months during the first growing season had no carry-over effect on growth during the following winter and early spring of the subsequent year, compared with that observed in the fully irrigated plots. It was found that the capability of roots to extract water, and the rate of recovery from water stress after rewetting in autumn was independent of the duration of the drought. Water extraction varied curvilinearly with soil depth regardless of soil water content. Good agreement was found between an exponential model which was fitted to water extraction data in our experiment and data of root mass distribution taken from experiments conducted in the United States. This gives reasonable confidence in the prediction of the use of soil water reserves by plants under stress. A balance between saving of irrigation water and the expected loss of yield was determined. It is suggested that when water resources are limited in summer, irrigation of an established stand of alfalfa can be adjusted to water availability, without a decrease in water use efficiency.