Evapotranspiration, water‐use efficiency and quality of six dryland planted pasture species and natural vegetation, in a semi‐arid rangeland¹

Abstract

Hydraulic, non‐floating lysimeters were used to determine evapotranspiration (Et) and water‐use efficiency (WUE) of several dryland planted pasture species over a period of three years. The species were Anthephora pubescens, Cenchrus ciliaris, Chloris gayana, Digitaria eriantha subsp. eriantha, Eragrosiis curvula and Panicum maximum. The WUE was expressed as the amount of above‐ground phytomass as well as the crude protein produced per unit volume of water evapotranspired. The water‐balances of the planted pastures were also compared with that of a natural grassland (veld) in good condition. Differences in Et between the various species were not significant (P>0.05). Deep percolation, beyond the root zone (i.e. more than 0.8 m), did not occur in any of the species nor in the veld treatment throughout the study. Chloris gayana produced more above‐ground phytomass (P≤0.01) than all the other species in both wet and drier conditions. The average WUE (7.2 kg dry matter (DM) ha^‐1 mm^‐1 and 0.39 kg crude protein (CP) ha^‐1 mm^‐1) of this species was the highest (P≤0.01) throughout the experimental period. During the first half of the season (July ‐ December) the crude protein content (7.94%) of Panicum was the highest (P≤0.01), while that of Anthephora (5.02%) was the highest (P≤0.01) during the second half (January – June). The exceptionally low (P≤0.01) crude protein content of natural grassland and Eragrostis during the second half of the season indicated that these are not well suited for use as foggage (grown out forage), while the high values for Anthephora and Digitaria suggests these to be suitable foggage species.