Water relations of wheat as affected by irrigation and nitrogen fertilisation

Abstract

Water potentials of flag leaves and ears on the same tiller of Kopara wheat were measured soon after ear emergence by a pressure-bomb technique. Water potentials of ears were nearly 0.5 bar higher than those of flag leaves. At soil water levels (0—15 cm) of 20%, water potentials of —8 to —9 bars were recorded at 0900 hr on a day of high solar radiation with relatively little advective heat transfer. In non-irrigated wheat, soil water levels were well below the permanent wilting point, and the water potentials of the ears were lower than— 20 bars. Nitrogen fertiliser had no direct effect on ear water potential, but in non-irrigated wheat it depleted soil water, probably by increasing leaf area index and transpiration. As a result soil water levels in non-fertilised, non-irrigated plots were well above the wilting point, and the water potentials of the ear of wheat growing in them were similar to those which were irrigated.