Fig. 1.

Controlled irrigation treatments performed in expt 3. Watering of compost-filled pots containing barley plants was stopped from 45 DAS and, at 65–75 DAS, the pots were randomly split into two groups. (A) One group of 35 pots were turned upside down and placed in a water-filled basin for 10 s. Bricks in the basin served as supports and ensured that only the first centimetre of the compost was wetted. Pots were then removed from the basin and placed upside down on bricks to drain for 15 min. Plants were then turned upright again and any compost adhering to the shoot was removed. Capacitance was then measured using an Extech LCR Meter between a needle electrode inserted into the stem of plants about 5 mm above the surface of the compost and a steel rod electrode in the compost. The pots were irrigated from above twice in the evening and once in the morning to a water content approaching field capacity. Capacitance was then remeasured. (B) The second group of 35 pots were placed in a basin which was then filled with water to a depth of 4 cm. After 20 s the pots were taken out and capacitance was measured using an Extech LCR Meter between a needle electrode inserted into the stem of plants about 5 mm above the surface of the compost and a steel rod electrode in the compost. Pots were returned to the basin, which was filled with water to a greater depth. After 20 s, pots were removed from the basin and capacitance was remeasured. This procedure was repeated until the water in the basin was level with the surface of the compost.