Intermittent evaporation, moisture distribution, and salt redistribution through saline-sodic clay soil as affected by irrigation frequency and quantity

We investigated the effects of three intervals (5, 10, and 20 d) and four total amounts of irrigation water (120, 240, 360, and 480 mm) applied at two rates (3 or 6 mm/d)³on intermittent evaporation, soil moisture distribution, and salt redistribution through saline-sodic clay soil columns with initial zonal distribution of salts. The results indicated that after a threshold period, which was longer for the lower rate of water application, cumulative evaporation (E) increased with decrease in irrigation interval. In accordance with previous findings, E was a linear function of the square root of time, i.e., E = c √t, where c, under the experimental conditions, is largely determined by the amount of water applied per irrigation. The transmission zone of the moisture distribution profiles lengthened and the wetting front advanced deeper, and consequently salt leaching improved as time progressed and as the irrigation interval and the amount of water applied increased. The sodium adsorption ratio profiles qualitatively followed the electrical conductivity, EC_1:5, redistribution patterns. The depth of the wetting front and the amount of the water stored accounted for 97.4 and 96.8% (r_.001= 0.872) of the variability of the depth of the desalinized zone, respectively. The amount of the stored water accounted for 68% (r_.01= 0.765) of the variability of the weighted mean EC_1:5of the desalinized zone.