Effects of Sunflower Cultivation, Manure and Sewage Sludge on Availability of Elements, pH and EC of an Alkaline Soil

Plant cultivation and application of organic matter can change chemical properties of soil and elements availability. In a greenhouse investigation, the effects of sunflower (Helianthus annuus L.) cultivation, animal manure and sewage sludge on changes in pH and EC of an alkaline soil solution after waterlogging were studied. A factorial experiment based on completely randomized design with two replications including duration of waterlogging at 10 levels (1, 3, 5, 7, 9, 12, 15, 17, 19, 22 days), source of organic fertilizer at two levels (animal manure, sewage sludge), amount of organic fertilizer at three levels (0, 15, 30 g/kg) and plant cultivation at two levels (cultivated and uncultivated) was carried out. The pots were waterlogged in the six-leaf stage of sunflower and during waterlogging period the water level was maintained 3-5 cm above the soil surface. The results showed that by increasing the duration of soil waterlogging, the pH of soil solution in uncultivated pots and all treatments increased. The pH of soil solution in uncultivated pots decreased after application of sewage sludge while increased after application of animal manure. The pH of soil solution in sunflower cultivated pots was lower than uncultivated pots. In control treatment, after waterlogging the EC of soil solution initially increased and then decreased after reaching a maximum. The EC of soil solution in uncultivated pots increased after application of sewage sludge and animal manure and the increase was greater with application of animal manure. In all treatments, the EC of soil solution in sunflower cultivated pots was different from uncultivated pots. The effect of sunflower cultivation on the availability of elements at the end of plant growth period was studied. The results showed that the availability of P, K, Na, Fe, Mn, Cu and Zn in sunflower cultivated pots was greater than uncultivated pots but the availability of Cd and Pb in cultivated pots was not significantly different from uncultivated pots.