Changes in ph, ec and concentration of phosphorus in soil solution during submergence and rice growth period in some paddy soils of north of Iran

Abstract

Changes in pH, EC and concentration of phosphorus in soil solution during submergence and rice growth period were studied in three paddy soils of North of Iran (one acid and two alkaline-calcareous soils). Also, changes in pH, EC and concentration of phosphorus in soil solution of an alkaline-calcareous soil after addition of 40 mg P/ kg of soil during submergence and rice growth period were studied. The experiment was performed in a set of specially fabricated pots equipped with a perforated sampling tube installed in the root zone area. At different times, pH, EC and concentration of phosphorus in soil solution of cultivated and uncultivated treatments were measured. The results are as follows: 1- After submergence, water soluble P increased initially and then decreased in all three soils in both cultivated and uncultivated treatments. 2- Both pH and concentration of water soluble P in both treatments was not significantly different at early stage of rice growth, but they were significantly lower in cultivated treatment afterward. 3- After submergence, the pH of alkaline soils decreased, while the pH of acid soil increased significantly. 4- The EC of rhizosphere soil solution changed differently in different soils during the rice growth period. In acid soil, the EC of rhizosphere soil was significantly lower than the bulk soil solution, while in one of the alkalinecalcareous soils, it was significantly higher than the bulk soil solution. 5- After P addition, the pH of the rhizosphere soil solution did not change significantly, but the pH of the bulk soil solution increased significantly. 6- Generally, the chemistry of rice rhizosphere was essentially different from the bulk soil.