Influence of Incubation Periods on Extractable Fluoride and Phosphorous at Different Exchangeable Sodium Percentage Levels

Abstract

The laboratory incubation experiment was accomplished to study the effect of incubation periods on the extractable Fluoride (F) and Phosphorous (P) in soil at different exchangeable sodium percentage (ESP) levels. The soils of different ESP levels (30, 45 and 60) were prepared by applying different amount of sodium bicarbonate dissolved in distilled water to the calculated volume of saturation percentage of the soil. The observed ESP of the prepared soil was 27.1, 43.7 and 54.9. Incubation studies were conducted with fluoride levels ranging from 40 to 160 mg/kg and phosphorus levels from 12.5 to 50 mg/kg with incubation periods of 1, 3,7, 14, 21, 28 and 35 days at temperature of 25±2℃. Moisture was maintained at field capacity by addition of distilled water. The results showed that the extractability of fluoride in soil increased with increasing levels of F and P application along with increased ESP. The increase was 100 percent at ESP 54.9 compared to ESP 6.2 at F level of 160 mg/kg at 1st day of incubation period. Similarly, Olsen’s extractable phosphorus in soil increased with increasing levels of F, P and ESP. It increased by 66 percent at ESP 54.9 compared to ESP 6.2 at P level of 50 mg/kg at 1st day of incubation period. However, extractability of both F and P decreased with increase in incubation periods. Fluoride extractability decreased by 65 percent at ESP 6.2 and 25 percent at ESP 54.9 with increasing days from 1st to 35th day of incubation period. Olsen’s extractable phosphorus decreased by 37 percent at ESP 6.2 and 48 percent at ESP with increasing days from 1st to 35th day of incubation period.