Mineralization and Chemical Properties Changes in Soil Amended with Azolla

Abstract

Azolla is a kind of bio-fertilizer that can be used as a nitrogen source for plants. It also contained high amount of other macro nutrients, which when decomposed will release them to the soils. Azolla can be used in both fresh and dried form, This research was to study the mineralization of plant nutrients and the change in chemical properties in soil amended with fresh and dried Azolla. Fresh and dried Azolla were incubated in soil (Pak Chong series) at the temperature of 30 °oC, water holding capacity of 60% for 154 days. Results revealed that in soil amended with fresh Azolla, amount of ammonium-N was higher than nitrate-N during the first 35 days of incubation period. After that, amount of ammonium-N declined, and by the end of the study time all was mineralized to nitrate-N. In comparison, the amount of  mmonium-N in the soil amended with dried Azolla was higher than nitrate-N only during the first 7 days then declined, thus enabled nitrate-N accumulation till the end of the study. Mineralization of phosphorus and potassium occurred in the similar pattern as that of nitrogen. The amount of available phosphorus and exchangeable potassium was found higher in the soil amended with dried Azolla than that amended with the fresh one. Mineralization of phosphorus and potassium occurred in more than 150 days of the study. We also found that soil amended with both fresh and dried Azolla had slightly lower pH but higher organic matter accumulation when compared with the unamended soil. However, the soil amended with dried Azolla had higher soil EC than that amended with fresh one.