Effect of Humic Acids Extracted From Different Organic Sources and Inoculation of Bacillus Subtilis or Aspergillus Niger in Alkaline Phosphatase Activity in Calcareous Soil

Abstract

Humic acids have received a large attention of researching and development as amendments for poor fertility conditions and deteriorating physical properties,  since the process of extracting  is an easy common process to implement, as well as dilution of these acids with water enables  to be used at economically acceptable levels over large areas. It is necessary to notice that the properties of these acids depending on the organic source and the concentration added to the soil.A laboratory experiment was conducted at the department of soil Sciences and water resources, collage of Agriculture ,University of Basrah ,Iraq to demonstrate the effect of humic acids extracted from different sources and inoculation with Bacillus subtilis or Aspergillus niger  on alkaline phosphatase activity in  calcareous soil calcareous, southern Iraq. Humic acids extracted from  wheat straw, alfalfa leaves, goat manure, and poultry manure which composted previously . Humic acid levels were 0, 25 and 50 L ha-1 .The soil also inoculated with  Bacillus subtilis or Aspergillus niger, then samples were incubated at  28±2°C. After 7 or 30 days of incubation the activity of  alkaline phosphatase  was estimated . Enzyme phosphatase activity was increased in soils treated with humic acid  as compared to control with highest activity at Poultry manure (391.54 µg p-nitrophenol gm-1 soil.1h-1).The results also indicated that increasing the level of humic acid  significantly increased enzyme activity. For soil treated with  Bacillus subtilis and Aspergillus niger , phosphatase activity increased-as compared to control with a higher activity at Bacilluas subtilis (373.1 µg p-nitrophenol gm-1 soil.1h-1).