Phosphatase activity and distribution of phosphorus in arid soil profiles under different land use patterns

The distribution of acid and alkaline phosphatases and the phosphorus status in arid soil profiles (0–60 cm) under crops, grass, trees and in fallow land has been studied. Significant increase in acid phosphatase activity was found below 45-cm depth under vegetation, whereas a gradual decrease in alkaline phosphatase activity with depth was noticed under all types of land use. Increases were observed in fungi under trees and in actinomycetes under crops. Surface soil (0–15 cm) had significantly higher available phosphorus. The available phosphorus content of the soil varies from 15 to 28 kg P/ha, depending upon the pattern of land use, while that of organic phosphorus is 96–110 kg P/ha (i.e. about 15–20% of total phosphorus). In general, a decreasing trend in organic phosphorus was observed in the soil profiles. Phosphatases were significantly and positively correlated with soil organic matter, available and organic phosphorus, and microbial populations.