Effects of Sulfur, Phosphorous, and Plant on Soil Microbial Biomass and Phosphatase Activities

The soil enzymes and microbial biomass play a key role in nutrient cycling and have higher sensitivity to management and environmental changes compared to most physical and chemical properties of soil. Thus، these parameters have been monitored as essential indicators of soil quality. Sulfur is one of the by-products of gas and petrochemical refinery that has potential use as soil amendment in oil rich countries. Recently، application of sulfur has been on the rise to decrease soil pH and increase some nutrients availability in calcareous soils. The aim of this study was to investigate the impacts of sulfur، phosphorus، and plant growth on soil microbial biomass carbon and phosphatases activity. A split factorial experiment consisting of four levels of sulfur (0، 500، 1000، and 2000 kgha-1)، three levels of phosphorus (control، application rate based on soil test، 65% soil test) and two levels of plant (with and without corn planting) arranged in a complete randomize block design with three replication under field condition. Microbial biomass carbon and alkaline and acid phosphatase activities were determined. The results showed that microbial biomass carbon and phosphatase activities were significantly greater in the presence of plant than in its absence. The addition of sulfur and phosphorus to soil decreased microbial biomass carbon as well as alkaline and acid phosphatase. Sulfur effect was significant on soil microbial carbon، alkaline and acid phosphatase، but effect of phosphorus was not significant on phosphatase activities.