Effect of Different Tillage Practices on Phosphatase and Urease Activities in a Calcareous Soil

Residue retention with less soil disturbance is a promising approach to maintain the soil quality. The study was conducted to determine the effects of tillage at three levels (conventional tillage (CT), reduced tillage (RT), and No-Till (NT)) as main plots and crop residue at two levels (residue removal and retention) as sub-plot on phosphatase and urease enzyme activitiesof calcareous soil in wheat-corn cropping system based on a split-plot design with three replications at the Zarghan in Fars province, Iran from 2015-16 to 2016-17. Results showed that applying tillage and residue significantly affected on soil bulk density (BD), organic matter (OM), and enzyme activities. In soil surface (soil depth: 0-10 cm), the highest BD was observed by NT practice when residue removed, whereas BD maximized as soil depth (10-20 cm) increased especially under CT. In contrast, OM was maximized under RT and residue retention (30% of residue) in wheat-corn rotation. The lowest alkaline phosphatase enzyme (917.00 and 443.00 µg PNP g-1 soil h-1 in wheat and corn, respectively) was obtained by CT and residue removal. Applying RT with 30% of residue was maximized acid phosphatase activity in wheat by 442.65 µg PNP g-1 soil h-1 and followed in corn by 374.17 µg PNP g-1 soil h-1. However, the highest urease enzyme activity (198.33 and 181.67 µg NH4 g-1 soil h-1 in corn and wheat, respectively) observed by NT when 30% of residue was retained. In general, adopting RT practice accompanied by retaining crop residue (30% of residue on the soil surface) to reduce BD, increase OM and improve enzyme activities of calcareous soil in the wheat-corn cropping system is recommended.