Assessment and kinetics of soil phosphatase in Brazilian Savanna systems.

Adão S Ferreira,Maria Rita C Campos,Suéllen P Espíndola

doi:10.1590/0001-3765201620140033

Adão S Ferreira, Maria Rita C Campos + Show 1 more

Open Access

https://doi.org/10.1590/0001-3765201620140033

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Abstract

The activity and kinetics of soil phosphatases are important indicators to evaluate soil quality in specific sites such as the Cerrado (Brazilian Savanna). This study aimed to determine the activity and kinetic parameters of soil phosphatase in Cerrado systems. Soil phosphatase activity was assessed in samples of native Cerrado (NC), no-tillage (NT), conventional tillage (CT) and pasture with Brachiaria brizantha (PBb) and evaluated with acetate buffer (AB), tris-HCl buffer (TB), modified universal buffer (MUB) and low MUB. The Michaelis-Menten equation and Eadie-Hofstee model were applied to obtain the kinetic parameters of soil phosphatase using different concentrations of p-nitrophenol phosphate (p-NPP). MUB showed the lowest soil phosphatase activity in all soils whereas AB in NC and NT presented the highest. Low MUB decreased interferences in the assessment of soil phosphatase activity when compared to MUB, suggesting that organic acids interfere on the soil phosphatase activity. In NC and NT, soil phosphatase activity performed with TB was similar to AB and low MUB. Km values from the Michaels-Menten equation were higher in NC than in NT, which indicate a lower affinity of phosphatase activity for the substrate in NC. Vmax values were also higher in NC than in NT. The Eadie-Hofstee model suggests that NC had more phosphatase isoforms than NT. The study showed that buffer type is of fundamental importance when assessing soil phosphatase activity in Cerrado soils.

Highlights

Phosphorus (P) availability in soils depends on phosphorus recycling from soil organic matter (Tabatabai and Bremner 1969, Albrecht et al 2010, Brooks et al 2013)
The study showed that the buffer type is of fundamental importance in order to assess the soil phosphatase activity in Cerrado soils
Low modified universal buffer (MUB) caused less interference in the measurement of soil phosphatase activity when compared to MUB

Summary

Introduction

Phosphorus (P) availability in soils depends on phosphorus recycling from soil organic matter (Tabatabai and Bremner 1969, Albrecht et al 2010, Brooks et al 2013). Enzyme kinetic parameters are affected by specific soil conditions such as metabolite concentration, microbial community, salinity, metals, and soil pH (Nannipieri and Gianfreda 1998, Marx et al 2001, Nannipieri et al 1982). These conditions are greatly affected by the land use, including soil management practices (Nannipieri et al 1982). Soil enzyme analysis varies with the pH, reaction buffer and substrate concentration (Malcom 1983, Nannipieri et al 1982)

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