Response of soil phosphatases to glyphosate and its formulations - Roundup (laboratory conditions)

Abstract

This paper assesses the impact on certain phosphatase activities in soil of glyphosate and its formulations, i.e.: Roundup 360 SL and Roundup TransEnergy 450 SL, which contain various glyphosate salts (isopropylamine and potassium) and various surfactants (polyethoxylated tallow amine and polyethoxylated ether amine). The experiment was carried out on sandy loam samples with organic carbon content of 10.9 g/kg. Aqueous solutions of pure glyphosate and its formulations were added to the soil. The amounts of applied glyphosate and its salts were: 1, 10 and 100 mg/kg. On days 1, 7, 14, 28 and 56 the activity of alkaline phosphomonoesterase (ALP); acid phosphomonoesterase (ACP); phosphodiesterase (PD); phosphotriesterase (PT) was measured spectrophotometrically. The effect of glyphosate and its formulations depended on the herbicide dosage and day of experiment. ALP and PD were the most susceptible to the presence of glyphosate. A comparison of the impact of glyphosate and its formulations showed that Roundup 360 SL was the most toxic. This could have resulted from the presence of surfactant polyethoxylated tallow amine in formulation. The correlation coefficients and principal component analysis indicated a significant positive relationship between the phosphatase activities in soil containing glyphosate. Significant correlation at P < 0.01 was noted among ALP and ACP, and among ALP and PD. Additionally, at P < 0.05, PD was significantly correlated with ACP, and PT with ALP and with PD.

Keywords

• decomposition
• soil enzymes
• phosphorus metabolism