soil - Lublin

ics behavior have been published (Katayama and Kuwatsuka 1991, Hekstra 1995,
Gisi et al. 1997, Vink et al. 1997, Singh et al. 1999, D'Angelo and Reddy 2000,
Picek et al. 2000, Accinelli et al. 2001).
Soil phosphatases are enzymes which are responsible for hydrolytic decomposition
of the esters and anhydrides of phosphoric acid. This class includes phosphomonoesterases
which catalyse the hydrolysis of organic phosphomonoesters to
inorganic phosphorus. Depending on their optimal pH, acid and alkaline phosphomonoesterases
can be distinguished (Alef and Nannipieri, 1995). These enzymes
are intracellularly and extracellularly active in soils where they can be secreted by
microbial and plant root cells. They are important for plant nutrition as they hydrolyze
organic phosphates, which amount to 20-85% of the total soil P, to phosphates
easily uptaken by plant roots (Alef and Nannipieri 1995; Marzadori et al. 1998;
Hayes et al. 2000; Schneider et al. 2001; Yadav and Tarafdar 2001). The phosphomonoesterase
activity is strongly influenced by soil depth and soil properties,
such as aeration status (Alef and Nannipieri 1995; Hýsek and Šarapatka 1998).
The aim of this work was to establish how two different doses of fonofos and
glyphosate treatment influence the dehydrogenase and phosphomonoesterase activity
under different soil aeration conditions in Haplic Phaeozem.
MATERIAL AND METHODS
Thirty grams of fresh Haplic Phaeozem (2.12 % organic carbon, pH 7.4; 38%
sand, 25% silt, 37% clay) containing 21% water, taken from the Ap horizon of a
meadow of the Tyśmienica river (Poland), was sieved (through a 2 mm sieve) and
(198 g) placed in glass columns (20 cm high and 3 cm in diameter), moistened to
full water capacity and allowed to drain the free water for two days. Then the soil
surface was sprayed with a 0.5 % water solution of glyphosate (Sigma-Aldrich) or
with a water solution of fonofos (Riedel-de-Haen). The amounts of glyphosate and
fonofos solution applied were 0 (control), 20 µl (as a normal dose, recommended
for weed treatment) and 200 µl (18.9 and 15 kg ha -1 for glyphosate and fonofos
respectively). Nine columns were incubated under flood conditions with one cm
water stagnating on the soil surface. The second group of nine columns was incubated
at water content corresponding to water holding capacity after the free water
was drained off. In each column 3 platinum electrodes (at three depths: 5, 10 and
15 cm) were installed for redox potential measurements. The incubation lasted 4
weeks at a temperature of 24°C. Once a week all the columns were eluted with
4.87 ml of water (corresponding to 7 mm of water head) to simulate average rainfall
of 360 mm per year. During the incubation, a Eh/pH was performed using Pt
electrodes/glass electrode. Both Eh and pH measurements were carried out with
pH/Eh-meter (type CPI-551, Elmetron, Poland). As a reference, a saturated calomel
electrode was used. Each treatment was triplicated.
In eluted waters, the concentration of used pesticides and their metabolites
were tested by the HPLC method.
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