Relationship between rimsulfuron degradation and microbial biomass content in a clay loam soil |
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Authors: | C Vischetti P Perucci L Scarponi |
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Institution: | (1) Centro di Studio sulla Chimica e Biochimica dei Fitofarmaci CNR, Borgo XX Giugno 72, I-06121 Perugia, Italy e-mail: vischett@unipg.it Fax: +39-075-5856239, IT;(2) DIBIAGA, Università degli Studi di Ancona, via Brecce Bianche, I-60131 Ancona, Italy, IT;(3) DISAPROV, Università. degli Studi di Perugia, Borgo XX Giugno 72, I-06121 Perugia, Italy, IT |
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Abstract: | The present research was conducted to determine the relationship between the degradation of rimsulfuron and soil microbial
biomass C in a laboratory-incubated clay loam soil (pH=8.1; organic matter=2.1%) under different conditions and at different
initial dosages (field rate, 10 and 100 times the field rate). The half-life values varied between 0.4 and 103.4 days depending
on temperature, soil moisture and initial dose. Evidence suggested that rimsulfuron could pose environmental risks in cold
and dry climatic conditions. Significant decreases in microbial biomass C content in rimsulfuron-treated soil, compared to
untreated soil, were observed initially, especially at higher temperatures and low moisture levels, but never exceeded 20.3%
of that in control soil. The microbial biomass C content then returned to initial values at varying times depending on incubation
conditions. The relationship between herbicide degradation and microbial biomass C content gave parabolic curves (P<0.005 in all cases) under all conditions tested. Generally, maximum biomass C decrease coincided with the decrease in the
concentration of rimsulfuron to about 50% of the initial dose, except at 10 °C and 100×, when biomass began to recover as
early as 65–70% of the initial dose. The final equations could be useful to deduce the decrease of soil microbial biomass
in relation to herbicide concentration. From the degradation kinetics of the herbicide, the time required to reach this decrease
can also be calculated.
Received: 19 July 1999 |
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Keywords: | Degradation kinetics Soil microbial biomass Rimsulfuron Herbicide Pedoclimatic conditions |
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