Identifying Soil and Transport Properties Using a Model
17
In this chapter we present an attempt to quantify some simple measures of
behavior (linear equilibrium sorption coefficient Kd and first-order decay rate A)
of three common herbicides - Atrazine (ATR), Bromacil (BRM), and
Terbuthylazine (TBA) - under natural field conditions. Field data from transport
experiments at the Volcani Agricultural Research Institute (Bet Dagan, Israel) are
interpreted using a model developed by Indelman et al. (1998) which is extended
to account for multiple infiltration-redistribution cycles and to compute
confidence intervals for estimates of Kd and A. Results are compared to laboratory
measurements made at Bet Dagan and to transport properties reported in the
literature.
Biological, chemical, and transport properties of the soil at Bet Dagan are
reported in numerous studies. Parameters controlling water flow were measured
by Russo and Bressler (1981), Russo and Bouton (1992), and Russo et al. (1997).
Chemical characterization and transport studies were carried out by Tauber-Yasur
et al. (1999) and Dror et al. (1999a,b). Shapir and Mandelbaum (1997) measured
biological characteristics of Bet Dagan soil and also studied degradation of
Atrazine in soil cultures in the laboratory.
2 Brief Description of the Field Experiment
Data for this study are from the reactive transport experiments of Dror et al.
(1999a,b), and a detailed description of the experiment and collected data are
presented there. Herein we provide a brief description of the field experiment and
information needed for our analysis. Transport experiments were conducted on a
noncultivated 6 by 20 m plot in the coastal area of Israel. The soil was classified
as a Hamra Red Mediterranean sandy loam. Before the experiment, the plot was
disk-tilled to a depth of 15 cm and, during the experiment, the soil surface was
kept bare.
During the 1996 summer, three chemicals, ATR (0.5 g m- 2 ), BRM (1.2 g m- 2 ),
and TBA (0.5 g m- 2 ) were applied together in a 1 :75 water dilution as a pulse
input onto the soil surface using a mechanical handsprayer. The spatial
distribution of the chemical application on the field surface was measured by
collecting deposited material in 5-cm diameter glass dishes. The mean mass of
tracer that reached the field was 0.94 g m- 2 for BRM and 0.38 g m- 2 for TBA and
ATR. The coefficient of variation of application rate was 0.2 for each chemical.
Immediately after application of the chemicals, the field was irrigated with 5 mm
of water to enhance incorporation of the chemicals into the soil and to prevent
losses at the soil surface.
After chemical application, the field was irrigated ten times at 7-day intervals
using a minisprinkler irrigation system. In each irrigation event, 50 mm of water
was applied over ta = 6-h period. The spatial distribution of the leaching water on
the field surface was determined by collecting water in tin cans randomly
distributed on the soil surface. The distribution of water applied on the field
17
In this chapter we present an attempt to quantify some simple measures of
behavior (linear equilibrium sorption coefficient Kd and first-order decay rate A)
of three common herbicides - Atrazine (ATR), Bromacil (BRM), and
Terbuthylazine (TBA) - under natural field conditions. Field data from transport
experiments at the Volcani Agricultural Research Institute (Bet Dagan, Israel) are
interpreted using a model developed by Indelman et al. (1998) which is extended
to account for multiple infiltration-redistribution cycles and to compute
confidence intervals for estimates of Kd and A. Results are compared to laboratory
measurements made at Bet Dagan and to transport properties reported in the
literature.
Biological, chemical, and transport properties of the soil at Bet Dagan are
reported in numerous studies. Parameters controlling water flow were measured
by Russo and Bressler (1981), Russo and Bouton (1992), and Russo et al. (1997).
Chemical characterization and transport studies were carried out by Tauber-Yasur
et al. (1999) and Dror et al. (1999a,b). Shapir and Mandelbaum (1997) measured
biological characteristics of Bet Dagan soil and also studied degradation of
Atrazine in soil cultures in the laboratory.
2 Brief Description of the Field Experiment
Data for this study are from the reactive transport experiments of Dror et al.
(1999a,b), and a detailed description of the experiment and collected data are
presented there. Herein we provide a brief description of the field experiment and
information needed for our analysis. Transport experiments were conducted on a
noncultivated 6 by 20 m plot in the coastal area of Israel. The soil was classified
as a Hamra Red Mediterranean sandy loam. Before the experiment, the plot was
disk-tilled to a depth of 15 cm and, during the experiment, the soil surface was
kept bare.
During the 1996 summer, three chemicals, ATR (0.5 g m- 2 ), BRM (1.2 g m- 2 ),
and TBA (0.5 g m- 2 ) were applied together in a 1 :75 water dilution as a pulse
input onto the soil surface using a mechanical handsprayer. The spatial
distribution of the chemical application on the field surface was measured by
collecting deposited material in 5-cm diameter glass dishes. The mean mass of
tracer that reached the field was 0.94 g m- 2 for BRM and 0.38 g m- 2 for TBA and
ATR. The coefficient of variation of application rate was 0.2 for each chemical.
Immediately after application of the chemicals, the field was irrigated with 5 mm
of water to enhance incorporation of the chemicals into the soil and to prevent
losses at the soil surface.
After chemical application, the field was irrigated ten times at 7-day intervals
using a minisprinkler irrigation system. In each irrigation event, 50 mm of water
was applied over ta = 6-h period. The spatial distribution of the leaching water on
the field surface was determined by collecting water in tin cans randomly
distributed on the soil surface. The distribution of water applied on the field